A. DNA— deoxyribonucleic acid; determines an organism’s traits by controlling when proteins in the body are made

1. Proteins and enzymes —control most aspects of cellular function in an organism

B. Structure of DNA1. Made of long chains of nucleotides

a. 3 parts of a nucleotide: - phosphate group - simple sugar

(deoxyribose) - nitrogen base

b. 4 types of nitrogen bases: - adenine (A)

- guanine (G) - cytosine (C)

- thymine (T)

Adenine (A)Guanine (G) Thymine (T)Cytosine (C)

Adenine (A)Guanine (G) Thymine (T)Cytosine (C)

d. Nucleotides join together in long chains to form nucleic acids.

c. Complementary base pairs: - A pairs with T - G pairs with C

2. All organisms are made up of the same nucleotides, just in

different ordera. Example: All words are made

up of the same letters, just in different order

A. Discovered by James Watson and Francis Crick in 1953.

1. Double Helix — double stranded, twisted ladder shape of DNA

2. If DNA is a ladder:a. Sugar and phosphate groups form the backbone or the sides of the ladderb. Nitrogen bases form the rungs of the ladder.

James Watson and Francis Crick

3. Individual nucleotides are joined by covalent bonds.

4. Nitrogen bases in the middle of the

helix are joined by hydrogen bonds.

B. How does DNA fit in the cell?1. Think about it! The DNA strand can be

incredibly LONG! Human DNA molecules contain up to 4,639,221,000 base pairs. That means there is about 1-2 meters of DNA in each cell. How can it be kept in such a small area?

2. The solution:a. Chromatin is made of DNA

packed around histone proteins.b. During interphase, these are

dispersed and uncoiled. When cells enter prophase, they pack tightly to form chromosomes.

A. DNA Replication - Whenever a cell divides, the DNA must be copied before it splits

1. DNA helicase, an enzyme, unzips the double helix (breaks the hydrogen bonds) to

form two single strands still joined at the replication forks.

Replication Fork Replication Fork

DNA helicaseDNA helicase

2. DNA polymerase, an enzyme, adds new nucleotides to each single strand according to their complementary base pairs

a. DNA polymerase also “proofreads” for errors

Replication Fork Replication Fork

DNA helicaseDNA helicase

DNA polymerase

3. DNA Ligase, an enzyme, reseals the gaps remaining in the sugar/phosphate backbone

to finish.

Replication Fork Replication Fork

DNA helicaseDNA helicase

DNA polymeraseDNA ligase

4. END RESULT: 2 new and identical molecules of DNA are formed

a. 1 strand made of “old” DNAb. 1 strand made of “new” DNA

Original DNA

Original DNA Strand

Original DNA Strand

Free NucleotidesNew DNA molecule

New DNA Strand

New DNA molecule

Replication

ReplicationDNA

5. Example Complementary Base Pairing a. (Find each complementary base pair for the strand of DNA)A—C—T—A—G—A—C—C—T—A—G—T | | | | | | | | | | | |

T G A T C T G G A T C A

6. Example of DNA Replication a. (Unzip the following molecule of DNA, and write the two new strands of DNA that would result from the replication)b. Original DNA Molecule

C—G—T—C—A—T—C—G—C—A—A—T—G | | | | | | | | | | | | |G—C—A—G—T—A—G—C—G—T—T—A—C

Molecule #1

C—G—T—C—A—T—C—G—C—A—A—T—G | | | | | | | | | | | | |G—C—A—G—T—A—G—C—G—T—T—A—C

Molecule #2

| | | | | | | | | | | | |G—C—A—G—T—A—G—C—G—T—T—A—C

C—G—T—C—A—T—C—G—C—A—A—T—G

A. DNA- Double stranded nucleic acid that is stored in the nucleus of the cell.

1. Gene- piece of DNA that controls a specific trait

B. RNA - a single stranded nucleic acid found all over the cell (nucleus, cytoplasm, and ribosome)

1. Made of long chains of nucleotides:

a. 3 parts of a nucleotide—

-phosphate group

- simple sugar (ribose)

- nitrogen base

b. 5 types of Nitrogen Bases- adenine (A)- guanine (G)- cytosine (C) - thymine (T)- Uracil (U)

c. Complementary base pairs - A pairs with U - T pairs with A - G pairs with C

d. Nucleotides join together in long chains to form nucleic acids.

2. Three Types of RNA

a. Messenger RNA (mRNA)- carries the information from the DNA in the

nucleus to the rest of the cell

Codon

b. Transfer RNA (tRNA)- helps build proteins by carrying amino acids to ribosomes, following instructions coded for in the mRNA.

Each tRNA carries only ONE type of amino acid

The code of the tRNA is complementary to the mRNA.

Amino acid

Chain of RNA nucleotides

Transfer RNA molecule

Anticodon

c. Ribosomal RNA (rRNA)- the site of protein synthesis; makes up the ribosome

Molecule DNA RNA

Sugar Deoxyribose Ribose

Structure Double strand Single strand

Nucleotides A, T, G, C

Adenine - thymine

A, U, T, G, C

Adenine - uracil

Thymine - Adenine)

Location in cell

Stays in the nucleus

Leaves nucleus to ribosomes

C. DNA/RNA Comparison

DNAtranscription

RNA Proteintranslation

D. Protein Synthesis - Using genetic information in DNA to make proteins

E. Steps of Protein Synthesis1. Transcription - Process of

making mRNA from DNA a. Why? DNA can’t leave

nucleus but RNA can

b. Steps of Transcription

1. RNA polymerase, an enzyme, unzips the double helix of DNA inside the nucleus and uses it as a template to create a complementary mRNA strand

2. RNA editing occurs Introns - sections of the DNA that don’t code

for proteins are cut from the mRNA Exons - sections of the DNA that code for

proteins are left on the mRNA

3. DNA rezips and mRNA leaves nucleus and goes to the cytoplasm to find a ribosome for protein synthesis

c. Example: Transcribe the DNA into mRNA.

A C C A T G A C C T G A C T T A C U G G U A C U G G A C U G A A U G

2. Translation: Making chains of amino acids (proteins) by reading/translating mRNA codons (a group of 3 nucleotides) in the ribosome

a. The amino acid sequence determines the structure and function of proteins

codon

b. Steps of Translation

1. mRNA travels to ribosome with a message from the DNA and attaches to the rRNA.

1.

2.

2. 3.

2. As each mRNA codon moves over the ribosome, it is matched with its

complementary tRNA anticodon, which is carrying amino acids.

1.

2.

2. 3.

3. Inside the ribosome, peptidase, an enzyme, helps form peptide bonds joining amino acids to make proteins and tRNA is released to go find another amino acid

1.

2.

2.

3.

c. Example: Translate the mRNA into proteins (USE CODON CHART!)

mRNA = A U G C A U G G A A G C U G A amino acid chain =

d. There are 20 amino acids created from a combination of the 4 nitrogen bases

- Each mRNA codon specifies a different tRNA anticodon to

bring amino acids to join to the protein

- Every different combination of amino acids forms new proteins

AlanineMethionine

Peptide bond

Special Codons - some codons signal start or stop

AUG (methoinine) = start building protein

UAA, UAG, and UGA = stop building protein

Stop codon

Process Transcription Translation

Location In Nucleus At the ribosome

Purpose Turn DNA into RNA

Turn RNA into proteins

Molecules involved

DNA, mRNA mRNA, tRNA, rRNA

3. Transcription/Translation Comparison

A. Mutation - Mistake or change in DNA sequence

1. The change in the DNA is HUGE since the codon is changed

a. If the codons are affected, the amino acids and proteins for the cell are also affected.

B. Types of Mutations1. Point Mutation - change in a

SINGLE base pair in DNAa. Substitution Mutation - one

nitrogen base is replaced with another

- Example: ACTAGGCAC to ACTAGTCAC

- Results in a change of one codon

Point mutation

mRNA

Protein

NormalmRNA

Protein

b. Frameshift Mutation - ONE base is added or deleted from DNA, and it shifts the reading of codons

- Example: Addition Mutation: ACTAGGCAC to

ACTAGGGCAC

Deletion Mutation: ACTAGGCAC to ACTAGCAC

- Results in EVERY codon after the mutation to change.

- Original Protein: Meth-Lys-Phenyl-Gly-Ala- Leu

- Mutated protein: Meth-Lys-Leu-Ala-Hist- Cys

Deletion of U

Without mutation

Frameshift mutation

mRNA

Protein

Addition(Frameshift)

Deletion(Frameshift)

Substitution (Point)

Normal

2. Which type of mutation is more serious? a. Frameshift - it affects EVERY amino acid/protein after the mutation

Deletion of U

Frameshift mutation

mRNA

Protein

3. Chromosomal mutations - Structural changes in chromosomes

a. Are especially common in plants.

4. Four Types of Chromosomal Mutations

a. Deletion -part of a chromosome left out (usually deadly)

A B C D E F G H

Deletion

A B C E F G H

b. Duplication/Insertion: chromosome part breaks off and reattaches to its sister chromatid

A B C D E F G H A B C B C D E F G H

Insertion

*Genes B and C were inserted into

the chromosome*

Insertion

c. Inversion - chromosome part breaks off and reattaches backwards

Inversion

A B C D E F G H A D C B E F G H

d. Translocation - chromosome part breaks off and adds to a different chromosome

Translocation

Inversion

InsertionDeletion

Translocation

C. Causes of Mutations

1. Spontaneous/Random mutations– ◦Some mutations just happen, ( amistake during

DNA replication, transcription, mitosis, meiosis). a. These lead to evolution.

2. Mutagen - Any agent that causes a change in DNA

a. Include radiation (uv or nuclear radiation) and chemicals (asbestos or formaldehyde)

B. Environmental agents