Genetics
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Transcript of Genetics
GeneticsChapter 10.2, 10.3, 11.1, and
11.2
Do Now- True for False if false, correct the statement. 1. Certain acquired characteristics, such as
mechanical or mathematical skill may be inherited. 2. Certain thoughts or experiences of a mother
mark or alter the hereditary makeup of an unborn child.
3. Color blindness is more common in males than in females.
4. A person may transmit characteristics to offspring which he/she does not show.
5. Certain inherited traits may be altered by the stars, planets or moon early in development.
6. The total number of male births exceeds female births each year.
Objectives 1. SWBAT hypothesize about the birth of
two twin boys. 2. SWBAT define homozygous,
heterozygous, gene, allele, and cross pollination
3. SWBAT discuss Mendel’s life and the importance of his study of pea plants.
The Problem…. Born October of 2006: These two boys are related… They are
twins. http://www.msnbc.msn.com/id/15447465/
Another Example…
How Can this be? Let’s Brainstorm.
Goal of this chapter on Genetics:
1866 Gregor Mendel “Father of Genetics” Austrian Monk that studied pea plants
Pure breeds Self Fertilization
Statistician who wanted to be a teacher
Discovered how traits were inherited in a population
How Genetics Began The passing of traits to the next
generation - inheritance or heredity.
Mendel performed cross-pollination in pea plants.
Mendel followed various traits in the pea plants he bred.
7 Traits Mendel Studied
Mendel studied seven different traits.
Seed or pea color Flower color Seed pod color Seed shape or texture Seed pod shape Stem length Flower position
Mendel’s Crosses P Generation:
F1 Generation:
F2 Generation:
Generations P Generation
Parents Pure –
F1 Generation Hybrid – 2 different types of genes for a trait
F2 Generation 3:1–Yellow : Green
Animation
Definitions Genetics:
Study of hereditary Gene:
Strand of DNA that codes for a protein (Trait) Allele:
A version of a gene
Phenotype vs. Genotype Phenotype:
Physical characteristics (What the individual looks like)
Ex) Red Petals
Genotype: Alleles Received (genes you have) Ex) RR
Homozygous and Heterozygous Homozygous:
Having two of the same alleles for a particular trait
Ex.
Heterozygous: Having two different alleles for a particular
trait Ex.
Dominant Vs. Recessive Dominant hides the recessive trait in the
heterozygous genotype.
Think – Pair - Share If Fred Flintstone is heterozygous for black hair. (B=Black, b=blonde)
What is Fred’s genotype?
What is Fred’s phenotype?
Tweety bird is yy. (Y= yellow feathers, y=brown feathers) 1. What is his genotype?
2. What is his phenotype?
3. Is he heterozygous or homozygous? Explain.
Objectives 1. SWBAT do a probability lab in which
they flip a coin to determine the outcome of crosses.
2. SWBAT will work in partners to create punnett squares.
Do Now Provide an example of the following
terms: Heterozygous Homozygous Genotype Phenotype Dominant Recessive Allele Gene
Mendels 3 Laws 1. Law of Segregation
Each allele a person has separates into different gametes
Ex. Ww – one W goes in one sperm and the other w goes into another sperm w W
w WSperm
Mendels 3 Laws 2. Law of
Independent Assortment Gene pairs
(homologous) will separate randomly into gametes
Mendels 3 Laws 3. Law of Dominance
Traits exist in two possible forms (dominant and recessive)
The dominant forms hides the recessive trait in the heterozygous condition
Monohybrid Cross R= Can roll your tongue r= Can’t roll your tongue
Genotype Ratio:
Phenotype Ratio:
R r
R
r
Genotypic vs. Phenotypic Ratios Phenotype Ratio:
Ratio of different physical traits Ex) Brown eyes ¼ or 25%
Genotype Ratio: Ratio of the different possible alleles Ex) Tt = ¼ or 25%
Sample Problems1) Daffy Duck is heterozygous for black
feathers. Daisy Duck is homozygous for yellow feathers. Set up a punnett square and determine probabilities of their potential offspring. (Both genotype and phenotype ratios!)
2) B = Black b = yellow
Do Now Sponge Bob Square pants is heterozygous
for brown eyes. Sandy is also heterozygous for brown eyes. Create a punnett square to determine the possible outcomes of their children.
Do Now Sleeping Beauty has freckles. Her prince
charming is heterozygous for no freckles. What are the chances of her children having freckles? Please show your work.
Setting up Dihybrid Crosses 1. Determine parent genotypes 2. Determine alleles to be passed down 3. Set up punnet square 4. Determine outcome
Phenotype Ratio Genotype Ratio
Dihybrid Crosses Looking at two different traits
Ex. Hair color and eye color
B=brown eyes b=blue eyes
R=Brown hair r=blonde hair
Mother is heterozygous for both traits Father is heterozygous for eye color and homozygous
dominant for hair color
The problem Aladdin and Jasmine want to have
children. Jasmine is homozygous dominant for black hair and black eyes.
Aladdin is homozygous recessive for brown eyes and brown hair.
B=black hair b=brown hairE=black eyes e=brown eyes
B=black hair b=brown hairE=black eyes e=brown eyes
Jasmine’s daughter falls in love with a man who is also heterozygous for hair and eye color. Determine possible genotype and phenotype ratios.
Do Now BbTt X BBTt
Math Method For a cross between TtBb and TtBB. Do each cross individually and multiply the
results together.
For TtBb
Do Now Mickey Mouse is heterozygous for Round ears
and homozygous for Black eyes. Minnie Mouse also is homozygous for Floppy ears and heterozygous for Black eyes. Determine genotype and phenotype ratios. (B=black, b=brown, R=round, r= floppy.)
Quiz next class on 10.2 QUIZ ON THURS ON:
Vocabulary words Mendel Mendel’s experiments Monohybrid crosses ONLY
Do Now Peter and Lois decide to try for a 4th child. Determine the possible genotype and
phenotype ratios of the following cross:
DdEe X ddEe
D= Brown hair d=red hair E=fluffy hair e=thinning hair
Do Now Two dogs have puppies! The male dog
is homozygous brown fur and heterozygous floppy ears. The female dog is heterozygous for brown fur and has straight ears.
B=brown fur b=blonde fur F=Floppy ears f= straight ears
What ratio of the dogs would have brown fur and floppy ears?
10.3 Gene Linkage and Polyploidy Several genes on a chromosome Gene Linkage:
When two genes are close to each other on the same chromosome
Gene Linkage Linked genes on a chromosome results in
an exception to Mendel’s law of independent assortment
Linked genes usually do not segregate independently
Drosophila (Fruit Flies) First organism with linked genes Linked genes typically travel together
during crossing over http://www.biologyreference.com/La-Ma/Li
nkage-and-Gene-Mapping.html
Chromosome Map Crossing over occurs more frequently
between genes that are far apart Map of genes on a chromosomes and
frequency of crossing over
Polyploidy Occurrence of one or more extra sets of all
chromosomes in an organism. Ex. A triploid organism (3n) - means that it
has three complete sets of chromosomes.
True or False – Correct false statements_______ 1. Crossing over occurs more frequently
between genes that are close together on a chromosome.
_______ 2. Gene linkage was first studied by using garden peas.
_______ 3. Scientists call a drawing like the one shown below a chromosome map.
_______ 4. Chromosome map percentages represent actual chromosome distances.
Matching
11.1 Basic Pattern of Human Inheritance
Recessive Genetic Disorders Cystic Fibrosis Albinism Tay Sachs Disease Galactosemia
Affects the mucus-producing glands, digestive enzymes, and sweat glands
Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat.
Without sufficient chloride ions in the cells, a thick mucus is secreted.
Cystic Fibrosis
Cystic Fibrosis Not too long ago CF was always fatal in
childhood, but better treatment methods developed over the past 20 years have increased the average lifespan of CF patients to nearly 30 years
Albinism Caused by altered genes, resulting in the
absence of the skin pigment melanin in hair and eyes
White hair Very pale skin Blue Eyes Pink pupils
Albinism Impaired Vision It is vital that people with
albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer
High risk of skin cancer
Tay-Sachs Disease Caused by the absence of
the enzymes (in lysosomes) responsible for breaking down fatty acids called gangliosides
Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration
Tay Sachs Disease Children with Tay-Sachs, a progressive
neurodegenerative disease that attacks nerve cells, usually die before age 5.
Children will go deaf, have seizures, and, ultimately, become unable to swallow or breathe.
Galactosemia Recessive genetic disorder characterized
by the inability of the body to digest galactose.
Lactose = Galactose + Glucose Symptoms: • liver damage or failure
• cataracts• brain damage• infection
Galactosemia Treatment requires the strict exclusion of
lactose/galactose from the diet.
Do Now Period 3
Dominant Genetic Disorders Dominant Gene results in disorder:
Huntington’s Disease Achondroplasia
Achondroplasia is a genetic condition that
causes small body size and limbs that are comparatively short.
Obesity Breathing problems (apnea) Recurrent ear infections
(otitis media). Other health problems
Matching Do Now Period 8
Huntington’s Disease affects the nervous system. Huntington's disease is a progressive,
degenerative disease that causes certain nerve cells in your brain to waste away.
As a result, you may experience uncontrolled movements, emotional disturbances and mental deterioration.
Huntington’s Disease Diminished memory,
immediate and short-term (long-term memory usually remains intact)
Disease usually manifests itself by age 35
Do Now Peter and Lois decide to try for a 4th child. Determine the possible genotype and
phenotype ratios of the following cross:
DdEe X ddEe
D= Brown hair d=red hair E=fluffy hair e=thinning hair
Do Now Explain how gene distances are
determined on a chromosome.
What does “3n” mean?
Pedigree Shows history of a trait in a family Allows researchers to analyze traits within
a family
Symbols for Pedigree
Using Pedigrees Inferring Genotypes
Knowing physical traits can determine what genes an individual is most likely to have.
Predicting Disorders Scientists use pedigree analysis to study: inheritance patterns determine phenotypes genotypes.
Sample Pedigree
Think – Pair - Share
Do Now Fill in the pedigree for Achondroplasia. Use
the variable A.
Dominant or Recessive Trait?
Dominant or Recessive Trait?
Test Cross When the genotype of an individual is
unknown, cross the individual with a homozygous recessive
The outcome of the cross determine the genotype of the unknown
11.2 Incomplete Dominance: Heterozygous phenotype is an
intermediate phenotype between the two homozygous phenotypes.
Two alleles are blended Ex) Four O’clock Flowers Red + WhiteWhite = Pink
Codominance Neither trait is dominant instead, both
traits are shown (No Blending) Ex) Roan Cows Red + WhiteWhite = RED AND WHITE
Sickle Cell Disease Affects red blood cells and ability to
transport oxygen.
Homozygous recessive alleles=
Heterozygous=
Homozygous dominant alleles=
Sickle Cell and Malaria People who are
heterozygous for sickle cell, have a higher resistance to malaria.
Do Now Fill in the genotypes for the following
pedigree B=brown eyes b = blue eyes
Do Now Explain how gene distances are
determined on a chromosome.
What does “3n” mean?
Multiple Alleles Traits determined by
more than 2 allelesEx. Blood Typing (3 alleles ABO) A and B are dominant
to O
Universal Donor
Sample Problem Determine the possible offspring of the
following crosses
1. AB and O 2. AA and BO 3. AB and AB
Coat Color of Rabbits Rabbits have a hierarchy of coat color 4 alleles (C, cch, ch, and c) Dominant C > cch> ch > c Recessive
C Full color cch Chinchilla ch Himalayan c albino
Complex Inheritance and Human Heredity
Coat Color of Rabbits
Full Color Himalayan
Albino
Chinchilla
Do Now period 6 cc x Ccch
Genotype and phenotype ratios
Do Now A parent with the blood type A and one
with B have a child with type O blood. What are the parents genotypes?
Draw out the punnett square.
Do Now Do the following cross between the these
rabbits. Cch x Ccch
What color were the parents? What are the genotype and phenotype
ratios of the offspring.
What do you see?
What do you see?
Sex Linked Traits Traits located on the sex chromosomes
(X or Y) X linked: gene is located on the X
chromosomes Y linked: gene is located on the Y
chromosome
What are the chances of having a girl?
How would you go about solving it?
Sex-Linked Traits A man who is color blind marries a woman
that is heterozygous for color blindness. What is the chance of having a color blind boy?
Do Now- per. 1 A man that is color blind marries a woman
that is a carrier for the disorder. What is the chance of having a color blind girl?
Hemophilia Sex linked disorder characterized by
delayed blood clotting Located on the X Chromosome Seen in the Royal Family of England
Hemophilia
Do Now – A man with hemophilia marries a woman
the is homozygous normal phenotype. What is the chance of having a boy with hemophilia?
A girl with hemophilia?
Complex Inheritance and Human Heredity
Polygenic Traits
Polygenic traits arise from the interaction of multiple pairs of genes.
Chapter 11
Skin Pigment
Polygenic Inheritance
Figure 9.22
P Generation
aabbcc(very light)
AABBCC(very dark)
F1 Generation
AaBbCc AaBbCcF2 Generation
Eggs Sperm
What is the difference between polygenetic and multiple alleles?
Complex Inheritance and Human Heredity
Environmental Influences
Environmental factors
Diet and exercise
Sunlight and water
Temperature
Complex Inheritance and Human Heredity
Twin Studies
Helps scientists separate genetic contributions from environmental contributions
Traits that appear frequently in identical twins are at least partially controlled by heredity.
Traits expressed differently in identical twins are strongly influenced by environment.
Let’s try to explain the inheritance of the babies’ skin color.