Unit 5: Heredity

Vocabulary flashcards covering key terms and definitions from AP Biology Unit 5 on heredity, including meiosis, genetic principles, statistical analysis, environmental effects, and chromosomal inheritance.

Meiosis

A two-stage cell division process in diploid organisms that produces haploid gametes and ensures genetic diversity through segregation and recombination.

Haploid (1n)

A cell or nucleus containing one complete set of chromosomes, characteristic of gametes produced by meiosis.

Diploid (2n)

A cell or organism with two sets of homologous chromosomes, one from each parent.

Homologous Chromosomes

Pairs of chromosomes with the same genes in the same order, but possibly different alleles; they separate during meiosis I.

Crossing Over (Recombination)

Exchange of genetic material between nonsister chromatids of homologous chromosomes during prophase I, increasing genetic variation.

Independent Assortment

Random orientation of homologous chromosome pairs during metaphase I, producing varied combinations of maternal and paternal chromosomes in gametes.

Genetic Diversity

Variation in heritable traits within a population, generated by crossing over, independent assortment, and fertilization.

Mendel’s Law of Segregation

Two alleles for a gene separate during gamete formation, so each gamete carries only one allele for each gene.

Mendel’s Law of Independent Assortment

Alleles of genes on different chromosomes distribute independently into gametes, producing new allele combinations.

Monohybrid Cross

A genetic cross involving one gene with contrasting alleles, often producing a 3:1 phenotypic ratio in the F2 generation.

Dihybrid Cross

A genetic cross tracking two genes simultaneously; when genes are unlinked, the expected phenotypic ratio in the F2 is 9:3:3:1.

Chi-Square Test (χ²)

A statistical method used to compare observed results with expected ratios to determine if differences are due to chance.

Null Hypothesis (H₀)

The statement that there is no significant difference between observed and expected data; any deviation is due to random chance.

Alternate Hypothesis (H₁)

The statement that observed data differ significantly from expected values, indicating that chance alone cannot explain the results.

Genotypic Ratio

The proportion of different genotype combinations produced in offspring (e.g., 1 AA : 2 Aa : 1 aa).

Phenotypic Ratio

The proportion of different observable traits among offspring (e.g., 3 tall : 1 dwarf).

Linked Genes

Genes located close together on the same chromosome that tend to be inherited together and deviate from independent assortment.

Map Distance

A measure of genetic linkage expressed in centimorgans (cM); calculated from recombinant frequencies between linked genes.

Sex-Linked Trait

A characteristic controlled by a gene on a sex chromosome, commonly the X chromosome, leading to criss-cross inheritance patterns.

Non-Mendelian Genetics

Inheritance patterns that do not follow Mendel’s predicted ratios, including linkage, incomplete dominance, codominance, and polygenic traits.

Non-Nuclear Inheritance

Transmission of traits controlled by mitochondrial or chloroplast DNA, typically maternally inherited in animals and plants.

Phenotypic Plasticity

The ability of organisms with the same genotype to exhibit different phenotypes under varying environmental conditions.

Environmental Influence on Phenotype

External factors such as temperature, pH, nutrition, or light that alter gene expression, leading to variable traits.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate properly during meiosis, resulting in aneuploid gametes.

Chromosomal Basis of Inheritance

Concept that genes are located on chromosomes, whose segregation and assortment during meiosis explain inheritance patterns.

Fertilization

Fusion of two haploid gametes (egg and sperm) restoring diploidy and creating new allele combinations in the zygote.

Probability Rule of Addition

For mutually exclusive events A and B, the probability that A or B occurs is P(A) + P(B).

Probability Rule of Multiplication

For independent events A and B, the probability that both occur is P(A) × P(B).

Ribosome

Universal cellular structure composed of rRNA and proteins that synthesizes polypeptides, supporting common ancestry among organisms.

Core Metabolic Pathways

Fundamental biochemical routes such as glycolysis and the Krebs cycle that are conserved across all domains of life.

DNA and RNA

Universal nucleic acid molecules that store (DNA) and transmit/express (RNA) genetic information in all living organisms.

XX/XY Sex Determination

Chromosomal system in which females are XX and males are XY, leading to sex-linked inheritance patterns.

ZW Sex Determination

System in birds and some reptiles where females are ZW and males are ZZ, differing from mammalian XY.

Haplodiploidy

Sex determination system in bees and ants where males are haploid and females are diploid.