Question

a. Explain chromosomal theory of inheritance.
b. What is southern blotting?
c. A scientist was studying an in vitro eukaryotic transcription system which produced both capped and uncapped mRNAs. For an experiment he incubated these mRNAs with mammalian cell nuclear extract and quatified the different products as shown. Which of the following graphs represent the expected result correctly?
d. The semi-conservative nature of DNA replication was established by Meselson and Stahl in their classic experiment with bacteria. They grew bacteria in N¹⁵- $\sf NH_4$Cl containing medium, washed and then incubated in fresh medium with N¹⁴- containing compounds and allowed to grow for three generations. CsCl density gradient centrifugation of isolated DNA established in nature of semi-conservative DNA replication. The pictorial representation (in the second attachment) shows the position of differentially labelled DNA in CsCl density gradient. Had the DNA replication being conservative, what would have been the pattern?
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Answer 1

Answer:

a)-The Chromosomal Theory of inheritance, proposed by Sutton and Boveri, states that chromosomes are the vehicles of genetic heredity. Neither Mendelian genetics nor gene linkage is perfectly accurate; instead, chromosome behavior involves segregation, independent assortment, and occasionally, linkage.

b)-Southern blotting is a laboratory technique used to detect a specific DNA sequence in a blood or tissue sample. ... The DNA fragments are transferred out of the gel to the surface of a membrane. The membrane is exposed to a DNA probe labeled with a radioactive or chemical tag.

c)-sorry don't know.

d)-As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions. This process is known as semi-conservative replication because two copies of the original DNA molecule are produced. Each copy contains one original strand and one newly-synthesized strand.

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Answer 2

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(A) So basically, The Chromosomal Theory of Inheritance is about the Mendel's abstract factors, that genes live on the chromosomes. These genes are kinda 'wagons' of genetic heredity, or something like that. They're carried by these chromosomes. And the fact that the choreography of the chromosomes is the same as the choreography of Mendel's genes, the correlation.

(B) Well, Southern Blotting is some kind of technique used for detecting the DNA sequence.

The DNA are extracted from the test article, non-transfected host cells, followed by UV quantitation and electrophoresis analysis. After restriction digests up to 4 enzymes, which cut once within the expression system, DNA samples are separated by electrophoresis and then transferred and UV cross-linked to a positive charged nylon membrane. Then the Probe DNA are prepared and labelled. After hybridization, the captured fragments are visualised by exposure of some X-Ray film. After producing the auto-radiogram, the estimation of integration site number and the size of transgene are reported. And hence, the DNA sequence.

(C) You see, Eukaryotic transcripts are composed of Exons as well as Introns and hence are called pre-mRNA. I'm really not sure about this, but I believe that these undergo processing to produce some functional mRNAS. This involves the cleavage into smaller segments tailing, capping and Splicing. The first step involves Splicing. It is, basically, the removal of introns and addition of exons to form some functional RNAs. This Splicing is followed by the addition of a tail and a cap which help in providing stability to the mRNA. Therefore, capped and polyadenylated tailed mRNA are the most stable of all other mRNAS. So, I believe, the correct answer is D.