MBG 2040 Lecture Notes - Lecture 3: Mendelian Inheritance, Chromosome, Centimorgan

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scarletjellyfish108

20 May 2014

School

University of Guelph

Department

Molecular Biology and Genetics

Course

MBG 2040

Professor

All

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Document Summary

Independent assortment: independent assortment can imply that two genes are on different chromosomes. These little ="s represent the 2 chromosomes homozygous recessive individual. A dihybrid test cross involves crossing a dihybrid individual with a. Some genes are located near each other on the same chromosome. Example: genes a and b are on the same chromosome and are tightly linked. If we did a dihybrid test-cross of the chromosome with the alleles in cis configuration: Crossing over occurs in prophase of meisosis i. Numerous crossing-over events can occur between two homologous chromosomes. *the frequency of crossing over between genes a and b is a measure of the distance between genes a and b. *q: what is the distance between gene a and gene b??? (see next page for answer) Map unit: a measure of distance between two linked genes. *a: the distance between gene a and gene b is.

Related Questions

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

1. What is the chromosome theory of inheritance?

2. Understand how independent assortment can cause gametes to have four combinations of alleles when an individual is heterozygous for two genes on two different chromosomes.

3. What are linked characters and linked genes? Understand why linked genes will not independently assort.

4. How can crossing over affect linked genes?

5. What are recombinant gametes?

6. Define recombinant frequency. Be able to use the recombinant frequency to determine how close two genes are on a chromosome.

7. What is a linkage map?

8. What is the function of the SRY gene on the Y chromosome? What happens if you don't have this gene?

9. Know how sex is determined in mammals, birds, bees and ants, and reptiles.

10. How many autosomes and sex chromosomes do normal human haploid and diploid cells have?

11. What does it mean for a gene to be X-linked or Y-linked?

12. Be able to answer word problems and fill out a Punnet square involving an X-linked recessive trait.

13. Which sex is more likely to have an X-linked recessive disorder? Understand why.

P.s The most simple answer would be preferable. I would be copping the notes over that you will provide to my noteb book and add my details to it.

greylocust179

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%

MBG 2040 Lecture Notes - Lecture 3: Mendelian Inheritance, Chromosome, Centimorgan

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