DNA

Chapter 12

DNA• DeoxyriboNucleic Acid• Sugar = deoxyribose• Adenine + Thymine• Guanine + Cytosine• Double-stranded helix with alternating

sugars and phosphate groups• Only found in the nucleus

DNA Replication• Takes place in nucleus

• Uses enzyme polymerase

• Separates double-strand….produces two single strands

• Complimentary strands are made using the original DNA strands as templates

• A + T, C + G

Transcription

• RNA Polymerase – separates complimentary DNA and original strand

• Complimentary strand is used as a template to make an RNA strand...Uracil replaces thymine

• DNA-GCATTAGC = • RNA-CGUAAUCG

RNA

• RiboNucleic Acid• Sugar = ribose• Single-stranded• Uracil + Adenine

–(There is NO thymine in RNA)• Cytosine + Guanine • Found in nucleus and outside nucleus

mRNA• Messenger RNA (carries a message)• Made during transcription inside

nucleus• Thymine is replaced with uracil in order

to fit outside the nuclear membrane• mRNA carries a message out the

nucleus to the ribosomes, where it is called rRNA (ribosomal RNA)

Translation

• In ribosomes…where proteins are made• Codon – group of 3 bases (AAT) that is found

on the rRNA…every 3 bases acts as a codon• A tRNA (transfer RNA) carries an amino

acid…tRNA are groups of three bases…this is called an anti-codon.

• An anticodon fits into specific codons that match the base sequences and brings along specific amino acids

Protein Synthesis

• The amino acids bond together with peptide bonds

• Amino acids are the building blocks of all proteins

• Every variety of amino acids codes for a different trait

• If the order of bases gets mixed up, the codon will change, changing the matching anti-codon, changing the amino acid, changing the protein it codes for, changing the trait