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Every living organism inherits a blueprint for life from its parent(s). Genetic information is carried inside each and every cell of all living things. INTRODUCTION TO GENETICS AND THE DNA MOLECULE Every living organism inherits a blueprint for life from its parent(s). Genetic information is carried inside each and every cell of all living things. INTRODUCTION TO GENETICS AND THE DNA MOLECULE INHERITANCE OF CHARACTERISTICS Experiments in the 19th century showed that there were heritable factors being passed on to offspring such as eye colour. How were offspring aquiring features from their parents? In the 20th century biologists confirmed that DNA found inside the cells of living things were responsible for these heritable features. INSIDE THE CELL OF PROKARYOTES AND EUKARYOTES DNA is found in the nucleus of the Eukaryotic cell DNA is found in the cytoplasm of the prokaryote as they do not have a nucleus. INSIDE THE NUCLEUS OF A HUMAN CELL There are 46 chromosomes 23 from each parent Each chromosome pair contains the genetic codes for thousands of features. Each genetic code is called a gene. For example, there is a gene which codes for hair colour. A GENE IS A LENGTH OF DNA THAT IS THE UNIT OF HEREDITY AND CODES FOR A SPECIFIC PROTEIN AN ALLELE An allele is one of a number of alternative forms of the same gene For example, the human genome has 23 pairs of chromosomes Lets look at one pair of those chromosomes Along the length of each chromosome are the same genetic codes for example: hair colour, eye colour HOWEVER, the fathers gene for eye colour may indeed be different to the mothers gene for eye colour One parent may be contributing blue eyes, whilst the other is contributing the gene for brown eyes These genes for eye colour are called ALLELES THE ALLELE This pair of chromosomes are homologous, they carry the same sequence of genes if both chromosomes carry the same allele this is called ‘homozygous’ If each chromosome is carrying a different trait of the same gene it is called heterozygous THE HUMAN GENOME CHROMOSOME NUMBER 23 INHERITANCE OF SEX THE COMPLEXITY OF THE GENOME FOUND IN EVERY LIVING THING A CLOSER LOOK AT THE DNA WHICH MAKES UP EACH LINEAR STRAND OF EACH AND EVERY CHROMOSOME A NUCLEOTIDE UNIT OF DNA CONTAINS A SUGAR, PHOSPHATE AND A BASE Nucleotides are the same in every living thing from bacterial cells and plants to cockroaches and elephants! Every living thing on earth contains these genetic components EVERY GENOME OF EVERY LIVING THING CONTAINS ONLY 4 BASES Adenine pairs with Thymine Guanine pairs with cytosine The sequence of these bases codes for each and every gene for every living thing. DEOXYRIBONUCLEIC ACID (DNA) The ‘double helix’ is held together by hydrogen bonds.