MDSA01H3 Chapter Notes - Chapter 6: Pyrimidine Dimer, Transposase, Restriction Site

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greentrout185

26 Dec 2016

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UTSC

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Media Studies

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MDSA01H3

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Mutation is a process by which the sequence of base pairs in a dna molecule is altered. A cell with a mutation is a mutant cell. If a mutation happens to occur in a somatic, it is a somatic mutation: mutant characteristic affects only the individual in which this mutation occurred and is not passed on. If a mutation happens in the germ line cells, it is a germ line mutation: may be transmitted by gametes to next generation, producing an individual with the mutation in their somatic and germ cell lines. Change of one or alter base pairs (may change the phenotype of organism it occurs within the coding region of a gene. Transition mutation: mutation from one purine- pyrimidine base pairs to the other purine- pyrimidine base pair. Transversion mutation: mutation from a purine- pyrimidine base pair to a pyrimidine- purine base pair. Purine on one strand (g) is change to pyrimidine (c )

Related Questions

Use this list of gene elements to answer the following questions: (a) Promoter
(b) Exon
(c) Enhancer

(d) Intron
(e) 5â untranslated region

(f) 3â untranslated region

Problem 1. Which of the above gene elements are transcribed? You may choose more than one answer.

Problem 2. Which of the above gene elements are translated? You may choose more than one answer.

Problem 3. Which of the above gene elements are regulatory? You may choose more than one answer.

Problem 4. Which of the above gene elements are coding? You may choose more than one answer.

Problem 6. A mutation occurs in a gene with the following sequence: AAGCT. An example of a deletion mutation in this sequence would be AACT (loss of G). Using AAGCT as your normal sequence, give an example for the following types of mutations

(a) Insertion (b) Transition

Problem 7. A mutation occurs in the coding region of a gene with the following sequence AAGTGC. The translated sequence is Lysine (AAG), Cysteine (TGC). Give an example of following types of mutation using AAGTGC as your normal sequence. Provide the translated sequence caused by the mutation. (Hint: You will need a codon table to translate the sequence)

(a) Synonymous mutation
(b) Non-synonymous missense mutation

Problem 8. Patient 1 has a tumor causing mutation in a pro-growth gene. The mutated protein allows the cell to grow without receiving growth signals from outside the cell. Is the mutated gene an oncogene or a tumor suppressor? Why? Which hallmark is the gene associated with?

Problem 9. Patient 2 has a tumor which contains a loss of function mutation in the P53 gene. How would you determine if it is a somatic or germ line mutation?

Problem 10. Patient 3 has a tumor causing mutation in a gene called telomerase. The function of telomerase is to lengthen the ends of chromosomes. What hallmark is telomerase associated with? Is the mutation gain of function or loss of function? (Hint: to answer this question, you need to understand which hallmark telomere length is associated with)

Part B

Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?

a) It could cause a frameshift nonsense or frameshift missense mutation because it would change the reading frame of the codon triplet.

b) It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.

c) It could cause a nonsense mutation because the sequence would no longer be the same, so the protein would be shorter and non-functional.

d) It could cause a silent mutation because A and T are complementary to each other so it is not really a substitution mutation.

Part C

Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?

a) A substitution missense mutation causes the protein to be shorter and thus non-functional.

b) A frameshift missense will cause the codons to be out of order, but a substitution missense does not change the order of the codons.

c) A frameshift missense mutation will cause an early Stop codon, but a substitution missense might be silent.

d) A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.

Part D

Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?

a) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAGAGUGA-3â

b) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACGUUGGAGUGA-3â

c) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUACAUCUGGAGUGA-3â

d) wild-type	5â-AUGCAUACAUUGGAGUGA-3â
mutant	5â-AUGCAUGUGACAUUGGAGUGA-3â

Part F

Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein?

5â-ATGCTAGCCTATCGTAAC-3â

a) The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.

b) The entire amino acid sequence would be altered due to the frameshift.

c) All of the amino acids after the deletion would be altered due to the frameshift.

d) All of the amino acids up to the deletion would be altered due to the frameshift.

mauvetrout554

GENETICS QUESTION: For this experiment we focused on forward genetics: First, his- mutants were identified and then complementation analysis was used in order to determine which of the 7 his genes was mutated. ( The exact data can be seen at the bottom). In this experiment we screened for his- mutants that were generated via a random mutation process resulting from errors in DNA replication or induced by EMS aka Ethyl methanesulfonate. We compared a mutagenized culture that was treated with EMS and an un-mutagenized culture that was not treated with EMS. However, both cultures went trhough an enrichment process to increase the frequency of his- mutants.

Point mutations involve the substitution of one type of base pair for another. If the substitution replaces a purine with a purine (or a pyrimidine with a pyrimidine), it is called a transition. If the substitution replaces a purine with a pyrimidine (or a pyrimidine with a purine), it is called a transversion. Many mutagenic chemicals cause this type of mutation by alkylation of a nucleotide base. The chemically altered base can then be misread during replication or repair. For example the mutagen, ethyl methanesulfonate (EMS), adds an ethyl (-CH2-CH3) group to both guanine or thymine bases causing the modified guanine to pair with thymine and the modified thymine to pair with guanine.

1. Why might one gene be more susceptible to EMS mutagenesis than another gene?

2. Why might we have expected to find a higher frequency of polar mutants (his4A^-B^-C^-) in the unmutagenized culture compared to the mutagenized culture?

Table 2. Experiment 1B class data summary (number of his^-mutants by section) Unmutagenized
Section	1	2	3	*4ABC*	4A	4B	4C	5	6	7	*Total his^-* mutants**
Tuesday	7	1	5	4	2	1	9	2	3	1	35
Wednesday	2	1	14	0	4	2	2	4	8	2	39
Total	9	2	19	4	6	3	11	6	11	3	74
% each mutant	12.1	2.7	25.7	5.4	8.1	4.1	14.9	8.1	14.9	4.1	~100%

Mutagenized
Section	1	2	3	4ABC	4A	4B	4C	5	6	7	*Total his^-* mutants**
Tuesday	2	5	4	2	6	5	5	0	4	1	34
Wednesday	9	1	15	0	9	1	2	2	9	4	52
Total	11	6	19	2	15	6	7	2	13	5	86
% each mutant	12.8	7.0	22.1	2.3	17.4	7.0	8.1	2.3	15.1	5.8	~100%

MDSA01H3 Chapter Notes - Chapter 6: Pyrimidine Dimer, Transposase, Restriction Site

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