Protein Synthesis Flashcards
(25 cards)
what are the features of prokaryotic DNA? (4)
- circular
- not associated with histones
- does not contain introns
- short (very few base pairs)
what are the features of eukaryotic DNA? (4)
- linear
- associated with histones
- does contain introns
- very long
what exactly are histones?
what is their job?
proteins
- make DNA very compact
define a gene
a sequence of DNA bases that codes for a polypeptide
genes within eukaryotic DNA
contain introns and exons
define an intron
do not code for a specific sequence of amino acids
define an exon
do code for a specific sequence of amino acids
define intergenic regions
sections between genes where there are multiple repeat sequences of DNA that do not code for proteins
define the genome
all the DNA in a cell
define the proteome
the full range of proteins produced by cells
how does the genome contribute to the creation of the proteome? (2)
via protein synthesis
- a sequence of three DNA bases (a triplet) codes for a specific amino acid
- during protein synthesis, the triplets are used to code for the primary structure of a polypeptide through processes such as transcription and translation
the genetic code is… (3)
- universal
- non overlapping
- degenerate
define universal
the same three bases used in DNA triplets / mRNA codons code for the same amino acids in all organisms
define non overlapping
each base is read only once in the triplet / codon
define degenerate
more than one triplet (DNA) / codon (mRNA) codes for a single amino acid
mRNA (4) vs tRNA (4)
mRNA
- single stranded
- linear
- has more nucleotides (longer)
- a copy of a gene
tRNA
- single stranded
- folds into a cloverleaf shape
- amino acid binding site
- contains an anticodon
what is an anticodon
made up of three bases that are complementary to mRNA codons
what is transcription?
where does this process take place?
- the production of mRNA from DNA
- takes place in the nucleus
describe the process of transcription (5)
- DNA HELICASE breaks hydrogen bonds between complementary base pairs
- only ONE DNA STRAND acts as a template
- FREE RNA NUCLEOTIDES align by complementary base pairing
- URACIL is used in place of thymine and pairs with adenine
- RNA POLYMERASE joins adjacent RNA nucleotides via phosphodiester bonds
what is the product of transcription?
pre-mRNA, which will still have introns
what happens to pre-mRNA following transcription?
in eukaryotes only, pre-mRNA is spliced so that the introns are removed
what is translation?
the production of polypeptides from the sequence of codons carried by mRNA
describe the process of translation (7)
- mRNA attaches to ribosomes
- **ribosome reads* the triplet codon to know which amino acid is needed
- tRNA brings a specific amino acid to the ribosome
- tRNA anticodons bind to complementary mRNA codons ; two can bind at any one time
- amino acids are joined by peptide bonds ; catalysed by the ribosome ; requires ATP
- tRNA is released
- ribosome moves along the mRNA to form the polypeptide
the first codon on mRNA is called the…
START codon
