Inheritance 2 Flashcards
Name 3 types of dominance and what they mean?
Complete- same as one of homozygous parents
Incomplete- intermediate between parents phenotype
Codominance- F1 is phenotype of both homozygous parents
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?
Incomplete dominance
F2= 1:2:1 ( RR:Rr:rr)
What type of inheritance is blood grouping an example of?
Codominance and multiple alleles
What are the alleles in blood grouping and which are dominant?
Alleles= I^A I^B i
A and B are dominant to I
A and B are codominant
What offspring ratio do lethal alleles show and why?
2:1
as 0.25 is lethal
Name an example of lethal genes
Chicken can be normal, creeper or Homozygous not hatched
Describe dihybrid gene interactions
Two gene loci (each with two alleles), interact to produce a single phenotype. Genes are located on different chromosomes (not linked)
What is multiple alleles and name 3 examples
Multiple Alleles
A gene locus has more than two alleles (Mammal coat colour, blood)
b.
What is multiple genes and name 3 examples
Multiple Genes (polygenic) Each gene with two alleles (skin pigmentation)
For Dihybrid inheritance what is the F2 offspring ratio?
9:3:3:1
Name 6 types of epistasis and their ratios of F2 offspring
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
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
Recessive Epistatsis 9:3:3:4 A-B-=black aaB-=brown A-bb yellow aa-bb yellowe
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
Dominant Epistasis
12:1:3
What is Reciprocal/duplicate Recessive epistasis and what is the F2 allelen offspring ratio?
Both dominant alleles from each step is needed for pigment.
Eg double recessive causes epistasis
7:9
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
Duplicate genes with cumulative effect
9:6:1
A-B- : A-bb aaB: aabb
Define duplicate dominant genes.
What is the F2 allele offspring ratio?
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
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
Dominant and recessive interaction
13:3
Polygenic inheritance
What is this?
Two or more genes each with two alleles have what EFFECT on phenotype
Inheritance of multiple genes
Two or more genes each with two alleles have ADDITIVE EFFECT on phenotype
Effect of on allele is small
For polygenic inheritance.
What shape is the F1 and F2 generation graph of relative frequency against Height
F1= one bar F2= normal distribution curve
Define penetrance
Proportion of individuals showing expected phenotype
100% penetrance = all individuals express the phenotype
Define expressivity
Degree of expression of phenotype in an individual
