New version page

U-M BIOLOGY 171 - Sex-linked Genetic Inheritance

Type: Lecture Note
Pages: 2

This preview shows page 1 out of 2 pages.

View Full Document
View Full Document

End of preview. Want to read all 2 pages?

Upload your study docs or become a GradeBuddy member to access this document.

View Full Document
Unformatted text preview:

BIO 171 1st Edition Lecture 6Outline of Last Lecture No previous lecture due to snow day!Outline of Current Lecture I. Gene by Gene Interactions II. Sex Chromosomes and Sex Linked Inheritance III. Linkage Between Genes Current LectureGene by gene interactions -Phenotypic ratios can be modified by interactions between genes oGenes that modify the phenotypic expression of other genes are said to show epistasis-Example of epistasis= when one gene codes for eye color and another gene codes for eyes or no eyes, if the offspring inherits the trait for no eyes than their eye color is irrelevant because it would not be expressed anyway. This gene by gene interaction modifies the organisms phenotype. Sex chromosomes and sex-linked inheritance -The Y chromosome (only found in males) contains very few genes, and is smaller than the X chromosome-The X chromosome is found in both males and females (females have two copies, males have one)oIf a trait is "X linked" or written as X^a, that means it is carried on the X chromosome -The regions of homology between the X and Y chromosomes allow them to pair during meiosisoWhen the non-sister chromatids of these homologous chromosomes perform "crossing over" during prophase I of meiosis, it helps them to align during metaphase I and separate properly in anaphase I. -X linked mutations are more likely expressed in males because they only posses one X chromosome. If their X chromosome carries the mutation then they express it, where as females would need both of their X chromosomes to posses it -Genes that are located on different chromosomes assort independently, but when two genes arelocated on the same chromosome (and recombination does not occur) then the four gametes produced will be identical to the parental chromosomes These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Linkage between genes -Recombination can break up linkage between genes that are on the same chromosome oRecombinants result from a crossover during prophase I, and contain alleles in a different combination than the parentsoNonrecombinants are present when crossing over does not occur and alleles are presentin the same combination as seen in the parentsoRecombination frequency (RF)= # of recombinants/# of offspring oCrossing over occurs more frequently between genes that are farther apart on a chromosome -The distance between adjacent genes (on the same chromosome) is given in map units. This distance is equal to the frequency of recombination when expressed as a percentage-Multiple alleles= a population of organisms may contain many different alleles of the same gene oIn the "mutant" alleles, DNA sequences are different from one another, and none of them produces a functional proteinoIn the "normal" alleles, DNA sequences are different from one another, but are able to produce a functional


View Full Document
Loading Unlocking...
Login

Join to view Sex-linked Genetic Inheritance and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Sex-linked Genetic Inheritance and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?