Amino Acids - structure
- H(2)NCHRCOOH
- amine (H2N) + carboxylic acid (COOH)
- peptide bond
- condensation reaction
Protein Structure- primary
- SEQUENCE and NUMBER of AMINO ACIDS in polymer
- determined by genes
Protein Structure - secondary
- INTERACTIONS between amino acids
- alpha helix - globular proteins, soluble
- beta pleated sheet - fibrous proteins, insoluble
Protein Structure - tertiary
- determines WHAT structure DOES
Protein Structure - quaternary
- only for proteins with MORE THAN ONE POLYPEPTIDE
- eg haemoglobin, collagen
Mucus Regulation - too runny
- NA IONS OUT of MUCUS through Na pump (ENaC) into tissue fluid
- POTENTIAL DIFFERENCE created - due to raised Na conc in tf
- ELECTRICAL GRADIENT formed causing Cl to MOVE put of MUCUS into tissue fluid - diffuse between gap in cells
- WATER drawn OUT of cell by osmosis into tissue fluid
Mucus Regulation - too sticky
- Cl IONS OUT of TISSUE FLUID through CFTR channel into mucus
- ELECTRICAL GRADIENT between mucus and tf
- Na ions diffuse out of tf into mucus
- WATER drawn out of cell INTO MUCUS - osmosis
Mucus Regulation - cystic fibrosis
- CFTR missing or non functional
1. Cl ions can’t pass into mucus
2. Na pump not blocked so Na drawn into tissue fluid
3. Cl follows it into tf (electrical gradient)
4. mucus becomes even thicker
Nucleotides - structure
Phosphate, Deoxyribose (sugar), Organic base (A,T,C,G)
- joined by condensation reaction
Polynucleotides
- Strand joined by phosphodiester bond
- two strands form DOUBLE HELIX - joined by hydrogen b
- antiparallel structure
Transcription - process
Copying a gene’s DNA sequence to make an RNA molecule
- RNA polymerase attaches to DNA
- Hydrogen bonds between bases break
- Template strand transcribed - mRNA molecule w/ same base sequence as DNA coding strand
- Complementary RNA nucleotides align into position
- Phosphodiester bonds form
- mRNA molecule produced
Translation - process
Turning sequence of bases into sequence of amino acids
- mRNA attaches to ribosome
- tRNA molecules comp base pair w/ mRNA
- Next tRNA molecule binds to mRNA and peptide bond forms between the two amino acids
- the ribosome moves along mRNA
- first tRNA molecule leaves - leaving the amino acid
Nature of Genetic Code - triplet code
- Non overlapping
- Degenerate - several code for same aa
DNA replication - process
- DNA unwinds - H bonds break
- free DNA nucleotides line up alongside DNA strand - H bonds form
- DNA polymerase links adjacent nucleotides w/ phosphodiester bonds - forming new comp strand (original strand as template)
- Two new DNA molecules formed - semiconservative replication
Genetic Screening
Amniocentesis - insert needle into amniotic fluid to collect foetal cells - 15-17 weeks - 1% chance miscarriage Chronic Villus Sampling - Placental tissue removed through wall of abdomen or vagina - 8-12 weeks - 1-2% chance miscarriage
Non Invasive methods of screening
Non-Invasive Prenatal Diagnosis
- analyse DNA fragments in mothers blood plasma - some DNA from embryo
- 7-9 weeks
- no miscarriage risk
Preimplantation Genetic Diagnosis
- IVF
- cell removed and tested - then implanted
- low success and live birth rate rate (30%)
