Biology Final Review: Cell Cycle, Genetics, and Evolution

G1 (Gap 1)

Cell grows, performs normal functions, prepares for DNA replication.

S (Synthesis)

DNA is replicated.

G2 (Gap 2)

Prepares for mitosis (protein and organelle synthesis).

Checkpoints (G1, G2, M)

Control transitions; ensure conditions are right.

Cyclins/CDKs

Proteins that regulate the cycle.

Apoptosis

Programmed cell death if errors are detected.

Diploid (2n)

Full set of chromosomes (e.g., somatic cells).

Haploid (n)

Half the number of chromosomes (e.g., gametes).

Gametes

Sex cells (sperm/egg), haploid.

Somatic Cells

All body cells, diploid.

Chromatin

Unwound DNA in interphase.

Chromosomes

Condensed DNA during cell division.

Chromatid

One of two identical DNA strands.

Centromere

Region joining sister chromatids.

Telomere

Protective ends of chromosomes.

Kinetochore

Protein where spindle fibers attach.

Prophase

Chromosomes condense, spindle forms, nuclear envelope breaks down.

Metaphase

Chromosomes align at cell center.

Anaphase

Sister chromatids pulled apart.

Telophase

Nuclear envelopes reform, chromosomes uncoil.

Cytokinesis

Cytoplasm divides (cleavage furrow or cell plate forms).

Mitosis

1 division round resulting in 2 identical diploid cells for growth & repair.

Meiosis

2 division rounds resulting in 4 unique haploid cells for sexual reproduction.

Genotype

Genetic makeup (e.g., Bb).

Phenotype

Physical expression (e.g., brown eyes).

Homozygous

Two identical alleles (AA or aa).

Heterozygous

Two different alleles (Aa).

Monohybrid Cross

1 trait (e.g., Aa × Aa).

Dihybrid Cross

2 traits (e.g., AaBb × AaBb).

Genotypic ratio

Count each genotype (e.g., 1:2:1).

Phenotypic ratio

Count dominant vs recessive traits.

Dominant/Recessive

One allele masks the other.

Codominance

Both alleles are expressed (e.g., AB blood).

Incomplete dominance

Blended phenotype (e.g., red + white = pink).

sex-linked traits

On X or Y chromosome (e.g., color blindness).

Polygenic Traits

Multiple genes (e.g., height, skin color).

Acquired Traits

Traits gained after birth; not inherited (e.g., scars, dyed hair).

Pedigrees

Circles = females, squares = males; shaded = expresses trait.

DNA Nucleotide

Deoxyribose + phosphate + A/T/C/G.

RNA Nucleotide

Ribose + phosphate + A/U/C/G.

Helicase

Unzips DNA.

DNA polymerase

Builds new strands.

Ligase

Seals fragments.

mRNA

Messenger RNA; carries code.

tRNA

Transfers amino acids.

rRNA

Makes ribosomes.

Transcription

Copy DNA to mRNA.

Translation

Make protein from mRNA.

Codon

3 mRNA bases (occurs during protein synthesis)

Anticodon

Complementary tRNA triplet.

Point mutation

Substitution.

Frameshift

Insertion/deletion.

Silent/Neutral mutation

No effect.

Missense mutation

Wrong amino acid.

Nonsense mutation

Stops early.

Natural Variation

Variations increase survival/reproduction → pass on traits.

Adaptation

Trait that improves survival/reproduction.

Fitness

Reproductive success.

Natural Selection

Nature selects traits best fitted for environment

Artificial Selection

Humans select traits (e.g., dog breeding).

Stabilizing Selection

Average favored.

Directional Selection

One extreme favored.

Disruptive Selection

Both extremes favored.

Speciation

New species form.

Genetic Drift

Random changes in small populations.

Bottleneck

Drastic reduction in population.

Founder Effect

New population from few individuals.

Hardy-Weinberg Principle

No evolution occurs if: No mutation, large pop, no migration, random mating, no selection.

Coevolution

Species evolve together.

Convergent Evolution

Similar traits, different ancestors.

Divergent Evolution

Different traits, common ancestor.

Taxonomic Order

Kingdom, Phylum, Class, Order, Family, Genus, Species.

Homologous Structures

Same structure, different function (common ancestor).

Analogous Structures

Different structure, same function (no common ancestor).

Mendel

Laws of inheritance; pea plant experiments.

Chargaff

Base pairing rules (A=T, G=C).

Watson & Crick

Discovered DNA double helix structure.

Darwin

Natural selection theory; On the Origin of Species.

Wallace

Co-discovered natural selection with Darwin.

Lamarck

Inheritance of acquired traits (later disproven).

Hardy & Weinberg

Principle of genetic equilibrium in populations.