Honors Biology

Unit 4 Review Questions

Spring 2009

Mr. Vermillion

Review Questions - Chapter 11 “Observable Patterns of Inheritance”

Ignore all page references.

1. What was the prevailing method of explaining the inheritance of traits before Mendel’s work with pea plants?

2. Garden pea plants are naturally __________-fertilizing, but Mendel took steps to __________-fertilize them for his experiments.

3. __________ are units of information about specific traits; they are passed from parents to offspring. What is the general term applied to the location of a gene on a chromosome?

4. Define allele; how many types of alleles are present in the genotypes Tt? tt? TT?

5. Explain the meaning of a true-breeding lineage.

6. When two alleles of a pair are identical, it is a __________ condition; if the two alleles are different, this is a __________ condition.

7. Distinguish a dominant allele from a recessive allele.

8. __________ refers to the genes present in an individual; __________ refers to an individual's observable traits.

9. Offspring of __________ crosses are heterozygous for the one trait being studied. [p.156]

10. Explain why probability is useful to genetics.

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11. Be able to use the Punnett-square method of solving genetics problems.

12. Define the testcross and cite an example.

13. Mendel's theory of __________ states that during meiosis, the two genes of each pair separate from each other and end up in different gametes.

14. Describe the testcross.

15. Be able to solve dihybrid genetic crosses.

16. Mendel's theory of __________ __________ states that gene pairs on homologous chromosomes tend to be sorted into one gamete or another independently of how gene pairs on other chromosomes are sorted out.

17. Distinguish between complete dominance, incomplete dominance, and codominance.

18. Define multiple allele system and cite an example.

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19. Explain why sickle-cell anemia is a good example of pleiotropy.

20. Gene interaction involving two alleles of a gene that mask expression of another gene's alleles is called __________.

21. List possible explanations for less predictable trait variations that are observed.

22. List two human traits that are explained by continuous variation.

23. Himalayan rabbits and garden hydrangeas are good examples of environmental effects on __________ expression.

24. List two human traits that are explained by continuous variation.

25. Himalayan rabbits and garden hydrangeas are good examples of environmental effects on __________ expression.

Review Questions - Chapter 12 “Human Genetics and Chromosomes”

1. The first abnormal chromosome tied to cancer was named the __________ chromosome.

2. A __________ is a preparation of metaphase chromosomes based on their defining features.

3. The units of information about heritable traits are known as __________. 4. Diploid (2n) cells have pairs of __________ chromosomes.

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5. __________ are different molecular forms of the same gene that are possible at a given locus; a __________-type allele is the most common form of a gene.

6. State the circumstances required for crossing over and describe the results. __________ __________ refers to the random alignment of each pair of homologous chromosomes at metaphase I of meiosis.

7.8. Name and describe the sex chromosomes in human males and females.

9. Human X and Y chromosomes fall into the more general category of __________ chromosomes; all other chromosomes in an individual’s cells are the same in both sexes and are called __________.

10. Define karyotype; briefly describe its preparation and value.

11. Explain meiotic segregation of sex chromosomes to gametes and the subsequent random fertilization that determines sex in many organisms.

12. A newly identified region of the Y chromosome called __________ appears to be the master gene for sex determination. All the genes on a specific chromosome are called a __________ group. Explain why the term "sex-linked genes" is less precise than the use of the terms, X-linked and Y-linked genes.

13. In whose laboratory was sex linkage in fruit flies discovered? Approximately when?

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14. State the relationship between crossover frequency and the location of genes on a chromosome.

15. __________ is a chart of the genetic connections between individuals; be familiar with the standardized symbols used in such charts.

16. A genetic __________ is a rare, uncommon version of a trait whereas an inherited genetic __________ is an inherited condition that sooner or later will cause mild to severe medical problems.

17. A __________ is a recognized set of symptoms that characterize a given disorder. 18. Describe what is meant by a genetic disease.

19. Carefully characterize patterns of autosomal recessive inheritance, autosomal dominant inheritance, and X-linked recessive inheritance. [pp.180-181]

20. Describe the characteristics of Hutchinson-Gilford progeria syndrome.

21. A(n) __________ is a loss of a chromosome segment; a(n) __________ is a gene sequence separated from a chromosome but then was inserted at the same place, but in reverse; a(n) __________ is a repeat of several gene sequences on the same chromosome; a(n) __________ is the transfer of part of one chromosome to a nonhomologous chromosome.

22. Cite evidence that tend to support the idea that chromosome structure does evolve.

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23. When gametes or cells of an affected individual end up with one extra or one less than the parental number of chromosomes, it is known as __________; relate this concept to monosomy and trisomy.

24. Having three or more complete sets of chromosomes is called __________. 25. __________ is the failure of the chromosomes to separate in either meiosis or

mitosis. 26. Trisomy 21 is known as __________ syndrome; Turner syndrome has the

chromosome constitution, __________; XXY chromosome constitution is __________ syndrome; taller than average males with sometimes mild mental impairment have the __________ condition.

27. Explain what is meant by double-blind studies.

28. List some benefits of genetic screening and genetic counseling to society.

29. Explain the procedures used in three types of prenatal diagnosis: amniocentesis, chorionic villi analysis, and fetoscopy; compare the risks.

30. Discuss some of the ethical considerations that might be associated with a decision of induced abortion.

31. A procedure known as preimplantation diagnosis relies on __________ fertilization.

Review Questions - “DNA”1. Before 1952, __________ molecules and __________ molecules were suspected

of housing the genetic code.

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2. The two scientists who assembled the clues to DNA structure and produced the first model were __________ and __________.

3. Summarize the research carried out by Miescher, Griffith, Avery and colleagues, and Hershey and Chase; state the specific advances made by each in the understanding of genetics.

4. Viruses called __________ were used in early research efforts to discover the genetic material.

5. Summarize the specific research that demonstrated that DNA, not protein, governed inheritance.

6. Draw the basic shape of a deoxyribose molecule and show how a phosphate group is joined to it when forming a nucleotide.

7. Show how each nucleotide base would be joined to the sugar-phosphate combination drawn in objective 6.

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8. DNA is composed of double-ring nucleotides known as __________ and single-ring nucleotides known as _________; the two purines are __________ and __________, while the two pyrimidines in DNA are __________ and __________.

9. Assume that the two parent strands of DNA have been separated and that the base sequence on one parent strand is A-T-T-C-G-C; the base sequence that will complement that parent strand is __________.

10. List the pieces of information about DNA structure that Rosalind Franklin discovered through her x-ray diffraction research.

11. Explain what is meant by the pairing of nitrogen-containing bases (base pairing), and explain the mechanism that causes bases of one DNA strand to join with bases of the other strand.

12. Describe how double-stranded DNA replicates from stockpiles of nucleotides. [pp.

13. 13. Explain what is meant by "each parent strand is conserved in each new DNA molecule."

14. During DNA replication, enzymes called DNA __________ assemble new DNA strands.

15. Distinguish between continuous strand assembly and discontinuous strand assembly.

16. Describe the process of making a genetically identical copy of yourself.

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Review Questions - Chapter 14 “DNA and Protein Synthesis”

1. State how RNA differs from DNA in structure and function, and indicate what features RNA has in common with DNA.

2. __________ RNA combines with certain proteins to form the ribosome; __________ RNA carries genetic information for protein construction from the nucleus to the cytoplasm; __________ RNA picks up specific amino acids and moves them to the area of mRNA and the ribosome.

3. Describe the process of transcription and indicate three ways in which it differs from replication.

4. What RNA code would be formed from the following DNA code: TAC-CTC-GTT-CCC-GAA?

5. Transcription starts at a __________, a specific sequence of bases on one of the two DNA strands that signals the start of a gene.

6. The first end of the mRNA to be synthesized is the __________ end; at the opposite end, the most mature transcripts acquire a __________ tail. Each base triplet in mRNA is called a __________.

7. State the relationship between the DNA genetic code and the order of amino acids in a protein chain.

8. Scrutinize Figure 13.7 in the text and decide whether the genetic code in this instance applies to DNA, mRNA, or tRNA

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9. Explain how the DNA message TAC-CTC-GTT-CCC-GAA would be used to code for a segment of protein, and state what its amino acid sequence would be.

10. Describe how the three types of RNA participate in the process of translation.

11. Cite an example of a change in one DNA base pair that has profound effects on the human phenotype.

12. Briefly describe the spontaneous DNA mutations known as base-pair substitution, frameshift mutation, and transposable element change.

13. List some of the environmental agents, or __________, that can cause mutations. 14. Using a diagram, summarize the steps involved in the transformation of genetic

messages into proteins. (see Figures in your text)

Review Questions - Chapter 44 “Human Reproduction and Development”1. Name the primary male reproductive organs; list secondary sexual traits

determined by these organs. [p.656]

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2. Follow the path of a mature sperm from the seminiferous tubules to the urethral exit. List every structure encountered along the path, and state the contribution to the nurturing of the sperm. [pp.656-657]

3. Describe how a man examines himself for testicular cancer. [p.657]

4. Name the four hormones that directly or indirectly control male reproductive function. Diagram the negative feedback mechanisms that link the hypothalamus, anterior pituitary, and testes in controlling gonadal function. [pp.658-659]

5. Diagram the structure of a sperm, label its components, and state the function of each. [p.659]

6. Trace the path of a sperm from the urethral exit to the place where fertilization normally occurs. Mention in correct sequence all major structures of the female reproductive tract that are passed along the way, and state the principal function of each structure. [pp.660-661]

7. Distinguish the follicular phase of the menstrual cycle from the luteal phase, and explain how the two cycles are synchronized by hormones from the anterior pituitary, hypothalamus, and ovaries. [pp.660-661]

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8. State which hormonal event brings about ovulation and which other hormonal events bring about the onset and finish of menstruation. [pp.662-663]

9. List the physiological factors that bring about erection of the penis during sexual stimulation and the factors that bring about ejaculation. [p.665}

10. List the similar events that occur in both male and female orgasm. [p.665]

11. Distinguish between the embryonic period and the fetal period. [p.666]

12. Describe the events that occur during the first month of human development; include the developed structures of the blastocyst as seen at about 15 days. [pp.666-667]

13. Describe the process of implantation. [p.666]

14. List and describe the four extraembryonic membranes and their functions. [p.667]

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15. Characterize the human developmental events occurring from day 15 to day 25. [p.668]

16. The __________ is a blood-engorged organ of endometrial and extraembryonic membrane [p.669]

17. Describe the characteristics of the developing human fetus during the second trimester. [pp.670-671]

18. The embryonic period of human development ends after the __________ week is over; the embryo is now clearly a human __________. [p.670]

19. Explain why the mother must be particularly careful of her diet, health habits, and life-style during the first trimester after fertilization (especially during the first six weeks). [pp.672-673]

20. Generally describe the process of labor or delivery. [p.673]

21. Milk production, or __________, occurs in mammary glands in the mother's breasts. [p.674]

22. An animal lifespan is divided into __________ (before birth) and __________ (after birth) stages. [p.674]

23. List the factors that bring about aging of an animal. [pp.674-675]

24. Cite the distinguishing characteristics of Werner’s syndrome. [p.675]

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25. Describe two different types of sterilization. [p.676]

26. Identify the three most effective birth control methods used in the United States and the four least effective birth control methods. [p.677]

27. For each STD described in Focus on Health, know the causative organism and the symptoms of the disease. [pp.678-679]

28. State the physiological circumstances that would prompt a couple to try in vitro fertilization.

Answer all of the multiple choice questions at the end of each of these chapters. Check your work with the key.

Monohybrid Cross Problems

Example ProblemIn summer squash, white fruit color (W) is dominant over yellow fruit color (w).  If a squash plant homozygous for white is crossed with a plant homozygous for yellow, what will the phenotypic and genotypic ratios be for:

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a. the F1 generation?     b. the F2 generation?c. What will the phenotypic and genotypic ratios of the offspring be if you perform a testcross with the F1 generation?

Solution1. Write down the cross in terms of the parental (P1) genotypes and phenotypes:

WW x ww white x yellow

2.  Determine the P1 gametes, place them in a Punnett Square and fill in the resulting genotypes:

P1 gametes W and w

W W

w

w

3. Determine the genotypic and phenotypic ratios for the F1 generation:

Genotype= 100% Ww and white

4. Write down the cross involving the F1 progeny:

5.  Determine the F1 gametes, place them in a Punnett Square and fill in the resulting genotypes:

W w

W

w

Ww WwWw Ww

WW WwWw ww

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6. Determine the genotypic and phenotypic ratios for the F2 generation:

Genotypic ratios:  1:2:1

Phenotypic ratios: 3:1

7.  Perform the testcross using the F1 generation:

Recall that a testcross is a cross between an individual (usually of unknown genotype, dominant phenotype) and a homozygous recessive individual, often used to determine the genotype of the first individual.

Test cross: Always use a homozygous recessive individual to mate with the dominant type

Case (1)

Ww * ww 50 % White and 50% Yellow 1:1

Case (2)

WW * ww 100% White 100% (no ratio, all are Ww)

Genotypic ratios: Case (1) 1:1 (Ww and ww) and case (2) 100% (Ww)

Phenotypic ratios: 1:1 (White: yellow and 100% (Ww will be yellow)

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Monohybrid Problem Set (Courtesy, University of Arizona)

Problem 1: The Monohybrid Cross In pea plants, spherical seeds (S) are dominant to dented seeds (s). In a genetic cross of two plants that are heterozygous for the seed shape trait, what fraction of the offspring should have spherical seeds? A. None B. 1/4 C. 1/2 D. 3/4 E. All

Problem 2: Mendel's First Law

A phenotypic ratio of 3:1 in the offspring of a mating of two organisms heterozygous for a single trait is expected when:

A. the alleles segregate during meiosis. B. each allele contains two mutations. C. the alleles are identical. D. the alleles are incompletely dominant. E. only recessive traits are scored.

Problem 3: Mendel's "Experiment 1" In Mendel's "Experiment 1," true breeding pea plants with spherical seeds were crossed with true breeding plants with dented seeds. (Spherical seeds are the dominant characteristic). Mendel collected the seeds from this cross, grew F1-generation plants, let them self-pollinate to form a second generation, and analyzed the seeds of the resulting F2 generation. The results that he obtained, and that you would predict for this experiment are: A. 1/2 the F1 and 3/4 of the F2 generation seeds were spherical. B. 1/2 the F1 and 1/4 of the F2 generation seeds were dented. C. All of the F1 and F2 generation seeds were spherical. D. 3/4 of the F1 and 9/16 of the F2 generation seeds were spherical. E. All the F1 and 3/4 of the F2 generation seeds were spherical.

Problem 4: A cross of F1-hybrid plants

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A genetic cross between two F1-hybrid pea plants for spherical seeds will yield what percent spherical-seeded plants in the F2 generation? (spherical is dominant over dented)

A. 100%

B. 75%

C. 50%

D. 25%

E. 0%

Problem 5: Another F1-hybrid cross

A genetic cross between two F1-hybrid pea plants having yellow seeds will yield what percent green-seeded plants in the F2 generation? Yellow seeds are dominant to green.

A. 0%

B. 25%

C. 50%

D. 75%

E. 100%

Problem 6: Predicting the dominant allele

When true-breeding tall stem pea plants are crossed with true-breeding short stem pea plants, all of the _________ plants, and 3/4 of the __________ plants had tall stems. Therefore, tall stems are dominant.

A. F1, F2.

B. G1, G2.

C. parental, F2.

D. F2, parental.

E. P1, P2

Problem 7: The test cross

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To identify the genotype of yellow-seeded pea plants as either homozygous dominant (YY) or heterozygous (Yy), you could do a test cross with plants of genotype _______.

A. y

B. Y

C. yy

D. YY

E. Yy

Problem 8: Predicting the results of a test cross

A test cross is used to determine if the genotype of a plant with the dominant phenotype is homozygous or heterozygous. If the unknown is homozygous, all of the offspring of the test cross have the __________ phenotype. If the unknown is heterozygous, half of the offspring will have the __________ phenotype.

A. dominant, incompletely dominant

B. recessive, dominant

C. dominant, epistatic

D. co-dominant, complimentary

E. dominant, recessive

Problem 9: Incomplete dominance

In Mendel's experiments, if the gene for tall (T) plants was incompletely dominant over the gene for short (t) plants, what would be the result of crossing two Tt plants?

A. 1/4 would be tall; 1/2 intermediate height; 1/4 short

B. 1/2 would be tall; 1/4 intermediate height; 1/4 short.

C. 1/4 would be tall; 1/4 intermediate height; 1/2 short.

D. All the offspring would be tall.

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E. All the offspring would be intermediate.

Problem 10: Disappearance of parental phenotypes in the F1 generation A genetic cross of inbred snapdragons with red flowers with inbred snapdragons with white flowers resulted in F1-hybrid offspring that all had pink flowers. When the F1 plants were self-pollinated, the resulting F2-generation plants had a phenotypic ratio of 1 red: 2 pink: 1 white. The most likely explanation is: A. pink flower color is epistatic to red flower color. B. pink flowers are the result of a blending of the red and white genotypes. C. flower color is due to 2 or more complementary genes. D. heterozygous plants have a different phenotype than either inbred parent because of

incomplete dominance of the dominant allele. E. flower color inheritance in snapdragons does not behave as a Mendelian trait.

Problem 11: Co-dominant alleles: The Human ABO markers Human blood type is determined by co-dominant alleles. There are three different alleles, known as IA, IB, and i. The IA and IB alleles are co-dominant, and the i allele is recessive. The possible human phenotypes for blood group are type A, type B, type AB, and type O. Type A and B individuals can be either homozygous (IAIA or IBIB, respectively), or heterozygous (IAi or IBi, respectively). A woman with type A blood and a man with type B blood could potentially have offspring with which of the following blood types? A. type A B. type B C. type AB D. type O E. all of the above

Problem 12: 2:1 segregation in Manx cats Manx cats are heterozygous for a dominant mutation that results in no tails (or very short tails), large hind legs, and a distinctive gait. The mating of two Manx cats yields two Manx kittens for each normal, long-tailed kitten, rather than three-to-one as would be predicted from Mendelian genetics. Therefore, the mutation causing the Manx cat phenotype is likely a(n) __________ allele.

Courtesy of PETNET in Australia

A. pleiotropic B. co-dominant C. epistatic D. lethal E. sex-linked Go to this site to check work: http://www.biology.arizona.edu/mendelian_genetics/problem_sets/monohybrid_cross/monohybrid_cross.html

Dihybrid Cross Problems*

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Problem 1: Predicting combinations of alleles in gametes of plants heterozygous for two traits. A pea plant is heterozygous for both seed shape and seed color. S is the allele for the dominant, spherical shape characteristic; s is the allele for the recessive, dented shape characteristic. Y is the allele for the dominant, yellow color characteristic; y is the allele for the recessive, green color characteristic. What will be the distribution of these two alleles in this plant's gametes? A. 50% of gametes are Sy; 50% of gametes are sY B. 25% of gametes are SY; 25% of gametes are Sy;

25% of gametes are sY; 25% of gametes are sy. C. 50% of gametes are sy; 50% of gametes are SY D. 100% of the gametes are SsYy

E. 50% of gametes are SsYy; 50% of gametes are SSYY.

Problem 2: When does a phenotype ratio of 9:3:3:1 occur? A phenotype ratio of 9:3:3:1 in the offspring of a mating of two organisms heterozygous for two traits is expected when: A. the genes reside on the same chromosome B. each gene contains two mutations C. the gene pairs assort independently during meiosis D. only recessive traits are scored E. none of the above

Problem 3: A genetic cross yielding a 9:3:3:1 ratio of offspring. Which of the following genetic crosses would be predicted to give a phenotypic ratio of 9:3:3:1? A. SSYY x ssyy B. SsYY x SSYy C. SsYy x SsYy D. SSyy x ssYY E. ssYY x ssyy

Problem 4: Predicting gametes of an SsYy plant. The gametes of a plant of genotype SsYy should have the genotypes: A. Ss and Yy B. SY and sy C. SY, Sy, sY, and sy D. Ss, Yy, SY and sy E. SS, ss, YY, and yy

Problem 5: A SsYy x ssyy test cross.

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Which of the following genotypes would you not expect to find among the offspring of a SsYy x ssyy test cross: A. ssyy B. SsYy C. Ssyy D. ssYy E. SsYY

Problem 6: Offspring of a SsYy x ssyy test cross. The expected phenotypic ratio of the progeny of a SsYy x ssyy test cross is: A. 9:3:3:1 B. 3:1 C. 1:1:1:1 D. 1:2:1 E. 3:1:1:3

Problem 7: Homozygous offspring of a dihybrid cross. In a dihybrid cross, AaBb x AaBb, what fraction of the offspring will be homozygous for both recessive traits? A. 1/16 B. 1/8 C. 3/16 D. 1/4 E. 3/4

Problem 8: Heterozygous offspring of a dihybrid cross. Following a SsYy x SsYy cross, what fraction of the offspring are predicted to have a genotype that is heterozygous for both characteristics? A. 1/16 B. 2/16 C. 3/16 D. 4/16 E. 9/16

Problem 9: Homozygous offspring of a dihybrid cross, again. In a dihybrid cross, SsYy x SsYy, what fraction of the offspring will be homozygous for both traits? A. 1/16 B. 1/8 C. 3/16 D. 1/4 E. 3/4

Problem 10: Exceptions to the 9:3:3:1 ratio of offspring?

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If Mendel's crosses between tall, spherical-seeded plants and short, dented-seeded plants had produced many more than 1/16 short, dented-seeded plants in the F2 generation, he might have concluded that: A. the dented seed and short traits are unlinked. B. he would not have concluded any of the above. C. all traits in peas assort independently of each other. D. the spherical seed and tall traits are linked. E. all traits in peas are linked.

Problem 11: Incomplete dominance in a dihybrid cross. In Mendel's experiments, the spherical seed character (SS) is completely dominant over the dented seed character (ss). If the characters for height were incompletely dominant, such that TT are tall, Tt are intermediate and tt are short, what would be the phenotypes resulting from crossing a spherical-seeded, short (SStt) plant to a dented-seeded, tall (ssTT) plant? A. All the progeny would be spherical-seeded and tall. B. 1/2 would be spherical-seeded and intermediate height; 1/2 would be spherical-seeded

and tall. C. All the progeny would be spherical-seeded and short. D. You cannot predict the outcome. E. All the progeny would be spherical-seeded and intermediate height.

Source*Go to this site for a complete tutorial for these problems:http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cross/dihybrid_cross.html

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Population Genetics and the Hardy-Weinberg Law

Population genetics is the study of changes in the frequency of alleles in a population

A population is defined as an interbreeding group. The fact that the frequencies of the alleles may change from one generation to the next is known as evolution. Only populations can evolve. Individual organisms within a population can not.

The environment will test the "fitness" of a combination of genes. Those that are not fit will be removed from the gene pool.

Gene pool - the sum total of all the genes possesed by all the eligible breeding individuals in a population. The gene pool links one generation to the next.

A population is not the same as a gene pool. Only those members of population capable of reproducing are in the gene pool. Immature juveniles and those unable to mate are not in the gene pool.

Gene frequency refers to the frequency of a given allele in a population. If the dominant allele occurs 90% (.9) of the time then the recessive allele must occur 10% (.1) of the time. Thus it follows that 81% of the population is homozygous dominant (AA), 18% is heterozygous (Aa), and 1% is homozygous recessive (aa). See the following tables.

Sperm

Egg0.9 A 0.1 a

0.9 A 0.81 AA 0.09 Aa0.1 a 0.09 Aa 0.01 aa

If the gene frequencies were equal 50% (0.5) A and 50% (0.5) a, then the following would be true: 25% of the population is homozygous dominant (AA), 50% is heterozygous (Aa), and 25% is homozygous recessive (aa).

Sperm

Egg0.5 A 0.5 a

0.5 A 0.25 AA 0.25 Aa0.5 a 0.25 Aa 0.25 aa

Hardy-Weinberg Law

In 1908, two mathematicians, Godfrey Hardy and Wilhelm Weinberg, wrote an equation to describe gene frequency changes in a population. It became known as the Hardy-Weinberg Law. The law states that under conditions of equilibrium both the gene frequencies and genotypic ratios remain constant from generation to generation in sexually reproducing populations. For equilibrium to occur the following conditions must be met:

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The population must be larger than 10,000 individuals with total random mating; therewise, chance alone can alter the gene frequencies. See genetic drift.

No gene mutations can occur in the population. No genes may enter of leave the population. There is no immigration (entrance of

organisms) or emigration (exit of organisms). There is no natural selection. There is no pressure to "select" a mate (due to

phenotype). In addition, it assumes that each member of the population mates and produces an

equal number of offspring.

Because no population can meet all of the above conditions of equilibrium the gene frequencies of a population will change. This is known as evolution.

Genetic drift is the result of random fluctuations in the allele frequencies due to a small population.

The Hardy-Weinberg problems can be solved using the following equations. The dominant allele, A is represented by the letter "p" and the recessive allele, a, by the letter "a". Therefore: AA = pp or p2 , Aa = pq, and aa = qq or q2

Equation 1p + q = 1 or 100%

Equation 2 (binomial)

(p + q)2 = p2 + 2pq + q2 = 100%

Name ___________________________

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Hardy-Weinberg Problems

Date _________________ Period._____

Instructions: Using a calculator, solve the following problems. Rounding off to the nearest whole number or 1/10 when solving for p or q. If you do not have a calculator, set the problem up without finding the square root. Use the following equations: ..............

p + q = 1 or 100% .............. p2 + 2pq + q2 = 1 or 100%

1. Assume the Rh negative blood factor to be recessive. If 16% of the U.S. population is Rh negative calculate the following:

1a. What is the frequency of the q allele?

1b. What is the frequency of the p allele?

1a ______________________

1b ______________________

2. Assume brown fur in guinea pigs to be dominant and white to be recessive. The allele for brown fur = 0.8. Calculate the following:

2a. The frequency of the white allele.

2b. The expected frequency of homozygous dominants.

2c. The expected frequency of heterozygotes.

2d. The expected frequency of homozygous recessives.

2a ______________________

2b ______________________

2c ______________________

2d ______________________

3. People who can taste PTC are homozygous recessive. If 25% of the population can taste PTC calculate the following:

3a. The frequency of the p allele.

3b. The frequency of the q allele.

3c. The percent of heterozygotes.

3d. The percentage of all tasters.

3a ______________________

3b ______________________

3c ______________________

3d ______________________

4a. If q = 0.2, calculate the gene frequency of p. 4a

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4b. How many people out of 8000 will be homozygous dominant?

4c. How many people out of 8000 will be heterozygous?

4d. How many people out of 8000 will be homozygous recessive?

______________________

4b ______________________

4c ______________________

4d ______________________

5. Assume resistance to be dominant. If 96% of a bacterial population is resistant to an antibiotic calculate the following:

5a. The frequency of the recessive allele.

5b. The frequency of the dominant allele.

5c. The number of resistant bacterial in a population of 2 x 106 .

5d. The number of heterozygotes in the population of 2 x 106

5a ______________________

5b ______________________

45 ______________________

5d ______________________

6. 96 out of every 100 fruit flies have normal wings. Assume normal wings are dominant over curly wings. Calculate the following:

6a The frequency of the recessive allele.

6b. The frequency of the dominant allele.

6c. The number of offspring with normal wings in a population of 1000.

6d. The number of flies in 1000 that would exhibit the recessive phenotype.

6e. The number of flies, in 1000, that would be homozygous dominate.

6f. The number of flies, in 1000, that would carry the recessive allele.

6a ______________________

6b ______________________

6c ______________________

6d ______________________

6e ______________________

6f ______________________

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Monohybrid Cross Problems

Example ProblemIn summer squash, white fruit color (W) is dominant over yellow fruit color (w).  If a squash plant homozygous for white is crossed with a plant homozygous for yellow, what will the phenotypic and genotypic ratios be for:

a. the F1 generation?     b. the F2 generation?c. What will the phenotypic and genotypic ratios of the offspring be if you perform a testcross with the F1 generation?

Solution1. Write down the cross in terms of the parental (P1) genotypes and phenotypes:

WW (true-breeding white fruit)  X ww (true-breeding yellow fruit)

2.  Determine the P1 gametes, place them in a Punnett Square and fill in the resulting genotypes:

WW       X        ww

wW Ww

3. Determine the genotypic and phenotypic ratios for the F1 generation:

All F1 progeny will be heterozygous (Ww)  and will therefore have white fruit color.

4. Write down the cross involving the F1 progeny:

Ww (white fruit)     X     Ww (white fruit)

5.  Determine the F1 gametes, place them in a Punnett Square and fill in the resulting genotypes:

Ww           X             Ww

   W  w W  WW  Ww

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 w  Ww  ww

 

6. Determine the genotypic and phenotypic ratios for the F2 generation:

Genotypic ratios:  1/4 will be homozygous dominant (WW), 1/2 will be heterozygous (Ww) and 1/4 will be homozygous recessive (ww).   This is a 1:2:1 genotypic ratio.

Phenotypic ratios: 3/4 will have white fruit color and 1/4 will have yellow fruit color.  This is a 3:1 phenotypic ratio.

7.  Perform the testcross using the F1 generation:

Recall that a testcross is a cross between an individual (usually of unknown genotype, dominant phenotype) and a homozygous recessive individual, often used to determine the genotype of the first individual.

Ww (F1)            X            ww (homozygous recessive)

   w W  Ww w  ww

Genotypic ratios: 1/2 heterozygous (Ww) and 1/2 homozygous recessive(ww).  This is a 0:1:1 genotypic ratio.

Phenotypic ratios: 1/2 will have white fruit color and 1/2 will have yellow fruit color.  This is a 1:1 phenotypic ratio.

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