BIOL 261 Lecture Notes - Lecture 4: Karyotype, Centimorgan, Genetic Linkage

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periwinklebutterfly705

25 Oct 2016

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Document Summary

Making genetic maps calculating the distance between genes on the chromosome by measuring recombination (genes relative to other genes) Can be used to isolate and clone genes, to distinguish between different genes that affect the same trait, can link traits to markers to assist genetic selection. Genes on the same chromosome can be linked. Linked alleles assort into the same gametes and are frequently inherited together. Physically linked alleles are inherited together except when there is a cross-over in the chromosomes between the genes. Linked alleles are inherited together except when there is a cross-over in the chromosomes between the genes. A cross-over between two genes is more likely for genes that are far apart on the chromosome. The frequency of cross over between genes is a measure of the distance between genes on a chromosome map. Crossing over occurs once or twice per chromosome pair during meiosis.

Related Questions

The syntenic genes A and Z are linked. A cross between two parents, AAzz and aaZZ, produces F₁ progeny with the AaZz genotype. What are the possible arrangements of alleles on the F₁ progeny's chromosomes?

A/Z or a/z

The answer is not AZ/az

Genes that are on the same chromosome can assort independently when

they are very close together on a chromosome and crossing over occurs rarely between the genes.

they are far apart on a chromosome and crossing over occurs rarely between the genes.

they are far apart on a chromosome and crossing over occurs frequently between the genes.

they are syntenic.

Genes on the same chromosome cannot assort independently.

Please help me with these two!

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