Inheritance 2

Question 1

Name 3 types of dominance and what they mean?

Answer 1

Complete- same as one of homozygous parents
Incomplete- intermediate between parents phenotype
Codominance- F1 is phenotype of both homozygous parents

Question 2

Red flowered RR crossed with White flower rr gives F1 with pink flowers Rr

What type of dominance is this ?
What is the F2 ratio and offspring?

Answer 2

Incomplete dominance

F2= 1:2:1 ( RR:Rr:rr)

Question 3

What type of inheritance is blood grouping an example of?

Answer 3

Codominance and multiple alleles

Question 4

What are the alleles in blood grouping and which are dominant?

Answer 4

Alleles= I^A I^B i

A and B are dominant to I
A and B are codominant

Question 5

What offspring ratio do lethal alleles show and why?

Answer 5

2:1

as 0.25 is lethal

Question 6

Name an example of lethal genes

Answer 6

Chicken can be normal, creeper or Homozygous not hatched

Question 7

Describe dihybrid gene interactions

Answer 7

Two gene loci (each with two alleles), interact to produce a single phenotype. Genes are located on different chromosomes (not linked)

Question 8

What is multiple alleles and name 3 examples

Answer 8

Multiple Alleles
A gene locus has more than two alleles (Mammal coat colour, blood)
b.

Question 9

What is multiple genes and name 3 examples

Answer 9

Multiple Genes (polygenic) Each gene with two alleles (skin pigmentation)

Question 10

For Dihybrid inheritance what is the F2 offspring ratio?

Answer 10

9:3:3:1

Question 11

Name 6 types of epistasis and their ratios of F2 offspring

Answer 11

9:7	Reciprocal Recessive epistasis

9:3:4	Recessive Epistasis

12:3:1	Dominant epistasis

9:6:1	Duplicate genes with cumulative effect

15:1	Duplicate Dominant genes

13:3	Dominant and recessive interaction

Question 12

What type of inheritance is this and what is the F2 ratio of offspring alleles?

Labrador fur colour
A dominant black fur, a recessive brown
B allows pigment to be deposited
b prevents deposition of dark pigment so yellow fur

Answer 12

Recessive Epistatsis
9:3:3:4
A-B-=black
aaB-=brown 
A-bb yellow
aa-bb yellowe

Question 13

What type of inheritance is this and what is the F2 ratio of offspring alleles?

One dominant allele (W) produces the same phenotype (white) regardless of the allelic status of the other

Answer 13

Dominant Epistasis

12:1:3

Question 14

What is Reciprocal/duplicate Recessive epistasis and what is the F2 allelen offspring ratio?

Answer 14

Both dominant alleles from each step is needed for pigment.

Eg double recessive causes epistasis

7:9

Question 15

What type of inheritance is this and what is the F2 ratio of offspring alleles?

Effect of both dominant alleles additive individual dominant allele’s have the same effect

Answer 15

Duplicate genes with cumulative effect
9:6:1
A-B- : A-bb aaB: aabb

Question 16

Define duplicate dominant genes.

What is the F2 allele offspring ratio?

Answer 16

Both dominant alleles have identical effect. Only one dominant allele of either other needed. No additive effect.

eg either enzyme A or B can catalyse reaction

15:1

Question 17

What type of inheritance is this?
What is the ratio?

Dominant allele from one gene and recessive allele from other gene have same phenotype: Gene A able to suppress expression at B gene

Answer 17

Dominant and recessive interaction

13:3

Question 18

Polygenic inheritance
What is this?

Two or more genes each with two alleles have what EFFECT on phenotype

Answer 18

Inheritance of multiple genes

Two or more genes each with two alleles have ADDITIVE EFFECT on phenotype

Effect of on allele is small

Question 19

For polygenic inheritance.

What shape is the F1 and F2 generation graph of relative frequency against Height

Answer 19

F1= one bar
F2= normal distribution curve

Question 20

Define penetrance

Answer 20

Proportion of individuals showing expected phenotype

100% penetrance = all individuals express the phenotype

Question 21

Define expressivity

Answer 21

Degree of expression of phenotype in an individual