Dihybrid Inheritance

Question 1

Dihybrid cross

Answer 1

Examine the inheritance of two different traits in individuals and therefore involve two genes. (Only for traits controlled by complete dominance)

Question 2

What does FOIL mean for dihybrid crosses for unlinked genes?

Answer 2

1. Combine First letters of both sets of alleles
2. Combine first and Outside letter of the second set of alleles
3. Combine the two Inside letters
4. Combine the Last letters

Question 3

What is the phenotypic ratio when two heterozygous individuals with unlinked genes are crossed?

Answer 3

9:3:3:1

Question 4

What is the phenotypic ratio when two unlinked genes are crossed?

Answer 4

9:3:3:1

Question 5

Can distantly linked genes cross over?

Answer 5

Crossing over may occur between then and chromatids exchange sections of genetic information, however the likelihood of them crossing over if reasonably low so there are few recombinant compared to the parent type.

Question 6

Can closely linked genes cross over?

Answer 6

Very unlikely therefore gametes will a high percentage of parental allele combinations and a low percentage of recombinants.

Question 7

Presence of linked genes will have no effect on..?

Answer 7

Individuals who have both homozygous dominant and homozygous recessive parents. Presence of linked genes will have no effect on the genetic variation.

Question 8

Linked genes do affect…?

Answer 8

Genetic variation if a parent is heterozygous. The recombinants occur less frequently when linked genes are present.

Question 9

Recombinants

Answer 9

Individuals with different combinations of alleles to their parents