Biology- Variation and Ineritance

• Characteristic can be inherited or environmental, an example of an inherited characteristic could be a red hair gene. An example of an environmental characteristic could be a height gene.
• Chromosomes are found inside the nucleus of a cell. There are 23 pairs of chromosomes in every human body cell. One of each pair of chromosomes comes from each parent. Chromosomes are made up of long lengths of DNA. A gene is a short section of a chromosome. Each gene codes for a different characteristic. There are different versions of each gene which we call alleles. One is often dominant over the others, which are recessive. DNA is short for Deoxyribonucleic acid. It is a long chain made of 2 strands wound together. This structure is called a double helix.
• If you have the same allele for a particular gene on each chromosome, you are homozygous for that gene
• If you have different alleles for a particular gene of each chromosome you are said to be heterozygous for that gene