DNA and RNA Flashcards
What’s the difference between RNA and DNA?
Deoxyribose and Ribose
Uracil instead of thymine
DNA - 2strands, RNA - 1strand
Whats a mononucleotide made of?
Sugar, Base, Phosphate
How do mononucleotides join together to form a polynucleotides?
Condensation reaction that forms phosphodiester bonds between the phosphate groups
How is a double helix formed?
2 DNA polynucleotide strands join together by hydrogen bonding between bases by complementary base pairing
Two antiparallel strands twist to form the DNA helix
How many bonds between A and T, C and G
A and T - 2
C and G - 3
Describe transcription
RNA polymerase breaks the hydrogen bonds in the DNA and the DNA unzips
DNA strand becomes a template and nucleotides line up and form hydrogen bonds with complementary base pairing forming mRNA
Leaves through the nuclear envelope and DNA zips up
Describe translation
mRNA moves to the ribosome
tRNA moves to the ribosome and the anticodon bonds to the mRNA via complementary base pairing
Another tRNA bonds and a peptide bond forms between the amino acids
the left over tRNA moves away leaving a peptide chain
Stop codon stops the translation and peptide chain moves away from the ribosome
Describe semi conservative replication
DNA helicase breaks the hydrogen bonds between bases causing the DNA to unwind
Both strands are templates
Free nucleotides line up and a condensation reaction occurs to form hydrogen bonds between the bases
2 double helixes form - each having an old and a new strand
Describe the difference between mRNA and tRNA
mRNA - nucleus, and carries genetic code to the cytoplasm
tRNA - cytoplasm, binding site for amino acids and an anticodon
What are mutations?
Change in the base sequence of DNA
What causes mutations?
Inversion, deletion, insertion, substitution
What do mutations do?
Causes a change in primary structure changing amino acids and therefore tertiary structure
Describe mutations in CF
CFTR channel open so less chloride ions, not working
DF508 - deletes 3 nucleotides loss of phenylanine misfolding the protein
Define genome
All genes in an individual
Describe ring structure of A,G,T and C
A&G have 2 ring structure, T&C have 1 making 3 ring structures overall
Describe genetic code
Non-overlapping: each base triplet is read in sequence, separate from the triplet before and after
Degenerative - several triplets can code for the same amino acid
Stop and start codon - Stop UAG
What is Meselson and Stahl’s model?
DNA from Ecoli had been grown in medium with heavy isotope Nitrogen
All nucleotides contain heavy N and DNA denser than normal
Bacteria moved into a medium with normal isotope - all new nucleotides incorporated into replicated DNA were light
Bacteria is allowed to divide and their DNA replicate once, extracted and centrifuged
Test tube is dissolved in solution and centrifuged heavy DNA sinks to bottom and light at top
Single band of medium - reject conservative
DNA extracted and centrifuged after 2 rounds - one medium and one light
Describe sickle cell anemia?
Sub in gene for haemoglobin A replaces T
mRNA has GUA not GAA
Non polar valine rather than polar glutamic acid so haemoglobin is less soluble
