BIOL1102 Lecture Notes - Lecture 11: Metaphase, Egg Cell, Zygote

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The cell cycle:
- Overview: the key roles of cell division
- The continuity of life:
o Is based upon the reproduction of cells, or cell division
Unicellular organisms:
- Reproduce by cell division
Multicellular organisms depend on cell division for:
- Development from a fertilised cell
- Growth
- Repair
Cell division:
- Cell division results in genetically identical daughter cells
- Cells duplicate their genetic material
o Before they divide, ensuring that each daughter cell receives an exact copy of
the genetic material, DNA
- A genome:
o Is a ells edowet of DNA, its geeti iforatio
Chromosomes: (what our DNA is when it is condensed)
- DNA molecules in a cell are packaged into chromosomes
Eukaryotic chromosomes:
- Consist of chromatin, a complex of DNA and protein that condenses during cell
division
- In animals:
o Somatic cells have two sets of chromosomes
o Gametes have one set of chromosomes
- In preparation for cell division:
o DNA is replicated and the chromosomes condense
- Each duplicated chromosome has two sister chromatids, which separate during cell
division
Eukaryotic cell division consists of:
- Mitosis, the division of the nucleus
o Cytokinesis, the division of the cytoplasm
- In meiosis:
o Sex cells are produced after a reduction in chromosome number
The cell cycle consists of interphase and the mitotic phase:
- The mitotic phase alternates with interphase in the cell cycle
- Interphase can be divided into subphases:
o G1 phase (G for gap. First gap phase)
o S phase (S for synthesis. DNA synthesis)
o G2 phase (Second gap phase)
- The mitotic phase:
o Is made up of mitosis and cytokinesis
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In a cell in which DNA synthesis has occurred:
- All the chromosomes are duplicated and thus each consists of two identical sister
chromatids
-
Homologous chromosomes:
- are the two chromosomes composing a pair
- have the same characteristics
- may also be called autosomes
Sex chromosomes:
- are distinct from each other in their characteristics
- are represented as X and Y
- determine the sex of the individual, XX being female, XY being male
A diploid cell:
- has two sets of each of its chromosomes
- in a human has 46 chromosomes (2n = 46)
A karyotype:
- is an ordered, visual representation of the chromosomes in a cell
-
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Document Summary

Overview: the key roles of cell division. Is based upon the reproduction of cells, or cell division. Cell division results in genetically identical daughter cells. Cells duplicate their genetic material: before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, dna. Is a (cid:272)ell(cid:859)s e(cid:374)dow(cid:373)e(cid:374)t of dna, its ge(cid:374)eti(cid:272) i(cid:374)for(cid:373)atio(cid:374) Chromosomes: (what our dna is when it is condensed) Dna molecules in a cell are packaged into chromosomes. Consist of chromatin, a complex of dna and protein that condenses during cell division. In animals: somatic cells have two sets of chromosomes, gametes have one set of chromosomes. In preparation for cell division: dna is replicated and the chromosomes condense. Each duplicated chromosome has two sister chromatids, which separate during cell division. Mitosis, the division of the nucleus: cytokinesis, the division of the cytoplasm. In meiosis: sex cells are produced after a reduction in chromosome number.

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