DNA and Genes

1. DNA and Genes Biology Chapter 11

2. Monomers and Polymers • polymer - large molecule formed when many smaller molecules are bound together • monomer- the smaller subunit that makes up a larger longer molecule • ex: chain • amino acids- proteins • monosaccharrides- carbohydrates

3. DNA • deoxyribonucleic acid • monomers- nucleotides • nucleotides • consist of: 1. deoxyribose (5 carbon sugar) 2. phosphate group 3. nitrogen base

4. 4 types of nitrogen bases: • adenine A • guanine G • cytosine C • thymine T • nucleotides look like a sideways T

5. DNA two stranded molecule w/ each strand consisting of chain of nucleotides hydrogen bond joins the nitrogen bases ladder sides made of sugar and phosphate rungs are the nitrogen bases

6. base pair- the 2 bases that make up the rung • in DNA, adenine ALWAYS bonds w/ thymine & cytosine ALWAYS bonds w/ guanine • C-C-T-G-G-A-T-G-A-C • G-G-A-C-C-T-A-C-T-G

7. double helix- spiral staircase • James Watson & Francis Crick • the order of the nitrogen bases determines the complexity of org and makes them different

8. DNA Replication • copying of DNA – takes place INSIDE the nucleus • steps: • begins w/ the enzyme DNA helicase attaching to the DNA molecule- breaks H bonds- unzipping it • free nucleotides in nucleoplasm begin bonding to DNA molecule to their complementary bases • continues until all the DNA is copied Result: 2 DNA molecules exactly identical to each other

9. contained in the DNA code are the recipes for making different proteins • proteins are polymers made up of amino acids • different proteins have different functions • proteins determine the structure & fxn of org • genetic code- sequence of N bases along 1 DNA strand that codes for production of proteins

10. RNA • Where is DNA located? • What organelle produces proteins? • Where is it located? • RNA- ribonucleic acid • structure different from DNA in 3 ways: • composed of ribose sugar • single strand • has uracil, instead of thymine, which pairs w/ adenine

11. RNA moves between DNA in nucleus & ribosomes in cytoplasm of cell • 3 forms of RNA: • messenger RNA- mRNA single stranded; made thru transcription carries info from DNA to ribosomes 2. ribosomal RNA -rRNA globular form; makes up ribosomes 3. transfer RNA –tRNA hair-pin shaped molecule; plays a role in translation by carrying amino acids to ribosomes

12. genetic code has to be copied from DNA ONTO RNA in a process called transcription • Transcription- process where genetic code is placed onto a mRNA strand • steps: • RNA polymerase “unzips” DNA • freely floating RNA nucleotides pair w/ the complementary DNA nucleotide

13. 3. when pairing is complete, the mRNA breaks away, moves into the cytoplasm, DNA rejoins • result: mRNA molecule that has the recipe for making proteins

14. Proteins info; • there are 20 different amino acids • A series of 3 nitrogen bases which is called a CODON represents an amino acid • Ex: AAG GUC • genetic code is universal

15. Translation • the process of converting info on mRNA into sequence of amino acids to make proteins • occurs at ribosomes • steps: 1. mRNA strand attaches to ribosomes where the 1stcodon is read (AUG-often the 1stcodon)

16. 2. tRNA carries specific amino acid; its anticodon matches the codon on the mRNA strand 3. mRNA slides up to the next codon, a new tRNA brings in the next amino acids as anticodon matches another codon 4. peptide bond joins the amino acids 5. process continues until stop codon is reached 6. new protein is released