Mendelian Genetics

Question 1

What is Mendel’s first law?

Answer 1

The law of segregation.

Question 2

What is the law of segregation?

Answer 2

Individuals inherent two alleles for each gene, and during reproduction, the two alleles are separated into each gamete in a 1:1 ratio. Gametes unite randomly at fertilization.

Question 3

What is the monohybrid cross phenotypic ratio?

Answer 3

3:1

Question 4

What is the monohybrid cross genotypic ratio?

Answer 4

1:2:1

Question 5

What is Mendel’s second law?

Answer 5

The law of independent assortment.

Question 6

What is the law of independent assortment?

Answer 6

Different genes are transmitted independently of each other. The random placement of an allele for one gene into a gamete does not influence which allele for another gene is found in the same gamete.

Question 7

What is the dihybrid cross phenotypic ratio?

Answer 7

9:3:3:1

Question 8

What is incomplete dominance?

Answer 8

When heterozygotes have a blend of phenotype between those of homozygous dominant and homozygous recessive individuals.

Question 9

What is the phenotypic ratio for incomplete dominance in one gene?

Answer 9

1:2:1

Question 10

What is the genotypic ratio for incomplete dominance in one gene?

Answer 10

1:2:1

Question 11

What is co-dominance?

Answer 11

When phenotypes from both alleles are expressed by heterozygotes?

Question 12

What is the phenotypic ratio for co-dominance in one gene?

Answer 12

1:2:1

Question 13

What is the genotypic ratio for co-dominance in one gene?

Answer 13

1:2:1

Question 14

What is the name for a gene with only one wildtype allele?

Answer 14

Monomorphic.

Question 15

What is the name for a gene with multiple wildtype alleles?

Answer 15

Polymorphic.

Question 16

What is pleiotropy?

Answer 16

When one gene controls more than one trait.

Question 17

What are conditional mutants?

Answer 17

Mutations that are only visible under specific condition, such as temperature, or exposure to specific chemicals/ treatments.

Question 18

What is epistasis?

Answer 18

When an allele at one locus hides the effects of the alleles at a second locus.

Question 19

What are complementary genes?

Answer 19

When two genes are required to make one phenotype.

Question 20

What is the phenotypic ratio for complementary genes?

Answer 20

9:7:1

Question 21

What is recessive epistasis?

Answer 21

When the presence of two recessive alleles for one gene masks all other phenotypes.

Question 22

What is the phenotypic ratio for recessive epistasis?

Answer 22

9:4:3

Question 23

What is dominant epistasis I?

Answer 23

The presence of a dominant allele for one gene masks all phenotypes for the other gene.

Question 24

What is the phenotypic ratio in dominant epistasis I?

Answer 24

12:3:1

Question 25

What is dominant epistasis II?

Answer 25

The dominant allele for one gene is epistatic to the othere gene, so the other gene’s phenotype only appears in the absence of the first gene. This differs from dominant epistasis I in that homozygous recessive individuals have the same phenotype as individuals with the dominant epistatic gene.

Question 26

What is the phenotypic ratio for dominant epistasis II?

Answer 26

13:3

Question 27

What are redundant genes?

Answer 27

When two genes have identical functions.

Question 28

What is the phenotypic ratio for redundant genes?

Answer 28

15:1

Question 29

What is penetrance?

Answer 29

The proportion of individuals with a genotype that have the expected phenotype.

Question 30

What is expressivity?

Answer 30

The severity of a phenotype (more expressive = more severe).