R4RIN – MCQs, Mock Tests | Biochemistry Biochemistry MCQS PAPER SET 2

The binding of lac repressor to DNA could be considered to be analogous to.

1. competitive inhibition of an enzyme
2. mixed-type inhibition of an enzyme
3. uncompetitive inhibition of an enzyme
4. allosteric effects in enzyme regulation

✅ Correct Answer: 1

Rho-dependent termination of transcription in E. coli

1. requires ATP
2. requires about 50 nucleotides of uncomplexed mRNA
3. both (a) and (b)
4. removes mRNA and holoenzyme from the DNA

✅ Correct Answer: 3

Enhancers are regions that

1. bind RNA polymerase
2. are adjacent to the TATA box
3. are CAT box binding proteins
4. modulate transcription

✅ Correct Answer: 4

Transcription by E. coli polymerase occurs in

1. four phases known as initiation, propagation, elongation and termination
2. three phases known as initiation, elongation and termination
3. two phases known as initiation and termination
4. none of the above

✅ Correct Answer: 2

Which of the following is necessary for transcription to occur?

1. DNA molecule
2. RNA polymerase
3. DNA polymerase
4. Both DNA & RNA polymerase

✅ Correct Answer: 4

Multiple copies of 5S genes, located at a chromosomal site distinct from the other rRNA genes

1. are transcribed by rRNA polymerase III and the 5S rRNA
2. are transcribed by rRNA polymerase II
3. are transcribed by rRNA polymerase I and the 5S rRNA
4. are transcribed by DNA polymerase I

✅ Correct Answer: 1

Each tRNA molecule has a cloverleaf secondary structure consisting of

1. three stem loops
2. two stem loops
3. four stem loops
4. either (a) or (b)

✅ Correct Answer: 1

What is a promoter?

1. A specific sequence of DNA to which a catabolic repressor binds
2. A specific sequence of DNA to which RNA polymerase binds
3. A specific DNA sequence to which a restriction endonuclease binds
4. None of the above

✅ Correct Answer: 2

The function of the sigma factor of RNA polymerase is to

1. assure that transcription begins at the proper point
2. assure that transcription ends at the proper point
3. assure that translation begins at the proper point
4. assure that translation ends at the proper point

✅ Correct Answer: 1

In both eukaryotes and prokaryotes, a promoter region that is rich in AT bases is called as

1. CATT
2. Shine Dalgarno region
3. TATA box
4. SV40 region

✅ Correct Answer: 3

The RNA polymerases that transcribe bacterial DNA are

1. multisubunit enzymes
2. only active inside the cell
3. interchangable with DNA polymerases
4. highly glycosylated in their active forms

✅ Correct Answer: 1

Immediately after transcription

1. a methylated guanine cap is added to the 51 end of the transcript
2. a methylated guanine cap is added to the 31 end of the transcript
3. both (a) and (b)
4. a poly adenylation signal is added

✅ Correct Answer: 1

Transcription factors are

1. promoters
2. proteins which bind to DNA and regulate transcription
3. TATA boxes
4. CATT boxes

✅ Correct Answer: 2

The major function of RNA polymerase's sigma factor is

1. recognition of the translational stop sequence
2. recognition of the transcriptional start sequence
3. recognition of the transcriptional stop sequence
4. recognition of the translational start sequence

✅ Correct Answer: 2

Most transcripts of protein coding genes are cleaved

1. at the 3' end just after a poly adenylation signal
2. at the 3' end just before a poly adenylation signal
3. at the 5' end immediately after a poly adenylation signal
4. at the 5' end immediately before a poly adenylation signal

✅ Correct Answer: 1

RNA is synthesized on a DNA template in a process called __________ , which utilizes the enzyme __________

1. translation, RNA polymerase
2. transcription, DNA polymerase
3. transcription, RNA polymerase
4. replication, DNA polymerase

✅ Correct Answer: 3

The closed complex at bacterial promoters is

1. in equilibrium with free RNA polymerase and the promoter
2. not affected by promoter mutations
3. bound more tightly when repressors are present
4. not affected by activator proteins

✅ Correct Answer: 1

Transcription begins

1. at the start codon
2. upstream from the start codon
3. downstream from the start codon
4. none of these

✅ Correct Answer: 2

Transcription results in

1. an amino acid chain
2. messenger RNA
3. complementary DNA
4. Okazaki fragments

✅ Correct Answer: 2

RNA polymerase holoenzyme initiates transcription which involves

1. recognition of the -10 sequence and -35 sequence
2. recognition of the -10 sequence only
3. recognition of the -35 sequence only
4. none of the above

✅ Correct Answer: 1

The transcriptional regulatory proteins in eukaryotes which induce transcription usually have

1. at least two distinct domains of protein structure, a DNA binding domain and an activation domain
2. at least two distinct domains of protein structure and a DNA binding domain
3. at least one distinct domains of protein structure, a DNA binding domain and an activation domain
4. none of these

✅ Correct Answer: 1

In prokaryotes, transcription is

1. terminated by the stop codon
2. terminated by a protein called rho
3. terminated by a poly A sequence
4. terminated by a start codon

✅ Correct Answer: 2

In eukaryotes, there are three different RNA polymerases. The RNA polymerase responsible for transcription of mRNA is

1. RNA polymerase I
2. . RNA polymerase II
3. RNA polymerase III
4. none of these

✅ Correct Answer: 2

The nucleons of eukaryotic cell has

1. RNA polymerase I
2. RNA polymerase II
3. RNA polymerase III
4. all of these

✅ Correct Answer: 4

Upstream regions which are essential for correct transcription are called

1. enhancers
2. start codons
3. promoters
4. transcription factors

✅ Correct Answer: 3

Transcription of each set of rRNA genes by RNA polymerasel produces

1. a single 45S rRNA precursor molecule
2. a single 5S rRNA precursor molecule
3. a single 18S rRNA precursor molecule
4. a single 28S rRNA precursor molecule

✅ Correct Answer: 1

The regions of a gene located at -10 and -35, with respect to the start of transcription, are termed

1. start codons.
2. oriC regions.
3. Shine Dalgarno sequences.
4. promoters.

✅ Correct Answer: 4

Which of the following conditions would cause the release of the lac repressor protein from the lac operator site on DNA?

1. Presence of glucose in the growth media
2. Presence of lactose in the growth media
3. Presence of IPTG (isopropyl thiogalactoside) in the growth media
4. Both (b) and (c)

✅ Correct Answer: 4

Beta pleated sheets are examples of protein's

1. primary structure
2. secondary structure
3. tertiary structure
4. quaternary structure

✅ Correct Answer: 2

BRACl, an inherited form of breast cancer, regulates cell division by

1. binding to a DNA sequence
2. complexing with cyclins
3. binding to the cell outer membrane
4. binding to the protein RAD 51 which repairs DNA damage

✅ Correct Answer: 4

Metastasis involves

1. ability of cells to dissolve cellular matrix
2. metalloprotein levels
3. decreased levels of proteins that regulate metalloproteins
4. all of the above

✅ Correct Answer: 4

Signal sequences are part of a protein that

1. signal folding of the protein
2. signal the protein synthesis on the ribosomes is ended
3. transport proteins to other sites within the cell
4. refold proteins in prion-associated diseases

✅ Correct Answer: 3

Individuals with PKU disease are mentally retarded unless

1. phenylalanine in the diet is restricted
2. tyrosine in the diet is restricted
3. homogentisic acid in the diet is restricted
4. none of the above

✅ Correct Answer: 1

Marfan's syndrome is thought to be a mutation affecting

1. hemoglobin synthesis
2. collagen synthesis
3. metabolism of homogentisic acid
4. insufficient thyroid production

✅ Correct Answer: 2

Cyclins are proteins that

1. regulate ability of cells to invade tissue
2. regulate passage from one stage of cell division to another
3. regulate apoptosis of damaged cells
4. none of the above

✅ Correct Answer: 2

Over 50% of common cancers are associated with damage to a protein, p53. This protein

1. is a cyclin
2. is a tumor supressor
3. is an oncogene
4. regulates apoptosis

✅ Correct Answer: 2

Protein folding is

1. automatic, mediated by the protein itself
2. mediated by other proteins called chaperones
3. mediated by the ribosomes
4. none of the above

✅ Correct Answer: 2

Sickle cell disease is due to

1. a mutation in the beta chain of Hb
2. a mutation in the alpha chain of Hb
3. infection with a parasite
4. none of the above

✅ Correct Answer: 1

The four subunits of the hemoglobin (Hb) gene represent protein's

1. primary structure
2. secondary structure
3. tertiary structure
4. quaternary structure

✅ Correct Answer: 4

A mutation in the tip binding site of the repressor would result in

1. constitutive trp operon expression
2. inducible trp operon expression
3. no operon expression
4. none of the above

✅ Correct Answer: 1

The first protein complex to bind to the TATA box is

1. transcription factor IIA
2. transcription factor IIB
3. transcription factor IID
4. all of these

✅ Correct Answer: 3

Which of the following is not part of the lac operon?

1. I
2. O
3. P
4. none of these

✅ Correct Answer: 1

The lac operon is transcribed in which segments?

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 1

A frameshift mutation occurs in the sigma subunit gene transcribed as part of SPOl early genes. What will be the immediate result?

1. Early genes will not be translated
2. Middle genes will not be transcribed
3. The bacterial host will lyse immediately
4. Infection will proceed as usual

✅ Correct Answer: 3

In the presence of high levels of tryptophan

1. attenuator allows transcription of trp structural genes
2. attenuator propogates transcription
3. attenuator terminates transcription
4. none of the above

✅ Correct Answer: 3

Tubulin is regulated by

1. binding of tubulin to tubulin mRNA
2. splicing of the tubulin transcript
3. binding of tubulin to the tubulin translational product
4. binding of tubulin to DNA

✅ Correct Answer: 3

Transcription factors are

1. regions of DNA in the promoter area
2. regions of DNA in the enhancer area
3. any protein which binds to DNA
4. proteins which bind DNAand initiate transcription

✅ Correct Answer: 4

Genes which need to be coordinately regulated but are not in operons may be regulated by

1. common transcription factor binding domains
2. TATA boxes
3. CAAT regions
4. GC regions

✅ Correct Answer: 1

What are genes?

1. The functional unit of inheritance
2. A fragment of DNA
3. A portion of a chromosome
4. All of the above

✅ Correct Answer: 4

Which of the following is not a transcription factor?

1. Helix-turn-helix proteins
2. Zinc finger proteins
3. Leucine zipper proteins
4. Steroid hormones

✅ Correct Answer: 1

Enhancers differ from promoters in that

1. they initiate transcription
2. they are adjacent to the start codon
3. their orientation can be inverted without effect
4. they are restricted to a specific gene

✅ Correct Answer: 3

Methylated gene are

1. active
2. silent
3. dynamic
4. either (a) or (b)

✅ Correct Answer: 2

Which of the following occur in the presence of glucose?

1. lac Z gene expression is increased
2. cAMP increases
3. Binding of CAP-cAMP complex to the promoter area decreases
4. none of the above

✅ Correct Answer: 3

Sex hormones activate transcription of specific genes by

1. binding to a transcription factor
2. binding to RNA polymerase
3. binding to DNA enhancer region
4. binding to DNA promoter region

✅ Correct Answer: 1

The lac operon is translated into __________ proteins.

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 3

In the presence of tryptophan in the cell, the repressor is __________

1. bound to tryptophan
2. bound to DNA
3. bound to both DNA and tryptophan
4. bound to neither tryptophan nor DNA

✅ Correct Answer: 3

Catabolite activating protein exerts __________ control on transcription of the lac operon genes.

1. positive
2. negative
3. may be positive or negative
4. none of these

✅ Correct Answer: 1

DNA is methylated at

1. AC sequences
2. TATA sequences
3. CAAT sequences
4. CG sequences

✅ Correct Answer: 4

Why are several structural genes regulated as a unit in bacteria?

1. An accident of evolution
2. It allows coordinating regulation of genes with a common function
3. The bacteria chromosome is so small; many different genes must be controlled by the same promoter
4. none of the above

✅ Correct Answer: 2

Alternate splicing of RNA transcripts is a mechanism to regulate

1. tubulin
2. tachykinins
3. DNA methylation
4. leucine zippers

✅ Correct Answer: 2

The viruses that can achieve neoplastic transformation are called

1. DNA tumor viruses
2. RNA tumor viruses
3. retroviruses HIV
4. none of these

✅ Correct Answer: 1

For gene transfer to be effective, transforming DNA must be.

1. incorporated into the bacterial chromosome
2. incorporated into a viral genome
3. free in the bacterial cytoplasm
4. none of the above

✅ Correct Answer: 1

Double stranded DNA denaturation with specified limit of temperature is

1. reversible reaction
2. irreversible reaction
3. either (a) or (b)
4. none of these

✅ Correct Answer: 1

From a single molecule of DNA, PCR can make

1. one additional copy
2. hundreds of copies
3. thousands of copies
4. millions of copies

✅ Correct Answer: 4

Genomic libraries are made from

1. genomic DNA of an organism
2. genomic RNA of an organism
3. genomic cDNA of an organism
4. genomic mRNA of an organism

✅ Correct Answer: 1

Bacteriophages are

1. cells in the blood that eat bacteria
2. a class of bacteria
3. bacterial viruses
4. none of the above

✅ Correct Answer: 3

Specialized transduction occurs when

1. the bacteriophage incorporates randomly in the bacterial chromosome
2. the bacteriophage never incorporates into the bacterial chromosome
3. the bacteriophage always incorporates at the same position in the bacterial chromosome
4. none of the above

✅ Correct Answer: 3

PCR is used

1. to diagnose genetic diseases
2. to solve crimes
3. to study gene function
4. all of these

✅ Correct Answer: 4

To clone into a plasmid vector, both the plasmid and the foreign DNA are cut

1. with the same restriction enzyme and mixed together
2. with different restriction enzyme and mixed together
3. with the combination of enzymes and then seperated
4. with the combination of enzymes and mixed together

✅ Correct Answer: 1