Lesson 5: Non-Mendelian Genetics: Multiple alleles And Polygenic Inheritance

Question 1

Multiple alleles- p1

Answer 1

-many genes are controlled by more than two allele
—example is human blood type w/ 3
alleles:
A, B, O
These three alleles create 4 blood types:
A, B, AB, O

Question 2

Multiple alleles- blood types dominant and recessive - p2

Answer 2

-each person has two of the three possible alleles that determine their blood type.
- the alleles A and B are co-dominant to e/o but both are dominant to the O allele

Question 3

Notation

Answer 3

-similar to co-dominance, for the human blood types and we use the uppercase I with the superscript A or B for the alleles A and B
-We use the lowercase letter i for the allele for O to indicate that it is recessive to the other two alleles
I^A, I^B, i

Question 4

Polygenic inheritance

Answer 4

• many traits are controlled by more than one gene: polygenic inheritance
  -the result of many genes working together is continuous in a trait
  Ex: human skin colour and eye colour

Question 5

Polygenic inheritance: example- eat length in corn

Answer 5

-ear length in corn is controlled by two genes (A and B)
—in order to get the longest eat of
corn both genes controlling the trait
must be homozygous dominant
(AABB)
-to get the shorter ear of corn, both genes of trait must be homozygous recessive (aabb)
-the combination of alleles together other than those two produces the whole range of ear length in between.

Question 6

Epistasis definition

Answer 6

—> epistatic genes are genes that mask the effect of other genes

Question 7

Epistasis function

Answer 7

The proteins produced by these genes bind to the promoter sites of other genes and prevent RNA poly. from binding. Thereby preventing the protein of that gene being made

Question 8

Epistasis example

Answer 8

An example is red hair in humans. This is the to the gene MCR1. It acts as a switch controlling whether eumelanin or phaeomelanin are produced.
—if MCR1 is active, the brown eumelanin is produced.
—when MCR1 is not active, the red phaeomelanin is produced

Question 9

Epistasis- coat colour in mice p1

Answer 9

in mice gene C controls the production of melanin (the pigment that gives colour) while gene B determine whether the he colour is black or brown
—In it’s homozygous recessive form,
gene C, blocks the expression of gene
B
—in order for the mouse to be white it’s
genotype must contain the
homozygous recessive form of gene C
( cc) the alles for gene B do not affect
the phenotype

Question 10

Epistasis- coat colour in mice p2

Answer 10

-in order to get a brown mouse, it must be homozygous recessive for gene B(bb) and must have at least one dominant allele for gene C
-to get a black mouse, it must have at least one dominant allele for gene B and gene C