In chickens, comb shape is determined by alleles at two loci (R, r and P, p). A walnut comb is produced when at least one dominant allele R is present at one locus and at least one dominant allele P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive alleles are present at the first locus and at least one dominant allele is present at the second (genotype rr P_). If two recessive alleles are present at the first and at the second locus (rr pp), a single comb is produced. A walnut is crossed with a pea chicken and the offspring consists of 3/8 walnut, 3/8 pea, 1/8 rose and 1/8 single. What are the probable genotypes of the parents


Answer 1


RpPp x RpPp


For the recessive trait to be expressed, both parents should have at least 1 allele for the recessive trait. Now you can see that both recessive traits were expressed in at least one of the off-springs, this means that both parents had the allele for each recessive trait.

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Bacteria and other microbes can be used to "clean up" an oil spill by breaking down oil into carbon dioxide and water. Two samples isolated from the Deepwater Horizon leak in the Gulf of Mexico were labeled A and B. The DNA of each was isolated and the percent thymine measured in each sample. Sample A contains 20.520.5 % thymine and sample B contains 30.730.7 % thymine. Assume the organisms contain normal double‑stranded DNA and predict the composition of the other bases.



In sample A,  

The percentage of thymine or T is 20.5 %. A = T, so the percentage of A will also be 20.5 %.  

Thus, A + T = 20.5 + 20.5 = 41 %

Therefore, G + C = 100 - 41 = 59 %

So, G = 59 /2 = 29.5 %

Also. G = C = 29.5 %

In sample B,  

The percentage of Thymine or T is 30.7 %. As A = T, so A will also be 30.7 %.  

Thus, A + T = 30.7 + 30.7 = 61.4 %

Also, G + C = 100 - 61.4 = 38.6 %

So, G = 38.6 / 2 = 19.3 %

Therefore, C will also be 19.3 %. As GC content is more found in the sample A, that is, 59 %. Hence, the sample A will possess the higher temperature to denature in comparison to B.  

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How do spindle fibers help distribute chromosomes to daughter cells ?


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Simultaneously, polar fibers, also known as interpolar microtubules, extend from one pole of the cell to the other. These fibers overlap in the cell's center and assist in separating the poles further apart, helping to elongate the cell during anaphase.

Overall, the combined action of kinetochore fibers and polar fibers ensures the accurate distribution of chromosomes to the daughter cells. The spindle fibers undergo a highly orchestrated process of assembly, attachment, tension generation, and depolymerization, all of which contribute to the successful partitioning of the genetic material during cell division.

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