Explanation:
a) p+e+n=18
mà p=e=z => 2p +n=18
câu a có thiếu dữ kiện không?
Answer:
See the answer below
Explanation:
a) The mode of inheritance of the bar mutant is X-linked and dominant.
Assuming that barness is represented by the allele B.
Bar female =
or 
Wild type male = 
Bar female x wild type male:
x 
All of the F1 flies are bar because a single B allele is required for the trait to be expressed.
Bar male x wildtype female
x 

All the female offspring are barred while all the males are wildtype barred resulting in a 50/50 (857/905 is approximately 50/50) ratio of barred/wildtype offspring.
b) Genotypes of each of the cross above, including the parents and the F1 generations.
1.
x 
2.
x 

The sequence of the genes will be ABCD, abCD and abCd, abcD.
Full question is attatched below.
<h3><u>Explanation:</u></h3>
The genes in the chromosomes are denoted as the sequence of genes present in a single chromatid of a particular chromosome. Thus, the genes here in this question are to be mentioned as ABCD and not as abab.
Crossing over is the process by which the homologous pair of chromosomes do pair up in the Prophase 1 of meiosis 1 division and they exchange a particular part of their DNA with each other. This leads to exchange of genes between the homologous chromosomes, which will form different gametes in near future. This brings about a variation between the offsprings of same individuals.
Here the d gene of the two chromosomes are getting exchanged.
So the chromosomes will become ABCD, abCD and abCd, abcD respectively.