Dominance and Traits

Question 1

Define phenotype

Answer 1

observable properties

Question 2

Define genotype

Answer 2

genetic makeup - alleles present - homozygous or heterozygous

Question 3

What is a testcross and what is it used for?

Answer 3

A test where an unknown individual is bread with a homologous recessive partner to distinguish genotype

Question 4

Define incomplete dominance

Answer 4

the heterozygous phenotype is somewhere between the 2 homozygous phenotype
e.g.: pink flower made from 1 red and 1 white parent

Question 5

What is co-dominance and give an example of it

Answer 5

The heterozygous phenotype is a mixture of both homozygous phenotypes
e.g.: ABO blood types, or short horn cow coat colour

Question 6

give 2 examples of lethal alleles

Answer 6

Manx allele - hetero have a tail while homos die in utero

Oruro alleles in horses - LWFS (lethal white foal syndrome)

Question 7

Define heterosis

Answer 7

new combinations give hybrids vigour, offspring out perform purebreds

Question 8

Define epistasis

Answer 8

When a gene at one locus influences the expression of another at another locus

Question 9

Give examples of sex linked genes

Answer 9

milk yield, egg production, cryptorchidism, cock-feathering

Question 10

What is the difference between sex-linked and sex-influenced genes?

Answer 10

Sex-influenced is expressed in both but more common in one sex while sex linked is only expressed by 1 sex

Question 11

Define a) polyploidy b) aneuploidy

Answer 11

a) Polyploidy - 3 or more complete sets of chromosomes

b) Aneuploidy - one or more extra/missing chromosome, for example trisomy21 causes down syndrome