Review Questions - Chapter 11 “Observable Patterns of Inheritance”1. What was the prevailing method of explaining the inheritance of traits before

Mendel’s work with pea plants? Blending of traits2. Garden pea plants are naturally _self_________-fertilizing, but Mendel took

steps to ___cross_______-fertilize them for his experiments. 3. Genes 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? loci

4. Define allele;(different molecular forms of a gene) how many types of alleles are present in the genotypes Tt? tt? TT? (2)

5. Explain the meaning of a true-breeding lineage.(they always produce offspring just like themselves; homozygous) When two alleles of a pair are identical, it is a __homozygous________ condition; if the two alleles are different, this is a __heterozygous________ condition.

6. Distinguish a dominant allele from a recessive allele. Dominant: only requires one gene to be expressed; recessive requires both alleles before expression)

7. ___Genotype_______ refers to the genes present in an individual; __phenotype________ refers to an individual's observable traits.

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

9. Explain why probability is useful to genetics. It allows one to predict the % of offspring that would have a particular combination of genes; hence phenotypes can be predicted.

10. Be able to use the Punnett-square method of solving genetics problems. 11.Define the testcross and cite an example. A phenotypic dominant individual is

crossed with a homozygous mate. Tt x tt and TT x tt are the possible genotypes of the mating. In the former case, the phenotypic ratio of the offspring is 1:1. In the latter 100% are Tt and express the dominant condition.

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

13. Describe the testcross. See above14. Be able to solve dihybrid genetic crosses. Refer to handouts, text and class

notes. 15. Mendel's theory of __independent________ __assortment________

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. When does this not hold true?

16. Distinguish between complete dominance, incomplete dominance, and codominance. Refer to text and class notes. Also PPP on the V drive.

17. Define multiple allele system and cite an example.

Whenever more than two forms of alleles exist at a given locus, it is called a multiple allele system. A,B, O blood group is an example. Four blood types: A, B, AB, and O, are the result of A, B, and i genes at work.

18. Explain why sickle-cell anemia is a good example of pleiotropy. Sometimes the expression of alleles at one location can have effects on two or more traits; this is termed pleiotropy.

Sickle Cell Anemia is a good example of pleiotropy because many traits are observed in an afflicted person such as: anemia, joint pain, organ failure; fatigue

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

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

Camptodactyly (immobile, bent fingers) can express itself on one hand only, both hands, or neither due the possibility that a gene product is missing in one of the several steps along the metabolic pathway.

Continuous Variation in PopulationsA given phenotype can vary, by different degrees, from one individual to the next in a population.

This is the result of interactions with other genes, and environmental influences.

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

In humans, eye color and height are examples.

22. Himalayan rabbits and garden hydrangeas are good examples of environmental

effects on ___gene_______ expression.