CBSE 12TH BIOLOGY - Online Test
Q1. The technique of DNA fingerprinting has many applications ranging from identifying paternity to finding criminals. The sensitivity of the technique has been increased by use of
Answer : Option C
Explaination / Solution:
Polymerase chain reaction (PCR) is a technique used in molecular biology to amplify a single copy or a few copies of a segment of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence.
This increae the sensitivity of the technique.
Q2. Which germinal layer forms blood, heart, blood vessels etc.?
Answer : Option B
Explaination / Solution:
Human beings are triploblastic. The outer layer is called ectoderm that forms central nervous system and nerves etc. The middle layer or mesoderm forms heart, blood and blood vessels. The inner layer forms liver, pancreas etc.
Q3. Which of the following is an example of environmental variation?
Answer : Option A
Explaination / Solution:
Environmental variation is the change in traits due to environmental factors like temperature, humidity, soil water precipitation etc. Dying hair colour blue or any other colour is environmental variation.
Q4. DNA fingerprinting involves identifying differences in some specific regions of DNA sequence called repetitive DNA because
Answer : Option A
Explaination / Solution:
In specific regions of DNA sequence, a small stretch of DNA is repeated many times. The repetitive DNA are separated from bulk genomic DNA during density gradient centrifugation.
Q5. Amniotic fluid is
Answer : Option B
Explaination / Solution:
The inner foetal membrane invests the embryo and forms a space called amniotic cavity. It is filled with fluid called amniotic fluid. It is useful for studying chromosomal abnormalities of foetus.
Q6. What was the most significant trend in the evolution of modern man (Homo sapiens) from his ancestors?
Answer : Option A
Explaination / Solution:
The most significant trend in the evolution of modern man from his ancestors is the increasing cranial cavity. Bony cavity inside which bone is located is called cranium. Cranial capacity increased from 900cc to 1400cc in course of evolution.
Q7. In human beings 99.9% of genome sequence are same in all individuals only 0.1% of genome differ that
Answer : Option B
Explaination / Solution:
Genome variations are differences in the sequence of DNA from one person to the next
In human’s 99.9% of the base sequences of DNA are same & are referred as Bulk genomic DNA.
The difference lies in remaining 0.1%. It is these differences which make every individual unique in their phenotypic appearance. This DNA has small stretches of repetitive sequences. They are referred as Repetitive DNA.
Q8. Haploid nucleus of sperms and a haploid ovum fuse together to form
Answer : Option B
Explaination / Solution:
Haploid nucleus of sperms and a haploid ovum fuse together to form diploid zygote. Zygote undergoes mitotic division to form embryo and fetus.
Q9. The extinct human who lived 1,00,000 to 40,000 years ago, in Europe, Asia and parts of Africa, with short stature, heavy eye brows, retreating foreheads, large jaws with heavy teeth, stocky bodies, a lumbering gait and stooped posture was
Answer : Option C
Explaination / Solution:
Neanderthals are recognisably human but have distinctive facial features and a stocky build that were evolutionary adaptations to cold, dry environments.
This species lived between 28,000 and 300,000 years ago.
Key physical features :
- Body size and shape: Neanderthals were generally shorter and had more robust skeletons and muscular bodies than modern humans.
- Brain size was larger than the average modern human brain and averaged 1500 cubic centimetres.
- Skull : distinctive skull shape that was long and low, with a rounded brain case. mid-face region showed a characteristic forward projection (this resulted in a face that looked like it had been ‘pulled’ forward by the nose). orbits (eye sockets) were large and rounded. Nose was broad and very large
- Jaws and teeth : jaws were larger and more robust than those of modern humans and had a gap called the retromolar space, behind the third molars (wisdom teeth) at the back of the jaw. jaw lacked the projecting bony chin that is found in Homo sapiens. teeth were larger than those of modern humans.
Q10. Depending on base composition, length of segment and number of repetitive units, the satellite DNA is classified into many categories such as
Answer : Option A
Explaination / Solution:
Satellite DNA contains short nucleotide sequences repeated thousands of time tandemly. Satellite DNA is divided into different categories according to their size i.e., micro-satellites, mini-satellites etc.
- Micro-satellite consists of 2 – 6 bp repeats.
- Mini-satellite consists of 10 – 100 bp repeats, they are referred as VNTRs.
These sequences generally do not code for any protein.
