Molecular Genetics Flashcards
No of strands in DNA
Double stranded molecule
Nitrogen bases in DNA
Purine bases:
- Adenine (A)
- Guanine (G)
Pyrimidine bases:
- Cytosine (C)
- Thymine (T)
Backbone of DNA
Covalently bonded deoxyribose sugar phosphate residues
In DNA, what is the bond between deoxyribose sugar and residues?
Covalent bond
In DNA, which nitrogen base pairs with which base?
Purine with pyrimidine:
- A and T: Adenine pairs with Thymine (by 2 H-bonds)
- C and G: Cytosine pairs with Guanine (by 3 H-bonds)
(A, G are purine bases & C, T are nitrogen bases)
In DNA, how are two antiparallel strands held together?
By hydrogen bonds
In DNA, how can the hydrogen bonds (bondage between 2 strands) be disrupted & re-formed?
Disrupted by heating
Reformed by cooling
Full form fo DNA & RNA
DNA = Deoxyribonucleic acid
RNA = Ribonucleic acid
Where does DNA transcription occur?
Nucleus
In the nucleus, DNA is transcribed into-?
mRNA (messenger RNA)
Where does translation of mRNA occur?
Ribosome of cytoplasm
In ribosome of cytoplasm, mRNA is translated into-?
Polypeptide chain
Main structural difference between DNA & RNA
Strand: DNA >> double-stranded & RNA >> single-stranded
Nitrogen base: Thymine of DNA is replaced by Uracil in RNA (Rests are same)
Sugar backbone: DNA >> deoxyribose sugar; RNA >> ribose sugar
Purpose of PCR (Polymerase Chain Reaction)
From very small samples of DNA >>>>> to generate large amounts of DNA
Can PCR be adapted to use with RNA?
Possible, if RNA is first converted to DNA
What was the traditional DNA sequencing method & its disadvantages
Traditional method:
Taken DNA of individual axons (length up to approx. 1-2 kilobases, kb) >>> amplified by single PCR reactions >>> sequenced by ‘dideoxy (Sanger) sequencing’
Disadvantages:
Very difficult & expensive to test >>
- mutation in large genes
- heterogenous disorders
What is the new DNA sequencing method & its advantage?
Massively parallel sequencing technologies (since mid-2000)
Advantages:
- Single experiment reads millions DNA bases
- Cost fallen dramatically
- Single investigation for heterogenous disorders (HOCM, retinal dystrophy etc.)
- Undiagnosed conditions/phenotype >>>>> offered sequencing of whole exome (all coding genetic material) >>>>> to indentify the responsible mutation
Disadvantage:
- Requires significant infrastructure & bioinformatic expertise
How to detect CFTR gene mutation in the delta F508 region of chromosome 7?
Routine molecular testing >> only looks for comonly identified mutations >> so, 15% cases are missed (& so can not exclude cystic fibrosis)
“Sequencing of whole CFTR gene” can demonstrate rare alleles
