Notes on Mitosis

P - Prophase - Apear
M- Metaphase - Middle
A- Anapahse - Apart
T- Telephase- Two

3.24 c

Recap: nucleus contains chromosomes, during interphase cells are involved in DNA replication.

Signs:

1.       Break down of nuclear membrane (nucleus breaks down) known as PROPHASE, chromosomes become visible as a pair of chromatids.

2.       With the nucleus gone, a network of protein molecules “spindle/fibres” extended from one side of the cell to the other. What occurs in late prophase the chromatids will move towards the spindle.

3.       METAPHASE:  chromatids are attached to the spindle fibre in the “middle”

4.       ANAPHASE: the spindle fibre shortens pulling one chromatid one way and the other chromatid another way, they are moving apart, they move to the poles of the cell, separate pair of chromatids.

5.       TELOPHASE: the nucleus begins to reform around the chromosomes at both ends of the cell, so we see the formation of 2 nuclei at opposite sides of the cell

6.       CYTOKINESIS: the cell splits into 2 NOT PART OF MITOSIS, the cell moves inwards dividing the cytoplasm in half, resulting in 2 halfs, NB: the each have 1 chromosome (same as parental cell)

7.       In humans we don’t see 1 cell dividing but 23 pairs separating at 1 time. 

3.24 b

More detail of Mitosis:

Recap: 2 “daughter” cells, same number/same set

Copying the cells is called DNA replication

In this process it forms and identical copy of its cell, held together by the centrolmere  “pair of chromatids” this takes place in the nucleus whilst it is still intact, it is called the “interphase” of the cell cycle

3.24 a

Mitosis: form of cell division which results in growth – occurs by increase in number of cells

OUTLINE of the process:

*cell* the number of chromosomes in the nucleus are knows as the diploid (2n)

Humans: 46 (2n)

Cats: 38 (2n)

This cell will divided into 2 each other them has a diploid nucleus, they are identical “daughter cells”

Identical:

1.       Same number of chromosomes

2.       Same set of chromosomes

How are the copied of chromosomes made?

How do they separate into 2 cells?

3.16

+ A chromosome contains thousands of genes
+ Looking at 1 gene loci you can magnify it to see a double helix - they apear parallel
+ Expanding more you can see the 2 sugar phosphate back bone sides and in between holding them together are the bases.
+ There are 4 types of bases:  Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
+ They are always found in DNA in pairs    T-A      G-C
+ On one side the order of them is ACTGAACCAG "order of bases" this is the order we call a gene
+ The gene is found in the nucleus of a cell: order of the bases and number of the bases = protein in cytoplasm -> characteristic.

3.15

+ A gene is a section of a molecule of DNA
+ Gene carries the information which forms the characteristic of the organism eg: petal colour, blood group
+ Located in the Nucleus the information is then passed onto the cytoplasm, transformed to protein - which controls characteristic.

3.14

+ Chromosomes are the genetic information within a cell.
+ Chromosomes have DNA which forms a shape called a "Double Helix"
+ Genes controls the production of protein which controls a characteristic eg: Blood type.

+ Each species has a different amount of chromosomes per cell: eg: Cat= 38  Chicken= 78  Chimp= 42  Human = 46

+ They operate in pairs "Homologous"   -> based on the length
+ Looking at the same length place on each chromosome there will be the same gene loci -> same gene -> same place
+ Therefore there are two versions of each gene with 1 characteristic = Alleles

3.1 Sexual and Asexual reproduction

#
+ Sexual reproduction: 
Show sex (genders – male/female)
Produce cells called gametes (male=sperm female=egg)
Meiosis- the type of cell division that produces gametes –effect: half the total number of chromosomes in the gamete cell (e.g. chromosomes. Humans: 46 per cell Gametes: 23 per cell, the process from going from 46 to 23 is called Meiosis.
Fertilisation (gametes cells from a male (sperm) fuse together with the gamete cell from a female (egg))
Broad variation (many differences in individuals of population)

+ Asexual reproduction:
DO NOT show sex (genders – male/female)
No gametes
Mitosis (in eukaryotic cells) /binary fission (in prokaryotic bacterial cells) cell with 20 chromosomes  2 cells (each with 20 chromosomes -identical)
No fertilisation (because no gametes)
Small variation – due to mutation (they are identical ‘clone’)


Quetion: What are eukaryotic cells and prokaryotic bacterial cells?