CBSE 12TH BIOLOGY - Online Test
Q1. Number of nitrogenous bases in a Codon is
Answer : Option A
Explaination / Solution:
A codon is a sequence of 3 nitrogenous bases located on mRNA that will pair up with the anticodon of tRNA to make the polypeptide (protein) I. 64 codons can be obtained from four nitrogenous bases if arranged in group of 3.
Q2. At the end of pregnancy, expulsion or delivery of foetus takes place due to
Answer : Option A
Explaination / Solution:
Expulsion or delivery of foetus takes place due to vigorous contraction of uterus at the end of pregnancy. Oxytocin hormone released from pituitary glands causes stronger contraction to cause expulsion of foetus.
Q3. 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.
Q4. Pseudo dormancy differs from normal pregnancy in
Answer : Option D
Explaination / Solution:
Pseudo dormancy differs from normal pregnancy in absence of foetus in the uterus. Developmental change in endometrium, and development of ovum occurs during menstrual cycles.
Q5. 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.
Q6. The gaseous hormone that help in switching over its respiratory and circulatory system just after delivery is
Answer : Option D
Explaination / Solution:
The gaseous hormone that help in switching over its respiratory and circulatory system just after delivery is Nitroc Oxide (NO).
Q7. 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.
Q8. Parturition is induced by complex
Answer : Option D
Explaination / Solution:
Parturition is induced by a complex neuroendocrine mechanism. Fully developed foetus triggers signal from uterus to release oxytocin hormone from pituitary hormones.
Q9. 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.
Q10. The mammary glands of female starts producing milk
Answer : Option B
Explaination / Solution:
Memory gland of female undergo differentiation during the pregnancy and start producing milk towards the end of pregnancy by the process of lactation.
