bio100 exam 2

patrick kibble

Why must mitosis result in identical daughter cells?

Mitosis must produce identical daughter cells so each new cell receives the same DNA needed for normal function, growth, and repair.

Phases of the cell cycle

G1: Cell growth; S: DNA replication; G2: Preparation for division; M: Mitosis and cytokinesis.

Stages of mitosis

Prophase: Chromosomes condense; Metaphase: Chromosomes align; Anaphase: Sister chromatids separate; Telophase: Nuclear envelopes reform.

Cytokinesis in animal vs. plant cells

Animal cells form a cleavage furrow; plant cells form a cell plate that becomes the new cell wall.

Cause of uncontrolled cell growth

Mutations in genes regulating the cell cycle, such as tumor suppressors and proto-oncogenes.

Cancer terms and relationships

Cancer results from uncontrolled cell division; benign tumors do not spread; malignant tumors invade tissues; metastasis is the spread of cancer; oncogenes promote cancer; proto-oncogenes are normal growth genes; telomeres limit cell division.

Sex chromosomes

X and Y chromosomes that determine biological sex.

Autosomes

All non-sex chromosomes.

Somatic cells

Body cells that are diploid.

Gametes

Haploid sex cells used in reproduction.

Diploid

Cells with two sets of chromosomes (2n).

Haploid

Cells with one set of chromosomes (n).

Relationship between meiosis and sexual reproduction

Meiosis produces haploid gametes that combine in fertilization to restore diploidy and create genetic variation.

Stages of meiosis

Meiosis I separates homologous chromosomes; Meiosis II separates sister chromatids.

Mitosis vs. meiosis

Mitosis makes 2 identical diploid cells; meiosis makes 4 genetically diverse haploid cells.

Self-fertilization

When an organism fertilizes itself.

Cross-fertilization

Fertilization between two separate organisms.

True-breeding organisms

Organisms that are genetically uniform (homozygous).

Genes

Units of heredity passed from parents to offspring.

Alleles

Different forms of a gene.

Hybrids

Offspring of genetically different parents.

P generation

The parental generation.

F1 generation

Offspring of the parental generation.

F2 generation

Offspring of the F1 generation.

Heterozygous

Having two different alleles for a trait.

Homozygous

Having two identical alleles for a trait.

Dominant allele

Expressed when present.

Recessive allele

Expressed only when homozygous.

Genotype

The genetic makeup of an organism.

Phenotype

The observable traits of an organism.

Genotypic ratio

Ratio of different genetic combinations in offspring.

Phenotypic ratio

Ratio of observed traits in offspring.

Monohybrid cross

A cross involving one trait.

Dihybrid cross

A cross involving two traits.

Monohybrid ratios (heterozygous × heterozygous)

Genotypic ratio 1:2:1; phenotypic ratio 3:1.

Dihybrid ratios (heterozygous × heterozygous)

Phenotypic ratio 9:3:3:1.

Pleiotropy

One gene influences multiple traits.

Polygenic inheritance

Multiple genes influence one trait.

Multiple alleles

More than two alleles exist for one gene.

Codominance

Both alleles are fully expressed.

Incomplete dominance

Heterozygous phenotype is intermediate between two alleles.

Pedigree usage

Used to trace inheritance patterns in families.

Law of segregation

Allele pairs separate during gamete formation.

Law of independent assortment

Alleles of different genes separate independently.

Why linked genes violate independent assortment

Linked genes are close together on a chromosome and tend to be inherited together.

Why sex-linked diseases are more common in males

Males have only one X chromosome; recessive X-linked traits are expressed.

Sources of genetic variation

Mutation, crossing over, independent assortment, random fertilization.

DNA researchers

Griffith, Avery, Hershey-Chase, Franklin, Watson, and Crick helped establish DNA’s role and structure.

DNA structure

Double helix with deoxyribose sugar and bases A, T, C, G.

RNA structure

Single-stranded nucleic acid with ribose sugar and bases A, U, C, G.

Chromosome structure

DNA wrapped around histone proteins forming chromatin, which condenses into chromosomes.

Chromatin vs. chromosomes

Chromatin is loose DNA; chromosomes are tightly condensed DNA.

Homologous chromosomes vs. sister chromatids

Homologous chromosomes have same genes but different alleles; sister chromatids are identical copies.

Autosomes vs. sex chromosomes

Autosomes are non-sex chromosomes; sex chromosomes are X and Y.

Steps of DNA replication

DNA unwinds, complementary bases pair, two identical molecules form.

Transcription

Producing mRNA from DNA.

Translation

Producing a protein from mRNA at the ribosome.

Mutation

A change in the DNA sequence.

How mutations create diversity

They generate new alleles and traits.

Gene regulation in eukaryotes

Controlled by transcription factors, chromatin structure, enhancers, and RNA processing.

Recombinant DNA

DNA combined from different organisms.

How recombinant DNA is made

Restriction enzymes cut DNA; ligase joins DNA fragments.

Advantages of gene therapy

Can treat genetic disorders by replacing or repairing faulty genes.

Genetic engineering controversy

Involves ethical concerns, safety issues, and environmental risks.

Lamarck’s contribution

Proposed inheritance of acquired traits (incorrect).

Darwin’s contribution

Proposed natural selection as mechanism of evolution.

Lyell’s contribution

Proposed that Earth changes gradually over time.

Wallace’s contribution

Independently theorized natural selection.

Darwin’s observations and deductions

Variation + overproduction lead to competition; individuals with beneficial traits survive and reproduce.

Natural selection

Individuals with advantageous traits leave more offspring.

How evolution occurs

Through genetic variation, natural selection, and allele frequency changes.

Relationship between genetics and evolution

Evolution is change in allele frequencies within a population.

Gene flow

Movement of alleles between populations.

Genetic drift

Random change in allele frequencies, strongest in small populations.

Founder effect

New population founded by a few individuals.

Bottleneck effect

Sharp population reduction reduces genetic diversity.

Evidence for evolution

Fossil record, biogeography, anatomy, molecular biology, embryology.

Major eras of geologic time

Precambrian, Paleozoic, Mesozoic, Cenozoic.

Homologous structures

Same origin, different function.

Analogous structures

Different origin, same function.

Biological species concept

Species can interbreed and produce fertile offspring.

Prezygotic barriers

Prevent mating (habitat isolation, timing, behavior).

Postzygotic barriers

Occur after fertilization (hybrid sterility or inviability).

Allopatric speciation

Speciation due to geographic isolation.

Sympatric speciation

Speciation without geographical separation.

Directional selection

Favors one extreme phenotype.

Disruptive selection

Favors both extreme phenotypes.

Stabilizing selection

Favors intermediate phenotypes.

Microevolution

Small changes in allele frequencies.

Macroevolution

Major evolutionary change leading to new species.

Speciation vs. nonbranching evolution

Speciation splits a lineage; nonbranching evolution changes a lineage without splitting.

Gradualism

Slow, steady evolutionary change.

Punctuated equilibrium

Long periods of little change interrupted by rapid evolution.

Exaptation

Trait evolved for one function but later adapted for another.

Sexual selection

Selection based on traits that improve mating success.

Taxonomy

The science of naming and classifying organisms.

Levels of classification

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

Phylogeny

Evolutionary history of a species.

Cladistics

Classification based on shared derived traits.

Cladogram

Tree-like diagram showing evolutionary relationships.