GENETICS (1.9) EXTERNAL

Intro  Genetics – study of inheritance. How genetic information is transferred from one generation to the next.

Genetic Code  Genetic code – instructions for growth and development of the entire organism.

Genetic Code  Genetic code – instructions for growth and development of the entire organism.  This code determines whether a fertilised egg develops into a tree, bird, human etc. 

Genetic Code  Genetic code – instructions for growth and development of the entire organism.  This code determines whether a fertilised egg develops into a tree, bird, human etc.  This code is carried on the DNA which is found in the chromosomes contained in the nucleus of each cell.

Draw them, and have arrows pointing the direction from smallest to largest.

Chromosomes  Long, thread-like structures found in the nucleus of every cell.

Chromosomes  Long, thread-like structures found in the nucleus of every cell.  Each member of a species has the same number of chromosomes (eg. Horses have 66, humans have 46)

Chromosomes  Long, thread-like structures found in the nucleus of every cell.  Each member of a species has the same number of chromosomes (eg. Horses have 66, humans have 46)  Chromosomes are made up of DNA (DeoxyriboNucleic Acid), as well as protein.

Chromosomes  Long, thread-like structures found in the nucleus of every cell.  Each member of a species has the same number of chromosomes (eg. Horses have 66, humans have 46)  Chromosomes are made up of DNA (DeoxyriboNucleic Acid), as well as protein.  Chromosomes come in pairs, of similar size and shape, called homologous pairs – humans have 23 pairs.

Chromosomes  The 2 chromosomes of an homologous pair carry genetic information for the same characteristics (eg. Hair colour).

Chromosomes  The 2 chromosomes of an homologous pair carry genetic information for the same characteristics (eg. Hair colour).  One chromosome of each pair is inherited from the male parent, and the other from the female parent.

Chromosomes  The 2 chromosomes of an homologous pair carry genetic information for the same characteristics (eg. Hair colour).  One chromosome of each pair is inherited from the male parent, and the other from the female parent.  Chromosomes are not visible until just before the cell divides, when each chromosome becomes shorter and thicker and can be seen through a microscope.

DNA  DNA is a long molecule that has the same basic structure in all living things.

DNA  DNA is a long molecule that has the same basic structure in all living things.  All genetic info a cell needs to grow, function, and reproduce is coded within the cell’s DNA.

DNA  DNA is a long molecule that has the same basic structure in all living things.  All genetic info a cell needs to grow, function, and reproduce is coded within the cell’s DNA.  DNA carries the info for which cells grow, when they grow, which cells make hair, or feathers/fur and what colour this will be.

Structure of DNA  Known as a double helix

Structure of DNA  Known as a double helix  When untwisted, it looks like a ladder. The ‘sides’ of the ladder are made up of thousands of sugar and phosphate groups

Structure of DNA  Known as a double helix  When untwisted, it looks like a ladder. The ‘sides’ of the ladder are made up of thousands of sugar and phosphate groups  The ‘rungs’ of the ladder are made of nitrogen bases – the bases join to the sugar molecules.

Structure of DNA  Known as a double helix  When untwisted, it looks like a ladder. The ‘sides’ of the ladder are made up of thousands of sugar and phosphate groups  The ‘rungs’ of the ladder are made of nitrogen bases – the bases join to the sugar molecules.  Bases are very important because their order forms the genetic code.

Base pairing  A – T  C – G ALWAYS

Proteins  The order of bases along the DNA molecule is the genetic code – this code ‘tells’ the cell what substances to make so the cell can live, grow and replicate.

Proteins  The order of bases along the DNA molecule is the genetic code – this code ‘tells’ the cell what substances to make so the cell can live, grow and replicate.  Three bases in a row are called a triplet and code for a particular amino acid

Proteins  The order of bases along the DNA molecule is the genetic code – this code ‘tells’ the cell what substances to make so the cell can live, grow and replicate.  Three bases in a row are called a triplet and code for a particular amino acid  Amino acids are the building blocks of proteins.

Proteins  The order of bases along the DNA molecule is the genetic code – this code ‘tells’ the cell what substances to make so the cell can live, grow and replicate.  Three bases in a row are called a triplet and code for a particular amino acid  Amino acids are the building blocks of proteins.  A gene is made of a sequence of amino’s coding for a particular protein.

Proteins  Are important because: - They form skin, bones, hair - Make up enzymes which control the chemical reaction of cells (eg. Pepsin and lipase are produced by cells to digest our food)

DNA replication  (I will draw on the board)

Mutations  Errors can occur in the base pairing when DNA replicates, giving a changed order of bases.

Mutations  Errors can occur in the base pairing when DNA replicates, giving a changed order of bases.  A mutation = a change in the genetic code.

Mutations  Errors can occur in the base pairing when DNA replicates, giving a changed order of bases.  A mutation = a change in the genetic code.  They may be spontaneous and random, or they can be influenced by environmental factors such as: - Radiation from the sun/nuclear reaction

Mutations  Errors can occur in the base pairing when DNA replicates, giving a changed order of bases.  A mutation = a change in the genetic code.  They may be spontaneous and random, or they can be influenced by environmental factors such as: - Radiation from the sun/nuclear reaction - Chemicals known as carcinogens (nicotine etc)