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3.  Walter Sutton discovered chromosomes were made of DNA and Protein  However, scientists were NOT sure which one (protein or DNA) was the actual genetic material of the cell 2

4.  Frederick Griffith in 1928 showed the DNA was the cell’s genetic material  In 1944, Oswald Avery demonstrated that DNA is the material responsible for transformation. 3

5.  In 1952, Alfred Hershey and Martha Chase, proved that the DNA of a virus is injected into the bacterial cells. That then causes the bacterial cells to produce more viral DNA and proteins. 4

6.  DNA.  DNA is often called the blueprint of life.  In simple terms, DNA contains the instructions for making proteins within the cell that make up you. 5

7. We study DNA for many reasons:  Important to all life on Earth  Medical benefits such as cures for diseases  Better food crops 6

8.  Gene – segment of DNA that is located in a chromosome and that codes for a specific hereditary trait.  Basic unit of heredity.  Each cell in the human body contains about 25,000 to 35,000 genes, which carry information that determines your traits.  Our genes are on our chromosomes. 7

9.  Chromosomes are made up of a chemical called DNA and proteins.  Chromosomes come in pairs, and there are hundreds, sometimes thousands, of genes in one chromosome.  There are 46 chromosomes in each human cell.  Draw and explain Figure 2 Chromosome structure on p.119 on the left side of your notebook. 8

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11.  Deoxyribonucleic acid  Stores hereditary information  Found in all cells  Organic Comound made up of C, H, O, N and P 10

12. Watson & Crick in the 1950’s built the 1 st model of DNA With the help of Chargraff’s observations and Wilkins and Franklin’s photographs (x-ray diffraction) 11

13.  DNA is a very long polymer.  The basic shape is like two strands twisted around each other, like a winding staircase.  This is called a double helix.  Read the first paragraph on p. 194; then summarize what you read in your notes. 12

14.  The DNA double helix has two strands twisted together. 13

15.  Each DNA strand is made of linked nucleotides.  Nucleotides are the subunits of DNA  Each nucleotide is made up of 3 parts: 1. phosphate group 2. 5 carbon sugar (deoxyribose) 3. nitrogen base 14

16.  The backbone of the molecule is alternating phosphates and deoxyribose sugar  The teeth are nitrogenous bases. 15 phosphate deoxyribose bases

17. One deoxyribose together with its phosphate and base make a nucleotide. 16 CC C O Phosphate O C C O -P O O O O O O O Nitrogenous base Deoxyribose

18.  One strand of DNA is a polymer of nucleotides.  One strand of DNA has many millions of nucleotides. 17 nucleotide

19.  Cytosine C  Thymine T  Adenine A  Guanine G 18 DNA has four different bases:

20.  Pyrimidines are single ring bases.  Purines are double ring bases. 19 C C C C N N O N C C C C N N N N N C

21.  Thymine and cytosine each have one ring of carbon and nitrogen atoms. 20 C C C C N N O N cytosine C C C C N N O O thymine C

22.  Adenine and guanine each have two rings of carbon and nitrogen atoms. 21 C C C C N N N Adenine N N C C C C C N N O N Guanine N N C

23.  Remember, DNA has two strands that fit together something like a zipper.  The teeth are the nitrogenous bases but why do they stick together? 22

24.  The bases attract each other because of hydrogen bonds.  Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA.  The bonds between cytosine and guanine are shown here with dotted lines 23 C C C C N N O N C C C C N N O N N N C

25.  When making hydrogen bonds, cytosine always pairs up with guanine  Adenine always pairs up with thymine  Adenine is bonded to thymine here 24 C C C C N N N N N C C C C C N N O O C

26. Adenine and Thymine always join together A T Cytosine and Guanine always join together C G 25

27.  Each cell has about 2m of DNA.  The average human has 75 trillion cells.  The average human has enough DNA to go from the earth to the sun more than 400 times.  DNA has a diameter of only 0.000000002 m. 26 The earth is 150 billion m or 93 million miles from the sun.

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30. What: The process of making a copy of DNA. When: DNA replication occurs during the synthesis (S) phase of the cell cycle, before a cell divides. How Long: One chromosome can be replicated in about 8 hours. 29

31.  Double helix unwinds  DNA helicases open the double helix by breaking the hydrogen bonds that link the complementary nitrogen bases. 30

32.  The areas where the double helix separates are called replication forks because of their Y shape. Once the 2 strands are separated, additional proteins attach to each strand, holding them apart. 31

33.  At the replication fork, enzymes known as DNA polymerases add nucleotides to the exposed nitrogen bases, according to the base-pairing rules.  As it moves along, two new double helixes are formed. 32

34.  Process continues until all of the DNA has been copied and the polymerases are signaled to detach.  Results in two identical DNA strands. 33

35.  Errors sometimes occur and the wrong nucleotide is added to the new strand.  An important feature of DNA replication is that DNA polymerases have a “proofreading” role.  It can backtrack to remove the incorrect nucleotide.  Reduces errors in DNA replication to about one error per 1 billion nucleotides. 34

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37. 1.RNA has a sugar ribose DNA has a sugar deoxyribose 2.RNA contains the nitrogen base uracil (U) so.. A pairs with U and C pairs with G DNA has thymine (T) 3.RNA molecule is single-stranded DNA is double-stranded Just like DNA…RNA is made up of the subunits called nucleotides. 36

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39.  Messenger RNA (mRNA) carries genetic information to the ribosomes  Ribosomal RNA (rRNA), along with protein, makes up the ribosomes  Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized  More recently discovered RNA:  Interference RNA (RNAi) inhibit gene expression inhibit gene expression 38.