Biology A2 Flashcards

Topic One: Applications of genetics

Abundance definition?

-The number of individuals of the same species in a given area or volume.

Distribution definition?

-The area or volume in which a species is found.

What does the capture-mark-recapture method measure?

-The abundance of individuals.

What are the two requirements/factors of the capture-mark-recapture method?

-The number of animals captured must be large enough to be valid.

-The animals must be quite highly mobile (it is useless in animals that move very little).

Can you recite the five steps of the capture-mark-recapture method?

-One: sample the population by capturing as many individuals as possible.

-Two: mark each animal in a way to distinguish it from the unmarked animals.

-Three: return the animals to their habitat and leave them for a long enough period for mixing with the remaining population to occur.

-Four: take another sample of the population.

-Five: determine the number of marked individuals in that sample and use the given equation to estimate the overall population size.

What is the equation for estimating the overall population size?

-Number on day one X Number on day two

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        Number of marked in sample two

It is problematic if too long or too short a time is left between the obtaining of the two samples. Can you explain why each of these are a problem?

-Too long: marked organisms are more likely to have died or moved out of the area.

-Too short: marked organisms would not have had enough time to mix with unmarked organisms.

When using this method (capture-mark-recapture) what assumptions are we relying on?

-Marked and unmarked organisms are captured randomly.

-Marks are not lost.

-Organisms are not territorial so mix back in with other organisms.

-Marking organisms does not impact their rate of survival.

Which two types of organisms would be unsuitable for this method?

-Non/slow moving organisms.

-Territorial organisms.

What are the different methods for marking organisms?

-Paint/dye (paint markings on fur).

-Banding (leg bands on birds).

-Tags (mammal ears, crayfish shell and skin).

Short tandem repeats definition?

-Non coding nucleotide sequences, typically 2 to 6 base pairs long which repeat themselves many times.

Primer's definition?

-Short sequences of single stranded DNA which are made to bind to the regions flanking the sections of DNA to be copied by PCR. 

-They allow DNA polymerase to attach.

Probes definition?

-Short pieces of DNA labeled with a fluorescent or radioactive marker. 

-Used to detect the presence of specific bases/sequences in another piece of DNA by complementary base pairing.

Genome definition?

-The complete set of DNA in an organism.

How many times can STR’s (Short Tandem Repeats) repeat?

-Up to 100 times.

What are STR’s also known as?

-Microsatellites.

Can you name the three main steps in DNA profiling using PCR?

-Step One: the extraction of DNA from a sample.

-Step Two: the amplification of microsatellites using PCR.

-Step Three: the visualisation of fragments on gel.

Can you describe step one of DNA profiling using PCR?

-A sample of DNA is collected from the tissue of an organism.

-It is treated with chemicals in order to extract it.

-Finally, it is separated and purified.

Can you describe step two of DNA profiling using PCR?

-Specific primers that attach to the flanking regions either side of the STR’s are used to make large quantities of the STR’s and the flanking regions.

-Only the STR’s and flanking regions are replicated, no other part of the DNA.

Can you describe step three of DNA profiling using PCR?

-The fragments are separated by length using gel electrophoresis.

-Negatively charged DNA moves towards the positive terminal/electrode and vice versa.

-Smaller fragments travel faster than larger ones which lag behind.

Where are microsatellites/STR’s found?

-In genes: specifically near centromeres and telomeres.

Can you describe the properties of STR’s which are important to the application of DNA profiling technology?

-They are non coding nucleotide sequences.

-They have a length of 2 to 6 base sequences.

-They repeat themselves many times over (up to 100 times).

-The human genome has many different STR’s.

-Equivalent sequences in different people vary in numbers of repeats (e.g. some repeat 20 times whereas others repeat 27 times).

What is the role of gel electrophoresis in the process of DNA profiling?

-It separates DNA fragments, according to size. 

-This is done to create the fingerprint.

-Smaller fragments travel further.

What is the role of PCR in the process of DNA profiling?

-It is used to make many copies of the STR.

-Only sites are amplified/copied because the primers are very specific.

What are the three steps of the polymerase chain reaction?

-Step One: Denaturation.

-Step Two: Annealing.

-Step Three: Extension.

What percentage of the human genome makes an individual's genetic fingerprint unique?

-0.1%.

What percentage of human DNA codes for proteins?

-Less than 2%.

How many bases repeat in introns?

-13 multiplied by several hundred.

How many copies of DNA does PCR make?

-Millions.

What is the optimum temperature of Taq polymerase?

-80 degrees celsius.

Which temperature is the original DNA heated to in order to separate the two strands?

-95 degrees celsius.

Which temperature is the DNA cooled to for the primers to anneal the bases?

-55 degrees celsius.

Which temperature is used for the complementary strand to form?

-70 degrees celsius.

At which rate does Taq polymerase make an error?

-1 in 9000.