3.4.2 DNA and protein synthesis Flashcards
1
Q
what is the structure of mRNA?
A
- linear.
- single strand.
- no hydrogen bonds.
- consists of many codons.
- no amino acid binding site.
2
Q
what is the structure of tRNA?
A
- clover leaf shape.
- linear.
- held in shape by hydrogen bonds.
- has a single anticodon.
- has an amino acid binding site.
3
Q
what is the route of protein synthesis?
A
DNA (nucleus)»_space;»transcription»_space;»mRNA (cytoplasm)»_space;»»translation»»> protein (ribosome)
4
Q
what are the steps of transcription?
A
- DNA helicase seperates DNA’s double stranded double helix into two single strands, which breaks the hydrogen bonding between the DNA base pairs.
- only one DNA strand acts as a template (antisense strand).
- free RNA nucleotides form hydrogen bonds with the template strand using complementary base pairing = adenosine pairs with uracil and guanine pair with cytosine.
- RNA polymerase joins the adjacent RNA nucleotides forming phosphodiester bonds.
5
Q
what is pre-mRNA?
A
a section of mRNA that has both introns (non-coding) and exons (coding) RNA.
6
Q
how do you form mRNA from pre-mRNA?
A
by splicing using spliceosome, which cuts the non-coding RNA (introns) out.
7
Q
what are the steps of translation?
A
- mRNA leaves the nucleus via the nuclear pores into the cytoplasm, where it attaches to a ribosome.
- tRNA enters the ribsome and their anticodon binds to the complementary mRNA codon = following complementary base pairing adenosine binds with uracil and cytosine binds with guanine.
- each tRNA brings a specific amino acid.
- hydrogen bonds form between mRNA and tRNA.
- the amino acids on the adjacent tRNAs are joined by peptide bonds which are formed by condensation reactions with the help of ATP.
- tRNA is released after amino acid is joined to the polypeptide chain.
- the ribosome moves along mRNA to form the polypeptide and when it meets a stop codon it detaches.
8
Q
where does RNA polymerase bind?
A
the promoter region.
