In genetics, a gene refers to which of the following?
- AOption (a)
A section of DNA that codes for a protein
- BOption (b)
A sex chromosome
- COption (c)
A unit of blood group
- DOption (d)
A type of chromosome
View answer & explanationHide answer & explanation
Correct answer
A section of DNA that codes for a protein
Why this answer is correct
The correct answer is A section of DNA that codes for a protein.
Key Points
- A gene is the fundamental physical and functional unit of heredity, consisting of a specific sequence of nucleotides in DNA (or RNA in some viruses).
- In molecular genetics, a gene is defined as a segment of DNA that contains the necessary instructions to synthesize a functional product, which is usually a protein or a functional RNA molecule.
- The process of decoding a gene begins with transcription, where the DNA sequence is copied into messenger RNA (mRNA), followed by translation, where the ribosome uses the mRNA template to assemble amino acids into a polypeptide chain.
- Genes are located at specific positions called loci (singular: locus) on chromosomes, and they act as the blueprint for an organism's phenotypic traits, such as eye color or enzyme production.
- Structurally, eukaryotic genes are composed of exons (coding regions), introns (non-coding intervening sequences), and regulatory sequences like promoters and enhancers that control when and how a gene is expressed.
Additional Information
- Chromosomes and Sex Chromosomes:
- A chromosome is a thread-like structure made of DNA and histone proteins that carries hundreds or thousands of genes; it is the container for genes, not the gene itself.
- Sex chromosomes (such as X and Y in humans) are a specific category of chromosomes that determine biological sex and carry sex-linked genes.
- Blood Groups:
- Blood groups like ABO and Rh are phenotypes or inherited traits determined by the expression of specific alleles (variant forms of a gene) located on Chromosome 9 and Chromosome 1 respectively.
- Genotype and Alleles:
- The term genotype refers to the actual genetic makeup of an individual, while alleles are different versions of the same gene that can lead to variations in inherited characteristics.