Lesson Board

3.14 Chromosome disorders

3.24c - Mitosis

When a cell first breaks down it shows that it is entering the process of mitosis and cell division.
Chromosomes become visible as "chromotids" in a pair after the breakdown of the membrane.
As cell division carries on fibres form and each end of the cells.
Chromotids line up in the middle of the cell and are pulled apart by fibres.
The nucleus forms around the chromosomes at each end causing two nuclies.

Phases:
INTERPHASE
PROPHASE
LATE PHROPHASE
METAPHASE
ANAPHASE
TELOPHASE

3.24b Mitosis

• Chromosomes make identical copies of themselves.
• Two daughter cells form with the identical chromosomes and the parent cells.
• When this happens it is DNA replication.
• What hold the DNA together is something called the centromere which is located in the middle of the chromosome.
• When this occurs they are know as a pair of chromotids.

3.24 a - Mitosis

mitosis - cell division --> growth/increase in number of cells

Outline of process:

- begin with cell - with nucleus.
- number of chromosomes in the nucleus - diploid number (2n)
- for humans 2n = 46
- for cats 2n = 38

- mitosis - cell divides into two cells, each with nucleus, each cell has a diploid nucleus - these cells are identical/daughter cells
- identical because 1. Same number of chromosomes. 2. same set of chromosomes

3.16 DNA and Genetic information

- One chromosome contains thousands of genes.
- There are 4 kinds of bases called: Adenine, Guanine, Cytosine and Thymine.
- gene loci --> double helix - parallel
- double helix --> 'sugar - phospate backbone'
- in the center, group of molecules called bases
- Adenine, thymine, cytosine and guanine
- in the molecule they are holding together the two helisis

- pairing between A-T and G-C - base pairs (ALWAYS in DNA)
- order of the bases on right side A, C, T, G, A, A, C, C, A, G --> this is the gene




- Gene in the nucleus - order of the bases (ATGC)
- number of the bases

this constructs a protein in the cytoplasm - gives characteristic