1 Genetics An Introduction

2 Genes – Made up of DNA Characteristics that you inherit from your parents are sometimes called traits Characteristics that you inherit from your parents are sometimes called traits These traits are coded for by genes which are passed on from your parents when their sperm and egg cells unite. These traits are coded for by genes which are passed on from your parents when their sperm and egg cells unite. Genes code for the production of all the proteins in your body and carry instructions for your development Genes code for the production of all the proteins in your body and carry instructions for your development Genes are made up of short segments of DNA Genes are made up of short segments of DNA

3 DNA DNA is made up of two strands (shown here in blue and red). The strands are held together by nitrogen bases (shown here in yellow) There are four nitrogen bases: Cytosine, Guanine, Adenine and Thymine What pairs with C? What pairs with A?

4 The Code In each gene there is a code for making protein. The code is determined by the order of the nitrogen bases A, T, G & C. The code is copied and then read by your cell machinery so proteins can be made.

5 Living things All living things contain DNA or a similar substance (RNA) which allow genetic information to be passed from one generation to another All living things contain DNA or a similar substance (RNA) which allow genetic information to be passed from one generation to another All living things reproduce All living things reproduce Some of the DNA that humans have is shared by other living things also Some of the DNA that humans have is shared by other living things also

6 We share 61% of our DNA with flies We’re 92% like a mouse! And 98% like a chimpanzee Source: Mouse Drosophila: Chimpanzee: WE ARE DIFFERENT IN MANY WAYS, BUT IN MANY WAYS WE ARE THE SAME!

7 Where do you find DNA? All mature cells contain DNA except your red blood cells. DNA is found in the nucleus. This is a large structure found in the cell. Nucleus Source:

8 chromosomes The DNA in the nucleus of your cells is tightly wound up to form chromosomes so as to take up less space and avoid being tangled

9 DNA is packed into chromosomes You have 46 chromosomes in each of your somatic cells. You inherited these from your parents: 23 from mum and 23 from dad The chromosomes you inherit determine what you look like. Source: Chromosome:

10 What are the chromosomes for? Of the 46 chromosomes, 2 determine the sex of the organism. These are called sex chromosomes (XX = F; XY = M) Of the 46 chromosomes, 2 determine the sex of the organism. These are called sex chromosomes (XX = F; XY = M) The other 44 are called autosomes they carry genes which code for other traits such as hair colour, eye colour and many proteins that you can’t see The other 44 are called autosomes they carry genes which code for other traits such as hair colour, eye colour and many proteins that you can’t see

11 How many chromosomes do we have in each cell? Haploid – cells that have 1 copy of each chromosome (eg. gametes) – 23 chromosomes Haploid – cells that have 1 copy of each chromosome (eg. gametes) – 23 chromosomes Diploid – cells that have 2 copies of each chromosome (eg. Somatic cells) – 46 chromosomes Diploid – cells that have 2 copies of each chromosome (eg. Somatic cells) – 46 chromosomes Gametes – sex cells Gametes – sex cells Somatic cells – body cells (not sex cells) Somatic cells – body cells (not sex cells)

12 How many chromosomes? Diploid cells Nucleus contains 46 chromosomes OvumC=23 SpermC=23

13 Gametes (Sex Cells) An egg has 23 chromosomes and a sperm has 23 chromosomes. The cell that results from fertilisation contains 46 chromosomes or 23 pairs.

14 Zygotes When the 2 haploid cells fuse, they form a new diploid cell called a zygote. When the 2 haploid cells fuse, they form a new diploid cell called a zygote. The fusion of sperm and ovum is called fertilisation The fusion of sperm and ovum is called fertilisation OvumC=23 SpermC=23 Ovum = Zygote, C = 46 Sperm+

15 Embryo Development Pictures from Nova Online All of your body cells come from this one fertilised cell. During mitosis they copy their DNA and pass it on to the daughter cells. This means that all of your body cells have the same copy of DNA or the same chromosomes as the original cell. Cells end up doing different jobs because of the genes that are turned on or off.

16 You have trillions of cells in your body! Source: Blood cells: Nerve cell: Fat cells: Muscle cells: Bone cell: Red blood cells to carry oxygen around the body And White blood cells to fight infections Fat Cells to store excess energy Nerve cells send electrical signals so your brain can communicate with the rest of the cells in your body Muscle cells for movement Here are some examples of cells in your body. Can you guess what they are and what they do? Bone cells produce calcium carbonate to support the body

17 Can you guess which photos belong to a developing pig, tadpole, human and chicken? Animals with a backbone look similar in early development. They all have many similar structures when they are mature as well. Pictures from Nova Online