Topic 2 - Genes And Health Flashcards
What are the two types of nitrogen- containing bases?
Purine - two rings. A and G
Pyrimidines - one nitrogen-containing ring. C, T and U
What is the phosphate group made of?
(PO4)^3-
What holds together the two strands in DNA?
Hydrogen bonds between complementary base pairs
What is the process of DNA replication?
DNA helicase splits strands
Free nucleotides form hydrogen bonds
DNA polymerase and DNA ligase join nucleotides together
What is the type of replication involved in DNA replication?
Semi conservative
How was it discovered that the method of DNA replication is semi conservative?
Grew e. Coli in medium with only 15N
Transferred to medium with only normal 14N
All DNA same density so semiconservative
What are nucleotides made of?
Phosphate
Pentose sugar
Organic nitrogenous base
Where does transcription occur?
In the nucleus
Where does translation occur?
On the surface of ribosomes
Which strand of DNA acts as a template for mRNA?
The antisense strand
What is the method of translation?
mRNA engulfed by ribosome tRNA attaches to specific amino acids tRNA molecule lines up against matching mRNA on ribosome Peptide links formed between amino acids tRNAs unbind to pick up more amino acids
What is a mutation?
A change in the genetic code
What are point mutations?
One or a small number of nucleotides miscopied
What are chromosomal mutations?
Changes in gene position within the chromosomes
What are gene deletion mutations?
Where a gene or set of genes are not copied
What is duplication mutation?
Where a gene or set of genes are copied multiple times
What are inversion mutations?
Where genes switch positions
What is s translocation mutation?
Where genes are copied onto the wrong chromosome
What are whole-chromosome mutations?
Where an entire chromosome is lost during meiosis or duplicated in one cell by errors in the process
What are anabolic reactions?
Reactions that build up new chemicals
What are catabolic reactions?
Reactions that break substances down
What is enzyme specificity?
Only catalyse specific reactions
What names do enzymes have?
Recommended name - urease
Systematic name
Classification number
What is the induced-fit hypothesis?
Active site not fully complementary to substrate until substrate fits into it
What is an enzymes molecular activity (turnover number)?
The number of substrate molecules transformed per minute by a single enzyme molecule
What is the temperature coefficient of an enzyme?
Rate of reaction at x+10C / rate of reaction at xC
What is a genes locus?
Its position on a chromosome
What is polygenic?
Controlled by several interacting genes
What is Thalassaemia?
Genetic disorder Affect haemoglobin polypeptide chains Prevents formation of either a or B chains in haemoglobin Symptoms of anaemia No cure Treated by blood infusion
What is alpha Thalassaemia?
Polygenic inheritance
Commonly caused by gene deletion
Various severities
Milder increases malaria resistance
What is beta Thalassaemia?
Mutations on one gene
Various severities
Most severe: Cooley’s anaemia
Recessive allele
What is albinism?
Melanin pigment does not form
Polygenic mutations
E.g. Tyrosinase not formed so no melanin produced
Recessive allele
What are multifactorial diseases?
Cause by combination of genes and lifestyle
What is the cell membrane structure?
Phospholipid bilayer (fatty acid tails away from solution Membrane proteins
Fluid mosaic model
What is facilitated diffusion?
Diffusion across a membrane through a protein
What is an isotonic solution?
Same osmotic concentration inside and outside
What is a hypotonic solution?
Osmotic concentration of solution lower than that of the cells
What is Fick’s law?
Rate of diffusion
= (surface area * concentration)/exchange membrane thickness
What is the structure of an alveoli?
Folded sac - high surface area
Lung surfactant - prevents collapse
Thin walls
Steep concentration gradient
What is the method of keeping mucus runny?
Chloride ions pumped into epithelial cells from surrounding tissue fluid
Chloride ions diffuse into fluid in airways through chloride channels(CFTR channels)
CFTR channel proteins prevent sodium ion exit from airways
Water moves out of cells and mixes with mucus
What does cystic fibrosis cause?
The CFTR channel to not work
Thick, sticky mucus
What are symptoms of cystic fibrosis?
Severe coughing fits - mucus build-up in lungs
Breathless
Pathogen build-up in lungs
Prevents digestive enzyme movement to gut - improper digestion and stay in pancreas (damage to pancreas)
More difficult for digested food to be absorbed into blood
Blocked cervix/tube carrying sperm out
Salty sweat
What are treatments of cystic fibrosis?
Physiotherapy Balanced diet Enzymes taken with food Drug therapies Transplant Infertility treatments Gene therapy
How does gene therapy work?
Restriction endonuclease cuts out gene and cuts plasmid
DNA ligase joins plasmid and gene
Recombinant DNA produced
Vector inserted
What are problems with gene therapy?
Extracellular barriers
Intercellular barriers
Keeping the gene expression going
What are methods of genetic screening?
Amniocentesis
Chorionic villus sampling
Preimplantation genetic diagnosis
How does amniocentesis work?
16th week of pregnancy
Amniotic fluid removed
Cells cultured
What are the disadvantages of amniocentesis?
Late in pregnancy
2-3 weeks before results
1% risk of spontaneous abortion
How does chorionic villus sampling work?
8-10 weeks of pregnancy
Embryonic tissue taken
What are the disadvantages of chorionic villus sampling?
2.5-4.8% risk of spontaneous abortion
Can’t detect problems in paternal X chromosomes
How does preimplantation genetic diagnosis work?
Egg and cell fertilised outside body
Secondary oocyte removed from each embryo
Genetic makeup checked and best implanted
