Hi there
So I am confused about dihydrid genes. If an induvial for example has the genotype CcDd how are the alles and genes placed on their homologous chromosomes. Are they all on the same chromosome or different? I have attached an image is that correct, if not would it please be possible to draw it out.
Hi
Dihybrid genes can be linked or unlinked.
I am not sure what you have drawn.
Was it supposed to be linked or unlinked?
Unlinked genes are when the genes are found on different chromosomes. (This is where an observed ratio of 9:3:3:1 is usually obtained if you cross two hetero zygotes together.
Imagine two homologous pair of chromosomes.
The first pair has the Aa alleles and the second pair has the Bb alleles.
(If you cross two heterozygote parents AaBb x AaBb, the common 9:3:3:1 ratio will be observed)
Linked genes are when the genes are found on the same chromosome, thus those alleles will often be inherited together.
(So if you crossed two heterozygotes together, a ratio of 1:1 will be observed for the parental trait and 1:1 for the recombinant trait.)
I am assuming this is what you have attempted to draw on your diagram? (Two different genes that are “LINKED”?
Hope that helps.
Hi there
Thank you very much for your answer
In your explanation when you said
Imagine two homologous pair of chromosomes.
The first pair has the Aa alleles and the second pair has the Bb alleles.
(If you cross two heterozygote parents AaBb x AaBb, the common 9:3:3:1 ratio will be observed)
When you say the first homologous pair has the Aa allele does that mean one chromosome of the homologues pair will have the A allele and the other chromomes in the homologous chromomse has the a allels.
Likewise on the second homologous pair one chromosome will have the B allele and the other will have the b allele.
Yup. That is correct.
So “A” allele on one chromosome, and on the other homologous pair the “a” allele.