Essential Genetics Terminology & Concepts
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Essential Genetics Terminology
Conjugation: Genetic Material Transfer
Conjugation is the transfer of genetic material between unicellular individuals through direct cell-to-cell contact.
Bacterial Conjugation: Not Sexual Reproduction
Bacterial conjugation is often incorrectly regarded as the bacterial equivalent of sexual reproduction or mating.
Spermatogenesis: Male Sperm Development
Spermatogenesis is the process by which male spermatogonia develop into sperm cells.
Oogenesis: Female Egg Development
Oogenesis is the process by which female oogonia develop into egg cells.
Monohybrid Cross: Single Trait Inheritance
A monohybrid cross is a method of tracking the inheritance of a single trait from a pair of homozygous grandparents through generation F1 to generation F2.
Mutation: DNA Sequence Change & New Traits
A mutation is a change in the base-pair sequence within the DNA of a gene or chromosome of an organism, resulting in the creation of a new character or trait not found in the wild type.
Autosomal Inheritance: Genetic Transmission Patterns
Autosomal inheritance describes the patterns of genetic transmission related to autosomal genes.
Genetic Ratios: Genotype & Phenotype
- Genotype Ratios: (2:1:1)n
- Phenotype Ratios: (3:1)n
Complete Dominance: Both Alleles Dominant
Complete dominance occurs when both alleles are dominant.
Incomplete Dominance: Partial Expression
Incomplete dominance occurs when one allele is dominant and the other is recessive.
Codominance: Heterozygote Exhibits Both Phenotypes
Codominance is when the heterozygote exhibits the phenotypes of both homozygotes.
Overdominance: Heterozygote Fitness Advantage
Overdominance occurs when the dominant relationship is modified, leading heterozygote individuals to develop higher phenotypic fitness than dominant homozygotes.
Multiple Alleles: More Than Two Gene Variants
Multiple alleles exist when there are more than two different alleles of one gene that affect a trait and occupy a given locus.
Pleiotropy: Single Gene, Diverse Effects
Pleiotropy is when a single gene or gene pair produces diverse phenotypic effects.
Gene Penetrance: Dominant Gene Manifestation
Gene penetrance is the frequency with which a dominant gene manifests itself in individuals within a population.
Gene Expressivity: Phenotypic Expression Degree
Gene expressivity is the degree to which a penetrant gene or genotype is phenotypically expressed in an individual.
Lethal Genes: Mutant Alleles Causing Death
Lethal genes are mutant alleles that can cause death.
Complementary Genes: Interacting Gene Pairs
Complementary genes are two interacting non-allelic gene pairs that modify each other's action.
Epistatic Genes: Masking Phenotypic Expression
Epistatic genes represent a form of gene interaction in which alleles of one gene pair mask or inhibit the phenotypic expression of another allele pair.
Polygenes: Multiple Genes, Small Phenotypic Effects
Polygenes are a group of allelic pairs that may affect the same trait, with each producing a small effect on the overall phenotype.
Linkage Group: Genes on the Same Chromosome
A linkage group refers to genes that occur on the same chromosome.
Complete Linkage: Genes Inherited Together
Complete linkage occurs when genes on the same chromosome do not separate and are jointly inherited in gametes.
Incomplete Linkage: Genes Separate in Gametes
Incomplete linkage occurs when linked genes separate and are inherited in different gametes.
Chiasmata: Chromosome Attachment Points
Chiasmata are the points of attachment within a chromosome.
Genetic & Linkage Maps: Gene Positions
A genetic map or linkage map illustrates the relative positions of genes on a chromosome.
Map Units (mu) & Centimorgans (cM)
Map units (mu) define the interval in which one percent of crossing-over takes place; also known as a Centimorgan (cM).
Interference: Chiasma Formation Reduction
Interference describes how one formed chiasma reduces the probability of another chiasma forming in the next chromosomal locus.
Coefficient of Coincidence: Interference Variation
The coefficient of coincidence measures the extent to which interference varies across different segments of a chromosome.