4.2 - DNA and protein synthesis Flashcards
define genome
the complete set of genes in cell
define proteome
full range of proteins a cell is able to produce
draw a diagram of messenger RNA and describe its structure
- linear
- more nucleotides than tRNA
- codons
- different mRNAs have different lengths
draw a diagram of transfer RNA and describe its structure
- clover leaf shape
- hydrogen bonds
- amino acid binding site
- anticodon
- all tRNAs are similar lengths
what is transcription?
production of mRNA from DNA
where does transcription occur?
nucleus
describe the process of transcription
- helicase breaks hydrogen bonds between complementary DNA bases so the two DNA strands separate
- only one DNA strand acts as a template
- free RNA nucleotides are attracted to exposed bases according to base pairing rule, forming complementary base pairs
- RNA polymerase joins adjacent mRNA nucleotides by phosphodiester bonds
- stops when stop codon is reached
- RNA polymerase moves away and DNA rejoins
- prokaryotes: mRNA made
eukaryotes: pre-mRNA made, which is then spliced to remove introns to form mRNA - mRNA leaves nucleus via pore and attaches to ribosome in cytoplasm ahead of translation
(extra detail: only 12 DNA bases are exposed at a time to reduce the chance of damage to DNA)
what is splicing?
the removal of introns from base sequence
what is translation?
production of polypeptide from the sequence of codons carried by mRNA
describe the process of translation
- mRNA attaches to ribosome
- ribosome finds start codon
- tRNA brings specific amino acid attached to its amino acid binding site to ribosome
- anticodon on tRNA binds to complementary codon on mRNA
- two molecules can attach to mRNA at a time
- amino acids join by peptide bonds in condensation reaction using ATP
- tRNA molecules released/detach from amino acids
- ribosome moves along mRNA forming polypeptide chain until stop codon reached
name the type of bond between complementary base pairs in DNA, and between adjacent nucleotides
hydrogen bonds
phosphodiester bonds
compare DNA, mRNA and tRNA
DNA:
- double helix
- deoxyribose sugar
- ATCG bases
- stays in nucleus
mRNA:
- single stranded
- ribose sugar
- AUCG bases
- moves from cytoplasm to nucleus
tRNA:
- clover-leaf shaped
- ribose sugar
- AUCG bases
- moves from cytoplasm to nucleus
- made up of around 80 nucleotides
what are ribosomes made up of?
RNA and protein
