Biology Flashcards

According to Darwin's theory of natural selection, which individuals in a population are most likely to survive and reproduce?

Answer: Individuals with traits best suited to their environment

Natural selection favours heritable traits that increase an individual's fitness — its ability to survive and reproduce in its specific environment.

What is a gene mutation?

Answer: A heritable alteration in the DNA nucleotide sequence

A mutation is a permanent, heritable change in the DNA sequence that can alter gene function and potentially be passed to offspring.

What is the function of restriction endonucleases in recombinant DNA technology?

Answer: Cutting DNA at specific recognition sequences to produce fragments

Restriction enzymes recognise specific short DNA sequences and cleave the double strand at those sites, producing fragments used in gene cloning.

In a Mendelian monohybrid cross between two heterozygous parents (Aa × Aa), what is the expected phenotypic ratio among offspring?

Answer: 3 dominant : 1 recessive

The cross produces genotypes AA, Aa, Aa, aa in a 1:2:1 ratio; since A is dominant, three-quarters show the dominant phenotype and one-quarter show the recessive phenotype.

What is the role of mRNA (messenger RNA) in protein synthesis?

Answer: Carrying the genetic code from DNA to the ribosome as a template for translation

mRNA is transcribed from DNA and carries codons to the ribosome, where it serves as the template specifying the sequence of amino acids in a protein.

Which laboratory technique is used to amplify a specific DNA sequence from a very small sample using thermal cycling?

Answer: Polymerase chain reaction (PCR)

PCR uses repeated cycles of denaturation, annealing, and extension with a heat-stable DNA polymerase to exponentially amplify a target sequence.

What is the term for the evolutionary process in which related species develop increasingly different characteristics as they adapt to different environments?

Answer: Divergent evolution

Divergent evolution occurs when populations of a common ancestor become isolated and adapt to different selective pressures, accumulating distinct traits over time.