B5

Uzair Arif
Mind Map by Uzair Arif, updated more than 1 year ago
Uzair Arif
Created by Uzair Arif about 5 years ago
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Mind Map on B5, created by Uzair Arif on 03/30/2015.

Resource summary

B5
1 DNA
1.1 A double helix of paired bases
1.2 Each strand is made up of little nucleotides
1.3 Each nucleotide contains a base: A, T, C, G
1.3.1 A-T and C-G
2 Proteins
2.1 Genes are sections of DNA that contain instructions for particular proteins
2.2 Cells make proteins by joining amino acids in a particular order
2.3 The order of the bases in a gene tell the cell in what order to put the amino acids together
2.4 They are made in the cytoplasm by ribosomes
2.5 DNA cannot move out of the nucleus because it is too big, so a copy of the DNA is made using mRNA
2.5.1 mRNA is shorter and only has one strand
2.5.2 1, The two DNA strands unzip and a molecule of mRNA is made using one strand of DNA as a template
2.5.3 2. The mRNA moves out of the nucleus and joins the ribosome In the cytoplasm
2.5.4 3. The ribosome sticks the amino acids together in a chain to make a protein, following the order of the bases in the mRNA
3 Cell Division
3.1 Mitosis
3.1.1 1. The cell has two copies of its DNA all spread out in long strings
3.1.2 2. Before the cell divides, the DNA forms X-shaped chromosomes. The two arms are duplicates of each other
3.1.3 3. The chromosomes line up at the centre of the cell and their fibres pull them apart; the two arms of each chromosome go to opposite ends of the cell
3.1.4 4. Membranes form around each sets of the chromosomes; these become the nucluei of the two new cells
3.1.5 5. Finally, the cytoplasm divides
3.1.6 You now have two new cells containg exactly the same DNA - they're genetically identical to each other and the parent cell
3.2 Meiosis
3.2.1 1. The cell duplicates its DNA - one arm of each chromosome is an exact copy of the other
3.2.2 2. The chromosome pairs line up in the centre of the cell
3.2.3 3. The pairs are pulled apart so each new cell only has one copy of each chromosome
3.2.4 4. The chromosomes line up again in the centre of the cell and the arms of the chromosomes are pulled apart
3.2.5 5. You get four gametes with only a single set of chromosomes in it
3.2.6 After two gametes join at fertilisation, the zygote grows by repeatedly dividing by mitosis
4 Animal Development
4.1 Embryonic stem cells can be divided to produce ANY type of specialised cell
4.1.1 Used to replace faulty cells in sick people
4.2 Adult stem cells can be divided into SOME but NOT all types of cells
4.2.1 Used to cure sickle-cell anaemia (blood disease) by bone marrow transplants as it contains stem cells that can turn into new blood cells to replace the faulty ones
4.3 Genes can be switched on if they're needed during development
4.4 Cloning
4.4.1 1. Remove a nucleus from an egg cell
4.4.2 2. A nucleus from a body cell of the adult you're cloning is inserted into 'empty' egg cell
4.4.3 3. Under correct conditions, inactive genes in the nucleus of the body cell can be reactivated (switched on) so that an embryo forms
4.4.4 4. Embryonic stem cells can then be extracted from the embryo - these stem cells could then be controlled to form any type of specialised cell
5 Meristem Cells
5.1 The only cells that are mitotically active are found here
5.2 Found in areas of a plant that are growing - roots and shoots
5.3 Produce unspecialised cells that are able to divide and form any cell type
5.4 Unspecialised cells become specialised to form tissues like xylem and phloem (the water and food transport tissues)
5.5 These tissues can group together to form organs like leaves, roots, stems and flowers
6 Phototropism
6.1 A certain direction in which a plant responds to light
6.2 Positive Phototropism - plants grow towards sunlight for photosynthesis
6.3 Negative Phototropism - plants grow away from light so the roots travel down into the soil where they can absorb water
7 Auxins
7.1 Chemicals that control growth near the tips of shoots and roots
7.2 Produced in the tips and diffuse backwards to stimulate the cell elongation process
7.3 If the tip of a shoot is removed, no auxins are available and the shoot may stop growing
7.4 When a shoot tip is exposed to the light, more auxins accumulate on the side that's in the shade than the side that's in the light
7.5 This makes the cell grow (elongate) faster on the shaded side, so the shoot grows towards the light
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