BIO001 Midterm 2

F₁ Generation

The initial generation from an experimental cross

F₂ Generation

Second generation from an experimental cross (F₁ offspring)

Recessive Allele

An allele with a phenotype that does not appear in heterozygous individuals

Dominant Allele

An allele with a phenotype that appears in heterozygous individuals

Homozygous

Having 2 copies of the same allele

Heterozygous

Having 2 different alleles for a gene

Principle of Segregation

Observation that alleles of the same gene separate from each other prior to gamete formation

Principle of Independent Assortment

Observation that alleles of different genes go into gametes independently of each other, making every combination of alleles from different genes equally likely.

Wild Type

The typical or most common version of an allele or phenotype, as opposed to novel, unusual, or low-fitness forms.

Co-dominant Alleles

Heterozygotes have the phenotype associated with both alleles present.

Loss-of-function alleles

Alleles that lead to a protein or RNA product that cannot function normally or is completely absent.

Sex chromosome

A chromosome associated with the sex of the individual.

Autosome

Any chromosome that is not a sex chromosome.

Sex-linked genes

Genes found on a sex chromosome.

Linked Genes

Genes found on the same chromosome.

Polygenic trait

A trait that shows continuous variation—usually normally distributed—due to the involvement of products from many different genes. Also called a quantitative trait.

Genetic locus

The physical location of a gene on a chromosome. The plural form is loci and is pronounced LOW-sigh.

Pedigree

A diagram summarizing the incidence of a genetic disease or other trait in a family. Pedigrees are used to identify the pattern of inheritance of specific traits and predict how likely offspring from a particular set of parents are to have a specific phenotype.

Genome

All of the DNA, and thus all genes, in an individual of a particular species.

Null model

A model that predicts the data you should expect to see if a process is not working—meaning, when a particular causative agent is not impacting the situation.

Hardy-Weinberg Principle

A null model stating that if no selection, drift, gene flow, or mutation occur, and if mating is random with respect to the gene in question, then allele frequencies will not change from one generation to the next and genotype frequencies will be in the proportions p2, 2pq, q2, where p and q are the frequencies of two alleles at that gene

Assortative Mating

Mate choice based on similarities or dissimilarities in phenotype.

Inbreeding

Mating among relatives.

Gene pool

A concept used in predicting the results from random matings among all of the individuals in a population, by supposing that all gametes are tossed into "pool" and then drawn out at random to produce offspring.

Genetic Drift

Any change that occurs in allele frequencies that is due to chance.

Founder events

One of the several types of events that can cause genetic drift. They occur when a relatively small number of individuals disperse to a new habitat and found a completely new population.

Genetic Bottlenecks

One of the several types of events that can cause genetic drift. They occur when a species undergoes a large and rapid decrease in population size due to a disease epidemic, catastrophic storm, or other change.

Gene flow

An evolutionary process that changes allele frequencies through the movement of individuals and their alleles from one population to another. Homogenizes allele frequencies among populations.

Maladaptive

Leading to lower fitness.

Mutation

Any change in the sequence of DNA, and thus a change in genetic information. Introduces new alleles into population.

Deleterious Mutation

A mutation or other event that lowers fitness.