HMB265H1 Lecture : Notes taken during lecture

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redtermite204

11 Feb 2011

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use closest markers to give the most accurate genetic maps: so double recombinant not hidden. Fewer crossover than expected under assumption of independence. presumably due to some physical interference: crossover here makes crossover somewhere nearby more difficult. only one gene order makes these types the rarest. Most common types are parental if linked, double crossovers rarest. Determining gene order and distance corresponds well with physical distance. centromere physical space but recombination suppressed here: genetic and physical distance doesn"t correspond here well. Recombination mapping key in genetics, disease genetics, evolutionary, developmental genetics . can locate gene that confers the particular phenotype without knowing the gene beforehand. segregation of genetically based phenotype and find where it is located in proximity to other molecular markers and genes made possible by mapping: linkage mapping identifies location. align where particular disease is and find genetic space address, link it to physical space address.

Related Questions

a) What is the diffference between physical and genetic maps ofchromosomes and how are genetic maps constructed?

b) What does genetic distance mean?

c) Define chiasma(ta), recombination frequency, crossover rate,and double crossover.

d) Draw one figure supporting your answer. You are required toexplain and show the difference between crossover rate andrecombination frequency. Explain the units of genetic distance.

sapphiretoad853

What is the difference between physical and genetic maps ofchromosomes? How are genetic maps constructed? What does geneticdistance measure? Underline the following terms in your answer:chiasma(ta), recombination frequency, crossover rate, and doublecrossover. Draw one figure supporting your answer. You are requiredto explain and show the difference between crossover rate andrecombination frequency. You are also required to explain the unitsof genetic distance.

taupeporpoise601

ANSWER ALL the PARTS you can

PART1 Alleles are considered linked if recombination is less than 50% in:

a) a Px P Fl cross

b) an F1 x F1F2 cross

c) an F2 x F2F3 cross

d) an Fl x homozygous recessive cross

e) any F2 progeny x homozygous recessive cross 1.

PART2 If two loci A/a B/b are 9 map units apart, and an Ab/aB individual is testcrossed,

a) There will be 9% AB individuals

b)There will be 91% Ab individuals

c) There will be 4.5% ab individuals

d) There will be 91% recombination individuals

If two genes a and b show 50% recombination genes a and c show 35% recombination, and genes b and show 32% recombination, then

a) Genes a and b are on the same chromosome, and 50 m.u. apart

b) Genes a and b are on different chromosomes

c)Genes a and b are on the same chromosome, and 67 map units apart

d) One cannot tell if genes a and b are on the same or different chromosomes from given data.

PART4 If two genes a and b are 8.3 m.u. a part, one expects to find

a) 8.3% recombinant gametes from a double heterozygous parent

b) 91.7% recombinant gametes from a double heterozygous parent

c) A chiasma between the a and b loci in 8.3% of the meiosis

d) A chiasma between the a and b loci in 91.7% of the meiosis.

PART5 Map distances are most accurate when genes are closely linked because as genes become further apart,

a) They always show independent assortment

b)The chance of multiple crossovers increases

c) They no longer recombine

d) There is chiasma interference

PART6 In a three-point testcross, the most frequent classes of progeny were ABc and abC. The less frequent classes of progeny were AbC and aBc. Which gene is in the middle?

a) Aa

b) B/b

c)C/c

d) It is not possible to tell from just these data

PART7 In a three-point testcross with 100 progeny, there were 16 single crossovers between genes A and B, 29 single crossovers between genes B and C, and 4 double crossovers. The correct gene order was determined to be A-B-C. What is the map distance between A and B?

a) 20%

b) 0.2 m.u

c) 20 m.u.

d) 16 m.u.

e) 29 m.u.

f) 16%

HMB265H1 Lecture : Notes taken during lecture

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