1
Q
What is the genome?
A
- complete set of genes in a cell of an organism
2
Q
What is the proteome?
A
- full range of proteins that a cell is able to produce
3
Q
Describe the structure of an mRNA molecule.
A
- single stranded
- linear
- has a codon
- bigger than tRNA
4
Q
Describe the structure of an tRNA molecule.
A
- single stranded
- folded into a cloverleaf shape held in place by H bonds
- has an AA binding site
- has an anticodon
5
Q
What are the 2 stages of protein synthesis?
A
- transcription: production of mRNA from DNA
- translation: production of polypeptides from sequence of codons carried by mRNA
6
Q
Describe transcription.
A
- DNA helicase breaks H bonds in a section of DNA, causing DNA helix to unwind, forming 2 strands w exposed nucleotide bases
- 1 strand acts as a template for free mRNA nucleotides, in nucleus, to join by complementary base pairing, using uracil instead of thymine
- RNA polymerase joins adjacent RNA nucleotides together by phosphodiester bonds to form mRNA in prokaryotes or pre-mRNA in eukaryotes
- in eukaryotes, pre-mRNA is then spliced to form mRNA
- mRNA then leaves nucleus via a pore in nuclear envelope
7
Q
Describe splicing in eukaryotic cells.
A
- pre-mRNA is converted into mRNA by removing introns + joining functional exons together
8
Q
What is alternative splicing?
A
- when exons of genes are spliced in diff ways, forming diff mature mRNA, meaning 1 gene can produce >1 polypeptide chain
9
Q
Describe translation.
A
- mRNA attaches to a ribosome in cytoplasm
- a tRNA molecule, w a specific AA on 1 end + an anticodon on the other, binds to complementary mRNA start codon
- another tRNA molecule w a diff AA binds to next codon on mRNA molecule
- as ribosome moves along mRNA, AAs join together via a peptide bond, using ATP + an enzyme catalyst, to form a polypeptide
- 1st tRNA is released after AA is joined to polypeptide
- process repeats until ribosome reaches a stop codon, which causes ribosome to detach + translation to end
