Biology: Genetics and Evolution Flashcards

Which evidence most strongly supports the common ancestry of all living organisms?

Answer: Universal use of the same genetic code (DNA/RNA/protein)

The near-universal genetic code—where the same codons specify the same amino acids across all life—strongly indicates common ancestry.

What is the difference between genotype and phenotype?

Answer: Genotype is the allele combination; phenotype is the expressed trait

Genotype is an organism's genetic makeup (alleles), while phenotype is the observable, expressed characteristic.

During crossing over in meiosis, which structures physically exchange segments?

Answer: Non-sister chromatids of homologous chromosomes

Crossing over (recombination) occurs between non-sister chromatids of homologous chromosomes at chiasmata during prophase I.

A population of beetles has 60% green (G) and 40% brown (g) alleles. A drought kills all brown beetles. This is an example of:

Answer: Directional selection

Directional selection shifts the population toward one phenotypic extreme (green) by eliminating individuals at the other extreme (brown).

Which statement best describes the role of mutations in evolution?

Answer: Mutations are the ultimate source of new genetic variation

Mutations introduce new alleles into populations, providing the raw genetic variation upon which natural selection and other evolutionary forces act.

What pattern of inheritance is shown when a trait appears more often in males than females and is passed from carrier mothers to affected sons?

Answer: X-linked recessive

X-linked recessive traits are expressed in males (XY) who inherit a single recessive allele from a carrier mother.

Which term describes the formation of new species from a single ancestral species that colonizes an environment with many unfilled ecological niches?

Answer: Adaptive radiation

Adaptive radiation occurs when one ancestral species rapidly diversifies into many new species filling available ecological niches.