Question

Explain briefly how a new polypeptide chain is elongated at the ribosome?

How does a change in nucleotide sequence of a gene lead to a change in the amino acid sequence of a protein?

What are the different kinds of mutations? Which ones lead to a change in the encoded protein? How can a mutation lead to disease?
What were the prevailing attitudes toward earth’s species and diversity before Darwin published Origin of Species?

What does evolution explain and what does it not explain?

Know the significance of the species found on the Galapagos Islands.

What were Darwin’s observations that led him to evolution and what was his key insight that
explained it?

Be able to discuss six lines of evidence that support the theory of evolution.

From an evolutionary view, what is the significance of a universal genetic code? What is the
significance of homologies (both molecular and anatomical)? Be able to interpret a phylogenetic
tree.

What is the contribution to survival and evolution of acquired vs. inherited traits?

What are five things that can drive evolution (mutation, natural selection, genetic drift, gene flow,
sexual selection)? What is genetic drift? What are the special cases of genetic drift?

What is meant by “showy males and choosy females?” How can this affect evolution?

Compare and contrast microevolution and speciation. What has to develop for a new species to evolve?

Why are there so many ways to define species? Which is used most often? What are the limits of the biological species concept?

How can different species evolve in the same region?

Answer 1

ANS1. The translation of the process of the protein is divided into three phases- initiation, elongation, and termination.

The ribosome has 3 sites:

A site: for incoming aminoacyl tRNA

P site: binds tRNA carrying growing polypeptide chains

E site: for exiting tRNA

The ribosome gets attached to the mRNA in the initiation process.

a). Now in the elongation process, the aminoacyl tRNA with an anticodon complementary to A site codon enters the A site.

b) A peptide bond is formed between the amino group of A site amino acid and the carboxyl group of recently attached amino acid in the growing polypeptide chain in the P site. The energy is derived from GTP.

c) The growing polypeptide chain is transferred to the amino end of the incoming amino acid at A site and the P site is empty now. (uncharged)

d)The ribosomes move three nucleotides ahead. Each tRNA moves to the next tRNA binding site.

e) In the E site the uncharged tRNA is expelled out. Again the new tRNA enetrs the A site and process of elongation carries on.