Your Name: Week 3 Worksheet Instructions Write a short response (100-150 words)

Question

Your Name: Week 3 Worksheet Instructions Write a short response (100-150 words) to each of the following questions. Use your own words, and cite references where applicable i. You have isolated a strain of Salmonella that is resistant to Ampicillin, Chloramphenicol and Tetracycline. You observe that when you mix these cells with another strain of E. coli sensitive to the antibiotics, the sensitive strain becomes resistant. Provide an explanation for why this has happened. What are the implications of this observation? 2. (a) What does the following diagram represent? (b) What is the significance or meaning of the arrows between DNA and RNA, and the RNA and protein? (c) Are there exceptions to this rule? RNA DNA Protein s. Replicate the following double-stranded fragment of DNA. In your answer, indicate which strands are the new strands (mark with N) and which strands are the already existing strands (mark with O as shown below. HINT You should have 2 double-stranded fragments after replication. O: AGTACATTACGAC O: TCATGTAATGCTG

Explanation / Answer

1.This might have happened due to genetic transformation. As a result of genetic transformation ,when the two different type of E.coli cells are mixed, the sensitive E.coli cells take up/incorporates the resistance factor (genetic material )from the resistant strain via their cell membrane and become resistant too.

2.a)The diagram represents gene expression that includes transcription and translation.

b)Arrow from DNA to RNA signifies the process of transcription in which RNA is formed from DNA and the arrow from RNA to protein signifies translation in which protein is formed from RNA that specifies the placing pf specific aminoacids .

c)Yes, there is an exception when DNA is formed from RNA by reverse transcriptase.

3.O:AGTACATTACGAC

N:TCATGTAATGCTG

O:TCATGTAATGCTG

N:AGTACATTACGAC

4.

Template: ATG CTA GAG GTG TAA

mRNA : UAC GAU CUC CAC AUU

protein : tyr asp leu his Ile

5a.

ATG CTA GAG GTG TAA

a)Insertion mutation: ATG C CTA GAG GTG TAA... Insertion of C after ATG

b)Deletion mutation: TG CTA GAG GTG TAA.....Deletion of A from ATG

c)substitution mutation: ATG CTA AAG GTG TAA....Substituion of A in GAG

5b.Insertion and deletions will result in shift in reading frame.

5c.

Insertion mutation: ATG C CTA GAG GTG TAA.

Transciption : UAC GGA UCU CCA CAU U

Translation : Tyr Gly Ser Pro His

b)Deletion mutation: TG CTA GAG GTG TAA

Transcription ACG AUC UAC ACA UU

Translation Thr Ile Tyr Thr

c)substitution mutation: ATG CTA AAG GTG TAA

Transcription UAC GAU UUA CAC AUU

Translation Tyr Asp Leu His Ile

5d.The substitution mutation is a silent mutation in which the aminoacid sequence is the same with no change in protein function.

6.The basic difference is that in horizontal gene transfer, the tranfer of genetic material takes place between unrelated organisms while in vertical gene transfer ,the transfer of genetic material takes place from parents to their progeny.

7.

Deleting one nucleotide is more detrimental than deleting three: True

Reason:Deleting one nucleotide will result in frame shift mutation that will change all amino acids taht will be translated after the deletion. Deletion of three nucleotides will result only in the deletion of one amino acid.

A change in genotype always causes a change in phenotype :True

Reason: It is the genotype that determines the phenotype and any change in it will change the phenotype as well

A mutation in DNA is more likely to be passed on to future generations than a change in RNA or protein.True

Reason:This is because DNA is the hereditary material that is transferred from parents to offsprings and any mutation in it will be passed to future generations.

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