4.7 Genetic Diversity Flashcards
What is intraspecific variation?
Variation within a species
What is interspecific variation?
Variation between different species
What are monozygotic twins?
1 fertilised egg that splits into 2 identical zygotes
Therefore has exactly the same genes
Any differences would be down to environment
What are dizygotic or fraternal twins?
2 eggs are fertilised by 2 different sperm cells and are therefore non-identical and have different genes
Any differences could be due to genetics and/or environment
What are causes of intra and interspecific variation?
Genetics and environment
What are some genetic causes of variation?
Mutations - a change in the base sequence
Meiosis - crossing over, independent segregation
Random fusion of gametes
What are some environmental causes of variation?
Different environments influence gene expression
I.e proper or insufficient nutrients supplied
What are the types of variation?
Monogenic - controlled by just one gene (discontinuous)
Polygenic - controlled by more than one gene (continuous)
What is normal distribution?
Mean, median and mode are all the same
Explain the differences between mono and polygenic variation with graphs?
Monogenic - discontinuous falls into categories and distinct groups: plotted as a bar chart
Polygenic - continuous shows a range of measurements as it had more of an environmental impact: plotted as a line graph (usually numerical)
How could we describe continuous data?
Central tendency: mean, median and mode
Range/ IQ range
Standard deviation
What is standard deviation?
The spread of data around the mean
The larger the value the more spread out they are
What are the percentages linked to standard deviation?
1 SD away from the mean = 68% of the data
2 SD away from the mean = 95% of the data
3 SD away from the mean = around 99% of the data
How to work out standard deviation on calculator?
Mode 2 1 Type in numbers = AC Shift 1 4 4
What does it mean if the standard deviations overlap?
They are likely to be from one data set
As there is probably no significant difference
What does it mean if the standard deviations don’t overlap?
It tends to indicate there is a significant difference
Why is it difficult for biologists to take measurements?
There is variation
It has to be random
It has to be representative
Why might a sample not be completely representative?
Sampling bias - not completely random
Double counting samples/subjects
Random sampling (by chance) could lead you to pick all the small ones of something accidentally
What are the stages of random sampling?
Set out 2 long tape measures at 90 degrees
Use randomly generated co-ordinates to place a quadrat randomly
Count number in quadrat - top right rule (top line + right line count)
Work out population size or density- by finding mean daisies per quadrat and multiply by the number of quadrats
How do we reduce the effect of chance in random sampling?
Larger sample size
Use statistical analysis
Why can we track phylum?
Because DNA codes for RNA which codes for the sequence of amino acids which determines a proteins tertiary structure
Similar sequencing = closer related
How does DNA hybridisation take place?
DNA for two species is extracted, purified and cut into short pieces
DNA from one species is radio or florescently labelled and mixed with the other unlabelled DNA
DNA is heated to 90 degrees to separate strands then cooled
Some strands which reform will be made from one strand from each species = hybridisation identified by 50% labelling
Hybrid strands are separated, slow increased temp, temp which the strands join is recorded
In DNA hybridisation, what do loop and helixes show?
Where the bases are complimentary they form a typical helix structure
Where the bases are non-complimentary it creates a ‘loop’ (circle in the middle of strand)
Loops are due to mutations
Why do some hybrid strands require greater heat to separate the strands?
The more complimentary base pairs the more hydrogen bonds between the strands therefore requiring more heat to overcome
How can DNA hybridisation help see relationships between species?
The more mutations within the hybridisation the further related the two species are
As more mutations occur over evolutionary history
How can comparing amino acid sequences in proteins tell you how closely related two species are?
You can infer they have similar DNA sequences if they have similar amino acid sequences because the DNA codes for those sequences
What could be wrong with a sample when comparing amino acid sequences?
Only looking at a few amino acids
Only 1 sequence per species
Degenerate code of DNA means the same amino acid can be produced from different code
Introns also make the coding different but not used in amino acid sequences
What is serum?
Clear liquid that is left after the blood has clotted and the clot has been removed
Therefore blood plasma without the clotting factor
What is albumin?
A blood protein, important in control of blood water potential in formation of tissue fluid
(Which all mammals have)
How can we conduct immunological comparisons of proteins?
We take serum from a species (eg human) with Albumin in it
Inject this into a ‘rabbit’ which will produce antibodies specific to the albumins antigens (as foreign body to the rabbit)
Serum is extracted from the rabbit containing those antibodies, which is mixed with other species serum
The more antigen antibody complexes that form the closer related the species is to the first
In the immunological comparisons of proteins why when more antigen antibody complexes form does it indicate closer relations?
The more complexes that form it creates agglutination which forms a precipitate
The more precipitate produced the closer related the species are as the more complementary the antigen and antibodies were
