These homologous chromosomes carry different alleles of the A and B genes. How could crossing over affect the distribution of th
e four alleles: A, a, B, and b? A. Crossing over would always keep A and B together on the same chromosome, and keep a and b together on the same chromosome. B. Crossing over would always put A and B on different chromosomes, and always put a and b on different chromosomes. C. Crossing over would sometimes, but not always, exchange the positions of A and a, and of B and b, on homologous chromosomes. D. Crossing over would sometimes, but not always, delete one or more of the four alleles from both homologous chromosomes.
1 answer:
Answer:
C. Crossing over would sometimes, but not always, exchange the positions of A and a, and of B and b, on homologous chromosomes.
Explanation:
Crossing over involves the exchange of chromosomal segments (and of course the respective genes on the chromosome segments) between non-sister chromatids in a tetrad during meiosis.
From the attached image, crossing over would sometimes exchange the positions of A and a, and that of B and b on the chromosome. However, this is not the case 100% of the time.
The correct option is C.
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Answer:
Smaller the size of the DNA fragment, farther it moves during electrophoresis. The sketch of the position of the fragments has been drawn in the figure below.
Explanation:
As we know DNA is a negatively charged molecule. So during electrophoresis the fragments move towards the positive electrode because opposite charges attract each other.
Different fragment move different distances according to their size during the electrophoresis. Smallest segment travels the largest distance in the gel medium while the largest one travels least distance.
In the question there are four DNA fragments with base pairs 4000, 2500, 2000 and 400 so the smallest segment with 400bp will be farthest from the starting point and the largest fragment with 4000bp will travel least distance in the gel medium. Their respective positions are shown in the figure below. The starting point is near the negative electrode.
