Worksheet for problem set #8 March 13, 2006

1.

Divide given map measurements by 100 to get the frequency of recombination.

p(SCO1)= _____

p(SCO2)=_____

__________ X __________

__________

Testcross: __________ X __________

Offspring category	Genotypes	Math with RF	# Offspring
NR	+k+ j+l	½(0.9)(0.8)=0.36= ½(0.9)(0.8)=0.36=	360 360
SCO1	++l jk+	½(0.1)(0.8)=0.04= ½(0.1)(0.8)=0.04=	40 40
SCO2	+kl j++	½(0.9)(0.2)=0.09= ½(0.9)(0.2)=0.09=	90 90
DCO	+++ jkl	½(0.1)(0.2)=0.01= ½(0.1)(0.2)=0.01=	10 10

HOWEVER, the ACTUAL number of offspring has to reflect the coefficient of coincidence given in the problem.

We calculate ____ fewer DCO using the COC, which means that there are _____ more SCO for EACH region (____ for each class). This alone gives us too many offspring, so we have to adjust by decreasing the NR by ______.

Tetrad analysis: examining recombination with fungi

Tetrad: the 4 haploid product cells from a single meiosis

Tetrad analysis: the use of tetrads to study the segregation of chromosomes and genes during meiosis.

first-division segregation: two different alleles (e.g. A and a) separate from one another at the 1^st meiotic division.

second-division segregation: two different alleles (e.g. A and a) separate from one another at the 2^nd meiotic division.

2. Mapping 2 loci and the centromere

parental ditype (PD): only 2 genotypes, same as the parents (NR/NCO or 2 strand DCO)

nonparental ditype (NPD): only 2 genotypes, not the same as the parents- all 4 recombinant (4 strand DCO)

tetratype (TT): all 4 possible genotypes- 2 parental, 2 recombinant (SCO or 3 strand DCO)

3. Ordered tetrads

In this species, each of the 4 meiotic product nuclei undergoes a further mitotic division→8 nuclei.