DNA, RNA, Protein Synthesis

• DNA Structure• DNA Replication : DNA DNA• RNA Structure• Protein Synthesis• Transcription : DNA RNA• Translation : mRNA amino acid

Human Genotype

• The human genotype contains 46 chromosomes

• Each chromosome has 2 chromatid legs• Each chromatid leg has thousands of

genes• Each gene has thousands of DNA

nucleotides in loose strands called chromatin

Role of DNA

• 1) DNA stores the genetic information in the nucleus until is time to pass the genetic information on to progeny

• 2) DNA is the blueprint for the cell to make proteins

DNA Structure

• DNA is a double helix = twisted ladder• DNA is a polymer of DNA monomers• Eg. DNA nucleotides in a DNA strand are

like beads in a necklace

DNA Nucleotide

• Each nucleotide has 3 sub-components• 1) 5 carbon sugar called deoxyribose• 2) phosphate group• 3) nitrogen-containing base

DNA Nucleotide Base

• There are four bases: adenine (A), thymine (T), guanine (G) and cytosine (C)

• The name of the DNA nucleotide is the name of the base

• The DNA nucleotides undergo “complementary” base-pairing: A=T , T=A, G=C, C=G

DNA Nucleotides

• Hydrogen bonding between complementary bases :

• A=T T=A G=C C=G• Keeps the two DNA strands together in the

double helix shape

DNA Replication

• DNA Replication = 1 “Parent” Double Strand DNA 2 “Progeny” Double Strand DNA

• DNA Replication is called “Semi-conservative” because each progeny double strand DNA has one original parent DNA strand and one new DNA strand

DNA Replication

DNA replication requires 3 enzymes:

1) DNA helicase : “unzips” the double helix by breaking hydrogen bonds between bases

2) DNA polymerase : attaches new DNA nucleotide to complementary DNA nucleotide in parent DNA strand

3) DNA ligase: ties the strands back together

RNA Structure• DNA• Double helix• Deoxyribose sugar

• A=T, T=A, G=C, C=G• DNA remains in

nucleus

• RNA• Single strand• Ribose sugar• Uracil base replaces

Thymine base• A=U, T=A, G=C,

C=G• RNA is made in

nucleus and moved to cytoplasm

Role of RNA

• Messenger RNA : carries protein synthesis information stored in DNA in the nucleus to the ribosome in the cytoplasm

• Transfer RNA: brings amino acids to the ribosome for protein synthesis

• Ribosomal RNA: combines with proteins to make the ribosomes