Topic 1.4 DNA and protein synthesis Flashcards
1
Q
How many rings do pyramidine bases have
A
one
2
Q
How many rings do purine bases have
A
two
3
Q
which are the pryamidine bases
A
cytosine
thymine
uracil
4
Q
which are the purine bases
A
adenine
guanine
5
Q
how many bonds form between adenine and thymine
A
2
6
Q
how many bonds between cytosine and guanine
A
3
7
Q
Why is complementary base pairing so important?
A
- key to stability of the DNA double helix (although individul H bonds are weak, millions provide strength)
- its the way the way in which genetic info can be transferred DNA to RNA
- its the way the way amino acids are assembled into polypetides –> proteins
8
Q
which is the sense which is the antisense strand
which is coding and which is template
A
sense: 5’–> 3’ (coding)
antisense: 3’–> 5’ (template)
9
Q
3 features of the genetic code
A
- non-overlapping
- degenerate
- universal
10
Q
3 types of RNA
what are they
A
- mRNA : messenger RNA carries a copy of a single gene to a cell’s ribosomes
- tRNA : transfer RNA carries indiviual amino acids to ribosomes during protein synthesis
- rRNA : ribosomal RNA forms part of the sub units of ribosomes
11
Q
describe the structure of tRNA
A
- single strand folded into clover shape (some paired bases)
- anticodon on one end, amino acid binding site on the other
(- anticodon binds to complementary mRNA codon and amino acid corrsponds to specific anticodon)
12
Q
Describe semi conservative DNA replication
A
- DNA helix unzips, H bonds broken between complementary base pairs. DNA helicase catalyses unravelling of helix
- antisense strand (3’–>5’) is used as template. Free nucleotides line up and complementary base pairing occurs between the template strand and free nucleotides.
- adjacent nucleotides are joined by phosphodiester bonds formed in condesation reactions
- this is catalysed by DNA polymerase
- the new DNA molecules automatically fold into double helices as H bonds are formed within the moelcule
- DNA ligase joins up newly synthesised sections of DNA
semi conservative
because one strand of original is maintained
