Tag: one gene - one enzyme hypothesis

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Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Today, it is most appropriate to state that a gene controls

  1. one enzyme

  2. one protein

  3. one polypeptide chain

  4. one amino acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

One gene one enzyme hypothesis had many defects so it changed to one gene-one polypeptide.  According to one gene-one polypeptide hypothesis, the information enclosed in one gene is sufficient to form one polypeptide only. Genes control the synthesis of all proteins. Some proteins are enzymes and some are hormones.  Hemoglobin molecule consists of two different polypeptides alpha and beta which are formed by two different genes.

So, the correct option is 'one polypeptide chain'.

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Slight difference is identical twins support the hypothesis that ________________.

  1. Dominance may be incomplete

  2. Single gene may produce multiple effects

  3. The expression of genetic character is affected by environment

  4. They developed from separate fertilized eggs
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Identical twins share the exact same genetic makeup since they develop from a single fertilized egg. Therefore, any slight differences observed between them later in life are due to environmental influences acting on gene expression.

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Which of the following regulates the activities integrator gene?

  1. Sensor site

  2. RNA

  3. Producer gene

  4. Receptor site
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Sensor sites are signal receiving genes. They are very sensitive for specific signals from the cell and its environment. 
A sensor site regulates activity of an integrator gene which can be transcribed only when the sensor site is activated. 
So, the correct option is 'Sensor site'.
Multiple choice zoology cell and cell organelles one gene - one enzyme hypothesis component of the cell molecular genetics

One-gene-one enzyme hypothesis was proposed by

  1. Beadle and Tatum

  2. Jacob and Monod

  3. Lederberg

  4. Watson and Crick
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The one gene-one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway. The concept was proposed by George Beadle and Edward Tatum in an influential 1941 paper.  Beadle and Tatum noted that it was "entirely tenable to suppose that these genes which are themselves a part of the system, control or regulate specific reactions in the system either by acting directly as enzymes or by determining the specificities of enzymes".

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

The idea that a single gene coded for a polypeptide rather than an enzyme was evident from the

  1. use of X-rays to make nutritional mutants in bread mold

  2. transformation of bacteria from rough and non-virulent to smooth and virulent

  3. presence of a mutation in one chain of hemoglobin but not in the other

  4. discovery that mutated genes changed enzymes in a biochemical pathway
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to one gene-one polypeptide hypothesis, the information enclosed in one gene is sufficient to form one polypeptide only. Genes control the synthesis of all proteins. Some proteins are enzymes and some are hormones. As we know that proteins are made up of polypeptides- long chains of amino acids. Some proteins consist of two or more polypeptides linked and twisted around each other. For eg, hemoglobin.

So, the correct option is presence of a mutation in one chain of hemoglobin but not in other'.

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Activator of phsphofructokinase enzyme is:

  1. AMP

  2. ATP

  3. CN

  4. CO
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

AMP is known as Adenosine monophosphate which is involved in many biological processess. It is a type of nucleotide phosphate. It  consists of phospate group and nucleobase adenine. It is used to regenerate ATP.

So, the correct option is 'AMP'.

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Which of the following sequence helps in modification but not in protein synthesis?

  1. Integrator site

  2. Sensor site

  3. Producer site

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Producer site produces pre mRNA, which after processing becomes mRNA. Its expression is under the control of many receptor sites. mRNA later takes part in protein synthesis during translation. 

Integrator gene is responsible for the synthesis of an activator RNA molecule that activates the receptor site. A sensor site regulates the activity of an integrator gene which can be transcribed only when the sensor site is activated.
So, the correct option is 'Both A and B'.

Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Match List I with List II and select the correct answer using the codes given:

List-I List-II
A. Theory of mutation 1. Beadle and Tatum
B. Theory of evolution 2. Jacob and Monod
C. One gene one enzyme hypothesis 3. Darwin
D. Operon concept 4. DeVries

  1. A - 4, B - 3, C - 2, D - 1

  2. A - 4, B - 3, C - 1, D - 2

  3. A - 3, B - 4, C - 1, D - 2

  4. A - 3, B - 4, C - 2, D - 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
 A. Theory of mutation  Hugo de Vries was a Dutch geneticist who was one among several scientists in the late 1800s studying heredity, how living things can pass traits from one generation to the next. He began his work not long after Charles Darwin introduced his concept of natural selection. De Vries' experiments and ideas helped shaped what we know about genetics, mutations, and evolution. According to de Vries' mutation theory, living organisms can develop changes to their genes that greatly alter the organism. These changes are passed down to the next generation, and lead to the development of new species. Once a new species has evolved, it becomes fixed and stops changing. The mutations are the mechanism de Vries proposed for his discontinuous variation model of evolution.So the correct option is 'DeVries'.
 B. Theory of evolution  The theory of evolution by natural selection, first formulated in Darwin's book "On the Origin of Species" in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits. Changes that allow an organism to better adapt to its environment will help it survive and have more offspring. Evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines, including paleontology, geology, genetics and developmental biology.So the correct option is 'Darwin'.
 C. One gene one enzyme hypothesis  The one gene–one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway. The concept was proposed by George Beadle and Edward Tatum in an influential 1941 paper on genetic mutations in the mold Neurospora crassa, and subsequently was dubbed the "one gene–one enzyme hypothesis" by their collaborator Norman Horowitz. In 2004 Norman Horowitz reminisced that "these experiments founded the science of what Beadle and Tatum called 'biochemical genetics.' In actuality they proved to be the opening gun in what became molecular genetics and all the developments that have followed from that." The development of the one gene–one enzyme hypothesis is often considered the first significant result in what came to be called molecular biology. Although it has been extremely influential, the hypothesis was recognized soon after its proposal to be an oversimplification. So the correct option is 'Beadle and Tatum'
 D. Operon concept  Operon Theory is the concept of gene regulation proposed by François Jacob and Jacques Monod (1961). An operon is a group of structural genes whose expression is coordinated by an operator. The  repressor encoded by a regulatory gene binds to the operator and represses the transcription of operon. In the presence of inducer, the repressor is inactivated and dissociates from operator to express the operon. Thus, the expression of the operon is controlled by a cis-acting operator and by a trans-acting  repressor.So the correct option is 'Jacob and Monod'.
Multiple choice zoology molecular genetics one gene - one enzyme hypothesis component of the cell cell and cell organelles

Studies by Beadle and Tatum that produced the one-gene one-enzyme hypothesis were conducted using the:

  1. bread mold Neurospora crassa

  2. bacterium Streptococcus pneumoniae

  3. bacterium Escherichia coli

  4. mushroom Agaricus bisporus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The one gene-one enzyme hypothesis, proposed by George Wells Beadle in the US in 1941, is the theory that each gene directly produces a single enzyme, which consequently affects an individual step in a metabolic pathway. Beadle and Tatum worked with a simple organism: common bread mold, or Neurospora crassa. Using Neurospora, they were able to show a clear connection between genes and metabolic enzymes. With a series of the experiment they first created mutant Neurospora and found which metabolic pathway was broken in mutants by growing them in a variety of nutritional medium. Their work produced a revolution in the study of genetics and showed that individual genes were indeed connected to specific enzymes. 

So, the correct option is 'bread mold Neurospora crassa'.