BIOCHEMISTRY 403/503 HOMEWORK I For all questions, give detailed explanations in
ID: 161591 • Letter: B
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BIOCHEMISTRY 403/503 HOMEWORK I For all questions, give detailed explanations in your answer, show all work. 1) macromolecule isolated from an extraterrestrial source superficially resembles DNA but A different base structures in place of Ar T G, and C (see upon closer analyses reveals quite figure), A. Could these DNA-like molecules have been derived from a living organism that uses principles of genetic inheritance similar to those used by cells on If can you say about its properties? B. Simply judged by their potential for hydrogen bonding. could any of these extraterrestrial bases replace terrestrial A, T, G. or C in terrestrial DNA? Explain your answers. 2) The table below shows the responses of blood samples from the individuals in the pedigree to anti-A and anti-B sera. A in the anti-A row indicates that the red blood cel A IRBCs) of that individual were clumped by anti-A serum and therefore the individual made antigens, and a "-"indicates no clumping and the absence of the antigen. The same notation is used to describe the test for the anti-B antigens. A. Deduce the blood type of each individual from the data in the table. B. Assign genotypes for blood groups as accurately as you can from this data, explain the pattern of inheritance shown in the pedigree knowing that A and B are codominant. Als genetic relationships are as presented in the pedigree. C, which of the two children of I12 arelis natural children? and/or II12)? her Explain your answer. anti-A anti-BExplanation / Answer
Answer:
1. No.
For a DNA to be double helical and follow the inheritance pattern starting from replication, through transcription and translation, it should have the following properties:
Adenine on one chain is always paired with a thymine on the second chain. And a guanine on one chain is always paired with a cytosine on the other one.
A smaller base is always paired with a bigger one. The effect of this is to keep the two chains at a fixed distance from each other all the way along. If you try any other combination of base pairs, they won't fit.
This mode of pairing and arrangement gives polarity and complementarity to the two chains which is crucial during DNA replication and repair.
i. The DNA like molecule presented above appear to lack polarity (as evident from the figure).
ii. The four components (V, W, X and Y) deviate from the chemical structure of A, T, G, C present in DNA (although V and X resembles C and G). So, it is expected their chemical behavior will also be different.
iii. The components are stabilized by 3 hydrogen bonds which will make it difficult for normal helicases to open them up during copying.
b. Structure and hydrogen bonding properties of V and X resembles to the structure and hydrogen bonding properties of C and G. So, probably, V and X may replace C and G in terrestrial DNA.
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