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VCE Biology: Unit 2 - Coggle Diagram
VCE Biology: Unit 2
Asexual Reproduction
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Parthenogenesis
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In bees, unfertilized eggs become males, fertilised eggs become
Binary Fission
In bacteria cells, the cell elongates and doubles its size, the DNA is replicated and the cell divides
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Spore Formation
Fungi produce spores (like seeds), if the spores are on a suitable substrate it will germinate and produce mycelium.
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Disadvantages
If a harmful change in the environment occurs, all organisms will be affected
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The Cell Cycle
Interphase
Synthesis (S): The parent cell synthesises or replicates its DNA. At the end of this stage, the cell will have two identical copies of DNA
G2: Further growth in preparation for division occurs, proteins for the mitotic spindle are synthesised. By the end, the cell has doubled in size
G1: The cell undergoes growth and produces more cytosol. The mitochondria divide (for plants the chloroplast)
Mitosis
Prophase
The nuclear membrane breaks down, chromosomes appear, spindles extend from the centrioles
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Metaphase
(M for middle) The chromosomes align in the middle of the cell The spindles attach themselves to the centromere of each pair of chromosomes
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Anaphase
(A for away)The chromosomes, divide in two and the chromatids are pulled to the other end of the cell by the spindles
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Telophase
The cytoplasm divides, the nuclear membrane reforms and two daughter cells are produced
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Growth, repair, maintenance
Cell Checkpoints
G2 checkpoint: The replicated DNA is checked for completeness and lack of damage. If this check is passed, the cell will begin mitosis
M checkpoint: This checks that the sister chromatids are attached to the right microtubule. This ensures that the sister chromatids are pulled in to the correct pole of the cell
G1 checkpoint: At this pint the cell is ready begin division, so the DNA is checked. If it is damaged or incomplete the cell discontinues the cell cycle and may be destroyed or enter the G0 phase
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Inheritance
Terms
Monogenetic traits: one gene codes for trait eg. attached or free earlobes, cystic fibrosis
Polygenic traits: many genes code for a trait. Eg. height. Expressions of this trait within a population exists on a bell curve
Crosses
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Test cross
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A pure-breeding organism for a recessive trait (r) is bred with the unknown. If the progeny is 50:50 Rr:rr, the unknown organism is heterozygous. If all progeny are Rr, it was homozygous dominant.
Dihybrid cross
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Inheritance combination of one parent, times each gene by the other
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Patterns of dominance
Incomplete dominance: Both alleles are expressed ad in intermediate between the two. Red x White = pink flower
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Co-dominance: Both dominant Alleles are expressed as a combination in the phenotype. Eg. red and white flowers breed, offspring is spotty red and white
Sexual Reproduction
Stem Cells
Types of Embryonic Cells
Unipotent
can form only one type of cell (epidermal, skin cells)
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Multipotent
Three types ells that can form certain organs. Ectoderm, Mesoderm, Endoderm
Pluripotent
Can form all types of cells in the body, except for those that are part of the placenta etc.
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The cells of embryo (totipotent) divide. At 16 cells,
Cloning
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Embryo splitting
An embryo is inseminated in a laboratory. When the Embryo begins to develop to form 8 cells, the embryo is split forming two identical embryos. These are then transferred back into the uterus of separate animals
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