Translation is the RNAdirected synthesis of a polypeptide a

Translation is the RNA-directed synthesis of a polypeptide: a closer look What molecule is responsible for \"interpreting\" the series of codons along a mRNA transcript? What does this molecule do? How does the structure of this molecule help it do its job? What is an anti-codon? What does the anti-codon interact with? Accurate translation of the genetic message requires two recognition steps: What are these two recognition steps? What is \"wooble\"? How does the concept of wooble account for the redundancy of the genetic code? What are ribosomes? How do ribosomes facilitate the construction of a polypeptide chain? What is the E site? What is the A site? What is the P site? What do each of these sites do? (h)Explain in general terms how to build a polypeptide chain. Point mutations can affect protein structure and function. What is a point mutation, what are the various types of point mutations we considered and what are the possible outcomes of point mutations in gene coding regions? What is the significance of point mutations from an evolutionary perspective? How might small-scale mutations be beneficial?

Solution

17.4:A.Ribosome molecules.

An mRNA sequence is decoded in sets of three nucleotides.

Each group of three consecutive nucleotide in RNA is called a codon, and each codon specifies either one amino acid or a stop to translation process from its structure.

B. Antiodon is a sequence of three nucleotides forming a unit of generic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA.

The Antiodon on tRNA are like the base pairs of DNA-they bond by hydrogen bonding. When tRNA binds to mRNA, A bonds with U and C bonds with G via hydrogen bonding.

There must be a correct match between a tRNA and an amino acid. The second recognition step involves match between the tRNA Antiodon and an mRNA codon.

C. A wobble base pair is a pairing between two nucleotide in RNA molecules that does not follow watson-crick base pair rule. The four main wobble base pair are- G-U, I-U, I-A, I-C.

Wobble pairing is just a phenomenon and not hard and fast rule. It accounts for redundancy of the genetic code by the following statement-the base on the third position of the codon and that on the Antiodon need not be complementary.

D. Ribosome is a cell structure that makes protein. Protein is needed for making cell functions such as repairing damage or directing chemical processes. Ribosome can be found floating within the cytoplasm or attached to the endo plastic reticulum.

E. Protein synthesis involves building a peptide chain using tRNA to add amino acids and mRNA as a blueprint for specific sequence.

F. The A site is the point of entry for the amino acrylic tRNA. The P site is where the peptide tRNA is formed in the ribosome. And E site which is exit side of the now unchanged tRNA after it gives it\'s amino acid to the growing peptide chain.

G. A site: functions as the acceptor for the growing protein during peptide bond formation.

P site: the ribosomal site most frequently occupied by peptidyl-tRNA i.e the tRNA carrying the growing peptide chain.

H. The sequence of nucleotide in DNA is related to the final sequence of the polypeptide by the genetic code. The code for polypeptide chain includes codons, which are nucleotides, read three at a time without spaces. Each polypeptide chain consists of smaller sub units or amino acids that are linked together. Amino acid serve as building block of polypeptide chain.

17.5:A.Point mutation is mutation of a single gene.

Two types.

1.A point mutation is an individual that is affected by a point mutation.

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2.Repeated induced point mutations are recurring point mutation.

Sometimes the term point mutation is used to describe insertion or deletion of a single base pair in genetic coding.

B. By point mutation many traits in the individuals can be created and omitted. If the deletion occurs in positive part, then the point mutation gains significance as those traits are created that are good for survival of the fittest.

C. Small scale mutation doesn\'t have more impact or beneficial as compared to large scale mutation. Since all cells in our body contain DNA, there are lots of places for mutation to occur, however some mutations cannot be passed on to the offspring and do not matter for evolution. If it is a deletion or insertion on negative area then it will get arrested only to that individual and not move on to generations.