Cancer cells may become resistant to amethopterin by (A) Developing mechanisms to destroy amethopterin (B) Amplification of dihydrofolate reducatse gene (C) Mutation in the dihydrofolate reductase gene so that the enzyme is no longer inhibited by amethopterin (D) Developing alternate pathway of thymidylate synthesis

Cancer cells may become resistant to amethopterin by (A) Developing mechanisms to destroy amethopterin (B) Amplification of dihydrofolate reducatse gene (C) Mutation in the dihydrofolate reductase gene so that the enzyme is no longer inhibited by amethopterin (D) Developing alternate pathway of thymidylate synthesis
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Amplification of dihydrofolate reductase gene may be brought about by (A) High concentrations of folic acid (B) Deficiency of folic acid (C) Low concentration of thymidylate (D) Amethopterin

Description : Amplification of dihydrofolate reductase gene may be brought about by (A) High concentrations of folic acid (B) Deficiency of folic acid (C) Low concentration of thymidylate (D) Amethopterin

Last Answer : Answer : D

Amplification of dihydrofolate reductase gene in a cancer cell makes the cell (A) Susceptible to folic acid deficiency (B) Less malignant (C) Resistant to amethopterin therapy (D) Responsive to amethopterin therapy

Description : Amplification of dihydrofolate reductase gene in a cancer cell makes the cell (A) Susceptible to folic acid deficiency (B) Less malignant (C) Resistant to amethopterin therapy (D) Responsive to amethopterin therapy

Last Answer : Answer : C

Methotrexate blocks the synthesis of thymidine monophosphate by inhibiting the activity of the enzyme: (A) Dihydrofolate reductase (B) Orotate phosphoribosyl transferase (C) Ribonucleotide reductase (D) Dihydroorotase

Description : Methotrexate blocks the synthesis of thymidine monophosphate by inhibiting the activity of the enzyme: (A) Dihydrofolate reductase (B) Orotate phosphoribosyl transferase (C) Ribonucleotide reductase (D) Dihydroorotase

Last Answer : Answer : A

Trimethoprim inhibits bacteria without affecting mammalian cells because: A. It does not penetrate mammalian cells B. It has high affinity for bacterial but low affinity for mammalian dihydrofolate reductase enzyme C. It inhibits bacterial folate synthetase as well as dihydrofolate reductase enzymes D. All of the above

Description : Trimethoprim inhibits bacteria without affecting mammalian cells because: A. It does not penetrate mammalian cells B. It has high affinity for bacterial but low affinity for mammalian dihydrofolate ... bacterial folate synthetase as well as dihydrofolate reductase enzymes D. All of the above

Last Answer : B. It has high affinity for bacterial but low affinity for mammalian dihydrofolate reductase enzyme

Conversion of deoxyuridine monophosphate to thymidine monophosphate is catalysed by the enzyme: (A) Ribonucleotide reductase (B) Thymidylate synthetase (C) CTP synthetase (D) Orotidylic acid decarboxylase

Description : Conversion of deoxyuridine monophosphate to thymidine monophosphate is catalysed by the enzyme: (A) Ribonucleotide reductase (B) Thymidylate synthetase (C) CTP synthetase (D) Orotidylic acid decarboxylase

Last Answer : Answer : B

Ras proto-oncogene is converted into oncogene by (A) A point mutation (B) Chromosomal translocation (C) Insertion of a viral promoter upstream of the gene (D) Gene amplification

Description : Ras proto-oncogene is converted into oncogene by (A) A point mutation (B) Chromosomal translocation (C) Insertion of a viral promoter upstream of the gene (D) Gene amplification

Last Answer : Answer : A

An allosteric enzyme is generally inhibited by (A) Initial substrate of the pathway (B) Substrate analogues (C) Product of the reaction catalysed by allosteric enzyme (D) Product of the pathway

Description : An allosteric enzyme is generally inhibited by (A) Initial substrate of the pathway (B) Substrate analogues (C) Product of the reaction catalysed by allosteric enzyme (D) Product of the pathway

Last Answer : Answer : D

In β-oxidation 3-ketoacyl-CoA is splitted at the 2, 3 position by the enzyme: (A) Hydratase (B) Dehydrogenase (C) Reducatse (D) Thiolase

Description : In β-oxidation 3-ketoacyl-CoA is splitted at the 2, 3 position by the enzyme: (A) Hydratase (B) Dehydrogenase (C) Reducatse (D) Thiolase

Last Answer : Answer : D

Bacteria become erythromycin resistant by the following mechanisms except: A. Becoming less permeable to erythromycin B. Elaborating an erythromycin esterase enzyme C. Elaborating a ‘protection protein’ which blocks the erythromycin binding site D. Altering the ribosomal binding site through a methylase enzyme

Description : Bacteria become erythromycin resistant by the following mechanisms except: A. Becoming less permeable to erythromycin B. Elaborating an erythromycin esterase enzyme C. Elaborating a protection ... the erythromycin binding site D. Altering the ribosomal binding site through a methylase enzyme

Last Answer : C. Elaborating a ‘protection protein’ which blocks the erythromycin binding site

A specific BRCA1 cancer-predisposing gene mutation seems to occur more frequently among women of which descent? a) Ashkanazi Jewish Expression of the BRCA1 gene is an example of inheritance in the development of breast cancer. b) Mediterranean Glucose-6-phosphate dehydrogenase deficiency (G6PD) is a common enzyme abnormality that affects millions of people throughout the world, especially those of Mediterranean, South East Asian, African, Middle Eastern, and Near Eastern origin.

Description : A specific BRCA1 cancer-predisposing gene mutation seems to occur more frequently among women of which descent? a) Ashkanazi Jewish Expression of the BRCA1 gene is an example of ... of treatment for tuberculosis) are at significantly increased risk for developing isoniazid-induced hepatitis.

Last Answer : a) Ashkanazi Jewish Expression of the BRCA1 gene is an example of inheritance in the development of breast cancer.

Amethopterin and aminopterin decrease the synthesis of (A) TMP (B) UMP (C) CMP (D) All of these

Description : Amethopterin and aminopterin decrease the synthesis of (A) TMP (B) UMP (C) CMP (D) All of these

Last Answer : Answer : A

Synthesis of polyunsaturated fatty acids involves the enzyme systems: (A) Acyl transferase and hydratase (B) Desaturase and elongase (C) Ketoacyl-CoA reductase and hydratase (D) Dihydroxyacetone phosphate

Description : Synthesis of polyunsaturated fatty acids involves the enzyme systems: (A) Acyl transferase and hydratase (B) Desaturase and elongase (C) Ketoacyl-CoA reductase and hydratase (D) Dihydroxyacetone phosphate

Last Answer : Answer : A

An enzyme required for the synthesis of ketone bodies as well as cholesterol is (A) Acetyl CoA carboxylase (B) HMG CoA synthetase (C) HMG CoA reductase (D) HMG CoA lyase

Description : An enzyme required for the synthesis of ketone bodies as well as cholesterol is (A) Acetyl CoA carboxylase (B) HMG CoA synthetase (C) HMG CoA reductase (D) HMG CoA lyase

Last Answer : Answer : B

True statements regarding eicosanoids include which of the following? A. Prostaglandins and thromboxanes are synthesized via the cyclo-oxygenase pathway. B. The vasoconstricting, platelet-aggregating, and bronchoconstricting effects of thromboxane A 2 are balanced by the actions of prostacyclin, which produces the opposite effects. C. Leukotriene synthesis is inhibited by the action of nonsteroidal anti-inflammatory drugs (NSAIDs). D. The principal prostaglandins have a short circulation half-life and exert most of their effects locally.

Description : True statements regarding eicosanoids include which of the following? A. Prostaglandins and thromboxanes are synthesized via the cyclo-oxygenase pathway. B. The vasoconstricting, platelet-aggregating, ... prostaglandins have a short circulation half-life and exert most of their effects locally.

Last Answer : Answer: ABD DISCUSSION: The eicosanoids are a group of compounds arising from the metabolism of arachidonic acid. The prostaglandins and thromboxanes are synthesized via the cyclo-oxygenase ... effects and may be involved in the physiologic responses associated with anaphylactic and septic shock

All of the following statements about thioredoxin reductase are true except: (A) It requires NADH as a coenzyme (B) Its substrates are ADP, GDP, CDP and UDP (C) It is activated by ATP (D) It is inhibited by dADP

Description : All of the following statements about thioredoxin reductase are true except: (A) It requires NADH as a coenzyme (B) Its substrates are ADP, GDP, CDP and UDP (C) It is activated by ATP (D) It is inhibited by dADP

Last Answer : Answer : A

The activity of HMG-CoA reductase is inhibited by (A) A fungal inhibitor mevastatin (B) Probucol (C) Nicotinic acid (D) Clofibrate

Description : The activity of HMG-CoA reductase is inhibited by (A) A fungal inhibitor mevastatin (B) Probucol (C) Nicotinic acid (D) Clofibrate

Last Answer : Answer : A

PRPP glutamyl amidotransferase, the first enzyme uniquely committed to purine synthesis is feed back inhibited by (A) AMP (B) IMP (C) XMP (D) CMP

Description : PRPP glutamyl amidotransferase, the first enzyme uniquely committed to purine synthesis is feed back inhibited by (A) AMP (B) IMP (C) XMP (D) CMP

Last Answer : Answer : A

Leishmania donovani is susceptible to certain antifungal drugs because both fungi and Leishmania: A. Utilise purine salvage pathway B. Utilise similar glycolytic mechanisms C. Have similar topoisomerase II enzyme D. Have ergosterol in their cell membranes

Description : Leishmania donovani is susceptible to certain antifungal drugs because both fungi and Leishmania: A. Utilise purine salvage pathway B. Utilise similar glycolytic mechanisms C. Have similar topoisomerase II enzyme D. Have ergosterol in their cell membranes

Last Answer : D. Have ergosterol in their cell membranes

If a gene mutation prevents formation of an enzyme normally used by a lysosomes, a disease may result known as (A) Lysosomal abstracted disease (B) Lysosomal secretory disease (C) Lysosomal storage disease (D) All A, B and C

Description : If a gene mutation prevents formation of an enzyme normally used by a lysosomes, a disease may result known as (A) Lysosomal abstracted disease (B) Lysosomal secretory disease (C) Lysosomal storage disease (D) All A, B and C

Last Answer : (C) Lysosomal storage disease

The rate limiting reaction in the lipogenic pathway is (A) Acetyl-CoA carboxylase step (B) Ketoacyl synthase step (C) Ketoacyl reductase step (D) Hydratase step

Description : The rate limiting reaction in the lipogenic pathway is (A) Acetyl-CoA carboxylase step (B) Ketoacyl synthase step (C) Ketoacyl reductase step (D) Hydratase step

Last Answer : Answer : A

The metabolic reaction requiring vitamin B12 but not folate is: A. Conversion of malonic acid to succinic acid B. Conversion of homocysteine to methionine C. Conversion of serine to glycine D. Thymidylate synthesis

Description : The metabolic reaction requiring vitamin B12 but not folate is: A. Conversion of malonic acid to succinic acid B. Conversion of homocysteine to methionine C. Conversion of serine to glycine D. Thymidylate synthesis

Last Answer : A. Conversion of malonic acid to succinic acid

The reaction catalysed by phosphofructokinase (A) Is activated by high concentrations of ATP and citrate (B) Uses fruitose-1-phosphate as substrate (C) Is the rate-limiting reaction of the glycolytic pathway (D) Is inhibited by fructose 2, 6-bisphosphate

Description : The reaction catalysed by phosphofructokinase (A) Is activated by high concentrations of ATP and citrate (B) Uses fruitose-1-phosphate as substrate (C) Is the rate-limiting reaction of the glycolytic pathway (D) Is inhibited by fructose 2, 6-bisphosphate

Last Answer : C

Which of the following enzymes in Glycolytic pathway is inhibited by fluoride? (A) Glyceraldehyde-3-p dehydrogenase (B) Phosphoglycerate kinase (C) Pyruvate kinase (D) Enolase

Description : Which of the following enzymes in Glycolytic pathway is inhibited by fluoride? (A) Glyceraldehyde-3-p dehydrogenase (B) Phosphoglycerate kinase (C) Pyruvate kinase (D) Enolase

Last Answer : D

Antibody diversity arises from (A) Gene amplification (B) Gene re-arrangement (C) Alternative splicing (D) All of these

Description : Antibody diversity arises from (A) Gene amplification (B) Gene re-arrangement (C) Alternative splicing (D) All of these

Last Answer : Answer : B

The alternate complement pathway doesn’t involve (A) Antigen-antibody complex (B) Complement 3 (C) Factors B and D (D) Membrane attack unit

Description : The alternate complement pathway doesn’t involve (A) Antigen-antibody complex (B) Complement 3 (C) Factors B and D (D) Membrane attack unit

Last Answer : Answer : A

Factors B and D are required in (A) The classical pathway of complement fixation (B) The alternate complement pathway (C) Both (A) and (B) (D) None of these

Description : Factors B and D are required in (A) The classical pathway of complement fixation (B) The alternate complement pathway (C) Both (A) and (B) (D) None of these

Last Answer : Answer : B

The complement system consists of a series of serum proteins that exist in a quiescent or very low-level state of activation in the uninfected host. Which of the following statement(s) is/are true concerning complement activation? a. The alternate (properdin) pathway of complement activation can occur directly through contact with fungal or bacterial cell wall compounds b. Complement component fragments may serve to decrease vascular permeability c. Excessive complement activation can produce deleterious effects d. Fragments of certain complement components serve as chemoattractants to additional cellular components of the host defense mechanism

Description : The complement system consists of a series of serum proteins that exist in a quiescent or very low-level state of activation in the uninfected host. Which of the following ... certain complement components serve as chemoattractants to additional cellular components of the host defense mechanism

Last Answer : Answer: a, c, d Complement activation can occur through either classic or alternate (properdin) pathways, both of which eventuate in deposition of terminal complement pathway components on the ... and release of lysosomal enzymes that can directly damage certain target tissues, such as the lung

Which enzyme will be produced in a cell if there is a nonsense mutation in the lac Y gene? (a) Transacetylase (b) Lactose permease and transacetylase (c) β-galactosidase (d) Lactose permease

Description : Which enzyme will be produced in a cell if there is a nonsense mutation in the lac Y gene? (a) Transacetylase (b) Lactose permease and transacetylase (c) β-galactosidase (d) Lactose permease

Last Answer : β-galactosidase

The regulatory i gene of lac operon (A) Is inhibited by lacotse (B) Is inhibited by its own product, the repressor protein (C) Forms a regulatory protein which increases the expression of downstream structural genes (D) Is constitutively expressed

Description : The regulatory i gene of lac operon (A) Is inhibited by lacotse (B) Is inhibited by its own product, the repressor protein (C) Forms a regulatory protein which increases the expression of downstream structural genes (D) Is constitutively expressed

Last Answer : Answer : D

In biosynthesis of cholesterol triparanol inhibits the activity of the enzyme: (A) ∆24 Reductase (B) Oxidosqualene-lanosterol cyclase (C) Isomerase (D) Squalene epoxidase ENZYMES 155

Description : In biosynthesis of cholesterol triparanol inhibits the activity of the enzyme: (A) ∆24 Reductase (B) Oxidosqualene-lanosterol cyclase (C) Isomerase (D) Squalene epoxidase ENZYMES 155

Last Answer : Answer : A

In the biosynthesis of cholesterol, the rate limiting enzyme is (A) Mevalonate kinase (B) HMG-CoA synthetase (C) HMG-CoA reductase (D) Cis-prenyl transferase

Description : In the biosynthesis of cholesterol, the rate limiting enzyme is (A) Mevalonate kinase (B) HMG-CoA synthetase (C) HMG-CoA reductase (D) Cis-prenyl transferase

Last Answer : Answer : C

For reduction enzyme HMG-CoA reductase requires cofactor: (A) NADPH (B) NADP (C) NAD (D) FAD

Description : For reduction enzyme HMG-CoA reductase requires cofactor: (A) NADPH (B) NADP (C) NAD (D) FAD

Last Answer : Answer : A

Conversion of fructose to sorbitol is catalysed by the enzyme: (A) Sorbitol dehydrogenase (B) Aldose reductase (C) Fructokinase (D) Hexokinase

Description : Conversion of fructose to sorbitol is catalysed by the enzyme: (A) Sorbitol dehydrogenase (B) Aldose reductase (C) Fructokinase (D) Hexokinase

Last Answer : Answer : A

The enzyme involved in essential pentosuria is (A) Reductase (B) Hydroxylase (C) Isomerase (D) Racemase

Description : The enzyme involved in essential pentosuria is (A) Reductase (B) Hydroxylase (C) Isomerase (D) Racemase

Last Answer : Answer : A

Catabolism of thymidylate gives (A) α-alanine (B) β-alanine (C) α-aminoisobutyrate (D) β-aminoisobutyrate

Description : Catabolism of thymidylate gives (A) α-alanine (B) β-alanine (C) α-aminoisobutyrate (D) β-aminoisobutyrate

Last Answer : Answer : D

Mitochondrial protein synthesis is inhibited by (A) Cycloheximide (B) Chloramphenicol (C) Diptheria toxin (D) None of these

Description : Mitochondrial protein synthesis is inhibited by (A) Cycloheximide (B) Chloramphenicol (C) Diptheria toxin (D) None of these

Last Answer : Answer : B

Porphyrin synthesis is inhibited in (A) Mercury poisoning (B) Lead poisoning (C) Manganese poisoning (D) Barium poisoning

Description : Porphyrin synthesis is inhibited in (A) Mercury poisoning (B) Lead poisoning (C) Manganese poisoning (D) Barium poisoning

Last Answer : Answer : B

Synthesis of prostaglandins is inhibited by (A) Glucocorticoids (B) Aspirin (C) Indomethacin (D) All of these

Description : Synthesis of prostaglandins is inhibited by (A) Glucocorticoids (B) Aspirin (C) Indomethacin (D) All of these

Last Answer : Answer : D

The synthesis of glucose from pyruvate by gluconeogenesis (A) Requires the participation of biotin (B) Occurs exclusively in the cytosol (C) Is inhibited by elevated level of insulin (D) Requires oxidation/reduction of FAD

Description : The synthesis of glucose from pyruvate by gluconeogenesis (A) Requires the participation of biotin (B) Occurs exclusively in the cytosol (C) Is inhibited by elevated level of insulin (D) Requires oxidation/reduction of FAD

Last Answer : A

All of the following statements about the enzymic complex that carries out the synthesis of ATP during oxidative phosphorylation are correct except (A) It is located on the matrix side of the inner mitochondrial membrane (B) It is inhibited by oligomycin (C) It can exhibit ATPase activity (D) It can bind molecular O2

Description : All of the following statements about the enzymic complex that carries out the synthesis of ATP during oxidative phosphorylation are correct except (A) It is located on the matrix side of the inner ... inhibited by oligomycin (C) It can exhibit ATPase activity (D) It can bind molecular O2

Last Answer : D

Synthesis of prostaglandinsis is inhibited by (A) Aspirin (B) Arsenic (C) Fluoride (D) Cyanide

Description : Synthesis of prostaglandinsis is inhibited by (A) Aspirin (B) Arsenic (C) Fluoride (D) Cyanide

Last Answer : A

The following statement(s) is/are true concerning cellular defense mechanisms. a. Macrophages function solely as antigen processing cells in the initial reaction to exposure to an antigen b. Macrophages may become activated and secrete cytokines c. Macrophages serve as phagocytic cells in the tissues but not within the bloodstream d. Polymorphonucleocytes (PMNS) are normally present in only small numbers within the tissue and enter an area of infection through diapedesis

Description : The following statement(s) is/are true concerning cellular defense mechanisms. a. Macrophages function solely as antigen processing cells in the initial reaction to exposure to an antigen b. Macrophages ... in only small numbers within the tissue and enter an area of infection through diapedesis

Last Answer : Answer: b, d A wide variety of cell types serve to provide host defense at several levels. Macrophages act as the initial antigen processing cell that serves to ... through diapedesis after chemotactic stimuli are excluded by macrophages, bacterial breakdown products, and complement activation

The enzyme aspartate transcarbamoylase of pyrimidine biosynthesis is inhibited by (A) ATP (B) ADP (C) AMP (D) CTP

Description : The enzyme aspartate transcarbamoylase of pyrimidine biosynthesis is inhibited by (A) ATP (B) ADP (C) AMP (D) CTP

Last Answer : Answer : D

In which of the following types of enzymes an inducer is not required? (A) Inhibited enzyme (B) Cooperative enzyme (C) Allosteric enzyme (D) Constitutive enzyme

Description : In which of the following types of enzymes an inducer is not required? (A) Inhibited enzyme (B) Cooperative enzyme (C) Allosteric enzyme (D) Constitutive enzyme

Last Answer : Answer : D

Phosphofructokinase key enzyme in glycolysis is inhibited by (A) Citrate and ATP (B) AMP (C) ADP (D) TMP

Description : Phosphofructokinase key enzyme in glycolysis is inhibited by (A) Citrate and ATP (B) AMP (C) ADP (D) TMP

Last Answer : Answer : A

A demonstrable inducer is absent in (A) Allosteric enzyme (B) Constitutive enzyme (C) Inhibited enzyme (D) Co-operative enzyme ENZYMES 141

Description : A demonstrable inducer is absent in (A) Allosteric enzyme (B) Constitutive enzyme (C) Inhibited enzyme (D) Co-operative enzyme ENZYMES 141

Last Answer : Answer : B

Explain the term Gene amplification. -Biology

Description : Explain the term Gene amplification. -Biology

Last Answer : An increase in the number of copies of a gene. There may also be an increase in the RNA and protein made from that gene. Gene amplification is common in cancer cells, and some amplified genes may cause cancer cells to grow or become resistant to anticancer drugs.

What is gene amplification? -Biology

Description : What is gene amplification? -Biology

Last Answer : answer:

What is gene amplification? -Biology

Description : What is gene amplification? -Biology

Last Answer : answer:

All the following statements about retino blastoma are true except (A) At least two mutations are required for its development (B) One mutation can be inherited from a parent (C) Children who have inherited one mutation develop retinoblastoma at a younger age (D) RB 1 gene promotes the development of retinoblastoma

Description : All the following statements about retino blastoma are true except (A) At least two mutations are required for its development (B) One mutation can be inherited from a parent (C) Children ... mutation develop retinoblastoma at a younger age (D) RB 1 gene promotes the development of retinoblastoma

Last Answer : Answer : D