Concept of Gene Questions and Answers

Answer: A

The link was first suggested by the discovery of in-born errors of metabolism in human.

Archibald Garrod, studying alkaptonuria in the early 1900s, saw that it was inherited as a Mendelian recessive trait and that patients failed to break down homogentisic acid. He proposed that the condition was an 'inborn error of metabolism' caused by the absence of a particular enzyme, the first suggestion that genes act through enzymes.

Beadle and Tatum's work on metabolic pathways in the fungus Neurospora (1941) gave the 'one gene, one enzyme' hypothesis its experimental proof, but it came decades later. Sex determination in insects and gene regulation in bacteria are not where the idea began.

Answer: D

The coding segment is called an exon.

In eukaryotic genes, the sequence is divided into exons, which are expressed and carry the information that is translated into the protein, and introns, which are non-coding sequences removed from the RNA by splicing before translation.

An intron is therefore the non-coding part. A codon is just one triplet of three bases coding for a single amino acid, not a whole coding segment. A muton is the smallest unit of DNA in which a mutation can occur (Benzer's term).

Answer: A

Genome size refers to the DNA in a Haploid genome.

Genome size is the C-value: the amount of DNA in one complete haploid set of chromosomes, as found in a gamete, given in picograms or base pairs. The human genome, for example, is about 3.1 billion base pairs, while a diploid human cell contains about twice that.

A diploid nucleus holds two genomes, so measuring it would double the figure; 'haploid as well as diploid' therefore cannot both be the genome size. The DNA of a complete organism would depend on the number of cells and is not a fixed property of the species.