Genetic Variation

Practice vocabulary flashcards covering genetic variation, mutations, meiosis, patterns of inheritance, and mechanisms of genetic change based on lecture notes.

Mutation

A permanent change to the DNA base sequence, which is the only source of new alleles.

Somatic Mutations

Mutations that occur in body cells (e.g., skin cells) and cannot be passed on to offspring.

Germline Mutations

Mutations occurring in reproductive cells (egg or sperm) that can be passed on to offspring.

Harmful Mutations

Mutations that can cause genetic disorders, such as cystic fibrosis, and negatively impact an organism's survival, health, and ability to reproduce.

Carrier

An individual who possesses a harmful recessive allele that is not expressed phenotypically, but can be passed on during reproduction.

Helpful Mutations

Beneficial mutations that give an individual an advantage or better chance of survival, allowing them to reproduce and pass on the mutated allele to increase its frequency in the gene pool.

Allele Frequency

The relative representation of an allele in a population, calculated as the total number of a specific allele divided by the total number of alleles in the population gene pool.

Meiosis

Cell division that produces $4$ genetically unique cells (gametes) from $1$ diploid parent cell.

Law of Segregation

The principle stating that the $2$ alleles for a gene separate during meiosis so each gamete receives only $1$ allele per gene.

Independent Assortment

The random lining up of homologous chromosome pairs at the centre of the cell during metaphase I, resulting in gametes receiving a random mix of maternal and paternal chromosomes.

Crossing Over

The process during prophase I where non-sister chromatids of homologous chromosomes exchange sections of DNA, producing recombinant chromosomes with new combinations of alleles.

Chiasma

The site on homologous chromosomes where crossing over occurs during prophase I.

Linked Genes

Genes located close to each other on the same chromosome that tend to be inherited together because they are less likely to be separated by crossing over, thereby limiting genetic variation.

Fertilisation

The process where any sperm can penetrate any egg (both with unique allele combinations), producing a genetically unique diploid zygote with a random combination of alleles.

Complete Dominance

An inheritance pattern where one dominant allele completely masks the effect of a recessive allele, requiring $2$ recessive alleles for the recessive phenotype to be expressed.

Co-dominance

An inheritance pattern where both alleles are expressed and neither allele masks the other, resulting in the individual displaying both phenotypes produced by each allele.

Incomplete Dominance

An inheritance pattern where both alleles are expressed, resulting in a phenotype that is an intermediate blend between the phenotypes produced by either allele.

Lethal Alleles

Versions of a gene that cause the organism to die, requiring either $1$ or $2$ copies of the allele to cause death depending on the gene.

Multiple Alleles

A condition where a single gene has more than $2$ possible alleles within a population, increasing genetic variation.

Dihybrid Inheritance

The study of the inheritance of $2$ different genes or characteristics at the same time, producing an expected phenotypic ratio of $9:3:3:1$ for an $AaBb \times AaBb$ cross assuming complete dominance and independent assortment.

Natural Selection

The process where selection pressures determine favourable characteristics, leading individuals with advantageous adaptations to survive, reproduce, and pass on their alleles, thereby increasing their allele frequency in the gene pool.

Genetic Drift

A random change in the frequency of alleles in a population, which has a greater impact on small populations and can cause the loss of alleles and reduced genetic diversity.

Bottleneck Effect

A reduction of a population to low numbers by a natural event that is often not a selection pressure, resulting in an over/under-representation or loss of alleles and low genetic diversity.

Founder Effect

The event occurring when a small group leaves a main population to start a new, smaller population, which may not be a representative sample of the original gene pool's alleles.

Inbreeding

Reproduction between closely related individuals, which reduces the number of new allele combinations (genetic diversity) and is frequently a problem in small populations.