Video Notes: Genetics – Variation, Meiosis, and Inheritance

Vocabulary flashcards covering genotype/phenotype, meiosis, genetic variation, inheritance, and related terminology from the lecture notes.

Genotype

All the alleles of all the genes within an individual, or the specific set of alleles under study.

Phenotype

Observable traits produced by the interaction of genotype and environment.

Regulator genes

Genes that influence the expression of other genes, affecting trait development.

Environmental pressures

External conditions that influence how phenotypes are expressed and selected in a population.

Convergent evolution

Different lineages independently evolve similar traits due to similar environmental pressures.

Ploidy

Number of chromosome sets in a cell.

Haploid

Having one complete set of chromosomes (1n).

Diploid

Having two complete sets of chromosomes (2n).

Chromosome

DNA-protein structure that carries genes; organized into sets within a cell.

Chromosome set

A complete set of chromosomes in a cell; e.g., humans have 23 chromosomes per set.

Homologous chromosomes

Pairs that carry the same genes, one from each parent; may differ in alleles.

Alleles

Different versions of a gene that occupy the same locus.

Locus

Location of a gene on a chromosome; the same locus across individuals in a population.

Dominance

An allele that is expressed in the phenotype even in the presence of a recessive allele at the same locus.

Meiosis

Process of producing gametes by halving the chromosome number through two cell divisions (Meiosis I and II).

Gamete

Haploid reproductive cell (egg or sperm).

Zygote

Diploid cell formed when two gametes fuse; contains the species' full chromosome number.

Tetrad

Set of four chromatids formed when homologous chromosomes pair during early meiosis I.

Non-sister chromatids

Chromatids from different homologs that can exchange genetic material during crossing over.

Sister chromatids

Two identical copies of a chromosome bound at the centromere.

Chiasma

Site where non-sister chromatids exchange genetic material during crossing over.

Crossing over

Exchange of genetic material between homologous chromosomes, creating variation.

Variation

Genetic differences among individuals arising from crossing over, independent assortment, mutations, etc.

Mutations

Changes in nucleotide sequence that can create new alleles; sources include mutagens and replication errors.

Mutations from environmental mutagens

Mutations caused by external factors such as radiation or chemicals.

Replication errors

Mutations arising during DNA replication that contribute to variation.

Nondisjunction

Failure of chromosome pairs to separate properly during Meiosis I or II.

Aneuploidy

Having too many or too few chromosomes in a cell (n±1 or other irregulars).

Down syndrome

Trisomy 21; three copies of chromosome 21 in cells.

Monosomy

Having only one copy of a chromosome (n-1).

Unequal crossing over

Misalignment during crossing over causing one chromatid to be longer or shorter, potentially leading to disorders (e.g., Huntington’s).

Alternation of Generations

Life cycle in which organisms alternate between haploid (sexual) and diploid (asexual) generations.

Asexual reproduction

Reproduction without fertilization; organisms typically reproduce by mitosis-like division, resulting in genetically similar offspring.

Genome

All the hereditary information within an individual, including non-gene DNA.

Gene pool

All the alleles of all the genes within a population.

Gene

Section of DNA on a chromosome that encodes a polypeptide or regulates other genes.

Descent with modification

Darwin’s idea that natural selection acts on heritable variation to shape evolution.

Heritability

The extent to which phenotypic variation is passed from one generation to the next.

Natural selection

Differential survival and reproduction based on heritable variation.

The Selfish Gene

Dawkins’ idea that genes propagate themselves; phenotype is the mechanism by which genes are passed on.