Di hybrid Crosses

1. Di-hybrid Crosses a.Dihybrid crosses predict the probabilities of the combinations of two factors. b.Example: An individual who is heterozygous for both brown eyes and brown hair has offspring with another individual who is heterozygous for both traits. i.Brown hair (H) is dominant to red (h) ii.Brown eyes (E) are dominant to blue (e)

g. Dihybrid Crosses HEHehEhe HE He hE he

g. Dihybrid Crosses HEHehEhe HEHHEE He hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEe He hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEE He hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe He hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEe hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHee hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEe hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEe he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEehhEE he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEehhEEhhEe he

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEehhEEhhEe heHhEe

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEehhEEhhEe heHhEeHhee

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEehhEEhhEe heHhEeHheehhEe

g. Dihybrid Crosses HEHehEhe HEHHEEHHEeHhEEHhEe HeHHEeHHeeHhEeHhee hEHhEEHhEehhEEhhEe heHhEeHheehhEehhee

c. How many offspring have….. i.Dark hair and brown eyes? HxEx? ii.Dark hair and blue eyes? Hxee? iii.Red hair and brown eyes? hhEx? iv.Red hair and blue eyes? hhee?

How many offspring have….. 1.Dark hair and brown eyes? HxEx? nine 2.Dark hair and blue eyes? Hxee? 3.Red hair and brown eyes? hhEx? 4.Red hair and blue eyes? Hxee?

How many offspring have….. 1.Dark hair and brown eyes? HxEx? nine 2.Dark hair and blue eyes? Hxee? three 3.Red hair and brown eyes? hhEx? 4.Red hair and blue eyes? hhee?

How many offspring have….. 1.Dark hair and brown eyes? HxEx? nine 2.Dark hair and blue eyes? Hxee? three 3.Red hair and brown eyes? hhEx? three 4.Red hair and blue eyes? Hxee?

How many offspring have….. 1.Dark hair and brown eyes? HxEx? nine 2.Dark hair and blue eyes? Hxee? three 3.Red hair and brown eyes? hhEx? three 4.Red hair and blue eyes? Hxee? one

2. Polygenic Inheritance

F. Polygenic Inheritance Traits in which the phenotypes are determined by many genes contributing to the overall phenotype. Each gene is on a different location on the chromosome and may not even be on the same chromosome. The best way to recognize polygenic inheritance is when the phenotypes exhibit a wide range of expression or variation. Examples:

skin color

Eye Color & Hair Color

d. Multiple Alleles – Instead of having two forms of an allele, there are more than two for one gene. i. The best example for humans is blood. There 3 alleles for blood types in humans: A, B and O. A and B are co dominant while O is recessive.

b. Multiple Alleles – Blood Type Type A genotypes could be: I A I A or I A i. Type B genotypes could be: I B I B or I B i. Type AB genotype is: I A I B Type O genotype is: ii

Practice A man who is heterozygous for type A blood marries a woman who is heterozygous for type B blood. Find the possible outcomes

e. Sex linked traits i.Sex linked traits – Are genes located on the X chromosome. There is almost no information located on the Y chromosome. ii.Since males have only one X chromosome they show whatever allele is on the X chromosome, regardless of whether it is dominant or recessive.

e. Sex linked traits iii. This is the only time that a single recessive allele is expressed. Two examples of sex- linked traits in humans are red/green colorblindness and hemophillia. (A recessive sex linked trait that keeps your blood from clotting.)

Color Test

Sex linked traits - Colorblindness 1.If normal vision (N) is dominant to colorblindness (n) give the genotypes for each of the following: A female carrier: X N X n A homozygous dominant female: X N X N Colorblind male: X n Y Colorblind female: X n X n A male with normal vision: X N Y

Sex linked traits Who does the male get the X chromosome from? Mother Who does a male inherit recessive sex linked traits from? Mother Who are colorblind more often, men or women? Men; no information on Y to mask the recessive trait on X.

Practice A female carrier has a child with a male with normal vision. What are the chances of colorblindness occuring in: Son? Daughter?

Practice A colorblind male has a child with a normal female. Fill out the cross.