Genetic crosses

Question 1

Draw a perfect genetic cross

Answer 1

Phenotype:
abc def
Parent’s Xx xx
Genotype:
Gametes: X,x x,x x x
X Xx Xx
x xx xx
Ratio:
2:2
50% abc
50% def

Question 2

Cross a dominant brown eyed mother (BB) with a recessive blue eyed father (bb)

Answer 2

Ratio=4:0
100% brown
0% blue

Question 3

Cross a recessive blue eyed mother (bb) with a dominant brown eyed father (Bb)

Answer 3

Ratio=2:2
50% brown
50% blue

Question 4

Cross a mother with straight hair who inherited a dominant allele from both of her parents and a father with curly hair who inherited a recessive allele from both of his parents

Answer 4

Ratio=4:0
100% straight
0% curly

Question 5

Cross a mother with straight hair who inherited one dominant and recessive allele from each parent and a father who inherited the same alleles

Answer 5

Ratio=3:1
75% straight
25% curly

Question 6

Two dogs (a mother and a father) both have an eyepatch and both have alleles Ee. Their offspring also has an eyepatch and has alleles EE. Their offspring (dog 1) is then crossed with another dog (dog 2) with alleles EE. They then end up giving birth to 4 dogs

Can you:

a) Draw a genetic cross for dog 1 and dog 2

b) Draw a family tree for all of the dogs including the alleles of all dogs. Refer to both dogs in the F1 generation as ‘mother’ and ‘father’, both dogs in the F2 generation as ‘dog 1’ and ‘dog 2’ and all dogs in the F3 generation as ‘offspring’.

Answer 6

a) Should have drawn genetic cross and ended up with:
Ratio=4:0
100% eye patch
0% no eye patch

b) mother (Ee) x Father (Ee)
Dog 1 (EE) x Dog 2 (EE)
offspring EE,offspring EE,ofspring EE,ofspring EE