Class 26: Heredity II

If parents are Tt and Tt, what is the probability of one offpring being TT? What is the likkelihoo of two offsrping being TT? ¼ x ¼ = 16 

Gametic probability: chance gamete will contain T or t is 1/2, becaue 2 gametes are requried, we have 2 independent events. So probability of t from first parent and T from second parent ½ x ½ = 1/4 . 

What is a dihybrid cross

A genetic experiment that trakcs two different traits

What is an example of dihybrid cross in pea plants

Tound yellow seeds RRYY

wrinkled green seeds rryy

What is mednels second law? what does it result from?

The principle of independent assortment: Alleles at different loci segregate independelty of each other (is located on different chromoosmes or far enough apart on same chromosome) 

Results from independent separation of homologous chromosomes in Anaphase I

Provide example of idenpendnet assortment

1. cell contains two pairs of homologous chromosomes

2. through DNA replication you get the x chapes chromosomes 

3. in anaphase of meiosis 1, each pair of homologous chromosomes seprates indepdnently 

4. there are differnt ways th pairs of chrtomosomes can separate 

5. in anaphase 2, the sister chromatids seperate into individual chromosomes so genes located on differnt pairs of chromosomes assort indepdendltym producing differnt combinations of allels in the gametes 

What are gametic ratios for heterzygote RrYy

25%RY, 25%rY, 25% Ry, 25%rY

What is a branch diagram 

it is another way to show the mathematical ratios in a multi trait cross

Split each trait in monohybrid cross 

then use multiplication event bc each event is independent

If you have parents AaBB and aabb what is likelihood of the offspring will be aaBb

Parent 1 - 50% chane it will contain a and 100% chance it will contain B, 0.5 × 1 = ½ 

Parent - 100% chance gamete will contain a and 100% chance gamete will contain b so 1 × 1 = 100%

cross the gametes - 0,5aB x 1ab = 0.5aaBb