Molecular Basis of Inheritance - Online Test
Q1. If 30 percent of an organism’s DNA is thymine, then
Answer : Option C
Explaination / Solution:
Thymine and Adenine bond with each other so, they are equal in number. Sum of cytosine and guanine is equal to 100-60=40 percent. So, percentage of guanine is 40/2= 20 percent.
Q2. In biochemical genetics the term gene is being replaced by
Answer : Option B
Explaination / Solution:
In biochemical genetics the term gene is being replaced by cistron. Cistron is a segment of DNA consisting of a stretch of deoxyribonucleotides which code for a biochemical controlling other cistron.
Q3. Select the two correct statements out of the four (a–d) given below about lac operon.
(a) Glucose or galactose may bind with the repressor and inactivate it
(b) In the absence of lactose the repressor binds with the operator region
(c) The z-gene codes for permease
(d) This was elucidated by Francois Jacob and Jacque Mono.
The correct statements are
(a) Glucose or galactose may bind with the repressor and inactivate it
(b) In the absence of lactose the repressor binds with the operator region
(c) The z-gene codes for permease
(d) This was elucidated by Francois Jacob and Jacque Mono.
The correct statements are
Answer : Option B
Explaination / Solution:
In lac operon, Francois Jacob and Jacque Mono elucidated that in absence of lactose the repressor binds with the operator gene and forms the particular protein to express itself.
Q4. E. coli cells with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because
Answer : Option B
Explaination / Solution:
Bacterium E.coli with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because E.coli cannot synthesize functional beta galactosidase essential for cell wall formation.
Q5. H-bonds between Cytosine and Guanine are
Answer : Option A
Explaination / Solution:
In DNA molecules nitrogenous base of complementary strands binds with hydrogen bonds. In cytosine and guanine there are 3 hydrogen bonds and in adenine and thymine, the number of hydrogen bond is 2.
Q6. Transcription of DNA into mRNA occurs in the nucleus of the cell but translation occurs in
Answer : Option D
Explaination / Solution:
Transcription is the process of copying DNA code into mRNA. It occurs in the nucleus of the cell. The mRNA comes out of nucleus then its translation occurs into cytoplasm to form protein.
Q7. In lac operon, lactose is the substrate for enzyme beta-galactocidase and its regulates
Answer : Option D
Explaination / Solution:
In lac operon, lactose is the substrate for enzyme beta-galactocidase and it regulates switching ON and OFF of the operon. Hence, lactose is called the inducer.
Q8. Lac operon consists of
Answer : Option D
Explaination / Solution:
Lac Operon consists of one regulator gene, i and three structural genes z, y and a. I gene code for repression of the lac Operon. Z gene code for beta-galactosidase, y code for permease and a gene code for transactylase.
Q9. Assertion: Regulation of lac operon by repressor is referred to as negative regulation.
Reason: Lac operon is under the control of positive regulation as well.
Answer : Option A
Explaination / Solution:
An operon is a cluster of coordinately regulated genes. It includes structural genes (generally encoding enzymes), regulatory genes (encoding, e.g. activators or repressors) and regulatory sites (such as promoters and operators).
The type of control is defined by the response of the operon when no regulatory protein is present.
The inducer–repressor control of the lac operon is an example of negative control, in which expression is normally blocked.
In contrast, the CAP-cAMP system is an example of positive control, because expression of the lac operon requires the presence of an activating signal.
Q10. The correct sequence of gene expression is
a. Formation of primary transcript
b. Regulation of splicing
c. Transport of mRNA from nucleus to cytoplasm>
d. Translation
a. Formation of primary transcript
b. Regulation of splicing
c. Transport of mRNA from nucleus to cytoplasm>
d. Translation
Answer : Option B
Explaination / Solution:
The correct sequence of events involving gene expression includes formation of primary transcript, regulation of splicing, transport of mRNA from nucleus to cytoplasm and translation.
