Question

19.A mutation that changes an amino acid-coding codon to a stop codon is classified as:

A – Silent

B – Missense

C – Nonsense

D – Neutral

20.Spontaneous mutations can arise from:

A – All answers are correct

B – A base gets damaged

C – DNA polymerase inserts an incorrect nucleotide

D – A loop occurs during replication

21.DNA Repair Systems:

A – Counteract spontaneous and induced mutations

B – Counteract induced mutations only

C – Counteract amino acid changes introduced by mutations

D – Prevent DNA damage

22.Which of the following general mechanisms appear to be involved in the formation of cancer cells?

A – Genomic instability, DNA repair failure, chromatin modifications

B – RNA failure, DNA phosphorylation, phosphorylation of adenyl cyclase

C – Transdetermination, mutation, allosteric interactions

D – Inversions, operon formation, methylation

23.Mutations in the ras gene family induce normal cells to proceed into the replication cycle. This convert the ras gene from a ____ gene to a ____ gene.                                         

A – Mutant; oncogene

B – Proto -oncogene; oncogene

C – Tumor suppressor; proto-oncogene

D – Oncogene; proto-oncogene

24.What is a potential carcinogen?

A – Any substance that damages DNA

B – Any pollutant

C – Any toxic chemical

D – Any chemical

Answer 1

19, Option C

If the mutation changes the amino acidp codon in to stop codon, so that the expression is stoped due to termination of translation, this is called as non sense mutatiomutation.If any codons are mutated to either UAA/UAG/UGA.

20. Option A is correct

yes, all options are correct because, spontaneous mutation is caused due to inversion, error in DNA replication, transposons etc.

21. Option A is correct.

DNA repair mechanism will repair both spontaneous and induced mutation which causes DNA damage by repair. It done in the DNA sequence but not in amino acid containing protein sequence.

22. option A is correct.

cancer is termed as abnormal cell multiplication which is due to the genomic instability that leads to uncontrolled DNA replication, and se reasons like failure in DNA repair mechanism when DNa get damaged either spontaneous or induced mutation, due to changes in the chromatin which leads to over expression of proteins whcih is termed as cancerous condition.

23. Option B is correct.

Ras is the suoer family protein which is used to regulate the expression of genes, the mutation in this gene family causes abnormal expression so that protooncogene which is normal gene is conveted to oncogene which is cancerous condition gene.

24. option A is correct.

carcinogen which is the chemicalmor substance that damages the DNA is called carcinogen, not all the chemicals will damage the DNA, but the chemical which capable of damaging DNA and causes cancerous condition is called as carcinogen. example ethedoum bromide is a potential carcinogen by binding to DNA as interchalating agent and damages causes cancer.

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