ANSC 221: G1-Lecture 21 (Genetics)

Genetics

Branch of biological science that relates to heredity and population variation.

Cell division

Mitosis and meiosis.

Genome

Cells genetic info (DNA); the blueprint; eukaryotic genomes consist of many DNA molecules.

Reproductive cells

Gametes (Sperm & eggs); one set of chromosomes (haploid, n).

Somatic cells

All body cells except the reproductive cells; have 2 sets of chromosomes (diploid, 2n); one set is inherited from each parent.

Chromosome

Consists of one DNA molecule associated with many proteins —> chromatin; chromatin varies in degree of condensation during the process of cell division.

Sex chromosomes

Responsible for determining the sex of an individual.

Autosome

Any chromosomes other than sex chromosomes.

Homologous chromosomes (homologs)

Two chromosomes of a pair; same length, centromere position, and staining pattern; both chromosomes carry genes at equivalent loci that control the same inherited traits.

Cell division in multicellular eukaryotes

Development from a fertilized egg; continues to function in renewal and repair.

Sexual reproduction

Two parents give rise to offspring.

Fertilization

Union of male and female gametes; transmits genes of parents to their offspring.

Offspring

Resemble parents but are not identical, even siblings.

Interphase

Phase of the cell cycle that includes G1 phase (metabolic activity and growth), S phase (metabolic activity, growth, and DNA synthesis), and G2 phase (metabolic activity, growth, and prep for cell division).

Mitosis

Division of nucleus; distribution of identical genetic material (chromosomes of DNA) to two daughter cells.

Cytokinesis

Division of cytoplasm; produces two daughter cells.

Stages of mitosis

1. Prophase: nuclear envelope disappears; 2. Prometaphase: kinetochores connect the chromosomes; 3. Metaphase: microtubules pull the chromosomes in the metaphase plates (middle of the cell); 4. Anaphase: microtubules rip them apart; 5. Telophase: division of the cytoplasm.

Meiosis

Reproductive cells, cell division that produces gametes (sperm, egg) with half the chromosome of parent cells; reduces the number of chromosome sets from two; has 2 cycles of division.

Crossing over

DNA molecules of nonsister chromatids of homologous chromosomes are broken and rejoined to each other.

Chiasmata

X-shaped regions where crossovers have occurred.

Function of cell division

Growth and repair (mitosis) and reproduction/genetic variation (meiosis).

Somatic cells definition

Any other cell other than gametes (diploid).

Reproductive cells definition

Gametes (haploid).