Question

DO YOU SEE WHAT EYE SEE CASE STUDY

1

One of Darwin’s main ideas was that evolution involves descent with modification from common ancestry. We know today that the modification can be simply divergence in gene sequences. The diagram to the right shows a phylogeny for the organisms represented in the sequences above. The degree of similarity in gene sequences is representative of how long ago two organisms have diverged from each other. In other words, organisms with a more recent common ancestor will have a greater similarity in gene sequences than organisms that have a much more ancient common ancestor. Make a hypothesis for which gene sequences listed above represent each branch of the phylogeny.

2

There is variation in nucleotide sequences, but the amino acid sequences for the partial sequence presented in this case are identical between the five species. Explain why natural selection might have favored conservation of the amino acid sequence.

3

How could different nucleotide sequences result in the same amino acid sequences? Explain the mechanism.

4

How is Pax6 and other master genes like HOX different from other genes? How does this difference affect evolution?

Thank you

Answer 1

The structure of an alpha amino acid in its un-ionized form

Amino acids are organic compounds containing amine (-NH₂) and carboxyl (-COOH) functional groups, along with a side chain(R group) specific to each amino acid.^[1][2][3] The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids. About 500 naturally occurring amino acids are known (though only 20 appear in the genetic code) and can be classified in many ways.^[4] They can be classified according to the core structural functional groups' locations as alpha- (?-), beta- (?-), gamma- (?-) or delta- (?-) amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid residues form the second-largest component (water is the largest) of human musclesand other tissues.^[5] Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis.

In biochemistry, amino acids having both the amine and the carboxylic acid groups attached to the first (alpha-) carbon atom have particular importance. They are known as 2-, alpha-, or ?-amino acids (generic formula H₂NCHRCOOH in most cases,^[6]where R is an organic substituent known as a "side chain");^[7] often the term "amino acid" is used to refer specifically to these. They include the 22 proteinogenic ("protein-building") amino acids,^[8][9][10] which combine into peptide chains ("polypeptides") to form the building-blocks of a vast array of proteins.^[11] These are all L-stereoisomers ("left-handed" isomers), although a few D-amino acids ("right-handed") occur in bacterial envelopes, as a neuromodulator (D-serine), and in some antibiotics.^[12]