Biology: Genetics, Evolution, and Homeostasis Review

A comprehensive collection of vocabulary terms from the lecture notes covering genetics, DNA/RNA structures, evolutionary selection, and homeostasis mechanisms.

Autosome

Any chromosome that is not a sex chromosome.

Sex chromosome

Chromosomes that determine biological sex ($X$ and $Y$ in humans).

Human chromosomes

46 total chromosomes (23 pairs).

Body cells

All non-reproductive cells.

Germ cells

Cells that produce gametes.

Gametes

Sex cells (sperm and egg); haploid.

Somatic cells

Body cells with 46 chromosomes.

Meiosis

Cell division producing 4 genetically different haploid cells.

Mitosis

Cell division producing 2 identical diploid cells.

Centrioles

Structures that help organize spindle fibers.

Phases of meiosis

Prophase I, Metaphase I, Anaphase I, Telophase I, then Meiosis II.

Prophase

Chromosomes condense; spindle forms; nuclear membrane breaks down.

Metaphase

Chromosomes line up in the middle.

Anaphase

Chromosomes/sister chromatids separate.

Interphase

G1 (growth), S (DNA replication), G2 (preparation).

Cytokinesis

Division of the cytoplasm.

Independent assortment

Chromosomes separate randomly during meiosis.

Crossing over

Exchange of DNA between homologous chromosomes in Prophase I.

Haploid

One set of chromosomes ($n$).

Diploid

Two sets of chromosomes ($2n$).

Traits

Inherited characteristics.

Gene

Segment of DNA that codes for a trait.

Allele

Different version of a gene.

Homozygous/Purebred

Two identical alleles (AA or aa).

Heterozygous/Hybrid

Two different alleles (Aa).

Genotype

Genetic makeup (AA, Aa, aa).

Phenotype

Physical expression of a trait.

Dominant & recessive

Dominant masks recessive; recessive shows only with two copies.

Nucleotide

DNA building block: phosphate, sugar, base.

DNA bases

Adenine, Thymine, Cytosine, Guanine.

DNA sugar

Deoxyribose.

Chargaff’s rules

A pairs with T; C pairs with G.

DNA shape

Double helix.

Replication

DNA copies itself before cell division.

RNA bases

Adenine, Uracil, Cytosine, Guanine.

RNA sugar

Ribose.

RNA base pairing

A-U and C-G.

mRNA

Carries code.

rRNA

Makes ribosomes.

tRNA

Carries amino acids.

Amino acids

20 common amino acids build proteins.

Monomer

Small building block of a polymer.

Polymer

Large molecule made of repeating monomers.

Codon

Three-base mRNA sequence coding for an amino acid.

Anticodon

Three-base tRNA sequence matching a codon.

Gene mutations

Changes in DNA sequence of a gene.

Chromosome mutations

Changes in chromosome structure or number.

Transcription

${DNA} \rightarrow {mRNA}$.

Translation

${mRNA} \rightarrow {protein}$.

Intron

Noncoding section removed from RNA.

Exon

Coding section kept in RNA.

Inbreeding

Breeding closely related organisms.

Selective breeding

Humans choose desired traits.

Genetic engineering

Direct modification of DNA.

Chromosome

DNA-containing structure carrying genes.

Homologous chromosomes

Chromosome pair with same genes.

Chromatid

One half of a duplicated chromosome.

Chromatin

Loose DNA-protein material.

Centromere

Region joining sister chromatids.

Gene pool

All genes in a population.

Stabilizing selection

Average traits favored.

Disruptive selection

Both extremes favored.

Directional selection

One extreme favored.

Gene flow

Movement of genes between populations.

Genetic drift

Random changes in allele frequency.

Fitness

Ability to survive and reproduce.

Evolution

Change in populations over time.

Tissue

Group of similar cells working together.

Surface area vs volume

Smaller cells exchange materials more efficiently.

Cell differentiation

Cells become specialized.

Binary fission

Asexual reproduction in prokaryotes.

Stem cells

Undifferentiated cells that can become specialized.

Homeostasis

Maintaining stable internal conditions.

Positive feedback

Amplifies a change (e.g., childbirth contractions).

Negative feedback

Reverses a change to maintain balance (e.g., body temperature regulation).

Stimulus

A change that causes a response.

Hormone

Chemical messenger.

Effector

Carries out a response.

Receptor

Detects a stimulus.

Set point

Normal target condition maintained by homeostasis.