Lecture 6

Question 1

if R/r and Y/y are on the same chromosome and the distance between them is 20 mu, what is the relative ratio of F2s that are wrinkled and green if F1s are self-pollinated?

Answer 1

wrinkled and green = ry

must be selfed so the only way for progeny to be ry is if F1s are both ry

proportion of F1s that are ry is 10% (total recombinants is 20%, 2 possible recombinants so ry is 10%)

0.1 x 0.1 = 0.01

Question 2

why are genetic crosses not feasible for mapping genes in humans? (3)

Answer 2

1. controlled crosses not possible
2. mating couples only have a few offspring
3. experiments would take many years

Question 3

what are molecular markers?

Answer 3

small DNA sequence differences/polymorphisms within a species, at specific chromosomal locations

Question 4

why are molecular markers helpful?

Answer 4

they have no biological function/phenotype but can be used to map a gene by determining linkage btwn gene of interest and the molecular markers

Question 5

what does SSLP stand for?

Answer 5

simple sequence length polymorphism

Question 6

what are SSLPs?

Answer 6

multiple repeats of short DNA sequences at specific location

Question 7

when do people have the same number of SSLPs?

Answer 7

if they are RELATED

Question 8

describe inheritance of SSLPs

Answer 8

1 maternal set, 1 paternal set is inherited

Question 9

how can we use SSLPs to see if ppl are related?

Answer 9

use primers that bind sequences that flank the SSLPs –> can see if they have similar patterns of SSLPs

Question 10

how much of DNA is identical btwn 2 unrelated ppl?

Answer 10

99.9%

Question 11

how much of DNA is different btwn 2 unrelated ppl? what are these differences?

Answer 11

0.1% –> most of the differences are SNPs

Question 12

are SSLPs or SNPs more frequent?

Answer 12

SNPs

Question 13

what classifies something as a SNP rather than a mutation?

Answer 13

SNP must be in 1% of people in a population

if not, it is just a mutation

Question 14

SNPs can be common within _______

Answer 14

SNPs can be common within a specific population or ethnicity

Question 15

3 possible locations for SNPs?

Answer 15

1. intergenic
2. within a gene
3. in regulatory region

Question 16

SNPs within a gene or in regulatory region may be involved in:

Answer 16

SNPs within a gene or in regulatory region may be involved in disease susceptibility or sensitivity to external factor

Question 17

do most SNPs cause health effect?

Answer 17

most SNPs have no health effect

Question 18

what does it mean if a specific set of SNPs is associated with disease? why?

Answer 18

the disease-causing gene must be close to those SNPs because things that are close to each other are often inherited together

Question 19

what is a haplotype?

Answer 19

grouping of genomic variants/polymorphisms that tend to be inherited together bc they are close

Question 20

what does it mean when specific haplotype is more common in certain population?

Answer 20

must be certain factors that favour the allele in that population

Question 21

describe the adaptation of Tibetans to high altitude vs Chinese

Answer 21

Tibetans and Chinese are closely related –> SNP variants occur at similar frequency in both groups BUT Tibetan SNPs are linked to a helpful gene (EPAS1) at higher frequency