Gregor Mendel Gregor Mendel was a monk who studied heredity using pea plants He came up with a couple of laws for determining heredity

F 1 : Yy (Yellow) Where did the green color go? What if you cross the F 1 ?

F 1 : Gametes F 2 Generation : YY-Yellow Yy – Yellow yy - Green The recessive gene shows up in the F 2 generation when both alleles for green are present.

Symbols of Heredity Homozygous (pure) –Having a pair of identical genes for a trait –Ex: Tall (T) = TT, or tt Heterozygous (hybrid) –Having two different genes (alleles) for a trait –Ex: Tt

Mendel’s Laws 1.Law of Dominance: In a cross between 2 pure contrasting traits (tall vs. short), only one of these traits appear in the next generation This is called the DOMINANT TRAIT The one that does not appear is called the RECESSIVE TRAIT

The Punnett Square Determines the probability of obtaining various results in genetic crosses Ex: cross a homozygous tall (TT) and a heterozygous tall (Tt) 1:2:1 ratio 1TT (Homozygous Tall) 2 Tt (Heterozygous tall) 1 tt (homozygous recessive- short)

TTTtTt TtTt tt

Cross 2 Heterozygotes 1:2:1 Ratio for a heterozygote trait which is what Mendel observed. 1: AA 2: Aa 1: aa

Monohybrid Cross Crossing one trait

Dihybrid Cross Crossing 2 traits

Let’s do some Punnett Squares!!!! 1.Cross a Pure Tall with a Pure short plant. (T=Tall t=short) Give ratios for genotype and phenotype 2. What is the expected ratio of offspring produced in crossed between hybrid tall pea plants and pure tall pea plants? 3. What ratios can be expected in the offspring of a cross between hybrid tall and short pea plants? 4. Mendel found that pure wrinkled plants crossed with pure round led to 100% round. What ratio can be expected in crossed between wrinkled and hybrid round? (R=round r=wrinkled)

Mendel’s Laws: 2.The Law of Segregation: The idea that genes separate from each other during meiosis (gamete formation) and then recombine at fertilization

3. Law of Independent Assortment Each Allele pair segregates independently of the other allele pairs during meiosis. This is true ONLY if the alleles are on different chromosomes.

Karyotype: A visual layout of all the chromosomes in the nucleus of a cell. Used to indicate if there are any genetic abnormalities. Each member of a homologous pair assorts independently

How can we use our knowledge of inheritance patterns to trace a disorder through a family and predict what future offspring might be like for a trait? Some traits operate according to the Law of Dominance Let’s see what your genotypes and phenotypes are!!! Trait Chromosome location Dominant Phenotype Possible Dominant Genotypes Recessive Phenotype Recessive Genotype Widow’s peak 4PeakPP or Pp No peak pp What is your genotype and phenotype?

Trait Chromosome Dominant Phenotype Possible Dominant genotypes Recessive Phenotype Recessive Genotype Hitchhikers thumb 17StraightTT or TtCurvedtt Ear Lobes 21FreeLL or LlAttachedll Tongue Rolling 22AbilityRR or RrNo ability rr

Take the person next to you and perform a Punnett Square for 2 of the traits described 1. Create a separate Punnett square for each trait. 2. Determine the genotypes of your children 3. Determine the phenotypes of your children. TP Tp tP tp Enrichment: Can you perform a dihybrid cross? Using the traits of tongue rolling and widow’s peak, create the possible gametes and use a 4X4 Punnett square to predict the outcomes for the offspring. Cross: TtPp X TtPp

Incomplete Dominance (Blending ) Crossing 2 homozygous parents whose offspring look totally different than parents Ex: Cross a pure red snapdragon (RR) and a pure white snapdragon (WW) Offspring Phenotype: ____________________

Codominance Two dominant alleles are expressed at the same time Roan cattleEx: Roan cattle Cross a homozygous red coat cow (RR) and a homozygous white coat cow (WW)

Multiple Alleles Ex: Human blood type Cross a man with AB blood (I A I B ) and a woman with type O blood (ii) Blood Type A: AA or Aa Blood Type B: BB or Bb Blood Type O: ii Classic Dominance and Recessive inheritance Blood Type AB: What type of inheritance is this? Co Dominance: Both surface antigens are produced equally.

Summary: Types of Dominance CompleteIncompleteCodominance Genotype: AA/Aa Genotype: Aa Genotype: Aa Phenotype: Only dominant allele is expressed Phenotype: Intermediate between both alleles Phenotype: Both alleles expressed equally

sex-linked Sex-linked Referring to a gene that is part of a sex chromosome. Since all of the genes on a chromosome are inherited as a package, they are essentially linked together. Common Sex Linked disorders: Color blindness Hemophilia

Pedigrees: A diagram that shows how family members are related (genetically)

2 Individual 2 is most likely a: A. normal male B. normal noncarrier female C. color-blind male D. carrier female E. color-blind female

If individual 8 is not color blind, what is the probability that this individual is a carrier? A. 0 B. 1/4 C. 1/2 D. 3/4 E. 1

4. Individual 11 must be a: A. carrier female B. color-blind male C. color-blind female D. normal male E. A or C

5. Which of the following describes individual 17? A. The daughter of individuals 10 and 11. B. A carrier female C. A mistake D. The result of a one night stand between individual 11 and a color-blind man. E. C or D

6. Let us say individual 12 marries a normal, non-carrier female. What is the probability that one of his sons will be color-blind? A. 0 B. 1/4 C. 1/2 D. 3/4 E. 1

7. Individual 5 has just married a woman who is not color-blind. This woman was previously married to a color-blind man, and together they had a color- blind son. As newlyweds, this couple seeks your help as a genetic counselor. What advice could you give? A. Go ahead and have children: there's no chance that any will be color-blind. B. 50% of your daughters may be color-blind. C. 50% of your sons may be color-blind. D. 25% of your sons may be color-blind. E. Sorry, I can't help. Anything I could tell you would just be a wild guess.

8. Individuals 4 and 6 can be best described as: A. Twins B. Brothers C. Color-blind D. Sisters E. A and D