Bio Genetic Variation Flashcards

Mutation

Is a permanent change in the base sequence of DNA, coding for a gene. It creates new alleles, so it’s the original source of genetic variation in populations

Gametic Mutation

Happens in a sex cell or in a cell that forms gametes. It can be passed onto offspring, so it can change allele frequencies over generations

Somatic Mutation

Happens in a body cell. It affects only that organism and is usually not inherited because it’s not in a gamete.

Meiosis

Is the cell division that makes haploid gametes. It increases variation because chromosome pairs separate and gametes receive different allele combinations.

Crossing over

Is the exchange of DNA between homologous chromosomes in meiosis. It produces recombinant chromosomes with new allele combinations.

Segregation

Is the separation of allele pairs when homologous chromosomes move apart in meiosis. Each gamete receives only one allele for each gene.

Independent Assortment

Is the random way homologous chromosome pairs line up in meiosis 1. This creates different combinations of chromosomes in gametes.

Linked Genes

Are genes on the same chromosome. They tend to be inherited together unless crossing over separates them.

Recombination

is the formation of new allele combinations, usually by crossing over and independant assortment during meiosis.

Gene Pool

Is all the alleles present in a population. Variation in this affects how a population can respond to selection pressures.

Allele Frequency

Is how common an allele is in a population. It can change through mutation, natural selection, genetic drift, migration or chance events.

Genetic Drift

Is a random change in allele frequency, especially in small populations. Alleles may become more common or be lost by chance, not because they’re advantageous.

Founder Effect

Happens when a small group starts a new population. It’s gene pool is less varied and may have different allele frequencies from the orginal population.

Bottleneck effect

Happens when a population is greatly reduced by chance events. The surviving population has less genetic variation and altered allele frequencies.

Natural Selection

Is when individuals with advantageous inherited traits survive and reproduce more successfully. Over time, favorable alleles become more common.

Selection pressure

Is an environmental factor that affects survival or reproduction, such as predation, disease, drought, or temperature. It drives natural selection.

Co-Dominance

Is when both alleles are fully expressed in the phenotype of a heterozygote. Neither allele masks the other.

Incomplete Dominance

Is when neither allele is completely dominant, and the heterozygote shows an intermediate phenotype, a blend of both alleles.

Multiple alleles

Means more than two alleles form for one gene existing in the population, even though one individual can inherit only two of them.

Lethal Allele

Is an allele that can cause death in a particular genotype, often before reproduction. This can change expected inheritance ratios.