Question

Which mutations can a geneticist identify with the G‑banding technique?(A) a nonsense mutation introducing a premature stop codon into a gene on chromosome 5(B) a reciprocal translocation of parts of chromosome 1 and chromosome 11(C) a translocation of a region of the short arm between sister chromatids(D) a deletion of half of the long arm of chromosome 20 a single nucleotide(E) substitution in which T replaces C on chromosome 2

Answer 1

The correct answer to the student's question is (B) a reciprocal translocation of parts of chromosome 1 and chromosome 11, and (D) a deletion of half of the long arm of chromosome 20, as these are the types of mutations that can be identified by the G-banding technique.

Step-by-step explanation:

The G-banding technique in genetics is used to visualize chromosomal abnormalities by staining the chromosomes with a dye that binds to certain chemical components of DNA, creating a pattern of light and dark bands along the length of each chromosome. This technique is particularly useful for identifying larger structural changes such as deletions, duplications, inversions, and translocations in chromosomes.

Answer Choices Analysis:

• (A) Nonsense mutation introducing a premature stop codon: G-banding would not detect this as it is a small scale mutation at the nucleotide level and does not alter the banding pattern of the chromosome.
• (B) Reciprocal translocation of parts of chromosome 1 and chromosome 11: G-banding can identify such large-scale structural changes where parts of one chromosome are exchanged with another.
• (em)(C) Translocation of a region of the short arm between sister chromatids: Similar to reciprocal translocations, G-banding can detect these changes if the translocation results in a visible alteration in the banding pattern.
• (strong)(D) Deletion of half of the long arm of chromosome 20: This is a large-scale mutation that G-banding can identify, as there would be a noticeable absence of bands where the deletion has occurred.
• (em)(E) Single nucleotide substitution in which T replaces C on chromosome 2: This is a point mutation and would be too small for G-banding to detect as it would not affect the overall banding pattern of the chromosome.

The correct answer to the student's question is (B) a reciprocal translocation of parts of chromosome 1 and chromosome 11, and (D) a deletion of half of the long arm of chromosome 20, as these are the types of mutations that can be identified by the G-banding technique.

Answer 2

The correct answer is options - C) and D).

Explanation:

G banding is a technique that is used in cytogenetics to make a visible karyotype by staining the condensing chromosomes and forms the light and dark bands. These bands obtained due to the difference between light staining and dark staining regions as these regions have different relative proportions or ratios.

This technique is used to identifying the genetic diseases or chromosomal abnormalities such as inversion and translocations due to the dark and light band patterns. GC rich bands are light bands whereas its dark at the AT-rich region.

Thus, the correct answer is C) and D).