Amino Acid Sequence Analysis and Comparison

Question 1

Similarly to mRNA, proteins are often easier to isolate from the cell than

Answer 1

DNA

Question 2

The sequence of amino acids of the same protein can be compared between individuals
The protein chosen must be found in all the …………..

Answer 2

individuals/species being compared eg. haemoglobin is used for many animals

Question 3

Amino acid sequences can also be determined from …………. sequencing

Answer 3

mRNA sequencing if the ‘frame’ is known (the correct start codon is determined)

Question 4

Amino acid sequences of proteins evolve much slower than

therefore

Answer 4

DNA, especially if the protein is of high importance

Therefore, it is likely that closely related species (eg. humans and chimpanzees) will have the same amino acid sequence even though these species split from their common ancestors millions of years ago

Question 5

This is because the shape, and therefore function and specificity, of a protein is determined by

Answer 5

the amino acid sequence as the position of amino acids determines the intermolecular forces between R groups

Question 6

In the exam, you could be given multiple nucleotide or amino acid sequences and asked to compare them. These questions require you to find matches and/or differences between the sequences to determine how closely related the individuals are. Remember, usually if there are more matches the closer related the individuals are. However, ensure that you also approach these questions with a critical mind and ask yourself questions such as:

Are the amino acid sequences the same because the evolution of proteins is very slow?

Have multiple different proteins / mRNA molecules / DNA sequences been sequenced or only one?

Can two separately classified species produce fertile, ‘hybrid’, offspring? If so, are they classified correctly?