Please answer ALL questions. 1) Circle any of the following sequences that are D

Question

Please answer ALL questions.

1) Circle any of the following sequences that are DNA palindromes:

5’ tattaata-3’ 5’-cgctacgc-3’ 5’-ttattatt-3’ 5’-tgacgtca-3’ 5’-ccccaaaa-3’ 5’-gcgcgcgc-3’

A ) Suppose you sequence a small region of a fruit fly cDNA and compare it to the corresponding chromosomal gene. Will your sequenced cDNA region be complementary to an exon, an intron, or the promoter of the chromosomal gene? (circle all correct answers.)

B) Regarding this fruit fly DNA, suppose you continue to study it, and you find a series of codons that translate as – glycine – proline – isoleucine – asparagine – leucine – lysine - aspartic acid - glutamic acid – leucine – STOP. What hypothesis does this provide you as you go forward with studying the fruit fly protein encoded by this cDNA?

C) Let’s say you have a population of ~10^12 yeast cells, and you bombard them with X-rays and look for temperature-sensitive mutants affecting the cell division cycle. You find one such mutant colony (its cells divide normally at 30°C but arrest during prophase when grown at 39°C). Next, in an attempt to identify the disrupted cell cycle gene in this mutant yeast strain, you introduce a cDNA library (produced from human cells) into a huge clonal population of these mutant yeast so that each cell receives, at most, one cDNA. If you spread these yeast onto hundreds of agar plates, make replicas of these plates, and then incubate the first set of plates at 30°C and the replica plates at 39°C, which of the following should you isolate for identifying the “rescuing” human cDNA? ______

a. Colonies that undergo normal cell division at both 30°C and 39°C

b. Colonies that cannot undergo cell division at either temperature

c. Colonies that undergo normal cell division at 30°C but cannot divide at 39°C

d. Colonies that show slower cell division at 30°C, and cannot divide at 39°C

D) Briefly, explain the differences in function of the toxins latrunculin and phalloidin.

Explanation / Answer

1) 5’ tattaata-3’   5’-tgacgtca-3’ 5’-gcgcgcgc-3’ are palindromes.A palindromic sequence is the one which read same from 5' to 3' on one strand and 3' to 5' on the other strand.

A)The cDNA region be complementary to an exon and the promoter of the chromosomal gene

B)The study shows the complexity of the fruit fly genome and indicates that one gene is responsible for the production of one protein.

C) Colonies that undergo normal cell division at both 30°C and 39°C

D)Latrunculin is a toxin secreted by sponges, binds the G-actin and will inhibits it rom adding to a filament end. The equilibrium between actin monomers and filaments are disturbed. This toxin will shifts the monomer-polymer equilibrium in the direction of dissociation. In live cells, this will disappear the actin cytoskeleton and will inhibit the locomotion and cytokinesis also will be affected. The phalloidin will have opposite effect on actin and will prevent the actin filaments from depolymerizing. This toxin will bind at the interface between subunits in F-actin and will lock the subunits. Once got polymerized, these phalloidin stabilized filaments will not depolymerize.

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