A
The process of cell division that produces four genetically unique haploid gametes.
Meiosis
The expected phenotypic ratio of a cross between two individuals heterozygous for two unlinked traits (AaBb x AaBb).
9:3:3:1
The permanent, unrepaired change in the base sequence of DNA.
The movement of alleles into or out of a population (due to immigration or emigration).
Migration (Gene Flow)
Environmental factors (like predators, diseases, or climate) that alter allele frequencies by favoring certain phenotypes over others.
Selection Pressures
The exchange of genetic material between non-sister chromatids during Prophase I.
Crossing Over
Genes located on the same chromosome that tend to be inherited together unless separated by crossing over.
Linked Genes
The total sum of all unique alleles present within a interbreeding population at a given time.
Gene Pool
Random changes in allele frequencies within a gene pool due to chance events, affecting small populations most severely.
Genetic Drift
The differential survival and reproduction of individuals due to differences in phenotype.
Natural Selection
This law states that alleles for a gene separate during gamete formation so each gamete carries only one allele per gene.
Law of Segregation
Inheritance pattern where both alleles are fully expressed in the heterozygous phenotype (e.g., ABO blood groups).
Co-Dominance
Type of mutation that occurs in body cells and cannot be passed on to offspring.
Somatic Mutation
Event where a small group breaks away from a larger population to establish a new isolated population with reduced genetic diversity.
Founder Effect
What happens to the frequency of beneficial alleles in a gene pool over successive generations under natural selection.
Frequency of beneficial alleles increases
The random alignment and separation of homologous chromosome pairs along the cell equator during Metaphase I.
Independent Assortment
An allele that causes the death of the organism carrying it, often modifying expected monohybrid phenotypic ratios to 2:1.
Lethal Allele
The only type of mutation that can be inherited and enter the gene pool.
Gametic (or germline) Mutation
Event where a population is drastically reduced in size by a catastrophic event, leaving a surviving population with reduced genetic variation.
Bottleneck Effect (genetic bottleneck)
The reason why natural selection acts directly on an organism's phenotype rather than its genotype.
The phenotype interacts directly with the environment, determining survival and reproductive success?
Why a test cross requires crossing an individual displaying a dominant phenotype with a homozygous recessive individual.
To determine if the dominant individual is homozygous dominant or heterozygous?
Inheritance pattern where the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes (e.g., red and white flowers making pink).
Incomplete Dominance
How new alleles enter a population, and how existing alleles are re-shuffled.
Mutation creates new alleles, while meiosis/fertilisation recombines existing alleles.
Why low genetic diversity increases a population's risk of extinction if environmental conditions change.
Fewer different alleles mean it's less likely any individuals possess phenotypes adapted to survive new selection pressures
Explain why a harmful (or lethal) dominant allele is removed from a population by natural selection much faster than a recessive harmful allele.
Harmful dominant alleles are expressed in both homozygous and heterozygous phenotypes, so every individual carrying the allele is exposed to selection