Chapter 12.3

Question 1

What is a test cross? Note it may also be referred to as a test cross

Answer 1

• it is used to determine an unknown genotype
• > here, an unknown genotype is crossed with an organism known to be homozygous recessive
• if all the offspring is dominant phenotype
• > then the unknown genotype is likely to be homozygous
• if there is a 1:1 distribution of dominant to recessive phenotypes
• > then the unknown genotype is likely to be heterozygous

Question 2

What is the phenotypic ration for two genotypes that are heterozygous

Answer 2

-9:3:3:1

Question 3

What is the recombination frequency

Answer 3

• it is the likelihood that two alleles are separated from each other during crossing over
• > it is roughly proportional to the distance between the genes on the chromosome
• therefore, tightly linked genes have a receombination frequency of 0 percent
• weakly linked genes have a recombination frequency approaching 50 percent

Question 4

Describe the five conditions of the Hardy Weinberg equilibrium

Answer 4

1) Population is very large(no genetic drift)
2) There are no mutations that affect the gene pool
3) Mating between individuals in the population is random(no sexual selection)
4) There is no migration of the individuals into or out of the population
5) Genes in the populations are all equally successful at reproducing

p^2+2pq+q^2=1

p+q=1