Question

25.You are studying a new type of cancer and you discover that there is a mutation in a gene that encodes a histone acetylase. You hypothesize that the mechanism by which this mutation causes cancer is:

A – Introducing random mutations

B – By altering the expression of a gene involved in the control a cell proliferation

C – Mutating DNA repair genes

D – By introducing a mutation in a gene involved in the control a cell proliferation

26.Often mutations in cyclin dependent kinases, CDKs, can cause cancer. This is because:

A – CDKs control apoptosis

B – CDKs control the cell cycle progression

C – CDKs affect DNA repair

D – CDKs affect chromatin remodeling

27.BAX proteins stimulate apoptosis. Mutations in BAX genes can help developing cancers but not necessarily trigger a tumor. This is because:

A – Mutations in BAX do not contribute to tumorigenesis, but BAX can prevent the formation of a tumor

B – Mutations in BAX may over-stimulate apoptosis

C – Mutations in BAX contribute to tumorigenesis only with other inhibitors of apoptosis

D – Mutations in BAX can prevent the formation of tumors

28.When lactose is present:

A – Lactose represses the activation of the genes in the lac operon by binding the operator

B – Lactose represses the activation of the genes in the lac operon by binding the repressor

C – Lactose induces the activation of the genes in the lac operon by binding the operator

D – Lactose induces the activation of the genes in the lac operon by binding the repressor

29.When both lactose and glucose are available to E.coli, which part of the lac operon regulation assures that glucose will be metabolized first?

A – The repressor binds to the operator in the absence of lactose

B – The repressor cannot bind to the operator in the presence of lactose

C – CAP binds to the promoter only in the presence of low glucose

D – RNA polymerase transcribes the lac operon to make a single RNA molecule

30.The tryptophan (trp) operon is a repressible system. This means:

A – The genes are normally repressed, but the presence of trp can activate the genes

B – The genes are normally repressed

C – The genes are normally expressed when trp is present

D – The genes are normally expressed, but the presence of trp can repress the operon

31.In eukaryotes, chromatin remodeling plays an important role is gene regulation. This is because:

A- Chromatin remolding activates gene expression

B – The nucleosomes contain important regulatory regions

C – Repositioning of the nucleosomes makes DNA accessible to transcription regulatory proteins

D – Chromatin remodeling represses gene expression

32.Alternative splicing:

A – Increase the number of proteins made from one gene

B – Increase the number of exons

C – Increase the number of introns

D – Increases the number of primary transcripts made from one gene

Answer 1

25. B – By altering the expression of a gene involved in the control a cell proliferation

       functioning od histone acetylase is with the regulation of gene transcription

26. B – CDKs control the cell cycle progression

       cyclin-dependent kinases are responsible for the passing of checkpoints during cell cycle progression

27. A – Mutations in BAX do not contribute to tumorigenesis, but BAX can prevent the formation of a tumor

       BAX regulation is upregulated by tumor suppressor factor p53. So the mutation in BAX cannot contribute to the formation of a tumor which is determined before one step before during the secretion of p53. BAX functioning as the mediator of apoptosis.

28. D – Lactose induces the activation of the genes in the lac operon by binding the repressor

29. D – RNA polymerase transcribes the lac operon to make a single RNA molecule

      When there is both glucose and lactose are present, lactose will bind to the repressor and allow the transcription of the lac gene in vary a small amount. If there is no glucose, the presence of cAMP will further enhance the transcription of 3 lac genes in large amounts.

30. D – The genes are normally expressed, but the presence of trp can repress the operon

31. C – Repositioning of the nucleosomes makes DNA accessible to transcription regulatory proteins

32. A – Increase the number of proteins made from one gene