1. Protein Synthesis How DNA Works LT’s 1-5

2. What DNA Is Recall that DNA is… long stringy molecule nucleus A long stringy molecule located in the nucleus of eukaryotic cells (or the cytoplasm of prokarytic cells) two complimentary strands It is made up of two complimentary strands bonded together by hydrogen bonds double helix The overall shape is a double helix (twisted ladder) discovered by Watson and Crick nucleotide. The base unit is a nucleotide. Each nucleotide is made up of a deoxyribose sugar, a phosphate and a nitrogen base. four nitrogen bases (A, T, C and G) There are four nitrogen bases (A, T, C and G) LT 1

3. How DNA is Copied Replication is the process by which the DNA molecule is copied parent strands act as templates The molecule is unzipped and the parent strands act as templates for creating new strands (recall…free nucleotides, helicase and DNA polymerase) two new molecules At the end of replication, two new molecules are formed – They are ½ the parent strand and ½ new identical to the original molecule – They are identical to the original molecule. One copy of each molecule goes to each new daughter cell

4. How DNA Works It is a double helix It can be copied and passed on But this does not tell But this does not tell us how it actually works! us how it actually works! Genes- segments of DNA/chromosomes that code for a particular set of instructions, specifically the production of PROTEINS!

5. How DNA Works Proteins are chains called polypeptides that do any number of jobs within the cell amino acids Proteins made up of smaller molecules called amino acids Amino acids are units made according to the instructions of DNA

6. How DNA Works 20 amino acids There are 20 amino acids found in nature – 10 – 10 we can make in our bodies – 10 – 10 are taken in from our foods The 20 amino acids are made from the nitrogen bases of DNA (A, T, G, and C) “alphabet” The nitrogen bases are the “alphabet” of DNA – 4 letters only in the alphabet 3 letters long – Each “word” created by the alphabet is only 3 letters long CODON – Each 3-letter word is called a CODON and AMINO ACID – Each codon represents an AMINO ACID

7. How DNA Works Example: A TE=ate, eat, tea ( the letters are the same but the words are different and have different meaning) Same goes with nitrogen bases A, T, C and G, the order will determine the meaning and the kind of amino acid kind of amino acid. like Some codons form amino acids and some act like punctuation. punctuation. Those that are punctuation cut the amino acid chain and form the protein Changes in the order and number of the amino acids can Changes in the order and number of the amino acids can give any number or proteins. give any number or proteins. DNA Codon Amino Acid ATCStop ACTStop TACStart TCASerine CATValine CTAaspartate

9. RNA RNA RNA- a kind of nucleic acid; copy of the DNA molecule or segment of the DNA molecule used to make proteins by assembling amino acids outside of the nucleus LT 2

10. DNA v. RNA DNA v. RNADescription Master molecule that stays in the nucleus Blueprint that can leave the nucleus SugarDeoxyriboseRibose # of strands 2 strands 1 strand Nitrogen Bases A, T, C and G A, U, C and G Jobs Master molecule that gives instructions for making proteins A copy of DNA that leaves the nucleus to make proteins

11. RNA 3 Types of RNA 1.Messenger RNA (mRNA)- 1.Messenger RNA (mRNA)-carries copies of instructions to make amino acids from DNA 2.Ribosomal RNA (rRNA)- 2.Ribosomal RNA (rRNA)-part of the ribosome where proteins will be made 3.Transfer RNA (tRNA)- 3.Transfer RNA (tRNA)-transfers/brings each amino acid to mRNA following the mRNA code

13. RNA Ribosome Ribosome is the organelle where… to make proteins. mRNA travels to from the nucleus to make proteins. brings each Also where the tRNA brings each amino acid amino acid Made of rRNA and proteins Made by the nucleolus Found on the rough ER and in the cytoplasm Involved in protein production (protein factories) Involved in protein production (protein factories)

14. Transcription When DNA is copied into RNA this is called transcription LT 3

15. Transcription Transcription is helped by an enzyme called RNA Polymerase (a specific sequence of DNA where RNA polymerase knows to bind to start copying DNA) – binds to DNA at the promoter (a specific sequence of DNA where RNA polymerase knows to bind to start copying DNA) – Separates DNA strands for transcribing transcribe just one strand of DNA – Needs to transcribe just one strand of DNA as its template – When transcription is done, a strand of mRNA is made

16. Transcription This process occurs in the nucleus When DNA is copied by mRNA the base pairing is as follows… ATGCACC DNAATGCACC UACGUGG mRNAUACGUGG Let’s Watch This Let’s Watch This

17. Translation LT 4 Protein Synthesis Transcription Translation PROTEIN

18. Translation Translation – the 2 nd step in protein synthesis; when the mRNA is translated/read by tRNA to make the protein ribosome Takes place at the ribosome in the cytoplasm tRNAbrings the appropriate amino acids tRNA brings the appropriate amino acids to mRNA based on the mRNA codons tRNA is amino acid specific tRNA is amino acid specific; in other words there is one tRNA for each codon and it brings only one kind of amino acid

19. Translation matching its own bases to those on mRNA tRNA translates mRNA by matching its own bases to those on mRNA anti-codon- the 3 base pairs on tRNA that pair with mRNA and tell tRNA which amino acid to bring

20. Translation As the amino acids are brought together by the tRNA’s they are bonded together by peptide bonds At the stop codon of mRNA, no more amino acids are brought and the protein is complete.

21. LT 3 & 4

22. Mutations Most of the time, DNA replication and protein synthesis take place without error, but mistakes do happen Mutation Mutation – any change in the genetic material; mistakes made when copying DNA. 2 Kinds of Mutations: 1.Gene mutation - 1.Gene mutation - change in the gene 1.Chromosomal mutation - 1.Chromosomal mutation - change in the chromosome LT 5

23. Mutations Gene Mutations – a change in 1 or a few nucleotide bases 1.Point Mutation 1.Point Mutation-change in one nitrogen base affects one amino acid – Usually only affects one amino acid, but can change the function of the whole protein one base is switched with another – Substitution-one base is switched with another T EX: THE DOG BIT THE CAT R THE DOG BIT THE CAR Ex: Sickle Cell Anemia

24. Mutations 2.Frameshift Mutation- one base is missing or added into the DNA sequence every amino acid after the mutation – Affects every amino acid after the mutation – Insertion – Insertion – adding one base to the sequence – Deletion – Deletion – loss of one base from the sequence – Ex: Tay Sachs and Crohn’s Disease

25. Mutations Chromosomal Mutations- changes in the chromosome 4 Kinds of Chromosomal Mutations: 1.Deletion –loss of all or part of the DNA EX: Inflammatory Disease 2.Duplication – extra parts of the chromosome are present EX: Bar duplication in Fruit Flies

26. Mutations 3.Inversion – part of a chromosome gets flipped in the reverse direction of its usual direction EX: Kinds of cancers 3.Translocation – when part of one chromosome breaks off and attaches to another, different chromosome Ex: Ewing’s Sarcoma

27. Mutations Causes: – Random, spontaneous mutations – Random, spontaneous mutations (errors in cell division or DNA replication) OR – Environmental Factors – Environmental Factors (radiation, chemicals, etc)

28. Mutations Significance of Mutations: 1.Harmlesscreates variation 1.Harmless-the change in the gene creates variation within the species but does not harm the individual having it. EX: different coat colors in mice 2.Harmfulchanges the way the organism should function 2.Harmful-the change in the gene or chromosome changes the way the organism should function EX: Cystic Fibrosis (gene) or Down Syndrome (chromosome) 3.Beneficialorganism survive better than other members of the species 3.Beneficial-creates a variation that helps an organism survive better than other members of the species EX: HIV-1 mutation (these people do not get HIV as easily b/c they can break down a protein in HIV)