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How does replica plating demonstrate that muta- tions to antibiotic resistance can arise even in cells that have never been exposed to the antibiotic?

What is the purpose of the liver extract in the Ames test for chemical mutagens?

What is “mismatched” in the process of mismatch repair?

What is “loss of heterozygosity,” and how is this phenomenon related to the progression of some types of cancer?

What is apoptosis, and what role does it play in preserving the integrity of the genome of a multi- cellular organism?

What is a cell-cycle checkpoint? Which check- points are emphasized in this chapter, and what does each “check” for?

What would happen if an electrolyte solution was not used to make the gel for gel electrophoresis?


The following fragments were obtained after digestion of a sequence using restriction enzymes: 5.3 kb, 2.1 kb, 6.8 kb, 3.6 kb, 1.1 kb, 2.2 kb. Order the fragments, moving from the fastest migration to the slowest migration on a gel. Which two fragments may be difficult to isolate on a gel? Why? Sketch the resulting gel after running the fragments on it. Assume that the fragments were all run in one lane. Label the positions of the positive and negative electrodes. 



Tay-Sachs disease is an inherited disease that is caused by a recessive allele. If a man and his wife, who are both carriers, have three children, what is the probability of each of the following? Show your calculations and give your answers as fractions.




a) All their three children do not have the disease.




d) At least one child is phenotypically normal without the disease.




b) One or more of their three children have Tay-Sachs disease.




c) All three children have the Tay-Sachs disease.

  1. You are a Geneticist employed by Thato Biotech Pty Ltd in a criminal case, which could not be solved due to the integrity of DNA used as evidence. You are requested to ascertain the integrity of DNA evidence. You decided to resuspend the purified DNA in a volume of 100uL of double-distilled nuclease-free sterile water. You then diluted 10uL of the DNA sample to a total volume of 100uL with water quality for spectrophotometric analyses. On measuring the absorbance of this diluted sample at 230, 260, and 280nm she obtained the following readings:

A280nm= 0.494; A260nm = 0.364; A230nm= 0.191


a) What is the DNA concentration of the 100uL aliquot, in 3 significant figures

b) How much total DNA was purified by the procedure?

c) Is this DNA pure? If yes, how do you know? if not, what is the most likely contaminant?

d) if this DNA was contaminated with salts what would you expect in the absorbance readings?

e) If DNA was contaminated with RNA, how would you purify your DNA?


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