In a pedigree, what does a circle represent? A square? A shaded symbol?
o Circle = Female
o Square = Male
o Shaded Symbol = An individual who expresses the trait/disorder (affected).
What is the difference between Mendel’s Law of Segregation and Law of Independent Assortment?
o Law of Segregation: The two alleles for a single trait separate during gamete formation.
o Law of Independent Assortment: Genes for different traits are sorted into gametes independently of one another.
Why are sex-linked disorders (like hemophilia) more common in males?
Males have only one X chromosome. If that single X carries a recessive disease allele, they have no second X chromosome with a potential healthy allele to mask it, so they will express the disorder.
What is the purpose of a Test Cross?
To determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual and observing the offspring.
Explain the difference between Codominance and Incomplete Dominance
o Codominance: Both alleles are fully and separately expressed (e.g., AB blood type).
o Incomplete Dominance: The heterozygous phenotype is a BLEND of the two homozygous phenotypes (e.g., red + white flowers → pink flowers).
What is a Bacteriophage?
A type of virus that specifically infects and replicates within bacteria.
Compare Prezygotic and Postzygotic Reproductive Barriers. Give an example of each
o Prezygotic: Barrier before fertilization. Example: Two species breed at different times of the year (temporal isolation).
o Postzygotic: Barrier after fertilization. Example: A mule is a sterile hybrid.
Define Exaptation.
A feature that evolved for one function but was later co-opted for a new, different function (e.g., bird feathers for insulation before they were used for flight).
What is the main idea of the Biological Species Concept?
A species is a group of populations that can interbreed and produce viable, fertile offspring, and are reproductively isolated from other such groups.
What is a Node on a Phylogenetic Tree?
A node represents the most recent common ancestor of the lineages that branch off from it.
In evolutionary terms, what does “Fitness” mean?
An organism’s relative ability to survive, reproduce, and pass its genes to the next generation. It’s about reproductive success.
What does the Hardy-Weinberg principle describe?
A theoretical population that is NOT evolving. It’s a model where allele frequencies remain constant from generation to generation.
What are the five assumptions required for a population to be in Hardy-Weinberg equilibrium?
- No Mutations
- Random Mating
- No Natural Selection
- Extremely Large Population Size (no genetic drift)
- No Gene Flow (no immigration/emigration)
What is the ultimate source of all new genetic variation in a population?
Mutation. It creates new alleles that natural selection, genetic drift, and gene flow can then act upon.
Are mutations directed or random? Do they usually create adaptations directly?
Mutations are random with respect to the needs of the organism. They are not directed by the environment. They provide the raw material (variation), but natural selection is the process that leads to adaptations
What are the four main mechanisms (forces) of evolution?
- Natural Selection
- Genetic Drift
- Gene Flow
- Mutation
What is Adaptive Radiation? Give an example.
The rapid evolution of a single ancestral species into many new species to fill available niches. Example: Darwin’s finches on the Galápagos Islands.
What is the best evidence for evolution from Molecular Biology?
Comparing DNA or protein sequences. The more similar the sequences, the more closely related the species are, indicating a recent common ancestor.
What are the “rungs” of the DNA double helix made of?
Complementary pairs of nitrogenous bases (A-T and C-G).
What is Molecular Systematics?
The use of DNA, RNA, and protein sequences to study evolutionary relationships and classify organisms.
What was a key adaptation that allowed plants to colonize land?
The waxy cuticle - a layer that helps prevent water loss in a dry, terrestrial environment.
What is the difference between Genotype and Phenotype?
o Genotype: The genetic makeup (e.g., Bb).
o Phenotype: The observable, physical trait (e.g., Brown hair). The phenotype is determined by the genotype AND the environment
What significant contribution did the first prokaryotic cells make to Earth?
They began performing photosynthesis, which released oxygen into the atmosphere, transforming it and paving the way for oxygen-dependent life.
