what is autosomal linkage, and.....

hey another question, not liking the syllabus now :frown:

, im stuck on

understand autosomal linkage and recombinants in relation to events of meiosis ; ecplain gene interaction between two unlinked genes

right, to start off with i know recombinants are individuals in a generation with different offspring geno and phenotype to their parents. and this usually occurs in F2 generation. thats all i can say, any suggestions would be useful

oh those the linkage and recombinants part have anything to do with the bateson Punnett experiment????

Reply 1

Revenged

linkage is when two genes on a chromosome tend to be inherited together...

the nearer to each other these two genes lie in the chromosome, the more likely they are inherited together since less likely that they are affected by recombination (crossing over of DNA)...

Reply 2

cujo

yea linkage is when two genes are present on the same chromosome and inherited together . ALl the genes on one chromosome form a linkage group. ALl genes that do not determine sex are said to be autosomal chromosomes. If complete linkage occurs there are NO recombinants however this is rare and in most cases some recombinants are formed. This is due to the non sister chromatids breaking and rejoining to form chiasma during prophase 1 of meiosis.

Gene interaction is when 2 unlinked genes control a single characteristic. Normally each gene controls each characteristic however this is not the case in gene interaction.

This is seen in the case of determining comb shape in domestic poultry

It was found that when chicken with rose comb were bred with chickens with pea combs the F1 generation had a new type of comb known as the walnut comb. Ill explain to you how this works it pretty darn easy.

Here its assumed that 2 genes both control comb shape. One gene has the dominant P allele which codes for the pea comb and another gene has a dominant R allele which codes for the rose comb.

Now if a chicken with a pea comb is bred this will have the genotype PPrr with a chicken who has a rose comb this chicken will have the RRpp genotype. The gametes produced will be Pr and Rp. When these are bred the F1 generation will have the genotype PpRr both dominant alleles are present hence a new type of comb is formed. Do you understand??

Reply 3

jones001

oh i kinda said what recombinants and linkage is and then i described the experiments of the flower pollen experiment by bateson....and then said what complete linkage is (no crossing over and recombinants) and showed some crossing over diagrams for the experiment and then showed a formula for the crossing over frequency. hopefully that will explain it all.

h thanks for the defo of gene interaction...should make everything clearer, yeh for this i explained about the chicken comb shape, but also i gave brief details on another flower experiment (two whites breeding to give purple) in F2: 9 purple: 7white which was an example of epistasis

thats about all i wrote on all of that.