Lecture 7 BIO200

Vocabulary flashcards covering key terms from the lecture notes on allele frequencies, population genetics, microevolutionary forces, mutation types, chromosomal mutations, and the genetic code.

Allele frequency

The proportion of all alleles in a population that a particular allele represents; used to track genetic change over time.

Population

A group of individuals of the same species that can interbreed and share a gene pool.

Allele

A variant form of a gene at a given locus.

Microevolutionary forces

The five processes that can change allele frequencies in a population: gene flow, nonrandom mating, genetic drift, mutation, and selection.

Gene flow

Movement of alleles between populations, usually via migration of individuals.

Nonrandom mating

Mating that is not random with respect to alleles; can alter genotype frequencies in a population.

Assortative mating

Mating with individuals that are phenotypically similar, which increases homozygosity and can reduce heterozygosity.

Heterozygosity

The presence of different alleles at a gene locus within individuals or within a population.

Homozygosity

Having two identical alleles at a gene locus within individuals.

Genetic drift

Random changes in allele frequencies due to chance, especially in small populations; includes founder effects and bottlenecks.

Founder effect

A new population started by a tiny subset of individuals, leading to allele frequencies that differ by chance from the original population.

Bottleneck

A drastic reduction in population size that changes allele frequencies and often reduces genetic variation.

Mutation

A heritable change in DNA that introduces new genetic variation; generally rare but the ultimate source of variation.

Point mutation

A mutation that affects a single nucleotide pair in the DNA.

Silent mutation

A point mutation that does not change the amino acid due to codon degeneracy.

Missense mutation

A point mutation that changes one amino acid into a different one in the protein.

Nonsense mutation

A mutation that creates a premature stop codon, truncating the protein.

Frameshift mutation

Insertion or deletion of nucleotides not in multiples of three, altering the reading frame of codons.

Reading frame

The way nucleotides are divided into codons from a starting point; shifting the frame changes downstream codons.

Codon

A sequence of three nucleotides that codes for a specific amino acid or a stop signal.

Degenerate code

The genetic code is redundant: multiple codons can code for the same amino acid.

Start codon

The codon that signals the start of translation, usually AUG.

Stop codon

Codons (UAA, UAG, UGA) that terminate translation.

Chromosomal mutation

Large-scale mutations that alter the structure or number of entire chromosome segments.

Deletion (chromosomal)

Loss of a chromosomal region; can be fatal if large or disrupt essential genes.

Duplication

Copying of a chromosome segment, resulting in extra genetic material.

Inversion

A chromosome segment is flipped in orientation, changing gene order without necessarily losing genes.

Translocation

A chromosome segment moves to a different chromosome; can disrupt meiosis and gene regulation.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate during meiosis, producing abnormal gametes.

Aneuploidy

Gain or loss of one or more chromosomes in a cell or organism.

Monosomy

A gamete or organism missing one chromosome from a pair (2n−1); often lethal in humans.

Trisomy

An extra chromosome in a set (2n+1); can be viable (e.g., Down syndrome is trisomy 21).

Down syndrome

A common trisomy (trisomy 21) resulting in characteristic phenotypes and health issues.

Turner’s syndrome (XO)

A sex chromosome monosomy where females have a single X chromosome (no second sex chromosome).

Klinefelter syndrome (XXY)

A sex chromosome aneuploidy in males with an extra X chromosome (XXY).

Polyploidy

Having more than two complete sets of chromosomes; common in plants and often leads to new traits.

Haploid

Having a single set of chromosomes (n) as in gametes.

Diploid

Having two complete sets of chromosomes (2n) as in most body cells.

Beneficial mutation

A mutation that increases the fitness of the organism in a given environment.

Neutral mutation

A mutation that has no effect on fitness; may be silent or occur in noncoding regions.

Harmful mutation

A mutation that reduces an organism’s fitness and is often deleterious.

Central dogma

The flow of genetic information: DNA is transcribed into RNA, which is translated into protein.

Transcription

The process of copying DNA into RNA.

Translation

The process of decoding RNA to synthesize a protein.

Codon degeneracy example

Some amino acids are encoded by multiple codons (degeneracy); e.g., proline is encoded by four different codons.