Biology: Page 10

Flashcards reviewing sex-linked traits, pedigrees, evolution by natural selection, and evidence for evolution.

How do you complete a Punnett Square for a sex-linked trait, given that a man is colorblind (recessive) and a woman is not colorblind (dominant)?

Set up the Punnett Square with X chromosomes carrying the B (dominant, not colorblind) and b (recessive, colorblind) alleles. For example, if the man's genotype is XbY and the woman's is XBXB, the Punnett Square would show the possible genotypes of their offspring.

Who is more likely to express a sex-linked trait, a man or a woman? Why?

A man is more likely to express a sex-linked trait because he only has one X chromosome. If he inherits the recessive allele on that X chromosome, he will express the trait, unlike a woman who would need two copies of the recessive allele.

What do the following structures represent on a pedigree: circles, squares, a horizontal line connecting the middle of two shapes, a vertical line with branches, a shape that is fully colored in, a shape that has no color, and a shape that is half colored in?

O=Woman, ☐=Man, Horizontal line = Partners/Relationship, Vertical line with branches = Children/offspring, Fully colored in = Has specific trait, Shape with no color = Does not have trait, Half colored in = Carrier of trait

What is Darwin's theory of evolution by natural selection?

Darwin's theory is that all living things descended from a common ancestor (LUCA). Organisms that are genetically adapted to their environment are more likely to survive and reproduce.

Describe genetic drift as a mechanism for evolution.

Genetic drift refers to random fluctuations in the frequency of alleles within a population, especially in small populations, potentially leading to the loss of genetic variation. Examples include bottleneck and founder effect.

Describe gene flow as a mechanism for evolution.

Gene flow is the movement of genes into or out of a population, typically due to migration. It can introduce new alleles or alter allele frequencies in the recipient population.

List and describe homologous structures as evidence for evolution.

Homologous Structures: Different species share physical features because of a common ancestor.

List and describe analogous structures as evidence for evolution.

Analogous Structures: Different species evolve similar features to adapt to the environment; no common ancestor.

List and describe vestigial structures as evidence for evolution.

Vestigial Structures - Structures inherited from ancestor but not used in modern organism. For example, the human appendix.