Question

question 4 of 10
which statement best describes two different alleles for the same gene?

a. they are found in different locations on a chromosome but code
for exactly the same amino acids.

b. they are found in different chromosomes and code for very
different sequences of amino acids.

c. they are found at the same location on a chromosome but have
very different sequences of nitrogenous bases.

d. they are found in the same location on a chromosome but have
slight differences in their sequences of nitrogenous bases.

Explanation:

To solve this, we recall the definition of alleles: alleles are different forms of the same gene. Genes are located at specific loci (positions) on chromosomes.

• Option A: Alleles at different locations would not be alleles of the same gene. Also, different alleles can code for different traits (so not exactly same amino acids always). Eliminate A.
• Option B: Alleles of the same gene are on homologous chromosomes (same chromosome pair), not different chromosomes. Eliminate B.
• Option C: While alleles are at the same locus, saying "very different" is inaccurate. Alleles have slight differences (e.g., single nucleotide polymorphisms) in nitrogenous base sequences, not very different. Eliminate C.
• Option D: Alleles are at the same location (locus) on a chromosome (or homologous chromosomes) and have slight differences in their nitrogenous base sequences (which leads to different traits, like blue vs brown eyes). This matches the definition.

Answer:

D. They are found in the same location on a chromosome but have slight differences in their sequences of nitrogenous bases.