3.1.5 - Nucleic Acids Flashcards
1
Q
DNA nucleotide structure
A
deoxyribonucleic acid:
- deoxyribose sugar
- adenine, thymine, cytosine, guanine
- phosphate group
2
Q
RNA nucleotide structure
A
ribonucleic acid:
- ribose sugar
- adenine, uracil, cytosine, guanine
- phosphate group
(RNA is shorter than DNA and 1 strand)
3
Q
structure of DNA
A
- polymer of nucleotides (polynucleotide)
- each nucleotide formed from deoxyribose, phosphate group and nitrogenous base
- phosphodiester bonds between nucleotides
- double helix (2 strands) held by hydrogen bonds
- pairing between adenine-thymine (A-T) and cytosine-guanine (C-G)
4
Q
semi-conservative replication of DNA
A
- DNA helicase breaks hydrogen bonds between base pairs and double helix unwinds
- each strand acts as a template
- free DNA nucleotides attracted to exposed bases on template strands → base pairing
- DNA polymerase joins adjacent nucleotides via condensation reactions forming phosphodiester bonds
5
Q
phosphodiester bond formation
A
- condensation reaction (loss of water)
- between phosphate and deoxyribose
- catalysed by DNA polymerase
6
Q
features of DNA important for replication
A
- weak/easily broken hydrogen bonds between bases allow two strands to separate/unwind
- two strands so both can act as templates
- complementary base pairing allows accurate replication
7
Q
why can new nucleotides only be added in a 5’ to 3’ direction?
A
- DNA polymerase enzyme has active site with specific shape
- only complementary with/binds to 5’ end of strand
- DNA has antiparallel strands
- shape of nucleotides at 5’ end and 3’ end are different
8
Q
what are ribosomes formed from?
A
RNA and proteins
9
Q
histone
A
protein associated with DNA in a chromosome
