Please...I Need Help!!!?

Hi everyone! I really need help understanding some things in biology. If you were trying to figure out whether hair color and eye color are linked, what would you do? On average how many genes are linked in the the human genome? Also, how would you make a punnet square for the non linked and linked case of genes? Please help me! Thanxx!

Please...I Need Help!!!?

first of all you need to understand that linked genes means that the genes are the on the same chromosome

as each chromosome carries different amounts of genes, and genes are not the same length and size and such, I think it would be difficult to quantify the average number of genes that are linked in the human genome

if genes are on the same chromosome, when calculating probabilities, it is almost like you only consider it to be one gene, but one that can code for two traits

for example F = more than five fingers, H = mid digit hair

if the genes are not linked they will look like this

(F;H/f;h) although not necessarily in that combination

if the genes are linked they will look like this

(FH/fh) again not necessarily in that combination

I assume that you know during prophase I of meiosis crossing over occurs between homologous chromosomes (recall that homologous chromosomes means the two chromosomes that have the same genes, just different alleles)

so if genes are on the same chromosome, they will cross over and new combinations will be formed

for example we have two (FH/fh) people mating

..........FH.......fh

FH|FH/FH..FH/fh

..fh|FH/fh....fh/fh

so the possible phenotypes of the children will be: more than five fingers with hair or five fingers with no hair in a 3:1 ratio

however when crossing over occurs, new combinations are formed that means the genes won't be (FH/fh) for sure they could be (Fh/fH) or (fH/Fh)

this means that new phenotypes are possible in the children, instead of there only being two possible phenotypes: more than five fingers with hair or five fingers with no hair, there could be children with more than five fingers with no hair or five fingers with hair

these new combinations are called recombinants, and when genes are linked the phenotypes are close to a 3:1 ratio, but the other phenotypes are present in small amounts

if these genes were not linked this would happen

.............F;H.........F;h.............

F;H|.F;F/H;H...F/F;H/h...F;f/H;H...F;f...

F;h|.F;F/H;h....F/F;h/h....F;f/H;h.......

.f;H|.F;f/H;H....F/f;H/h.....f;f/H;H.....

..f;h|.F;f/H;h.....F/f;h/h.....f;f/H;h...

as you can see the phenotypes would be: more than five fingers and mid digit hair; more than five fingers and no hair; five fingers and mid digit hair; five fingers and no hair in a 9:3:3:1 ratio

so if you recorded the children of humans with known phenotype for their hair and eye color and the ratios in phenotype you observed were 3:1 with recombinants then the genes are linked, if the ratios were closer to a 9:3:3:1 ratio then the genes are not linked

you calculate this 'goodness of fit' with the chi squared test

Please...I Need Help!!!?

get to work! http://www.google.com/search?hl=en%26amp;q=hai...