DNA & DNA & Protein Protein

SynthesisSynthesis

Chapter 4 Section 3

Vocabulary

1. DNA2. nucleotide3. nitrogen bases4. base pairing5. double helix6. DNA replication7. gene8. messenger RNA9. ribosomal RNA10. transfer RNA11. transcription

12. uracil 13. codon14. translation15. mutation

I. Chromosomes & DNAA. 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

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Cell & DNA Size

• Get a feel for how microscopic cells and DNA truly are:

• http://learn.genetics.utah.edu/content/begin/cells/scale/

Chromosome Structure of Eukaryotes

Chromosome

Supercoils

Coils

Proteins

DNA double helix

D. DNA Parts1. 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

Purines Pyrimidines

Adenine Guanine Cytosine Thymine

Phosphate group

Deoxyribose

DNA Nucleotides

E. DNA Structure1. 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 DNAa. 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 unzips2. DNA unzips

3. New DNA forms3. New DNA forms

4. Daughter DNA4. Daughter DNA

DRAW:DNA Replication

DNA Replication

Growth

Growth

Replication fork

DNA polymerase

New strand

Original strand

DNA polymerase

Nitrogenous bases

Replication fork

Original strandNew strand

II. RNA and Protein SynthesisA. 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. RNA1. sugar is ribose (instead of

deoxyribose)2. single strand3. 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 mRNArRNA

E. Transcription = process when DNA is “photocopied”, creating a strand of mRNA

1. 1st step in making protein

2. in the nucleus

3. RNA nucleotides bond to DNA nucleotidesa. A - U and G - C

4. mRNA leaves the nucleus to go to the ribosome

RNA DNA

RNApolymerase

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 does1. Each 3 nitrogen bases from

mRNA is a “word” called a CODON

2. Each codon tells the ribosome which amino acid comes next

3. 64 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 ribosome2. 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

RibosomeRibosome

DRAW Figure 12-18, pg 304 Step B

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

tRNA

RibosomeRibosomemRNA

protein

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H.Why are Proteins so Important?1. Genes contain instructions for putting

together proteins2. 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)

characteristicb. 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.

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Review of DNA to Protein Process

III. MutationsA. 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 RegulationA. Genes are turned on and offB. 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