10.4 Investigating diversity

Question 1

How was genetic diversity measured traditionally

Answer 1

-Observing the characteristics of organisms
-This method is based on the fact that each observable characteristic is determined by genes or a gene (with environmental influences)

The variety within a characteristic depends on the number and variety of alleles of that gene

Question 2

What is an allele

Answer 2

An alternative form of a gene that arises by mutation

Question 3

What are the limitations of measuring genetic diversity by observing characteristics

Answer 3

• A large number of observable characteristics are coded by more than one gene
  They are polygenic.
  So they are not discrete from one another and vary continuously.
  This means it is difficult to distinguish one from another

Characteristics can also be modified by environment so difference may be a result of environmental conditions eg diet rather than different alleles.

Height in humans is controlled by lots of genes, but also environmental factors

Question 4

How is genetic diversity measured now

Answer 4

. Directly observe DNA sequences
. Observe mRNA sequences
. Compare amino acid sequences
. Frequency of observable characteristics

Question 5

How do we observe DNA sequences

What colour is each base on computer

Answer 5

We can read the base sequence due to new gene technology
We can find the exact order of nucleotides

Eg on these computer systems that find DNA sequences, each nucleotide base can be tagged with a different coloured dye:

Adenine: green
Thymine: Red
Cytosine: Blue
Guanine: Yellow

Question 6

How do we use the computer systems to find the genetic diversity of a species

Answer 6

Sample DNA of its members and sequence it to find a pattern of coloured bands

Analyse these patterns and allow us to compare different individuals in the same species to determine how diverse they are

Patterns are scanned with lasers and interpreted on computer software to give the DNA nucleotide base sequence

Question 7

How and why would the base sequence between species before and after evolution differ

Answer 7

• When one species gives arise to another, the DNA of the new species will be very similar to the original species

-Due to mutations, the sequence of nucleotide bases change in the new DNA and over time the new species will keep mutating its DNA

So as a result, closely related species will have similar DNA base sequences

Question 8

How can we use base sequence of mRNA to measure genetic diversity

Answer 8

. As mRNA is coded for by DNA, and is a complimentary strand, we can compare base sequences of mRNA of different organisms

Question 9

How can we compare amino acid sequences in proteins to measure genetic diversity

Answer 9

• Sequence of amino acids in proteins is determined by mRNA, which is determined by DNA
• So compare amino acid sequences of proteins between individuals in the same species

The degree of similarity in the amino acid sequence in the same protein in two species will reflect how closely related they are.
Compare two sequences by counting number of similarities or differences in each sequence

Question 10

What is interspecific variation

What is intraspecific variation

Answer 10

Variation between individuals of different species

Variation between individuals of the same species