In some parts of Africa, the frequency of heterozygosity sickle-cell anemia alle

Question

In some parts of Africa, the frequency of heterozygosity sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria, Such a relationship is related to which of the following? a. Mendel's law of independent assortment b. Mendel's law of segregation c. Darwin's explanation of natural selection d. the material parasite changing the allele Which of the following human cells contains a gene that specifies skin color? a. skin cells b. liver cells c. egg and sperm cells d. brain cells e. all body cells _____ are the building blocks of proteins and are held together by ___ bonds a. nucleotides/phosphodiester b. amino acids/phosphodiester c. amino acids/peptide d. amino acids/glyosidic e. nucleotides/peptide If a DNA sample were composed of 10% thymine, what would be the percentage of guanine? a. 10 b. 20 c. 40 d. 80 e. impossible to tell from the information given During replication of a DNA molecule, the leading strand is made toward the replication fork, while the lagging strand is made in fragments in the opposite direction. What is the reason for this difference in the synthesis of the two strands? a. DNA polymerase is not efficient enough to make two good strands of DNA b. the two template strands arc antiparallel, and DNA polymerase only makes DNA in the 5' to 3' direction c. the lagging strand is the result of DNA breakage due to UV light d. the cell does not contain enough nucleotides to make two complete strands

Explanation / Answer

39. The frequency of heterozygosity for the sickle cell anaemia allele is usually high presumably because this reduces the frequency of malaria. Such a relationship related to

Ans: c. Darwin’s explanation of natural selection.

Heterozygous People (Aa) for sickle-cell recessive trait have resistance to malaria because some of their red cells are misshapen and deflated. Heterozygous condition rarely develops anemia. However homozygous dominant (AA) are produce normal red blood cells, thus they became a good host for malaria. Therefore, in case of falciparum malarial environments nature selects for heterozygous population against homozygous population.

40. Which of the following cells contains gene specific for skin colour-

Ans: e. All body cells.

Genes are present in all cells but they are expressed in skin cells.

41. _________ is building blocks of protein and is held together by _________ bonds.

Ans: c. amino acid/ peptide bond.

42. If DNA sample contains 10% thymine, then the percentage of guanine is

C.40

Because in DNA, A=T and G=C, then A+T=20 % thus G+C=80%, G=40%

But, this answer only applicable where DNA is double stranded, it the DNA is single stranded the answer is ‘e. Impossible to tell from this information.

43. Reason for the difference in two strands is --

Ans: b. the two template strands are anti parallel and DNA polymerase only makes DNA in the 5’ to 3’ ditection.

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