biology paper 2

Biology paper 2

DNA- deoxyribonucleic acidègenetic material cell is made from

Contains coded info- instructions to put an organism together and make it work

DNA determined inherited characteristics

Found in nucleus in plant and animal cells in chromosomesèusually in pairs

DNAèpolymer- 2 stands coiled together in a double helix

Gene= small section DNA found on chromosome. Each codes for a particular sequence of amino acids which are put together to make a specific protein. Only 20 used but make 1000s of proteins

Genes tell what order to put amino acids together

DNA determines what protein cell produces e.g. haemoglobin which determined the type of cell.

Genomeèentire set of genetic material in an organism

Scientists worked out whole human genomeèunderstanding = important for science and medicine

¨  Identify genes in genome liked to different kind of diseases

¨  Knowing what genes are connected to inherited diseases and research them better

¨  Trace the migration of certain populations. Genome is almost identical in each personèslight differences in people from different places.

Sexual reproduction-

Genetic info from 2 organisms combine to produce an offspring- genetically diff to each parent.

M+D produce gametes (sex cells) by meiosis- egg and sperm

Each gamete has 23 chromosomes= ½ of normal cellè1 of each chromosome in the cell

Egg and sperm fuse together (fertilisation)= cell with full chromosomes

Sexual reproductionèfusion of male and female gametes- offspring has a mixture of parent’s genes

Receive genes from both parents èdetermines what you are like= variation in offspring

Flowering plants can reproduce but the sperm is pollen

Asexual reproductionèproduce genetically identical cells

Only 1 parent= offspring identical

Happens by mitosisèdivides into 2= a clone

There is no fusion of gametes or mixing of chromosomes or genetic variation the offspring are clones of the parent

Bacteria, some plants, some animals

Gametes-

Produced by meiosisèhalf the normal number of cells

1.  Cell duplicates genetic info= 2 armed chromosomes- 1 arm is and exact copy of the other and arrange into pairs

2.  1^stdivision the pairs line up in the centre of cell and are then pulled apart so each new cell has only 1 copy of each chromosome some father and some mother go into each cell

3.  2^nddivision, chromosomes line up in the centre and arms are pulled apart

4.  Then have 4 gametes with only a single set of chromosomes, each gamete is genetically different as chromosomes are shuffled up- each gamete gets half at random.

After 2 gametes have fused during fertilisation- cell divides by mitosis to copy itself. Repeats to produce an embryo. Cells the differentiate into specialised cells and produce a whole organism.

Chromosomes control gender-the 23^rdpair of chromosomes control your gender ** or XY

Male = XY èthe Y causes the male characteristic èfemale = **

When making…