Evolution

PCR

polymerase chain reaction

\-create multiple copies of a specific section of DNA from a sample (amplification)

\-useful when only small amounts of DNA available for analysis

Stages of PCR

1. Denaturing = heating DNA to separate the two strands

2. Hybridisation/Annealing = primer added to DNA & bind to complementary base sequences on separated strands (starting point for replication)

3. synthesis/Elongation = DNA polymerase synthesis DNA code and build complementary strand of DNA (34 min)

Thermocycling

process of repeated heating and cooling

Gel electrophoresis

technique - separate DNA strands based on their lengths

Process of gel electrophoresis

\-DNA pieces placed in wells in semi-solid gel - immersed in solution of an electrolyte

\-electrodes at either end of gel (negative electrode close to DNA & positive opposite side)

\-electric current passed through gel, DNA (- charge) move towards + electrode

\-small DNA pieces move faster = located further away from negative electrode when current stopped

DNA profile

banding pattern on gel electrophoresis

\-used to establish individual’s identity/parentage

Filling the wells

\-wells = depressions in gel

\-DNA accurately placed in wells using micropipette (disposable tips can be put on n off without contact = ↓ chance of cross-contamination)

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DNA ladders

\-run at the same time as samples

\-contain segments of DNA with known lengths = compare unknown sample to determine length of DNA strands in sample

Visualising DNA

\-ethidium bromide added to agar prior to get being set = DNA picks up chemical

\-DNA fluoresce under special uv light

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\-methylene blue = dye binds to DNA

\-areas containing DNA stain = a deeper blue = visible to naked eye

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DNA probes = short sections of a single strand of DNA with. radioactive or fluorescent molecule - binds to DNA tested

DNA sequencing

determination of precise order of nucleotides in a sample of DNA

\-identify mutations/ compare DNA from different organisms

\-useful in identifying inherited disorders = sickle cell anaemia, cystic fibrosis + some cancer

\-maternity and paternity tests

\-compare species - track evolutionary changes

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When DNA forms

each nucleotide loses two phosphate groups

sugar molecule loses a Hydrogen atom from OH group (hydroxy) when bond to phosphate group of an adjacent nucleotide

Sanger method

\-nucleotides that lack OH group added to growing strand (ddNTPS = dideoxyribonucleotides/ dideoxyribonucleotide triphosphate)

\-stop elongation of sequence because no OH group for next nucleotide to attach to = create different lengths of DNA

\-separated (gel electrophoresis) - know which base was added - create each length length = determine order of nucleotides

Autonomy

\-respect for right to be self-determining & choose whether or not to be tested

\-right of individual to decide their own future, independent of genetic information

Confidentiality

use of genetic information is treated sensitively, is accessed only by those who are authorised to access it

Equity

right to fair and equal treatment regardless of genetic information

Privacy

right to be ‘left alone’ and to make decisions regarding genetic testing & resulting information, independent of others

evolution

gradual process of change in the inherited traits of a population of organisms from one gen to the next

\-permanent change in a population’s gene pool from one gen to the next

Fossil record

organisms in the past not same as organism alive today (phylogeny of the horse)

Amino acid sequencing

\-proteins = long sequences of amino acids

\-sequences very similar = closely related species

\-sequence less similar = distantly related species

\-indicate evolution from common ancestor

Ubiquitous proteins

\-found n all living organisms

e.g. Cytochrome C = protein used to produce energy

\-contain 104 amino acids = strong evolution for ancestral evolution of all species

Comparative studies of DNA

\-sequences of bases (AT,G,C) similar in closely related species

\-sequence less similar = more distantly related species

\-similarity of DNA indicates evolution from a common ancestor

Mitochondrial DNA (mtDNA)

\-small amt of DNA present in mitochondria )small & circular with 37 genes needed of mitochondrial function)

\-mtDNA extraction easier than nucleic DNA

\-only inherited from mother’s egg

\-mutation rate of mtDNA high,

Bioinformatics

involves use of computers (software, statistics, mathematics & engineering) = describe molecular components of living things

\-trace evolution of organisms by looking at changes in DNA

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Annotation

whole genomes have been compared in a process

Mineral replacement

\-varying degrees of mineral replacement (0-100%)

Stage 1 - minerals from groundwater fill pores in the bone or shell (permineralisation)

Stage 2 -minerals forming the bone matrix/shell - dissolved away and replaced by minerals in groundwater

carbonisation

occurs in very fine-grained rocks

mummification

occurs when soft and/or hard tissues exposed to chemicals, extreme cold, very low humidity, or lack of air (bodies sealed in fine sediment, resin or tar)

Relative dating

\-compare age of one thing with that of something else

Superposition

lower beds in a sedimentary sequence are older than rocks above

Youngest

↑

|

↓

Oldest

Comparative stratigraphy

study of sedimentary rocks

\-sequence of sedimentary rocks in different areas is similar = likely are of same age

index fossil

fossil of a species that can be used for relative dating

\-distinctive appearance, short time span + have broad geographical distribution

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Radiometric dating

absolute dating method for determining chronological age of a rock or mineral by measuring proportions of original radioactive material and its decay product

Half life

unique rate of decay - time taken for half of any given amount of isotope to decay

Common radioisotopes commonly used for radiometric dating

Carbon-14 → Nitrogen-14

Potassium-40 → Argon-40

Limitations of radiometric dating methods

C14 dating - must be organic (has carbon), maximum is 50000 - 60,000 years

Potassium-argon dating must be igneous rock, minimum age 200,000 years