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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance4 Marks
Question
Explain Methodology of HGP
✓

Answer

→ The methods involved two major approaches. One approach focused on identifying all the genes that are expressed as RNA (referred to as Expressed Sequence Tags (ESTS).
→ The other took the blind approach of simply sequencing the whole set of genome that contained all the coding and non-coding sequence, and later assigning different regions in the sequence with functions (a term referred to as Sequence Annotation).
→ For sequencing, the total DNA from a cell is isolated and converted into random fragments of relatively smaller sizes (recall DNA is a very long polymer, and there are technical limitations in sequencing very long pieces of DNA) and cloned in suitable host using specialised vectors.
→ The cloning resulted into amplification of each piece of DNA fragment so that it subsequently could be sequenced with ease.
→ The commonly used hosts were bacteria and yeast, and the vectors were known as BAC (bacterial artificial chromosomes); and YAC (yeast artificial chromosomes).
→ The fragments were sequenced using automated DNA sequencers that worked on the principle of a method developed by Frederick Sanger. (Remember, Sanger is also credited for developing method for determination of amino acid sequences in proteins).
→ There sequences were then arranged based on some overlapping regions present in them.
→ This required generation of overlapping fragments for sequencing. Alignment of these sequences was humanly not possible.
→ Therefore, specialised computer based programs were developed.
→ These sequences were subsequently annotated and were assigned to each chromosome.
→ The sequence of chromosome 1 was completed only in May 2006 (this was the last of the 24 human chromosomes - 22 autosomes and X and Y - to be sequenced).
→ Another challenging task was assigning the genetic and physical maps on the genome.
→ This was generated using information on polymorphism of restriction endonuclease recognition sites, and some repetitive DNA sequences known as microsatellites (one of the applications of polymorphism in repetitive DNA sequences shall be explained in next section of DNA fingerprinting).

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In a study to test a new vaccine against a viral disease, mouse model testing is done. In this process, mice are vaccinated and their blood samples were tested. Mice developed mild disease symptom. After few days those mice were again infected with the virus. This time they do not show any disease symptoms. Their blood samples were tested. Two graphs show antibody concentration for the first and second infection in mice blood.

Based on the above information, answer the following questions.

  1. P and Qin the given graphs indicate.
  1. IgM and IgG respectively.
  2. IgG and IgM respectively
  3. IgG and IgM respectively
  4. IgM and IgA respectively.
  1. Which form of pathogen is used in vaccination?
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  2. Inactivated and weakened pathogenic antigen.
  3. Hyperactive and strong pathogen.
  4. Preformed antibodies.
  1. Which of the following is incorrect for P?
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  2. It is found in blood, lymph, and intestine.
  3. It is unable to cross the placental barrier.
  4. It is a monomer.
  1. How does vaccination work?
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  1. Assertion: Mice do not show any disease symptoms during second exposure to the pathogenic virus.

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Kangaroo rat seldom drinks water. It has thick coat to minimise evaporative desiccation. TI1e animal seldom comes out of its comparatively humid and cool burrow during the day time. 90% of its water requirement is met from metabolic water (water produced by respiratory breakdown of fats) while 10% is obtained from its food. Loss of water is minimised by producing nearly solid urine and faeces. As the animal faces acute water scarcity, it develops two types of adaptations : reducing water loss and ability to tolerate desert conditions.

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  1. Both assertion and reason are true and reason is the correct explanation of assertion.
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  1. Refer to the given figure and select the correct statement regarding it.

  1. This type of ovule is found in cactus.
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S. No A B C D
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(b) Chalaza NuceIIus Embryo sac Micropyle
(c) Micropyle Egg Embryo sac Chalaza
(d) Micropyle Nucellus Embryo sac Chalaza
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A technique known as amniocentesis is used to determine fetal abnormalities. This test chromosomal pattern in amniotic fluid. However, this technique is legally banned now.

  1. Identify X and Y in the above given figure.
S. No
X
Y
(a)
Amnion
Chorion
(b)
Uterine wall
Placenta
(c)
Placenta
Uterine wall
(d)
Uterine wall
Amnion
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  3. Jaundice.
  4. Cystic fibrosis.
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Reason: Amniocentesis was being misused for aborting normal female fetus.

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  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
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The anther is a four-sided structure consisting of four microsporangia located at the corners, two in each lobe. TI1e microsporangia develop further and become pollen sacs. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers-the epidermis, endothecium, middle layers and the tapetum.

  1. A dithecous another consists of (A) microsporangia, (B) in each lobe.

Select the option that correctly fills the blanks.

S. No
A
B
(a)
Four
Two
(b)
Two
One
(c)
Two
Two
(d)
Four
One
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(a)
A-Middle layer
B-Endothecium
C-Tapetum
(b)
A-Endothecium
B-Tapetum
C- Middle layer
(c)
A-Endothecium
B-Middle layer
C-Tapetum
(d)
A-Tapetum
B-Middle layer
C-Endothecium
  1. The function of labelled part X is:

  1. Dehiscence.
  2. Mechanical.
  3. Nutrition.
  4. Protection.
  1. Select the incorrect statement.
  1. Microsporangium is generally surrounded by four wall layers-epidermis, endothecium, middle layers and tapetum.
  2. Outer three layers perform functions of protection and dehiscence of anthers.
  3. Cells of tapetum possess dense cytoplasm and generally have more than one nucleus.
  4. Cells of tapetum undergo meiosis and produce microspore tetrads.
  1. Which function oftapetum is correct?
  1. Helps in pollen wall formation.
  2. Transportation of nutrients to inner side of another.
  3. Synthesis of callase enzyme for separation of microspore tetrads.
  4. All of these.
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