B6- Inheritance, Variation and Evolution

DNA

Chromosomes are ealy long molecules of DNA...

-DNA stands for deoxyribonucleic acid. It contains coded information (instructions to put an organism together and make it work)

-So whatever is in your DNA determines what inherited characterists you have.

-DNA is found in the nucleus of animal and plant cells in really long structures called chromosomes

-Chromosomes come in pairs

-DNA is a polymer. It is made up of two strands coiled together in the shape of a double helix

A Gene Codes for a Specific Protein...

- A gene is a small section of DNA found on a chromosome. Each gene codes for a particular sequence of amino acids which are pt together to make a specific protein.

-Genes tell cells in what order to put amino acids together.

-DNA also determines what proteins the cell produces

Every Organism has a Genome...

-Genome is the entire set of genetic material in an organism

- The genome allows us to; identify genes in the genome that are linked to different types of disease, to know what genes are linked to inherited genes which could help us to understand them more to be able to develop effective treatements ect.

Reproduction

Sexual reproduction produces genetically different cells...-Sexual reproduction is where genetic information from two organisms are combined to produce offspring which are genetically different to either parent.-In sexual reproduction the parents produce gametes by meiosis-In humans each gamete contains 23 chromosomes. The egg and the sperm cell then fuse together to form a cell with the full number of chromosomes.

SEXUAL REPRODUCTION INVOLVES THE FUSION OF MALE AND FEMALE GAMETES. BECAUSE THERE ARE TWO PARENTS, THE OFFPRING CONTAIN A MIXTURE OF THEIR PARENTS GENES.

The offspring inherits features from both parents because it has recieved a mixture of chromosomes from its mum and dad. This allows variation to occur.

Asexual reproduction produces genetically identical cells...-In asexual reproduction there is only one parent so the offspring are genetically identical to that parent.-Asexual reproduction happens by mitosis- an ordinary cell makes a new cell by dividing in two.-The new cell has exactly the same genetic information as the parent cell - this is called a clone.

IN ASEXUAL REPRODUCTION THERE IS ONLY ONE PARENT. THERE IS NO FUSION OF GAMETES, NO MIXING OF CHROMOSOMES AND NO GENETIC VARIATION BETWEEN THE PARENTS AND OFFSPRING. THE OFFSPRING ARE GENETICALLY IDENTICAL TO THE PARENT.

Bacteria, some plants and some animals reproduce asexually

Meiosis

Gametes are produced by meiosis

Meiosis produces cells which are half the normal number of chromosomes...1. Before the cell divides it duplicates its genetic information forming two armed chromosomes. One arm of each chromosomes is an exact copy of another arm. After replication the chromosomes arrange themselves into pairs.2. In the first division in meiosis the chromosme pairs line up in the centre of the cell.3. The pairs are then pulled apart so each new cell only has one copy of each chromosome. Some of the fathers chromosomes and soem…