What is dna?


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Grade 5/6 DNA lesson

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What is dna?

  1. 1. How is a human made?
  2. 2. A human is made from:1 egg (from Mum) and 1 sperm (from Dad)The information stored to grow a person is in 46chromosomes.23 chromosomes come from the egg and 23 come fromthe sperm.
  3. 3. What is achromosome?
  4. 4. A chromosome is made up of tightly coiled DNA.Every cell in the human body contains 23 pairs ofchromosomes. 22 of the pairs look the same in malesand females. The 23 rd is different: females have two Xchromosomes and males have one X and one Y.
  5. 5. This means that each cell, with its 23 pairs ofchromosomes has the information to make anythingrequired in the whole human body.It is like a pantry with all of the ingredients you need.Sometimes a cell just needs to make another skin cell,sometimes it needs to make a liver cell. Just like thepantry ingredients could make a cake, or they couldmake a pasta bake.
  6. 6. Each chromosomecan contain around 1000 genes.
  7. 7. What is agene?
  8. 8. Genes, which are made up of DNA, act as instructions tomake molecules called proteins.The Human Genome Project has estimated that humanshave between 20,000 and 25,000 genes.Each gene has one set of instructions or ‘recipe’ toperform one function in our body.Most genes are the same in all people, but a smallnumber of genes (less than 1 percent of the total) areslightly different between people. These smalldifferences contribute to each person’s unique physicalfeatures.
  9. 9. What isDNA?
  10. 10. DNA is deoxyribonucleic acid.It is a double sided helix.The information in DNA is stored as a code made up offour chemical bases: adenine (A), guanine (G), cytosine(C), and thymine (T)
  11. 11. The order, or sequence, of these bases determines theinformation available to carry out a certain function,similar to the way in which letters of the alphabetappear in a certain order to form words and sentences.DNA bases pair up with each other, A with T and C withG, to form units called base pair.
  12. 12. An important property ofDNA is that it can replicate,or make copies of itself.When it ‘unzips’ one sideprovides the pattern forthe creation of the otherside.Duplication is critical whencells divide because eachnew cell needs to have anexact copy of the DNApresent in the old cell.
  13. 13. How much DNA do we have?
  14. 14. Genes are all different sizes from a few hundred DNAbases to two million bases.Humans have 25,000 genes, so that’s a lot of DNA!The smallest gene is 500 base pairs long and makes thehistone protein.
  15. 15. So what dogenes really do?
  16. 16. The DNA in genes create proteins.Proteins are everything to do with our bodies:• Structure : making skin, organs, nerves etc etc• Function : antibodies for immunity, blood cells, enzymes etc etc
  17. 17. The End Now, do this tour: http://learn.genetics.utah.edu/content/begin/tour/ and play some games here: http://www.routesgame.com/games/?challengeId=7 and make some origami DNA here:http://www.wellcome.ac.uk/Education-resources/Teaching-and-education/Big- Picture/All-issues/Genes-Genomes-and-Health/WTDV027165.htm