Heredity and Gene Expression Genetics – the study of heredity
Lesson Objectives At the end of this topic you should be able to Discuss the variation and diversity of organisms Define the term species Define the term heredity Give an example of heredity Define the term gene expression Example of a gene expression Definition of a gene Outline the role of a gene Know the structure of a chromosome – refer to DNA and protein structure
Variation Variation means that there are differences between members of the same species i.e. a population Think of all the variations within your class even though you are all human
Species A group of organisms capable of interbreeding and producing fertile offspring. Humans Cats Dogs Oak Trees Ash Trees
Tiger – a member of the cat family http://commons.wikimedia.org/wiki/File%3APanthera_tigris_tigris.jpg
Lion – a member of the cat family http://commons.wikimedia.org/wiki/File%3ALion_in_masai_mara.jpg
Liger = Male Tiger + Female Lion http://commons.wikimedia.org/wiki/File%3ALiger_couple.jpg
Liger Family in Chinese Zoo http://files.redux.com/images/f2f1c0d86ce7601a4ce421f71d994f40/raw
Tigon = Male tiger + Female Lion http://www.lifeinthefastlane.ca/wp-content/uploads/2007/10/tigons_sfw.jpg Males are sterile but female are fertile – so not a new species
Learning Check What is meant by variation? Give the definition for species Why is a liger not a new species?
Heredity Heredity is the passing on of features from parents to offspring by means of genes Also called Genetic Inheritance
Genes A gene is a length of DNA that codes for a specific protein It is the unit of inheritance It is found on a chromosome It contains instructions to make a particular protein It directly influences the characteristics of an organism
Genes • Characteristics are controlled by genes. • For example everyone has genes which determine hair colour. • But not everyone has the same version of those genes. • So there is more than one type of gene for hair colour that you could have.
Gene Expression Not all genes are expressed Genes produce characteristics or traits that are inherited Eg: Gene for Tallness Organism is small – Why? Maybe due to poor nutrition
Characteristics Characteristics = heredity + environment
Learning Check Heredity is the passing on of _________ from parents to ______________ by means of ______. A gene is the unit __________________. They are found on a _________________. Theycontain ________________ to make a particular _______________. Gene expression is the way in which _____ ________ in a gene is decoded.
Chromosomes Chromosomes contain a number of genes
Chromosome Structure Chromosomes are made up of 60% protein 40% DNA Genes are arranged along the DNA of the chromosome
Non Coding DNA Large sections of the chromosome do not contain genes This DNA is called Non Coding DNA It’s function is not yet clear
Chromosomes Thread like structures Contain DNA Contain Protein Contain Genetic Information Occur in pairs Found in the nucleus of all cells
What have you learned? Can you ……………. Define the term heredity Define the term gene Outline the role of a gene Define the term gene expression Know the structure of a chromosome