DNA Structure And Function Flashcards
Scientists believed that …. carried genetic information
Proteins
Frederick Griffiths 1928 experiment
R and S strains Bacteria
S strain virulent
Mixed heat-killed S and R, mice died
R strain took up a transforming principle
Hersey-Chase Experiment
Sample 1= 35 S, only showed in proteins- remained outside of cell&supernatant
Sample 2= 32P, found in DNA and hence in infected bacteria&pellet
DNA Structure
Nitrogenous base
Deoxyribose
Phosphate group
A-T
C-G
RNA Structure
Nitrogenous base
Ribose sugar
Phosphate group
A-U
C-G
Purines
Two ring structure
Pyrimidines
Single-ring structure
A-T has how many hydrogen bonds?
2
C-G has how many hydrogen bonds?
3
Phosphate groups are …… charged and hence ….
Negatively
Repel
Nucleotides are joined by ….. bonds
Phosphodiester
Phosphate groups are the source of…
H+ (acidity)
DNA is an antiparallel structure with the strands…
5’-3’
3’-5’
3 nucleotide letters
Codon
Polymer of nucleotides
Nucleic acid
Initiates the translation of the first amino acid
Start codon
Central dogma
DNA —> RNA —> PROTEIN
Exception of Central dogma Is?
Viruses that use reverse transcriptase to make DNA from RNA
Technique based on selective incorporation of chain-terminating deoxynucleotides by DNA polymerase
Sanger sequencing
Technique to separate DNA fragments by mass
Gel electrophoresis
Each strand of a double helix acts as a template for new, complementary strand
Semi-conservative replication
Meselson and Stahl experiment
DNA replication in 14N and 15N (density difference)
1st gen= mixture of both
2nd gen= two distinctive 50/50 bands
Enzyme that unwinds the two strands by temporarily breaking parts of the backbone
Topoisomerase
Breaks the hydrogen bonds between nitrogenous bases
Helicase
Adds RNA primer at leading strand
Adds DNA polymerase III to add nucleotides in 5’-3’ direction
PRIMASE
Removes RNA primer and replaces it with newly synthesised DNA
DNA POLYMERASE I
When strand is interiors during transcription it creates…
Okazaki fragments
Links Okazaki fragments
DNA LIGASE
Helps hold DNA polymerase in place whilst nucleotides are being added
Siding clamp
Binds to single-stranded DNA to avoid DNA rewinding back
Single-stranded binding proteins
DNA sequences at the end of the chromosome involve a single sequence TTAGG repeated
TELOMERES
Telomeres act as…
Caps that protect interal regions of chromosomes
The 3’ overhang is due to…
Shortening chromosome due to rod-shape and linear
Does not get covered by Okazaki fragments and leaves a gap
Complementary RNA is provided for the 3’ overhang by…
TELOMERASE
Replaces bases by exonuclease
Mismatch repair
Exchange base for another, length unchanged
Substitution
Adds a base, length increases
Insertion
Removes a base, length decreases
Deletion
