DNA and Mutations
- Created by: Natalie Simon
- Created on: 20-12-14 15:10
Nucleoacids
Purine: Adenine -NH2 -N, Guanine -NH2 =O -N (2 Rings)
Pyrimidine: Cytosine -NH2 -N =O, Thymine =O =O -CH3 -N (1 Ring)
Uracil =O, =O, -N
Base- 1'- Ribose (2'(OH or H) 5'-CH2OH- Phosphate
5'-3' end
0.34nm internucleotide distance
3.4nm one full twist (10 nucleotide turn-1)
2.0nm diameter of helix
RIGHT-HANDED
G-C: 3 hydrogen bonds
A-T: 2 hydrogen bonds
3 x 10^9 nucleotide pairs: 5um diameter: 146bp of DNA wrapped around a protein core of 8 histones = nucleosome
Genes: 4.6 x 10^7 nucleotides (1.5% of genome encodes protein)
23,000 genes (2,000 bases each)
Nucleoacids
Exons 1.5%
Introns 23%
Untranscribed areas near genes 2%
Repetitive DNA 50%
-Viral (LINES L1 6500bp)
-Non-Viral (SINES Alu repeat 160bp)
Satellite DNA (8%)
Semi-Conservative Replication
1. Helicase separate to form two replication forks
2. Primase makes RNA 5'-3' DNA polymerase 3 extends the primers DNA polymerase 1 removes the RNA and replaces with DNA
3. DNA ligase makes 5'-3' phosphodiester bond (join adjacent fragments)
3'-5' exonuclease
Telomerase makes telomeres at the ends (extends 3' end)
N-Ras (oncogene in rhabdosarcoma) - Gln-> His
CCR5 loss of 32 bp (individuals homozygous for 32 CCR5 allele are resistant to HIV-1)
CAG 36> Huntingtin (Htt) Huntigton's disease
Cri-du-Chat: Deletion chromosome 5
CML: 9/22 pieces chromosome swap
Mutations
Deamination: C->U (Pairs with A) A->Hypoxanthine (Pairs with C)
UV: Thymine dimers
UV-B (290-320nm) major mutagenic
UV-C: (180-290nm) lethal
Nitrous acid: C->U
Alkylating agents: Guanine modification
Free radicals: strand breaks
Repair:
Dealkylation by MTase
Nucleotide excision repair (NER)
NER defect: xeroderma pigmentosum (XP-D mutation)
HIV: AZT targets reverse transcriptase
Genetics and Inheritance
Down's: 21: ****** growth and development, cardiac abnormalities, acute leukaemia
Patau's: 13: Heart defects, incomplete brain development, spinal defects and seizures, small or missing eyes
Edward's: 18: Heart defects, intestines protruding outside body, kidney (5-10% survive 1 year)
**Y Klinefelter's: Small testes, infertility
X Turner's: Amenorrhoea, infertility
XYY: Increased growth
** Male: SRY (Transfer to X) (1/2000)
X Linked: Red-green colour blindness, Duchenne muscular dystrophy, X-linked ichthyosis
Mitochondria: 13 polypeptides r/tRNA
MELAS myopathy encephalopathy lactic acidosis stroke like episodes
LHONS Leber's herediatary optic neuropathy
-passed on by mother
Transcription/ Translation
RNA polymerase 5'-3' direction in phosphodiester bonds
Promoter Region + sigma factor + RNA polymerase
Termination Region + rho GC rich stem loop (STOP)
Eukaryotes
Capping 5' (mRNA) methylation at 7' end Guanosine
Polyadenylation (Poly A tail)
Transcription/ Translation
Translation
CCA-OH 3' end + 61 amino acids
A.A + tRNA + ATP -> aminoacyl-tRNA + PPi + AMP
70S Ribosome: 50S (23S rRNA + 5S rRNA + 34 proteins)
30S (16S rRNA + 21 proteins)
AUG- Shine-Dalgarno 16S rRNA
Initiaition: IF1/IF3 + 30S fmet-tRNAfmet AUG initiation codon + GTP-IF2 (Bind 50S subunit GDP + Pi)
Elongation: AA2 + EF-Tu GTP --> Peptidyl transferase -->
Translocation EF-G-GTP-->GDP + Pi
Termination: Stop codon: RF1/2 + IF3 + Ribosomal recycling factor + GTP hydrolysis
Transcription/ Translation
Translation
CCA-OH 3' end + 61 amino acids
A.A + tRNA + ATP -> aminoacyl-tRNA + PPi + AMP
70S Ribosome: 50S (23S rRNA + 5S rRNA + 34 proteins)
30S (16S rRNA + 21 proteins)
AUG- Shine-Dalgarno 16S rRNA
Initiaition: IF1/IF3 + 30S fmet-tRNAfmet AUG initiation codon + GTP-IF2 (Bind 50S subunit GDP + Pi)
Elongation: AA2 + EF-Tu GTP --> Peptidyl transferase -->
Translocation EF-G-GTP-->GDP + Pi
Termination: Stop codon: RF1/2 + IF3 + Ribosomal recycling factor + GTP hydrolysis
Antibiotics
Actinomycin: Bind to DNA prevent elongation by RNA polymerase
Rifamycin: Bind to RNA polymerase inhibit RNA synthesis
Streptomycin: 30S
Erythromycin: 50S (prevent translocation)
Chloramphenicol: peptidyl transferase inhibition by binding onto 50S
Tetracycline: inhibit aminoacyl-tRNAs by binding to ribosome
Puromycin: premature chain termination
a-aminitin: RNA polymerase II inhibitor
Cycloheximide: Translocation
Diphteria: RNA translational inhibitor by EF-2
Haemoglobin
yo2= po2/p50+po2 Sigmoidal curve
Increase in pH and decrease pCO2 increases affinity for O2 and BPG lowers it
HbF a2y2
HbA a2b2
Proximal His F8- O2Fe-His F8 Distal makes Co 200x not 20000x stronger
Moves 0.4Ao towards heme plane (F helix moving)
Hb transports 40% of H+ produced CO2 binds with Hb N-termini to produce carbamino terminal residues
transports 15% CO2 produced
Protonated His HC3 and Asp FG1 bind (stabilise T form) deoxy
p50 increases as BPG increases
HbF has H143S mutation and therefore BPG is less efficient
Regulation of Cell cycle
G1 (in absence of growth factors- G0) / S / G2 / M
Prophase: chromosomes condense, nucelolus disappears, cytoplasmic MT breakdown, spindle
Prometaphase: nuclear envelope breakdown, chromosome attach to spindle via. kinetochores
Metaphase: line up
Anaphase: sister chromatids split
Telophase: chromosomes decondense, nucleolus reforming and cytoplasmic MT reform
Cytokinesis: actin
Centrosome: pair of centrioles (0.5 x 0.2 um diameter) wall made up of 9 triplets of MT
MPF: Cdk1 cyclin B
SPF: Cdk 2 cyclin A/E
Rb represses E2F (p107 p130) Rb-P by Kinase Cyclin D1
Ras-GTP (low -ase activity) point mutation 12, 13, 61
HER2 EGFR
p53-p21-inhibits Cdk (S/M)
Mad1 prevents anaphase onset at kinetochores
Protein Synthesis
ER: Signal sequence: Non-Polar + Glu repeats
Mitochondria: Chaperones: Polar/Non-Polar + Arg repeats
Nucleus: Positive Lys/Arg + Importin
Lysosome: Mannose-6-Phosphate Inclusion cell disease
Related discussions on The Student Room
- DNA multiple choice question »
- What is DNA repair »
- 25 marker essay biology »
- Biology Paper 2 AQA Triple Higher 2023 »
- 25 mark essay question »
- Bacterial Cells »
- A question about DNA electrophoresis »
- Number of DNA molecules containig these two genes in each cell »
- Edexcel IGCSE science answering question »
- Classification, species concept and phylogeny - biology »
Comments
No comments have yet been made