What is DNA polymorphism? Why is it important to study it?
Polymorphism (variation at genetic level) arises due to mutations. Allelic sequence variation has traditionally been described as a DNA polymorphism if more than one variant (allele) at a locus occurs in human population with a frequency greater than 0.01. In simple terms, if an inheritable mutation is observed in a population at high frequency, it is referred to as DNA polymorphism.
Polymorphism become very useful identification tool in forensic applications. Further, as the polymorphisms are inheritable from parents to children, DNA fingerprinting is the basis of paternity testing, in case of disputes.
Now, sequencing of total genomes getting is less expensive day by the day. Soon it may be affordable for a common man to get his genome sequenced. What in your opinion could be the advantage and disadvantage of this development?
Define transformation in Griffith's experiment. Discuss how it helps in the identification of DNA as the genetic material.
Would it be appropriate to use DNA probes such as VNTR in DNA finger printing of a bacteriophage?
Explain (in one or two lines) the function of the followings:
(a) Promoter (b) tRNA
(c) Exons
During in vitro synthesis of DNA, a researcher used 2′, 3′ – dideoxy cytidine triphosphate as raw nucleotide in place of 2′-deoxy cytidine. What would be the consequence?
The total number of genes in humansds far less (< 25,000) than the previous estimate (upto 1,40,000 gene). Comment.
Name a few enzymes involved in DNA replication other than DNA polymerase and ligase. Name the key functions for each of them.
A low level of expression of lac operon occurs at all the time. Can you explain the logic behind this phenomena?
If the sequence of the coding strand in a transcription unit is written as follows: 5-ATGCATGCATGCATGCATGCA TGCATGC-3′
Write down the sequence of mRNA.
Differentiate between the followings:
(a)Repetitive DNA and Satellite DNA
(b)mRNAand tRNA
(c)Template strand and Coding strand
Comment on the utility of variability in number of tandem repeats during DNA finger printing.
In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.
What is the cause of discontinuous synthesis of DNA on one of the parental strands of DNA? What happens to these short stretches of synthesised DNA?
Based on your understanding of genetic code, explain the formation of any abnormal hemoglobin molecule. What are the known consequences of such a change?
If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
You are repeating the Hershey-Chase experiment and are provided with two isotopes: 32P and 15N (in place of 35S in the original experiment). How do you expect your results to be different?
Briefly describe the following:
(a) Transcription (b) Polymorphism
(c) Translation (d) Bioinformatics
Sometimes cattle or even human beings give birth to their young ones that are having extremely different sets of organs like limbs/position of eye(s) etc. Comment.
In an experiment, DNA is treated with a compound which tends to place itself amongst the stacks of nitrogenous base pairs. As a result of this, the distance between two consecutive base increases from 0.34 nm to 0.44 nm. Calculate the length of DNA double helix (which has 2 x 109 bp) in the presence of saturating amount of this compound.
What would happen if histones were to be mutated and made rich in acidic amino acids such as aspartic acid and glutamic acid in place of basic amino acids such as lysine and arginine?
How did Hershey and Chase differentiate between DNA and protein in their experiment white proving that DNA is the genetic material?
During the course of evolution why DNA was chosen over RNA as genetic material? Give reasons by first discussing the desired criteria in a molecule that can act as genetic material and in the light of biochemical differences between DNA and RNA.
There is a paternity dispute for a child'. Which technique can solve the problem? Discuss the principle involved.
Do you think that the alternate splicing of exons may enable a structural gene to code for several isoproteins from one and the same gene? If yes, how? If not, why so?
What are the functions of (i) methylated guanosine cap, (ii) poly-A "tail"in a mature on RNA?
Give an account of Hershey and Chase experiment. What did it conclusively prove? If both DNA and proteins contained phosphorus and sulphur do you think the result would have been the same?
The enzyme DNA polymerase in E.coli is a DNA dependent polymerase and also has the ability to proofread the DNA strand being synthesised. Explain. Discuss the dual polymerase.
How has the sequencing of human genome opened new windows for treatment of various genetic disorders. Discuss amongst your classmates.
Discuss the significance of heavy isotope of nitrogen in the Meselson and Stahl's experiment.
Replication was allowed to take place in the presence of radioactive deoxynucleotides precursors in E. coli that was a mutant for DNA ligase. Newly synthesised radioactive DNA was purified and strands were separated by denaturation. These were centrifuged using density gradient centrifugation. Which of the following would be a correct result?
Distinguish between heterochromatin and euchromatin. Which of the two is transcriptionally active?
Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesized from it (DNA or RNA), list the types of nucleic acid polymerases.
If the sequence of one strand of DNA is written as follows:
5′-ATGCATGCATGCATGCATGCA
TGCATGC-3′
Write down the sequence of complementary strand in 5′ -> 3′ direction.
Recall the experiments done by Frederick Griffith, Avery, MacLeod and McCarty, where DNA was speculated to be the genetic material. If RNA, instead of DNA was the genetic material, would the heat killed strain of Pneumococcus have transformed the R-strain into virulent strain? Explain.
A single base mutation in a gene may not ‘always' result in loss or gain of function. Do you think the statement is correct? Defend your answer.
What background information did Watson and Crick have made available for developing a model of DNA What was their contribution?
Define a cistron. Giving examples differentiate between monocistronic and polycistronic transcription unit.