What is asexual reproduction?
- Binary fission: cell division in unicellular organisms that produces two new individuals.
- Offspring are genetically identical to parent.
- Does not require fusion of gametes.
What is the cell cycle?
A series of events that takes place in a cell as it grows and divide.
What are the sets of chromosomes in humans?
- Humans have 23 pairs of chromosomes or 46 single chromosomes.
-Autosomes: 22 pairs in humans that are found in somatic cells ( body cells ).
-Sex cells:1 pair in humans found in gametes ( sex cells). - Ploidy: number of chromosomes occurring in nucleus.
- Diploid: humans have 23 pairs of chromosomes (1+1).
- Halpoid: gametes have 1 member of each pair of chromosomes or 23 total chromosomes (1).
What are homologues?
- Autosomes: each homologue nearly identical in size and genetic information.
- Sex chromosomes: X & Y differ in size and genetic composition (X+X).
What are the stages of cell cycle?
- Interphase (90%).
- Mitosis (10%).
What are the phases of interphase?
- G0: substitutes for G1 for cells postponing cell division or never diving again.
- G1 phase: cell organelles grow and doubles.
- S phase: synthesis of DNA.
4, G2 phase: preparing for mitosis by producing microtubules.
What are the stages of mitosis?
- Prophase.
- Metaphase.
- Anaphase.
- Telophase.
What happens in prophase?
- Nucleolus & nuclear envelope disappear.
- Nuclear membrane dissociates.
- Chromatids condense.
- Sister chromatids interact with mitotic spindle.
What happens in metaphase?
Sister chromatids are aligned across the metaphase plate.
What happens in anaphase?
- Connections between sister chromatids are broken.
- Kinetichore microtubules shorten while poles pull away from each other pulling chromosomes towards the pole.
What happens in telophase?
- Chromosomes reach their destination and de-condense.
- Nucleolus & nuclear envelope are formed.
- Nuclear membrane is formed and produces two nuclei.
What happens in cytokinesis?
Division of cytoplasm separates two nuclei to two daughter cells.
What happens in meiosis l?
- Prophase l.
- Metaphase l.
- Anaphase l.
- Telophase l.
- Cytokinesis.
What happens in prophase l?
- Chromosomes condense.
- Crossing over between chromatids takes place (bivalent or tetrad is formed).
- Nuclear envelope and nucleolus disappear.
- Nuclear membrane dissociates.
- Mitotic spindle is formed and interacts with chromatids.
What happens in metaphase l?
Tetrad or bivalent is aligned along the metaphase plate.
What happens in anaphase l?
Connection between tetrad or bivalent is broken as the kinetochore microtubules pull away from each other.
What happens in telophase l?
- Sister chromatids have reached their destination.
- Chromosomes de-condense.
- Nuclear envelope and nucleolus forms.
- Nuclear membrane is formed again and two nuclei are formed.
What happens in cytokinesis of meiosis l?
Two nuclei are separated to two haploid daughter cells by formation of cytoplasm.
What does meiosis ll produce?
Four haploid daughter cells (sex cells).
