MOLECULAR GENETICS

DNA- deoxyribonucleic acid

• 1953- James Watson and Francis Crick discover the structure of the DNA molecule

• DNA is a double helix (twisted ladder)

The sides of molecule are:

• 1. a sugar molecule called deoxyribose

• 2. a phosphate group

The middle molecules are called:

• Nitrogen bases

There are four nitrogen bases:AdenineGuanineCytosineThymine

Nucleotide- the building block molecule of DNA

1 sugar 1 phosphate group1 nitrogen base

Nitrogen base pairs

Adenine always pairs with ThymineGuanine always pairs with Cytosine(Often calledComplimentary base pairs)

• The bases are held together with Hydrogen bonds

Functions of DNA:

1. Replication- so that genetic material and information is passed from one generation to another and to succeeding cells

2. Control of cellular activities: DNA carries the code for assembling enzymes and other proteins that cells need

Quiz: answer these questions on a piece of paper

1. Describe the basic structure of DNA.2. Describe the parts of a nucleotide.3. What are the complimentary base pairs?4. What type of bond holds nucleotides

together?

DNA Replication

• DNA makes a copy of itself just before the cell divides

Steps of replication:

1. DNA double helix molecule unwinds and unzips.

2. New DNA nucleotides find their complimentary base pair.3. Results in two identical molecules of DNA

The amount of Adenine is equal to the amount of Thymine and the amount of Cytosine is equal to the amount of Guanine

*********** REMEMBER A GENE IS A SECTION OF DNA THAT CODES FOR A PROTEIN!!!!!!!!!!!!!!!!!!Each chromosome has many genes!!!

Gene (DNA)

RNA formation

Protein formation

Cell structure Cell enzymes

Cell function

CENTRAL DOGMA

DNA RNA PROTEIN

RNA- ribonucleic acid

1. The sugar in RNA is ribose2. RNA is single stranded3. The nitrogen base uracil replaces thymine

(what base is complimentary to Uracil)

RNA transcription-DNA is used as a template for producing an RNA molecule

How does RNA form?

1. DNA is used as a template (model) to make RNA2. RNA has three forms: messenger RNA (mRNA)

transfer RNA (tRNA) ribosomal RNA (rRNA)

3. The molecule of DNA unwinds and unzips4. One side of DNA acts as a template for producing a complimentary RNA strand 5. RNA molecules strip away from DNA, leave the nucleus and enter the cytoplasm

• RNA now has the instructions for how to make a specific protein.

Triplet codon

• Every three bases on the RNA molecule code for the placement of a specific amino acid

• FOR EXAMPLE: UCG AAA CCU Tryptophan lysine proline

• RNA will travel to the ribosome, the site of protein synthesis

Transfer RNA- tRNA

• tRNA has an anticodon• Anticodon- three nitrogen bases that

are complimentary to the triplet codon of mRNA

Transfer RNA (tRNA)

• Function- to carry amino acids from the cytoplasm to the ribosome

PROTEIN SYNTHESIS

• tRNA carries amino acids from the cytoplasm to the ribosome• the anticodon on tRNA finds its

complimentary triplet codon on mRNA

• When the amino acids are next to each other they form a bond, and as amino acids are added to the chain , a protein forms