DNA Replication,

Transcription and

Translation

Structure of DNA and RNADNADeoxyribonucleic Acids are

nucleotides made of:– Base pairs

(Adenine, Thymine, Guanine, Cytosine)

– Deoxyribose sugar group

– Phosphate group– Double stranded, in

helix coil form

RNA Ribonucleic Acids are nucleotides made of:

– Base pairs (Adenine, Uracil, Guanine, Cytosine)

– Ribose sugar group

– Phosphate group

– Single stranded

Base pairs come in two combinations:

C bonds to G A bonds to T

RNA uses Uracil, in place of Thymine. (A bonds to U)

DNA structure

Makes a ladder shape

• Phosphates bond to Sugars ( uprights )

• Base pairs bondA to T, and C to G between sugars

• The two strands twist into double helix form

DNA structure compared to RNA• Both have a ladder shape

made when Phosphates bond to Sugars (uprights or backbone)

• Both Base pairs are attached to this backbone

• Both the strands of DNA or strand of RNA twist

DNA Replication - “Xeroxing”- Happens in the nucleus1.DNA unzip - with help of

enzymes2.Two strands DNA form (sense

and anti-sense)3.Enzymes help new nucleotides

pair with free ends on single strand of DNA: A-T and C-G

4. A-T and C-G form hydrogen bonds between new nucleotide and the strand of DNA

Sense Anti- sense

DNA Replication

Final Product: 2 double helix DNA formations that are exact copies of the original DNA strand

Transcription of DNA-monks re-writing manuscripts

letter by letter (messenger writing down the plans before

they are carried away)• Happens in nucleus• Then mRNA exits into

cytoplasm carrying message

• Involves DNA and mRNA, and enzymes (polymerase)

Transcription

• 1. DNA "unzips " - enzyme breaks double and triple bonds between nitrogen base pairs (A-T, C-G)

• 2. Two strands DNA formed (sense and anti-sense)

• 3. Enzyme reads DNA base pairs and adds new nucleotides to match base pair (Uracil in place of Thyamine) (A-U, C-G)

Transcription - Final stages

• 4. The nucleotides are bonded at the phosphate and sugar creating the new strand of RNA.

• 5. RNA introns spliced out, leaving mRNA.

• Final Product: coded strand of mRNA

• Occurs in the cytoplasm (Endoplasmic reticulum)

• Molecules involved mRNA, tRNA, codons (3 bases), ribosomes, amino acids, and enzymes

Translation of mRNA- deciphering the code, like spies in WWII

(builders building the structure, using plans carried by messenger)

= Protein!

Translation - begins

• 1. First codon of mRNA strand attaches to a Ribosome (codon is 3 base pair combination)

• 2. tRNA carrying a specific amino acid, approaches ribosome.

• 3. Enzyme helps tRNA anti-codon to pair with codon on mRNA.

• 4. tRNA remains with amino acid attached to it.

Translation - continued

• 5. Next codon on mRNA slides along to ribosome, New tRNA anti-codon with specific amino acid is paired with codon on mRNA.

• 6. Amino acid is bonded with previous amino acid. (peptide bonds) tRNA breaks off, leaving bonded amino acids.

Translation - Finale

• 7. Process continues as each codon is paired with anti-codon, until STOP codon on mRNA is reached.

Final Product: Polypeptide chain also known as Protein!

Summary of Transcription and Translation