DNA / Protein Synthesis

I. DNA StructureA. Made up of 1000s of repeating units

(nucleotides)

B. Each nucleotide has 3 parts: phosphate, sugar (deoxyribose) and a nitrogenous base

Phosphate

Sugar

Nitrogenous Base

I. DNA Structure

C. DNA Nucleotides can have 4 different bases

1. Adenine

2. Cytosine

3. Guanine

4. Thymine

I. DNA Structure

D. Watson – Crick Model of DNA1. 2 connected chains of

nucleotides

2. Sides = phosphates and sugars held together by strong ionic bonds

3. Rungs = N. base pairs held together by weak hydrogen bonds

4. 2 chains are twisted in a spiral (double helix)

I. DNA Structure

E. The 4 bases only bind in a certain way1. Adenine – Thymine (A – T)2. Cytosine – Guanine (C – G)

F. The 2 strands are complimentary (A on one and T on the other)

I. DNA Structure

II. DNA ReplicationA. DNA can copy itself with the help of

enzymesB. Happens during mitosis and meiosis in

the nucleus of the cellC. Process

1. DNA unwinds2. 2 strands separate between the bases3. Free nucleotides in cytoplasm enter

nucleus and bind with complimentary bases on DNA strand

4. Makes 2 identical DNA moleculesDNA replication

III. Gene Control of Cell Activities

A. Genes for a trait (phenotypes) are determined by the DNA nucleotide sequence

B. Genes control protein and enzyme synthesis and these control cell activities

III. Gene Control of Cell Activities

C. Example1. Dominant gene for production of lactase

(digests the milk sugar, lactose). 2. People who are recessive cannot make

lactase, so they cannot digest lactose

D. The sequence of DNA nucleotides determines the sequence of amino acids in enzymes and other proteins

E. There is over 1 meter of DNA in EACH human cell

IV. RNA

A. Made of nucleotides but have 3 main differences

1. Sugar is ribose, not deoxyribose

2. Uracil (U) is substituted for Thymine (T)

3. Single stranded, not double stranded

IV. RNA

B. Messenger RNA (mRNA)1. Made in nucleus and moves to ribosome

2. Formation (Transcription)a. DNA unwinds and unzips

b. RNA nucleotides bind w/ complementary bases on DNA strand

3. DNA serves as a template (pattern) for the synthesis of RNA

Transcription

IV. RNA

4. Sequence of nucleotides in mRNA contains the genetic code which determines the sequence of aa in proteins

5. EACH aa is represented by a SPECIFIC sequence of 3 nucleotides (codon)

IV. RNA

C. Transfer RNA (tRNA)1. Found in cytoplasm2. 20 different kinds of aa in cells, w/ at least

one tRNA for each3. Each tRNA has a 3 nucleotide sequence

(anticodon) that is complimentary to the codon on the mRNA

4. tRNA carry the specific aa to ribosome and temporarily bind to mRNA during protein synthesis

V. Protein Synthesis

A. mRNA is made in nucleus from a section of DNA (gene for protein) (transcription)

B. mRNA moves to cytoplasm and binds to ribosome

C. aa are carried to mRNA/ribosome by tRNA

D. Anticodons on tRNA bind w/ codons on mRNA (bringing the aa with it)

E. aas bind together (forming PEPTIDE bonds)

V. Protein Synthesis

F. Once the aa binds, the tRNA breaks away to find a new aa

G. This continues (forming an aa chain that will eventually form a protein) until a STOP codon is reached. The STOP codon tells the ribosome to break away and release the protein

Translation

VI. Gene Mutations

A. ANY change in the sequence of nucleotides in DNA

B. MUST happen in sex cells in order to be passed on to offspring

C. Types1. Addition (AAGCCA AAGGCCA)

2. Deletion (AAGCCA AGCCA)

3. Substitution (AAGCCA AGGCCA)

4. Inversion (AAGCCA ACGACA)

VII. Cloning

A. Make identical offspring from parentB. Inject nucleus of body cell (2n) into an

egg which had the nucleus removedC. “Fertilized” egg is implanted into

surrogate mother and new organism forms

D. Has been achieved in plants, frogs, mice, sheep, goats, cows and monkeys

VIII. Genetic EngineeringA. Transfer of genetic

material from one organism to another

B. Process1. Restriction enzyme

is used to cut out a piece of DNA that has a desired gene from a donor organism’s DNA

VIII. Genetic Engineering

2. The piece of DNA is placed into a circular piece of bacterial DNA (plasmid) that was cut with the same restriction enzyme

3. The “recombined” DNA is placed into the new organism. The protein from the trait can now be made.

VIII. Genetic Engineering

C. Used to make human growth hormone and insulin

D. Genes were placed into bacteria. Now all of the offspring have the gene (mitosis) and they make the chemical

E. Get large amounts @ low costF. Plants can now contain genes to make

chemicals that kill insects feeding on the plants

IX. Gel Electrophoresis

A. Used to compare DNA from different organism

B. Procedure1. DNA is cut using restriction enzymes.

This cuts at specific points making different sized fragments of DNA

2. Fragments are placed into wells on one side of gel

IX. Gel Electrophoresis

3. Electricity is run through the gel causing the (-) charged DNA to the (+) end (away from the wells)

4. Smaller fragments travel faster through gel, making them further away

5. Gel is then stained to show the “bar” pattern for the DNA sample

Gel Electrophoresis

IX. Gel Electrophoresis

C. Used for:1. Relating different DNA samples to each

other

2. Determining the father of a child

3. Proving hospital mistakes (wrong child)

4. Proving guilt / innocence in a crime

5. Determining the genes responsible for some genetic diseases