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DNA and the GENOME

​Lesson Objectives

• To state that DNA contains a code to build proteins.

• To describe the relationship between DNA, genes, and chromosomes and describe some of the benefits of studying the human genome.

• To explain why knowledge of the genomes of other species is useful.

DNA

• Inside the nuclei of cells, chromosomes are made up of long molecules of DNA.

• DNA stands for deoxyribonucleic acid – it is the chemical that all of out genetic material is made of.

• DNA is a polymer – a large molecule built from a chain of smaller molecules.

• These long strands of DNA twist and spiral to form a double helix structure.

• If you were to take all of the DNA in a single cell and unravel it into a single strand, it would be 2m in length – this is why it is split across 46 chromosomes.

Structure of DNA

Nucleotide and Bases

• DNA strands are polymers made up of many repeating units called nucleotides.

• Each nucleotide consists of a sugar, a phosphate group and a base

• There are four types of bases – A, C, G, and T. Each sugar joins to a base.

• The sugars and phosphate groups form a ‘backbone’ to the DNA strands.

• It is the order of bases in a gene that decides the amino acids in a protein.

• Each amino acid is coded for by a sequence of three bases in the gene, and the amino acids join to form proteins.

• Each base in a DNA strand links to a base on the opposite strand in the helix. A base will only pair up with its complimentary pair:

•A and T / T and A

•C and G / G and C

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​Complimentary Base Pair

Gene

• A gene is a small section of DNA found on a chromosome.

• Each gene codes for a particular sequence of amino acids which are put together to make a specific protein.

• Only 20 amino acids are used, but they make up thousands of different proteins.

• Genes simply give the instructions for the sequence of amino acids that need to be put together.

Gene

Eyes upfront...Pay attention to the video!!

​Human Genome Project

• Genome à the entire set of genetic material in an organism

• This includes all of the chromosomes and the genetic material found in the mitochondria as well.

• Mitochondria have their own DNA that is always inherited from the mother because it comes from the mitochondria in the egg.

• The human genome contains over 3 billion base pairs and almost 21,000 genes that code for proteins.

​Human Genome Project

• The Human Genome Project started in 1990 and was completed in 2003.

• Scientists from different universities across the world collaborated to determine the sequence of base pairs that made up the genome of a random man and women.

• Since the initial human genome was read, scientists have carried on with their work – they are currently busy with the 100,000 genomes project. The overall aim is to find out as much as possible about human DNA.

​Why does Genome matter?

• Understanding the genome has taken years and comes at a considerable financial cost, however the effort is deemed worthwhile in facilitating:

• Understanding the genome helps us to understand inherited disorders such as cystic fibrosis and sickle cell disease.

• Furthering the search to linking genes to different types of disease such as Type 2 diabetes.

• Analysis of genomes of cancer cells to select the best treatment for individuals.

• Understanding evolution and history, such as migration patterns.