Identify the Role of Cell Division in Growth and Repair

1. Identify the role of cell division (mitosis) in growth and repair.

There are 2 types of cell division:

Mitosis produces 2 daughter cells that are identical to the parent cell. This is the type of cell division involved in growth and repair of the body.

Meiosis is the process of cell division that produces the gametes- sperm and eggs.

Mitosis causes growth and repair by providing more identical cells to replace old, damaged or missing cells for repair or to produce more tissue for growth.

1. Explain using an example what is meant by the term mutation.

Mutation is a change in a gene that produces different characteristics.

A mutation is a permanent change in the sequence of DNA. The term mutation means a change in a gene or chromosomes during the process of reproduction. E.G Radiation (X-Ray), chemicals and Cancer.

1. During reproduction the transmission of heritable characteristics from one generation to the next involves DNA and genes. Genes which control eye colour, hair colour and skin colour.
2. Outline the Watson-Crick model of DNA ie. The 4 bases and the sugar phosphate backbone and how this results in the exact replication of DNA

The two scientists discovered the double helixr structure o DNA are James Watson and Francis Crick. There are 4 nitrogen bases Adenine (A), Thymine (T), Cytosine (C) and Guanine (G).The nitrogen bases pair up to form the rungs. This means that they can only pair up in one way, a characteristic known as complementary base pairing A-T and G-C.  The basic units or building blocks of DNA are called Nucleotides. A nucleotide is composed of a Nitrogenous base, a phosphate and sugar. A nucleotide is a strand of DNA that consists of genetic materials in the form of chromosomes.

[pic 1]

1. Use models and diagrams to represent the relationship between DNA, genes and chromosomes.

Chromosomes are X shaped objects found in the nucleus of most cells. They consist of long stands of a substance called deoxyribonucleic acid or DNA for short. The cells in the human body each contain 46 chromosomes arranged in 23 pairs. The only exceptions are Gametes- The sperm and egg cells, which only contain 23 chromosomes (one of each pair). The number of chromosomes in your body cells is known as the diploid number.

Gene lie in long strands of DNA called chromosomes. A gene consists of a long combination of 4 different nucleotide bases. The 4 nucleotides are A,C,G,T. Your genes make you what you are.

DNA is composed of 4 unites that pair together and the pairs join together in long strings. This is sometimes referred to as the double helix.

[pic 2]

1. The child has black hair because the gene for black hair is more powerful than the gene for blond hair. It dominates the gene for blond hair and produces the final colour. Genes who dominate other genes are called dominant genes. Genes who are dominated are called recessive genes. When a dominant gene pairs up with a recessive gene, the dominant one produces the final effect. Capital letters are used for dominant genes and small letters for recessive genes.

Homozygous and heterozygous:

A person with 2 identical gens for a characteristics is are homozygous for that characteristic.(HH is a homo gene) A person with two different genes (1 dominant and 1 recessive) for a characteristic are heterozygous for that characteristic.

Heredity- The passing of traits from parents to child is the basis of heredity.

Daughter cells- the new cells which are formed from pre existing cells as a result of division are called daughter cells. Pre existing cells are known as mother cells.