Lecture 4

Question 1

what is independent assortment?

Answer 1

assortment of 1 trait doesn’t affect other traits –> i.e. genes for seed colour and seed shape are on diff chromosomes so sorted independently

Question 2

what is the ratio of genotypes in dihybrid cross that undergo independent assortment?

Answer 2

equal ratio of the 4 genotypes (1:1:1:1)

Question 3

in dihybrid cross, what determines the final genomes in the gametes?

Answer 3

pairings of homologous chromosomes in anaphase

in 1st division:
AB and ab
or
Ab and aB

Question 4

with independent assortment in humans, what is the probability that paternal chromosome 1 and paternal chromosome 2 are transmitted to a single gamete?

Answer 4

50% chance of maternal, 50% of paternal

therefore, 1/2 * 1/2 = 25% chance

Question 5

how many different genotypes of a gamete can a human produce during meiosis via independent assortment alone?

Answer 5

humans have 23 chromosomes –> 2 diff gametes per chromosome so 2^23

Question 6

what is the phenotype ratio of F2 generation in dihybrid cross with independent assortment?

Answer 6

9:3:3:1

Question 7

what are the gametes made from dihybrid cross of R/r and Y/y? what are the proportions of each?

Answer 7

R;Y, R;y, r;y, r;Y

25% chance of each –> equal probability

Question 8

in dihybrid cross of R/r and Y/y, what is probability of round and yellow?

Answer 8

3/4 * 3/4 = 9/16

round: RR, Rr, Rr (3/4)
yellow: YY, Yy, Yy (3/4)

Question 9

in dihybrid cross of R/r and Y/y, what is probability of round and green?

Answer 9

3/4 * 1/4 = 3/16

round: RR, Rr, Rr (3/4)
green: yy (1/4)

Question 10

what is the purpose of a dihybrid testcross?

Answer 10

to detect recombinants

Question 11

what does dihybrid testcross produce? in what proportions?

Answer 11

equal number of parental and recombinant progeny, i.e. half are parental, half are recombinant

Question 12

in dihybrid testcross, why are parental and recombinant progeny found in equal proportions?

Answer 12

bc independently assorted, i.e. on separate chromosomes

Question 13

without independent assortment, why are parental progeny found in much higher proportions than recombinant?

Answer 13

recombinant is more rare bc requires breaking chromosome, aka crossover

Question 14

what is Morgan’s chromosome theory of inheritance?

Answer 14

traits related to each other correspond to genes that are close together on the chromosome

Question 15

what does it indicate when there are fewer recombinants found compared to parental?

Answer 15

the genes are able to undergo crossover because the genes are close to each other

Question 16

what is the equation for Chi2 test?

Answer 16

X^2 = sum of [((O-E)^2)/E]

Question 17

what does it mean if p < 0.05?

Answer 17

REJECT hypothesis –> assumption is not correct

Question 18

what does it mean if p > 0.05?

Answer 18

hypothesis NOT REJECTED –> assumption is correct