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GeneticsGenetics

An IntroductionAn Introduction

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Genes – Made up of DNAGenes – Made up of DNA

Characteristics that you Characteristics that you inheritinherit from your from your parents are sometimes called parents are sometimes called traitstraits

These traits are coded for by These traits are coded for by genesgenes which which are passed on from your parents when their are passed on from your parents when their sperm and egg cells unite.sperm and egg cells unite.

Genes code for the production of all the Genes code for the production of all the proteins in your body and carry instructions proteins in your body and carry instructions for your developmentfor your development

Genes are made up of short segments of Genes are made up of short segments of DNADNA

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DNADNA

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)

http://academy.d20.co.edu/kadets/lundberg/dnapic2.html

http://www.tokyo-med.ac.jp/genet/picts/dna.jpg

There are four nitrogen bases:

Cytosine, Guanine, Adenine and Thymine

What pairs with C?

What pairs with A?

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The CodeThe Code

In each gene there is a code for making In each gene there is a code for making protein. The code is determined by the protein. The code is determined by the order of the nitrogen bases A, T, G & C.order of the nitrogen bases A, T, G & C.

The code is copied and then read by your The code is copied and then read by your cell machinery so proteins can be cell machinery so proteins can be

made.made.

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Living thingsLiving things

All living things contain DNA or a All living things contain DNA or a similar substance (RNA) which allow similar substance (RNA) which allow genetic information to be passed from genetic information to be passed from one generation to another one generation to another

All living things reproduceAll living things reproduce Some of the DNA that humans have is Some of the DNA that humans have is

shared by other living things alsoshared by other living things also

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We share 61% of We share 61% of our DNA with our DNA with fliesflies

We’re 92% like a We’re 92% like a mouse!mouse!

And 98% like a And 98% like a chimpanzeechimpanzee

Source:Mouse http://animals.timduru.org/dirlist/mouse/mouse.jpgDrosophila: http://www.innate.se/drosophila.jpgChimpanzee: http://www.utalii.com/Hotels/images/Chimpanzee.jpg

WE ARE DIFFERENT IN MANY WAYS, WE ARE DIFFERENT IN MANY WAYS, BUT IN MANY WAYS WE ARE THE SAME!BUT IN MANY WAYS WE ARE THE SAME!

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Where do you find DNA?Where do you find DNA?All mature cells contain DNA except your red blood All mature cells contain DNA except your red blood

cells. cells. DNA is found in the nucleus. This is a large structure DNA is found in the nucleus. This is a large structure

found in the cell. found in the cell.

Nucleus

Source: Source: http://www.tokyo-med.ac.jp/genet/picts/cell-e.jpghttp://www.tokyo-med.ac.jp/genet/picts/cell-e.jpg

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

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DNA is packed into DNA is packed into chromosomeschromosomes

You have You have 46 46 chromosomes in each chromosomes in each of your somatic cellsof your somatic cells..

You inherited these from You inherited these from your parents: 23 from your parents: 23 from mum and 23 from dadmum and 23 from dad

The chromosomes you The chromosomes you inherit determine what inherit determine what you look like.you look like.

Source:

Chromosome: http://data.over-blog.com/lib/0/4/3540/pics/Articles/chromosome.jpg

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What are the chromosomes What are the chromosomes for?for?

Of the 46 Of the 46 chromosomes, 2 chromosomes, 2 determine the sex determine the sex of the organism. of the organism. These are called These are called sex chromosomes sex chromosomes (XX = F; XY = M)(XX = F; XY = M)

The other 44 are The other 44 are called called autosomes autosomes they carry genes they carry genes which code for which code for other traits such as other traits such as hair colour, eye hair colour, eye colour and many colour and many proteins that you proteins that you can’t seecan’t see

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How many chromosomes do we How many chromosomes do we have in each cell?have in each cell?

HaploidHaploid – cells that – cells that have 1 copy of each have 1 copy of each chromosome (eg. chromosome (eg. gametes) – 23 gametes) – 23 chromosomeschromosomes

Diploid Diploid – cells that – cells that have 2 copies of each have 2 copies of each chromosome (eg. chromosome (eg. Somatic cells) – 46 Somatic cells) – 46 chromosomeschromosomes

GametesGametes – sex – sex cellscells

Somatic cellsSomatic cells – body cells – body cells (not sex cells)(not sex cells)

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How many chromosomes?How many chromosomes?

Diploid cellsDiploid cells

Nucleus contains Nucleus contains 46 chromosomes46 chromosomes

OvumOvumC=23C=23

SpermSpermC=23C=23

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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.

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ZygotesZygotes

When the 2 When the 2 haploid haploid cells fuse, they cells fuse, they form a new form a new diploid diploid cell called acell called a zygote zygote..

The fusion of The fusion of sperm and ovum is sperm and ovum is called called fertilisationfertilisation

OvumOvumC=23C=23

SpermSpermC=23C=23

OvumOvum

= Zygote= Zygote, C = 46, C = 46

SpermSperm++

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Embryo DevelopmentEmbryo 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.

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You have trillions of You have trillions of cells in your body!cells in your body!

Source:Blood cells: http://images.encarta.msn.com/xrefmedia/sharemed/targets/images/pho/35a5c/35A5C297.jpgNerve cell: http://www.technovelgy.com/graphics/content/nervecell.jpgFat cells: http://casweb.cas.ou.edu/pbell/Histology/Images/Slides/Connective/pl.skin.adipose.jpgMuscle cells: http://www.meddean.luc.edu/lumen/MedEd/Histo/HistoImages/hl3A-42.jpg Bone cell: http://www.meddean.luc.edu/lumen/MedEd/Histo/HistoImages/hl4A-40.jpg

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

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Can you guess which photos belong to a Can you guess which photos belong to a developing pig, tadpole, human and developing pig, tadpole, human and

chicken?chicken?

Animals with a Animals with a backbone look backbone look similar in early similar in early development. development. They all have They all have many similar many similar structures when structures when they are mature they are mature as well. as well.

Pictures from Nova Online