4.7 Genetic Diversity

Question 1

What is intraspecific variation?

Answer 1

Variation within a species

Question 2

What is interspecific variation?

Answer 2

Variation between different species

Question 3

What are monozygotic twins?

Answer 3

1 fertilised egg that splits into 2 identical zygotes
Therefore has exactly the same genes

Any differences would be down to environment

Question 4

What are dizygotic or fraternal twins?

Answer 4

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

Question 5

What are causes of intra and interspecific variation?

Answer 5

Genetics and environment

Question 6

What are some genetic causes of variation?

Answer 6

Mutations - a change in the base sequence

Meiosis - crossing over, independent segregation

Random fusion of gametes

Question 7

What are some environmental causes of variation?

Answer 7

Different environments influence gene expression

I.e proper or insufficient nutrients supplied

Question 8

What are the types of variation?

Answer 8

Monogenic - controlled by just one gene (discontinuous)

Polygenic - controlled by more than one gene (continuous)

Question 9

What is normal distribution?

Answer 9

Mean, median and mode are all the same

Question 10

Explain the differences between mono and polygenic variation with graphs?

Answer 10

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)

Question 11

How could we describe continuous data?

Answer 11

Central tendency: mean, median and mode

Range/ IQ range

Standard deviation

Question 12

What is standard deviation?

Answer 12

The spread of data around the mean

The larger the value the more spread out they are

Question 13

What are the percentages linked to standard deviation?

Answer 13

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

Question 14

How to work out standard deviation on calculator?

Answer 14

Mode 2
1
Type in numbers
=
AC
Shift 1
4
4

Question 15

What does it mean if the standard deviations overlap?

Answer 15

They are likely to be from one data set

As there is probably no significant difference

Question 16

What does it mean if the standard deviations don’t overlap?

Answer 16

It tends to indicate there is a significant difference

Question 17

Why is it difficult for biologists to take measurements?

Answer 17

There is variation
It has to be random
It has to be representative

Question 18

Why might a sample not be completely representative?

Answer 18

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

Question 19

What are the stages of random sampling?

Answer 19

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

Question 20

How do we reduce the effect of chance in random sampling?

Answer 20

Larger sample size

Use statistical analysis

Question 21

Why can we track phylum?

Answer 21

Because DNA codes for RNA which codes for the sequence of amino acids which determines a proteins tertiary structure

Similar sequencing = closer related

Question 22

How does DNA hybridisation take place?

Answer 22

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

Question 23

In DNA hybridisation, what do loop and helixes show?

Answer 23

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

Question 24

Why do some hybrid strands require greater heat to separate the strands?

Answer 24

The more complimentary base pairs the more hydrogen bonds between the strands therefore requiring more heat to overcome

Question 25

How can DNA hybridisation help see relationships between species?

Answer 25

The more mutations within the hybridisation the further related the two species are

As more mutations occur over evolutionary history

Question 26

How can comparing amino acid sequences in proteins tell you how closely related two species are?

Answer 26

You can infer they have similar DNA sequences if they have similar amino acid sequences because the DNA codes for those sequences

Question 27

What could be wrong with a sample when comparing amino acid sequences?

Answer 27

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

Question 28

What is serum?

Answer 28

Clear liquid that is left after the blood has clotted and the clot has been removed

Therefore blood plasma without the clotting factor

Question 29

What is albumin?

Answer 29

A blood protein, important in control of blood water potential in formation of tissue fluid

(Which all mammals have)

Question 30

How can we conduct immunological comparisons of proteins?

Answer 30

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

Question 31

In the immunological comparisons of proteins why when more antigen antibody complexes form does it indicate closer relations?

Answer 31

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