BIOC 302 Lecture Notes - Lecture 21: Purine, Radiography, Pyrimidine

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sapphirehyena95

10 Apr 2016

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Codon: a nucleoide triplet in the dna sequence that codes for a speciic amino acid residue (or stop signal) Start codon: generally atg (encodes methionine); also ttg & ctg. Open reading frames: a group of coniguous, nonoverlapping nucleoide codons in a dna or rna sequence that being with a start codon and do not include any stop codons. Missense: change in dna sequence and in aa sequence. Nonsense: you create a stop codon earlier in the chain. Frameshit: you delete one nucleoide and you shit everything one nucleoide over. Mutaion: a permanent, transmissible change in the dna (usually a single gene) Mutagen: a substance that causes an increase in the rate at which mutaions occur. Carcinogen: a substance that causes cancer, most carcinogens are mutagens. Transiion: exchange of a purine with a purine or a pyrimidine with a pyrimidine, more common than transversion, oten the result of tautomeric shits.

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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

1. Gennie is wild type. Below is a segment of her DNA. The topstrand is the coding region, and the reading frame begins with thefirst codon that codes for met (start codon).

5' GCATGTTCTTGT 3'

3' CGTACAAGAACA 5'

Kevin is mutant. Below is a segment of his DNA. The top strandis the coding region, and the reading frame begins with the firstcodon that codes for met (start codon).

5' GCATGTTTTTGT 3'

3' CGTACAATAACA 5'

What type of mutation does Kevin have?

A) silent

B) misssense

C) nonsense

D) frameshift

2) A type of dwarfism results from the production of mutantSHR-1 protein. You look at the length of the mutant SHR-1 and thenormal (wild-type) SHR-1 protein, and discover that the mutantSHR-1 protein has fewer amino acids.

What do you expect to find when you examine the DNAsequence?

A) nucleotides were deleted

B) additional nucleotides were added

C) one nucleotide was changed

D) without additional information, any of the above arepossible.

3) Below are two DNA coding strand sequences. The 5' ATG encodesthe in-frame strat codon.

Tom's DNA sequence is:

5' ATG CGC TTA CCC TTA CTC CTA TAA 3'

Harry's DNA sequence is:

5' ATG CGC TAA CCC TTA CTC CTA TAA 3'

Harry's mutation causes the premature termination of:

A) Replication

B) Transcription

C) Translation

D) Answer B and C

E) All of the above

carmineoyster108

A. Please identify the mRNA and polypeptide sequence for the below DNA using the genetic codon table. (Note: the direction of mRNA is important! Keep in mind that the genetic codons are read from 5â to 3â direction on mRNA. Also, RNA bases are A, U, C, G instead of A, T, C, G)

3â â GTT â TAC â CTT â CTC â TCC â TCA â GAC â ATC â GCA â 5â (Template strand)

5â â CAA â ATG â GAA âGAG â AGG â AGT âCTG â TAG â CGT â 3â (Non-template/Coding strand)

B. Please identify the mutation type (silent, missense, nonsense, frameshift) on the following DNA sequence as compared to the original sequence from question A.

3â â GTT â TAC â CTT â CTC â TTC â TCA â GAC â ATC â GCA â 5â (Template strand) 5â â CAA â ATG â GAA âGAG â AAG âAGT â CTG â TAG â CGT â 3â(Non-template/Coding strand)

C. Please identify the mutation type (silent, missense, nonsense, frameshift) on the following DNA sequence as compared to the original sequence from question A.

3â â GTT â TAC â CTT â ATC â TCC â TCA â GAC â ATC â GCA â 5â (Template strand)

5â â CAA â ATG â GAA âTAG â AGG â AGT â CTG â TAG â CGT â 3â(Non-template/Coding strand)

BIOC 302 Lecture Notes - Lecture 21: Purine, Radiography, Pyrimidine

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