MCDB 2150 Lecture Notes - Lecture 30: Zygosity, Penetrance, Meiosis

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tealhedgehog29

4 Apr 2017

School

CU-Boulder

Department

Molecular Cell & Developmental Biology

Course

MCDB 2150

Professor

Jennifer Knight

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Document Summary

Review: genes can be linked" on the same chromosome, homologous chromosomes can undergo recombination with each other in meiosis. 1, changing the assortment of alleles that is present on a particular chromosome. Haplotype: the allele makeup and organization for one chromosome of a pair of homologous chromosomes: example: imagine an individual with aabb genotype, in which a/a and b/b genes are linked on the same chromosome. Simple mendelian inheritance: dominant or recessive clear cut, 2 alleles for a trait, 1 gene = 1 characteristic. Dominance/recessive at the molecular level: wild-type allele: the most prevalent allele in a population. Encodes normal functioning protein: mutant allele: allele that has been change by mutation. Mutant alleles are very rare in natural populations. Incomplete or partial dominance: heterozygote resembles neither pure-breeding parent. Three types of dominance for heterozygotes: complete phenotype of 1 parent, incomplete phenotype of neither parent.

Related Questions

For genetics:

how do we parental classes in meiosis come about ? Is there no recombination or crossing over occurring? But in my textbook it says that if recombination did not occur, nondisjunction during meiosis I would be a common, rather than a rare occurrence, and species could not retain the same number of chromosomes in successive generations.

I am confused on how linked genes have more parental types than recombination types, i understand that the linked genes are inherited together because they are close together on the same chromosome.

I guess my question is, do all chromosomes undergo recombination and crossing over in meiosis? And the parental classes are parental because were just looking for those certain linked genes that are inherited together?

thank you!

aquamarineduck901

Which of these statements is incorrect?

Syntenic genes are located on the same chromosome.

Independent assortment results in recombinant chromosomes.

You can reliably predict the relative genetic distance fromgenesâ physical distance on a chromosome.

Linked genes are always syntenic.

What is the relative genetic distance between two linked genesif the recombination frequency is 0.49?

0.49 cM

4.9 cM

49 cM

490 cM

What statement best explains the distortion in Mendelian ratiosobserved by Bateson & Punnett in 1905? (Reminder: they found anoverrepresentation of F2 offspring showing both dominant orrecessive phenotypes, and an underrepresentation of offspringdisplaying one dominant and one recessive phenotype)

Human error: they should have been more careful about theirexperimental setup.

Gene linkage: Genes for flower color and pollen shape arephysically close on the same chromosome, leading to a breakdown inthe independent assortment of the alleles for these traits.

Chromosome crossover: Homologous recombination of twochromatids during meiosis caused the alleles to shuffle, resultingin a breakdown of the independent assortment of the alleles forthose genes.

Random variation: No two situations are alike. In finitepopulations, you are going to get some variation across a mean.

When determining the relative genetic distance between twogenes, why is dihybrid back-cross preferable over traditionaldihybrid cross?

9:3:3:1 phenotypic ratio is easier to work with than 1:1:1:1ratio.

Genotypes of the offspring can be determined based on theirphenotype.

If the genes are independently assorted, the dihybrid back-crosswould result in only 2 genotypes in the F1 generation.

B and C

Why do we map genes?

To understand how genes interact with each other

Comparative genomics analysis

To determine the genotype of an organism

All of the above

coralox210

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%

MCDB 2150 Lecture Notes - Lecture 30: Zygosity, Penetrance, Meiosis

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