BIOL240 Study Guide - Final Guide: Sos Response, Shotgun Sequencing, Joshua Lederberg

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cerisemole687

16 Oct 2011

School

University of Waterloo

Department

Biology

Course

BIOL240

Professor

Cheryl Duxbury

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Document Summary

Penicillin selection is used for non-selectable mutants (kills actively dividing cells) Only mutants remain and can be screened screening: identification of cells with a phenotype such as colour, morphology, or no growth. Uv rays (nonionizing) produce pyrimidine dimers which covalently bond t and. C, leading to a greater probability of the sequence being misread. Sos dna repair: very error-prone, triggered by dna damage, regulon regulated by. Lexa (respressor) and reca, form of negative control single strand damage undamaged strand becomes template double strand damage requires recombination, very error-prone translesion synthesis when replication stalls because of damage, replaces dna polymerase with special polymerases. Ames test: evaluates potential mutagens, the auxotroph is grown then a chemical (possible mutagen) is added. Dna transfer transformation: transfer of free floating dna transduction: transfer of genes from one to another by a virus conjugation: transfer involving cell-to-cell contact.

Related Questions

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%

Words Beginning With "Trans-" Match the definitions with the words that are used in medical and biological terminology.

A translation

B transition

C transfusion

D transamination

E transmission

F transformation

G transposon

H transversion

I transcription

J transduction

1. In public health, the movement of an infectious disease from one host to another, as in "the mode of trans_______."

2. In molecular biology, the synthesis of protein by a ribosome that is reading a strand of mRNA.

3. In genetics, a type of point mutation that results in the change of a purine to a pyrimidine.

4. In genetics, a type of point mutation that results in the change of a purine to the other purine.

5. In medicine, when blood or plasma is taken from a human donor and given IV to a patient

6. In bacterial genetics, when a bacterial strain acquires DNA that came from the genome of another cell but is packaged in a defective bacteriophage particle.

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Hypothesis I: The same histidine synthesis gene is defective in both strains B and C.

Hypothesis II: Different histidine synthesis genes are defective in strains B and C.

Results:

Strain	Growth on SD + HIS	Growth on SD
B	-	-
C	+	-
B x C	+	+

In Question Set 4, two hypotheses were discussed regarding the HIS mutations in strains B and C. Do your SD plate and SD+HIS plate results support Hypothesis I or Hypothesis II from Question Set 4?

3. A. ) Keeping in mind your answer to question #2 above, what is the predicted genotype of the diploid arising from the BxC mating?

B. ) Can you explain your SD plate and SD+HIS plate results in regards to the URA and LEU genotype of the new diploid that you have made?

BIOL240 Study Guide - Final Guide: Sos Response, Shotgun Sequencing, Joshua Lederberg

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