BIO 198 Lecture 14: BIO 198_Sept. 19

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lavendergiraffe572

15 Oct 2016

School

University of Rochester

Department

Biology

Course

BIO 198

Professor

Elaine Sia

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Document Summary

Genetic linkage mapping helps us plot the positions of genes on chromosomes and depicts gene order along a chromosome. Genes located on the same chromosome are called syntenic genes. If genes are close to each other so that the alleles are unable to assort independently genes are linked to each other. Chromosomes that do not undergo crossing over = parental chromosomes/nonrecombinant chromosomes. Linked genes are always syntenic and located near one another in the chromosome. Genetic linkage = production of greater # of gametes containing chromosomes with parental combinations of alleles. Crossing over less likely to occur between linked genes because closer together on the gene. In genetic linkage: the parental phenotypes for the genes occur significantly more often than predicted by chance. This is because with genetic linkage, the rate of recombination among the alleles is low and the parental allele combinations usually stay together during meiosis more production of parental gametes.

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!

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