BSCI 223 Lecture Notes - Lecture 13: Dna Ligase, Reca, Repressor

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maroonarmadillo314

25 Mar 2016

School

University of Maryland

Department

Biological Sciences Program

Course

BSCI 223

Professor

Dr.Mc Iver

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Document Summary

Lecture 13- dna mutaions and horizontal gene transfer. Mutaions in dna impact on transcripion and translaion: a mutaion is a ixed change in the nucleoide base sequence of a genome haploid organisms. Mutaions can be neutral, harmful or (more rarely) improve growth and survival. Mutaions are heritable traits that are passed down from bacterial mother to daughter cells. Inserion or deleion of a nucleoide, which then shits the frame of the reading frame, so the codons are now diferent. A change in a nucleoide, but the codon sill codes for the same amino acid. Dna sequence and rna sequence is changed, but the amino acid (translaion) is not. A change in a nucleoide, but then changes the codon to code for a stop codon, making it not a sense strand anymore nonfuncioning. A change in a nucleoide then changes what amino acid that codon codes for- it changes the amino acid.

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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

5). The table shows five different mutations of a small section of a gene.

Use the base-pairing rules to complete the second column. For each mutation, write the sequence for any mRNA codons that will be changed as a result of the mutation in bold. Write any codons that wonât be changed in regular font.

Using the genetic code chart from question #3, identify any stop codons in the mRNA molecules â write these codons in red

For each mutation, write any amino acids that will be changed in the last column in bold font. Use red XXXs to indicate any amino acids that will be missing as a result of stop codons and use use regular font indicate any amino acids that will not be changed.

DNA (Template Strand)	mRNA codon	Polypeptide
Original DNA = GCAAGTACCTGA	CGU UCA UGG ACU	arg â ser â trp â thr
Mutation = GCCAGTACCTGA (nucleotide change underlined)	____ ____ ____ ____	___ ___ ___ ___
Mutation = GCACGTACCTGA (nucleotide change underlined)	____ ____ ____ ____	___ ___ ___ ___
Mutation = GCAAGTACTTGA (nucleotide change underlined)	____ ____ ____ ____	___ ___ ___ ___
Mutation = GAAGTACCTGA (first C deleted)	____ ____ ____ ____	___ ___ ___ ___
Mutation = GCAAGTACTGA (second C deleted)	____ ____ ____ ____	___ ___ ___ ___

ambergnu488

The amino-acid sequence shown in the following table was obtained from the central region of a particular polypeptide chain in the wild-type and several mutant bacterial strains: Codon 1 2 3 4 5 6 7 8 9

a. Wild-type: Phe Leu Pro Thr Val Thr Thr Arg Trp

b. Mutant 1: Phe Leu His His Gly Asp Asp Thr Val

c. Mutant 2: Phe Leu Pro Thr Met Thr Thr Arg Trp

d. Mutant 3: Phe Leu Pro Thr Val Thr Thr Arg

e. Mutant 4: Phe Pro Pro Arg

f. Mutant 5: Phe Leu Pro Ser Val Thr Thr Arg Trp

Each mutant represents a single nucleotide change from the original wild-type gene. For each mutant, explain what SINGLE nucleotide mutation at the DNA level accounts for the change(s) in amino acid sequence. Also, state in which codon and which position the mutation took place and then fully characterize the mutation as a base-pair substitution mutation (transversion or transition; and missense, nonsense, etc.) or a frameshift mutation. Finally, recreate as much of the original wild-type mRNA sequence as possible.

greyjackal857

BSCI 223 Lecture Notes - Lecture 13: Dna Ligase, Reca, Repressor

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