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Gametes
Sperm and egg that fuse to form a zygote.
Meiosis
A single cell divides twice to produce four haploid gametes.
Gametogenesis in males
Males produce four sperm.
Gametogenesis in females
Females produce one egg and three polar bodies.
Genetic variation mechanisms
Crossing-over, independent assortment, and random fertilization.
Haploid gametes
Needed so that after fertilization, the chromosome number remains constant.
Prophase I of meiosis vs prophase of mitosis
Homologous chromosomes pair up in meiosis but not in mitosis.
Independent assortment
Randomly distributes maternal chromosomes into different gametes.
Crossing-over
The exchange of genetic material between non-sister chromatids.
Human sperm
Are haploid.
Sister chromatids during meiosis I
Do not separate.
Cells produced after meiosis
Four cells are produced.
Metaphase I
Stage of meiosis where homologous chromosomes line up in the center.
Anaphase II
Stage where sister chromatids separate.
Anaphase I
Stage where homologous chromosomes separate.
DNA before cell division
Chromatin condenses into chromosomes.
Phases of mitosis
Prophase, metaphase, anaphase, telophase.
Cytokinesis in animal cells
The cytoplasm divides, forming two cells.
Mitosis vs cytokinesis
Mitosis divides the nucleus; cytokinesis divides the cytoplasm.
X-shaped chromosome
Represents a replicated chromosome before cell division.
Chromosome components
Centriole is NOT part of a chromosome.
Sister chromatids not separate
One daughter cell gets too many chromosomes.
Order of cell division steps
DNA replication → DNA condensation → chromosome alignment → chromatid separation → cytokinesis.
Nuclear envelope breakdown during mitosis
Allows spindle fibers to attach to chromosomes.
Spindle fibers
Fibers that attach to centromeres during mitosis.
Chromosomes during anaphase
Do not begin to uncoil.
Sister chromatids during cytokinesis
Do not line up along the equator.
Mitosis
Results in two daughter cells with identical DNA.
Eukaryotic cell cycle phases
Interphase and M phase.
Phases of interphase
G1, S, G2.
Cell cycle control
Through checkpoints and regulatory proteins.
Cancer and the cell cycle
Cancer cells ignore checkpoints and divide uncontrollably.
Complexity of eukaryotic cell division
Due to multiple chromosomes and a nucleus.
Major steps of eukaryotic cell division
Mitosis and cytokinesis.
Interphase duration
Cells spend most of their lives in interphase.
Phases with twice the normal DNA
S and G2 phases.
Damaged gene for cell cycle regulatory protein
The cell may lose control and divide uncontrollably.
Cell splitting during interphase
A cell does not fully split into two.
G1 checkpoint failure
Cells enter G0.
Cytokinesis in prokaryotes and eukaryotes
Occurs in both.
G2 phase
The interphase phase is where the cell prepares for division.
