As we described in class, in the early 1960's Francis Crick and colleagues set out to determine how many nucleotide bases make up a codon, before it was possible to sequence DNA and before Nirenberg and his colleagues solved the genetic code. To do this, they used a chemical mutagen that they knew made single nucleotide changes, used this mutagen to conduct a screen for mutations that disrupted a particular gene, and collected a number of different mutations in this gene. Briefly describe the logic they used to deduce that the codon length is 3 nucleotides long.

As we described in class, in the early 1960's Francis Crick and colleagues set out to determine how many nucleotide bases make up a codon, before it was possible to sequence DNA and before Nirenberg and his colleagues solved the genetic code. To do this, they used a chemical mutagen that they knew made single nucleotide changes, used this mutagen to conduct a screen for mutations that disrupted a particular gene, and collected a number of different mutations in this gene. Briefly describe the logic they used to deduce that the codon length is 3 nucleotides long.

Name: As we described in class, in the early 1960's Francis Crick and collea
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Description: As we described in class, in the early 1960's Francis Crick and colleagues set out to determine how many nucleotide bases make up a codon, before it was possible to sequence DNA and before Nirenberg and his colleagues solved the genetic code. To do t

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter15: Genomes And Genomics

Section: Chapter Questions

Problem 10QP: What percentage of the DNA in the genome actually corresponds to genes? How much is actually...

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You have isolated a transposable element from the human genome and have determined its DNA sequence. How would you use this sequence to determine the copy number of the element in the human genome if you just had a computer with an Internet connection? (Hint: see Chapter 14.)
You are studying the tryptophan synthetase gene that Yanofsky also examined to determine the relationship between the nucleotide sequence and the amino acid sequence of the gene. Yanofsky found a large number of mutations that affected the tryptophan synthetase gene. A) If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located? B) Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein?
What percentage of the DNA in the genome actually corresponds to genes? How much is actually protein-coding exons? What makes up the rest?
Now that you understand how the CRISPR-Cas9 system works, think back to the experiments discussed in the introduction to this chapter, in which researchers used CRISPR-Cas9 genome editing to treat mice with Duchenne muscular dystrophy. Why did the researchers choose to cut out the entire exon 23 in the mice with the disorder? Why not replace the specific mutation using a donor piece of DNA and homologous recombination? Propose some possible explanations.
If I clone a complete eukaryotic gene, including the eukaryotic promoter region, ligate it into a plasmid, and transform it into E. coli, will I be able use the transformed E. coli to make the corresponding protein? Explain why, or why not? If you decide to do this, what would your cloning strategy be?
If you knew the mRNA sequence for the human insulin gene could you know what size cDNA fragment you would find on your DNA gel when you ran it against a size standard (a “molecular ruler”)? Would you continue with your insulin cloning experiment, if the DNA from your PCR was very different in size from that predicted by the insulin mRNA? Why or why not? Primers can sometimes bind and target the wrong gene, especially if the primers are allowed to bind to the DNA strands at a low temperature. PCR also preferentially amplify short segments of DNA. Would it be important to actually run the cDNA after the PCR on a DNA gel in order to check for a PCR product of the predicted size for the insulin gene? Why or why not?
You obtained the sequence of the frog gene X you amplified in Question #16 through a process called automated sequencing. In automated sequencing, you are given a printout of the sense strand of your DNA. The first thing you need to do is use the correct reading frame. Having done this, the next thing to do is to write out the mRNA sequence using this sense strand reading frame. The last thing to do is to translate the sequence. a.The reading frame DNA sequence is: b.The mRNA sequence is: c.The polypeptide sequence is: A disease in frogs which causes their tongue to fall out of their mouths is killing the frog population in LA County. You obtain a dead frog and isolate its gene Xf. When you sequence this mutated gene, you find that the last ‘G’ at the end of the first line of this sequence has been deleted (i.e. the G at position 86). In order to determine how this mutation changes the resulting polypeptide, write the mutated polypeptide sequence in the space below. What kind of…
In studies of frameshift mutations, Crick, Barnett, Brenner, andWatts–Tobin found that either three nucleotide insertions ordeletions restored the correct reading frame. Question: Assuming the code is a triplet, what effect would the addition or loss of six nucleotides have on the reading frame?
What is mutagen? Give an example?
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You obtained the sequence of the frog gene X you amplified in Question #16 through a process called automated sequencing. In automated sequencing, you are given a printout of the sense strand of your DNA. The printout is shown below. The first thing you need to do is use the correct reading frame. Having done this, the next thing to do is to write out the mRNA sequence using this sense strand reading frame. The last thing to do is to translate the sequence. Do these steps in the space below. The reading frame DNA sequence is: 2.The mRNA sequence is: The polypeptide sequence is: