Genetics Definitions

A process in genetics where a beneficial mutation increases in frequency within a population, leading to a reduction in genetic variation among nearby genetic sequences. This occurs because the advantageous mutation and its linked alleles are “selected” together, often referred to as genetic hitchhiking

a genetic interaction where the beneficial effect of a mutation decreases as the fitness of the organism increases, meaning that additional beneficial mutations provide less advantage when the organism is already fit. This phenomenon often leads to declining adaptability in evolving populations

an interaction between nonallelic genes in which the genotype at one locus affects the expression of alleles at another locus

a point mutation that results in the substitution of one amino acid by another.

a process in evolutionary genetics where asexual populations accumulate harmful mutations over time, leading to a decline in fitness and potentially extinction. This occurs because, without recombination, offspring inherit at least as many mutations as their parents, and the least mutated individuals can be lost due to random chance

the loss of genetic diversity within a population, often due to factors like inbreeding, habitat loss, and the death of individuals before they can reproduce. This process can lead to a weakened gene pool, making species more vulnerable to extinction

a point mutation in a sequence of DNA that results in a nonsense codon, or a premature stop codon in the transcribed mRNA

also called a stop-loss variant; a point mutation that occurs within a stop codon; nonstop mutations cause the continued translation of an mRNA strand into what should be an untranslated region

a type of genetic mutation where a change in the DNA sequence occurs, but it does not alter the amino acid sequence of the resulting protein. This happens because multiple codons can code for the same amino acid, making some mutations effectively “silent”

a type of nucleotide mutation that changes the amino acid sequence of a protein by altering a codon in the DNA or RNA

used to estimate the balance between neutral mutations, purifying selection and beneficial mutations acting on a set of homologous protein-coding genes. It is calculated as the ratio of the number of nonsynonymous substitutions per non-synonymous site, in a given period of time, to the number of synonymous substitutions per synonymous site, in the same period. The latter are assumed to be neutral, so that the ratio indicates the net balance between deleterious and beneficial mutations

Any of several small, basic proteins most commonly found in association with the DNA in the chromatin of eukaryotes

a specific region of DNA located upstream of a gene that serves as the binding site for RNA polymerase and transcription factors, initiating the transcription of that gene into RNA. Promoters play a crucial role in regulating gene expression by controlling when and how much a gene is expressed

A complex of nucleic acids and proteins, primarily histones, in the cell nucleus that stains readily with basic dyes and condenses to form chromosomes during cell division

The study of heritable changes in gene expression that are caused by factors such as DNA methylation rather than by a change in the sequence of base pairs in DNA itself

a series of cellular processes that detect and repair damage to DNA, ensuring the integrity of the genome. It involves signaling pathways that activate repair mechanisms or trigger cell cycle checkpoints to prevent the replication of damaged DNA, ultimately protecting against diseases like cancer

A group of genes that code for cell-surface histocompatibility antigens and are the principal determinants of tissue type and transplant compatibility

a cellular mechanism that fixes damaged DNA by removing small, non-helix-distorting base lesions

a DNA repair mechanism that removes damaged sections of DNA, particularly those caused by ultraviolet light and other mutagens. It involves recognizing the damage, excising a short segment of the DNA strand containing the lesion, and then synthesizing a new DNA segment to fill the gap

a cellular process that identifies and corrects errors in DNA, such as incorrect base pairings that occur during DNA replication. This system helps maintain genetic stability by repairing erroneous insertions, deletions, and mis-incorporations of bases

a DNA repair pathway that fixes double-strand breaks by directly ligating the broken ends without needing a homologous template; fast but prone to errors

a process in genetics where similar or identical DNA molecules exchange genetic information. This mechanism is important for repairing DNA breaks and generating genetic diversity during the formation of gametes in sexual reproduction

a genetic interaction where the combination of two non-lethal genetic defects leads to cell death, while the individual defects alone do not affect cell viability

a high frequency of mutations within the genome of a cellular lineage, which can include changes in DNA sequences, chromosomal rearrangements, or aneuploidy. It is significant in processes like cancer development and some neurodegenerative diseases