Question

33. Which of the following conditions are necessary for a gene to be expressed? A. condensed chromatin with DNA tightly coiled around nucleosomes B. open chromatin making the gene available for transcription C. specific signals from the environment D. active retrotransposons E. Both A and C are true F. Both B and C are true G. all of the above 34. Which of the following histone modifications results in more open chromatin? A. methylation B. acetylation C. restriction enzyme digest D. BAC fingerprinting E. all of the above 35. What is the term describing the preferential expression of only the maternal or only the paternal allele of a gene? A. restriction enzyme digest B. imprinting C. EMS mutagenesis D. BAC fingerprinting E. all of the above 36. Which of the following describes transposition of retrotransposons? A. slippage during DNA replication creates variation in the number of short sequence repeats B. a DNA copy of a DNA element is created before being inserted back into the genome C. a DNA element is first transcribed to RNA, reverse-transcribed back to DNA and then inserted back into the genome D. a DNA element is excised from one region of the genome and inserted directly into another site. 37. Which type of mutation at the DNA level can create a stop codon A. Non-synonymous B. Synonymous G. B and C C. Nonsense H. B, C and D D. Frameshift I. A and D E A and B J. A, C and D 38. Which type of mutation at the DNA level can lead to no change in amino acid sequence? A. Non-synonymous F. A, B and C B. Synonymous G. B and C C. nonsense H.B, C and D D. frameshift LA and D E A and B J. A, C and D

Answer 1

33. F. Both B and C

Gene expression takes place only when chromatin is less condensed. Highly compactable chromatin makes less availability of enzymes nedded for transcription, translation and gene expression. Gene expression mostly begins with transcription, but with activation of some environmental factors enzymes controlling gene expression can be activated.

34. E. All the above

Acetylation- it adds negative charge to lysine residueson the N terminal, it relaxes chromatin by repelling negatively charged DNA.

Methylation- It relaxes DNA by transcriptional activation and repression depending on the methylation site.

Resctrion Endonucleases- It cleaves the target genomic DNA sequence.

BAC fingerprinting - It uses restriction digested fingerprints of BAC cones to rearrange and detect the human genome.

35. B. Chromosome imprinting

Genes are expressed in parent of origin specific manner. It is maintained through mitotic cell divisions in somatic cell of the organism.

EMS mutagenesis- used to produce alleleic variation in the genes involved in the required metabolism.

36. C. DNA element is first transcribed to RNA, reverse transcribed back to DNA and then inserted back into the genome.

    Transpons are genetic cmponents that copy and paste themselves to different genomic locations by reverse transcription using RNA transposition intermediate.

37. J. A, C and D

Non synonymous leads to amino acid replacing, Nonsense means stopping of gene expression using stop codons and by frame shift stoppage and either occur or not occur, because in here changing of nucleotide sequence takes place by either adding or deleting a base .

38.  B. Synonymus

It is a silent mutaion.