Meiosis Flashcards

Meiosis Overview

• Meiosis produces four haploid cells from a single diploid cell.
• Purpose is to generate genetic diversity for sexually reproducing organisms.

Cellular Preparation

• Interphase is the phase when chromosomes duplicate in preparation for meiosis.

Prophase I Details

• Homologous chromosomes form pairs during prophase I.
• This stage includes the process of crossing over, where segments of nonsister chromatids exchange genetic material, increasing genetic variability.

Meiosis Events Sequence

• The sequence of meiosis events: prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.

Definitions of Key Terms

• Meiosis: The division of a diploid nucleus into four haploid daughter nuclei, producing gametes in reproductive organs.
• Mitosis: The process where a single nucleus divides into two genetically identical daughter nuclei, part of the mitotic (M) phase of the cell cycle.

Chromosome Types and Counts

• Diploid: Cells containing two homologous sets of chromosomes (2n); in humans, this is 46 chromosomes.
• Haploid: Cells with a single set of chromosomes (n); in humans, this is 23 chromosomes.

Cell Types

• Somatic Cells: Any cell in a multicellular organism excluding sperm and egg cells.
• Gametes: Haploid sex cells (sperm or egg) that unite during fertilization to form a zygote.

Chromatids and Structures

• Sister Chromatids: Identical copies of a duplicated chromosome.
• Tetrads: Paired homologous chromosomes consisting of two sister chromatids, formed during prophase I.

Genetic Mechanisms

• Crossing Over: The exchange of genetic segments between chromatids during prophase I, enhancing genetic diversity.
• Nondisjunction: An error in cell division where homologous chromosomes or sister chromatids fail to separate during anaphase.

Genetic Variation and Mutations

• Mutation: A change in the DNA nucleotide sequence; the ultimate source of genetic diversity in organisms.
• Types of mutations include:
  • Deletion: Loss of a DNA segment.
  • Duplication: An extra segment of DNA is added.
  • Inversion: A segment breaks off and reattaches in reverse order.
  • Translocation: A segment from one chromosome attaches to a different chromosome.

Chromosomes and Karyotypes

• Karyotypes: Displays of metaphase chromosomes arranged by size and centromere position.
• Homologous Chromosomes: Matched pairs of chromosomes in diploid cells, having the same genes at corresponding loci.
• Autosomes: Non-sex chromosomes that do not determine the organism's sex.
• Sex Chromosomes: Chromosomes that determine the sex of an individual (X and Y chromosomes).