DNA & RNA Flashcards
what did Friedrich Miescher discover?
- found acid molecules rich in phosphate isolated from cells in the pus (in wounds)
- called it nuclein (DNA)
Eukaryotes VS Prokaryotes
Eukaryotes
- membrane bound organelles (e.g, mitochondria, Golgi apparatus)
- 20 micrometres
- in nucleus
DNA made of chromosomes (complexes of proteins and DNA –> chromatin)
Prokaryotes
-small & simple
- 2micrometres in diameter
- not membrane bound
-DNA is circular, supercoiled (naked DNA)
what is a chromosome?
Single DNA molecule, associated with proteins, folded into compact structure
what is a full set of chromosomes?
Karyotype
How can chromosomes be seen?
By staining with dyes
–> dark and light regions show condensed and less condensed regions
what are condensed regions in chromosomes called?
heterochromatin
(more gene pores)
(has more AT rich regions)
what does less condensed regions show?
more GC-rich
more gene-coding areas
what is the human genome size?
3 billion base pairs
How do genetic diseases occur?
by chromosomal abnormalities
what does non-disjunction mean?
Pair of chromosomes fail to separate during formation of gametes (sperm or egg)
- conditions are mostly caused by non-disjunction
What is a Philadelphia chromosome?
chunks of chromosomes moving to another chromosome
- Translocation of material between chromosome 9 and chromosome 22 –> forms BCR-ABL oncogenic fusion gene
(production and activation of BCR-ABL gene)
How does cystic fibrosis occur?
due to mutation in CFTR (channel that regulates influx of chloride ions) gene
most common mutation is deltaF508 –> deletion of 3nucleotides resulting in loss of 1 amino acid
Describe Griffiths experiment
bateria infection model
- experiments with streptococcus Pneumoniae injected into mice
-2 strains available (non-virulent (R) strain - didn’t kill mice & virulent strain (S) - killed mice)
virulent (s) - smooth, has polysaccharide coat surrounding it which makes it unrecognisable by immune system of mouse
non-virulent (R) - rough, doesn’t have polysaccharide coat so recognisable by immune system, can be pathogenic to mouse
- Took virulent strain, heat killed it (destroyed bacteria), mixed with non virulent strain & injected into mouse
–> found that can also kill mice
Why did the non-virulent strain also kill the mice?
Transformation principle
- transformation was permanent
- something from dead cell transformed living cell
Describe Avery’s experiment (1944)
(used Griffiths experiment)
- used fractionation techniques to purify DNA from solution of heat killed strain
- can treat those components with different enzymes (protease, RNase, DNase)
- took live rough strain and heat-killed smooth strain, treated with DNase, RNase, protease and then injected into mice
–> with DNase, found that the longer you have live smooth strain, animal survived
–> with RNase & protease, found that transformation still occurred and animal died
Supported idea that DNA was a genetic information that was being transformed
Describe Hershey & chase (1952) experiment
Used bacteriophage (T2, E.coli)
T2 bacteriophage labelled with sulphur 35 (protein) & phosphorus 32 (DNA)
Showed that only DNA from T2 enters not bacterium (E.coli), enabling to produce own coat protein
