Protein Synthesis: Transcription and Translation
DNA→RNA→Protein
Protein Synthesis occurs in two major parts:
transcription and translation.
1) DNA _Transcription - the process of producing an RNA molecule from a
DNA molecule (DNA→RNA)
a) Occurs in the Nucleus
b) The part of the DNA that is copied is determined on what protein_is needed
to be made.
c) Steps of DNA Transcription:
1. The DNA uncoils/ unzips
2. Hydrogen bonds between the nitrogen bases are
broken by an enzyme.
3. Free RNA nucleotides match the complimentary
DNA nitrogen bases.
4. The phosphate of one RNA nucleotide bonds to the
ribose of the next RNA nucleotide.
5. The RNA molecule leaves the DNA molecule and the
DNA nitrogen bases bond together again.
(zip back up).
d) Outcome: one single stranded RNA (called mRNA).
RNA Nucleotide Structure:
1. Ribose
2. Phosphate
3. Base
Compare DNA and RNA:
DNA
RNA
Double Strand
Single Strand
Deoxyribose (sugar)
Ribose (sugar)
Contains Thymine
Contains Uracil
Stays in nucleus
Leaves nucleus
Forms of RNA:
1. mRNA= messenger RNA
a. Carries code of DNA bases used for
protein synthesis
b. Single strand
2. tRNA= transfer RNA
a. Picks up amino acids in cytoplasm
and brings them to the ribosome.
b. Cloverleaf shape
3. rRNA=
ribosomal RNA
a. Produces the enzymes needed
to form peptide bonds.
b. Globular in shape
3) DNA Translation- the process of converting the
nitrogen base code of the
mRNA into sequence of Amino Acids (RNA→Protein)
a) Occurs on the ribosome.
b) There are 20 different amino acids determined by the codon on the mRNA
c) Codon= A sequence of nitrogen bases (humans have 64 different codons
i) Types include: DNA codon, mRNA codon, and tRNA anticodon