DNA & Protein Synthesis Chapter 4 Section 3

Vocabulary 1. DNA 2. nucleotide 3. nitrogen bases 4. base pairing 5. double helix 6. DNA replication 7. gene 8. messenger RNA 9. ribosomal RNA 10. transfer RNA 11. transcription 12.uracil 13.codon 14.translation 15.mutation

I. Chromosomes & DNA A. DNA = chemical code for a cell to make proteins 1. DNA carries your information like an instruction manual 2. DNA stands for deoxyribonucleic acid B. Prokaryotes vs. Eukaryotes 1. Prokaryotes – small, single DNA loop 2. Eukaryotes – over 1000X more DNA C. Chromosome structure 1. Nucleus of a human cell contains 1 meter of DNA 2. DNA is tightly wrapped around proteins and supercoiled to form chromosomes

4 Cell & DNA Size Get a feel for how microscopic cells and DNA truly are: egin/cells/scale/ egin/cells/scale/

Chromosome Structure of Eukaryotes Chromosome Supercoils Coils Proteins DNA double helix

D. DNA Parts 1. Nucleotide = repeating units of DNA made of: a. 5-carbon sugar (deoxyribose) b. phosphate group c. nitrogenous base 1) adenine 2) guanine 3) cytosine 4) thymine DRAW - Nucleotide

PurinesPyrimidines AdenineGuanine CytosineThymine Phosphate group Deoxyribose DNA Nucleotides

E. DNA Structure 1. Base Pairing a. adenine pairs with thymine b. guanine pairs with cytosine c. A = T and G = C 2. Rosalind Franklin used x-rays to see a pattern in the DNA a. Picture shows DNA looking at it from the top b. X shaped pattern in center indicates that strands of DNA are twisted like a helix DRAW: X-ray Picture of DNA

3. Watson & Crick a. Figured out the structure of DNA in 1953 b. DNA is shaped like a double helix (looks like a twisted ladder) 1) Outside = sugar and phosphate 2) Steps = nitrogen bases DRAW - Picture of DNA *** must have color with a key!

Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Structure of DNA

F. DNA replication = process by which a cell copies its DNA 1. occurs during interphase (before cell division) 2. enzymes “unzip” the molecule of DNA 3. nucleotides base-pair with each side of the parent strand creating two separate DNA double helixes 4. an enzyme corrects errors that are found

1. Parent DNA 2. DNA unzips 3. New DNA forms 4. Daughter DNA DRAW: DNA Replication

Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strandNew strand

II. RNA and Protein Synthesis A. gene = a section of DNA that codes for one protein B. RNA’s purpose is to get information from DNA to the ribosomes to make proteins! C. RNA 1. sugar is ribose (instead of deoxyribose) 2. single strand 3. contains uracil (U) instead of thymine

D. 3 types of RNA 1. messenger RNA (mRNA) = copies part of DNA code and carries it to ribosome 2. ribosomal RNA (rRNA) = helps the ribosomes 3. transfer RNA (tRNA) = brings amino acids to ribosomes and putting them in the right order to make a protein tRNA mRNA rRNA

E. Transcription = process when DNA is “photocopied”, creating a strand of mRNA 1. 1 st step in making protein 2. in the nucleus 3. RNA nucleotides bond to DNA nucleotides a. A - U and G - C 4. mRNA leaves the nucleus to go to the ribosome

RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) DRAW: Fig.15 page 112

F. Reading mRNA like a ribosome does 1. Each 3 nitrogen bases from mRNA is a “word” called a CODON 2. Each codon tells the ribosome which amino acid comes next different codons, 20 amino acids DRAW - mRNA Codon

The Genetic Code

4. Example mRNA sequence: –AUGUCGCACGGUUAA –Read it three bases at a time as: –AUG-UCG-CAC-GGU-UAA –Codons represent the different amino acids: –AUG – UCG – CAC – GGU – UAA –Methionine – Serine – Histidine - Glycine – (stop)

G. Translation = process that reads mRNA and puts the protein together 1.After transcription, mRNA moves to a ribosome 2.ribosomes read mRNA and produce amino acid chains (proteins) mRNA nucleus

3.Each tRNA brings the right amino acid for each codon. Amino acids tRNA mRNA Ribosome DRAW Figure 12-18, pg 304 Step B

4.The ribosome joins the amino acids together, making the protein. tRNA Ribosome mRNA protein

25 H.Why are Proteins so Important? 1.Genes contain instructions for putting together proteins 2.What do proteins have to do with characteristics like a flower’s color, the shape of a leaf, or human blood type? a.gene  protein (enzyme)  characteristic b.So, every characteristic we have comes from a protein made by our cells! c.Ex: A plant gene codes for an enzyme that produces a pigment which creates the color of a flower’s petals.

26 Review of DNA to Protein Process

III. Mutations A. mutation = change in the DNA code by deleting or adding nucleotides B. Cause of mutations - errors in replicating DNA, making mRNA, or from environmental sources like UV radiation C. most are corrected by enzymes, but a small percentage are not corrected D. can be a change in a whole section of a chromosome or just one nucleotide.

Deletion Duplication Inversion Translocation Chromosomal Mutations

IV. Gene Regulation A. Genes are turned on and off B. Only a tiny fraction of genes needs to be expressed in cells of different tissues throughout the body 1. Ex: the gene for making the protein melanin (gives skin a darker color) would be turned off in nerve cells