Genetic terms and problems

Question 1

What is the probable locations of eye color alleles on chromosomes of a Gg individual?

Answer 1

G and g must be on homologous chromosomes, on 2 different chromosomes (1.GG 2.gg)

Question 2

What does true-breeding mean?

Answer 2

Homozygous.

Question 3

What are normal proportions using Punnett square for 1 gene?

Answer 3

1/4 AA, 2/4 Aa, 1/4 aa.

Question 4

You have a SOLID rabbit mixed with a SPOTTED rabbit. All offsprings are SPOTTED. Which phenotype is dominant?

Answer 4

Spotted.

Question 5

When working with 2 different genes, should you add or multiply the proportions?

Answer 5

Look at them separately and multiply.

Question 6

What is the principle of dominance?

Answer 6

If an individual has 2 different alleles, dominant masks recessive. Recessive allele can come back in future generations.

Question 7

Define Incomplete Dominance.

Answer 7

The dominant allele cannot completely hide the recessive allele. The heterozygote has a phenotype between the dominant and recessive phenotype.

Question 8

Give an example of incomplete dominance.

Answer 8

Flowers: Red + White = Red, PINK, white

Question 9

Define Codominance.

Answer 9

Both alleles are fully expressed in heterozygotes and are visible. Nothing is hidden.

Question 10

Give an example of codominance.

Answer 10

Roan coat color on horses, a mix of red and white that gives an orange color from a far, but still has red ans white hair.

Question 11

Give a genotypic example of codominance.

Answer 11

RR, RR’, R’R’

Question 12

Define Recessive Lethality.

Answer 12

The homozygous recessive genotype does not survive because the recessive allele is lethal without the dominant allele.

Question 13

Give an example of Recessive lethality.

Answer 13

Manx cat born without a tail. AA is normal. Aa is no tail. aa is not born.

Question 14

What are the phenotypic proportions for recessive lethality?

Answer 14

1/3 Normal.

2/3 Not normal.

Question 15

What are possible proportions and genotypes when 2 genes are involved?

Answer 15

9/16, 3/16, 3/16, 1/16, AABB, AaBB, aaBB, AABb, AAbb, AaBb, Aabb, aaBb, aabb.

Question 16

Define Epistatis.

Answer 16

Interaction of more than one gene at different loci on a single trait. 1 gene product hides or modifies the expression of another gene.

Question 17

Give an example of epistasis.

Answer 17

Colour gene and hair gene. Brown or blonde and Hair or bald.

Question 18

Give possible genotypes and phenotypes for epistasis.

Answer 18

3/16 blonde, 9/16 brown, 4/16 bald. (2 genes involved)

Question 19

Define Sex-linkage

Answer 19

The phenotype is associated with a certain sex. Males only carry 1 allele. Alleles on the X chromosomes only.

Question 20

What type of pattern usually skip generations?

Answer 20

Recessive (autosomal)

Question 21

What type of pattern is more seen in man and skips a generation.

Answer 21

X-linked recessive.

Question 22

What type of pattern can have different phenotypes of the parents then child?

Answer 22

Dominant (autsomal)

Question 23

What type of pattern can have the father only passing it to his daughters?

Answer 23

X-linked dominant.

Question 24

A man has X-linked trait of baldness, but his spouse doesn’t. What proportion of their sons inherit the baldness allele from their father?.

Answer 24

Zero. The father gives his Y chromosome to his sons.