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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance4 Marks
Question
Explain Methodology of HGP
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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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Similar questions

Read the following and answer any four questions from (i) to (v) given below:
The foundations of recombinant DNA (rDNA) were laid by the discovery of restriction enzymes. These enzymes are present in many bacterias where they function as a part of their defense mechanism called the Restriction Modification system (RM system). Molecular basis of this system was explained first by Werner Arber in 1962. The Restriction Modification system consists of two components:
  • A restriction enzyme (called restriction endonuclease) identifies the introduced foreign DNA and cuts it into pieces.
  • The second component is a modification enzyme (methylase) that adds a methyl group to DNA at specific site to protect it from the restriction enzyme cleavage.
  1. Restriction endonucleases are enzymes present in ________ where they function as a part of _______ mechanism.
  1. (i) bacteria (ii) digestive
  2. (i) protists (ii) transcription
  3. (i) plant cells (ii) replication
  4. (i) prokaryotes (ii) defence
  1. Which of the following statements regarding modification enzyme is correct?
  1. It adds methyl group to one or two bases usually within the host DNA sequence to protect it from the restriction enzyme.
  2. It adds ethyl group to one or two bases usually within the sequence recognised by the restriction enzymes.
  3. It adds methyl group to only one of bases within the foreign DNA sequence that is recognised by the restriction enzymes.
  4. None of these.
  1. Which of the following is a type II restriction enzyme?
  1. Alu I
  2. EcoR I
  3. BamH I
  4. All of these.
  1. Which of the following is the first discovered restriction endonuclease?
  1. Sal I
  2. EcoR I
  3. Hind II
  4. EcoR II
  1. Components of Restriction Modification System include?
  1. Restriction enzyme.
  2. Modification enzyme.
  3. Lysing enzyme.
  4. Both (a) and (b).
→
​​​​Read the following and answer any four questions from (i) to (v) given below:

Edward Wilson described diversity at all levels of biological organisation ranging from macromolecules inside the cells to biomes. It is of three inter-related hierarchial levels-genetic diversity, species diversity and conununity ecosystem diversity. Species diversity is the variety in the number and richness of the species of a region. For example, the Western ghats have a greater amphibian species diversity than the Eastern ghats.

  1. The number of species per unit area is called.
  1. Species evenness.
  2. Species richness.
  3. Species equitability.
  4. Both (a) and (c).
  1. The table below gives the population (in thousands) of ten species (A - J) in four areas (I - IV) consisting of the number of habitats given within brackets against each. Study the table and answer the question which follows:
Area and number of habitats
Species and their population (in thousands) in the area
A
B
C
D
E
F
G
H
I
J
I(11)
23
12
0.52
6.0
-
3.1
1.1
9.0
-
10.3
II(11)
10.2
-
0.62
-
1.5
3.0
-
8.2
1.1
11.2
III(13)
11.3
0.9
0.48
2.4
1.4
4.2
0.8
8.4
2.2
4.1
IV(12)
3.2
10.2
1.1
4.8
0.4
3.3
0.8
7.3
1.3
2.1
Which are out of I to IV shows maximum species diversity?

  1. II
  2. III
  3. IV
  4. I
  1. Study the given populations and choose the correct answer in relation to species diversity.
Population
Species
Species
Individuals
Population A
I
Mammals
3
II
Birds
2
III
Amphibians
2
Population B
I
Mammals
2
II
Mammals
2
III
Amphibians
1
Population C
I
Mammals
3
II
Mammals
2
III
Mammals
4

 

 
Maximum diversity
Minimum diversity
(a)
Population B
Population C
(b)
Population A
Population C
(c)
Population A
Population B
(d)
Population B
Population A
  1. The concept of species diversity has two components : evenness and richness. Evenness is based on the relative abundance of species. Richness is based on the total number of species present. Diversity indices combine a measure of richness and evenness. The Simpson index (D) is calculated from the following equations:

$\text{D}=\displaystyle\sum_{\text{i}=1}(\text{n}_\text{i}/\text{N})^2$

where, n = total number of organisms of particular species

N = total number of organisms of all species

Below are data collected in two terrestrial plant conununities that represent part of a successional chronosequence. ln this case the values were measured as percent cover.

Early Successional Community
Late Successional Community
Species
Percent Cover
Species
Percent Cover
A
83
F
24
B
5
G
20
C
9
H
18
D
2
I
23
E
1
J
15
The data indicate that, relative to the early successional community, the late successional community has which of the following characteristics?

 
Species Richness
Evenness
(a)
Higher
Higher
(b)
Higher
Lower
(c)
Same
Lower
(d)
Same
Higher
  1. Select the incorrect statement regarding species diversity.
  1. It results in polymorph formation and is useful in adaptation to changes in environmental conditions.
  2. Number of individuals of different species represent species evenness.
  3. It influences biotic interactions and stability of the community.
  4. It is a trait of the community.
→
Read the following and answer any four questions from (i) to (v) given below:
RNA or ribonucleic acid is a single chain polyribonucleotide which functions as carrier of coded genetic or hereditary information from DNA to cytoplasm for taking part in protein and enzyme synthesis. Six types of RNAs are ribosomal, transfer, messenger, genomic, small nuclear and small cytoplasmic RNA. Out of these, rRNA, mRNA and tRNA are major classes of RNAs that are involved in gene expression.
  1. Which one is referred to a soluble RNA?
  1. mRNA
  2. tRNA
  3. rRNA
  4. hnRNA
  1. The RNA that picks up specific amino acid from amino acid pool in the cytoplasm to ribosome during protein synthesis is?
  1. rRNA
  2. hnRNA
  3. mRNA
  4. tRNA
  1. Which of the following is found in both DNA and messenger RNA?
  1. Double helix structure
  2. Ribose
  3. Sugar-phosphate chain
  4. Thymine
  1. Which of the following statements regarding RNA is correct?
  1. Messenger RN As carries coded information for synthesis of polypeptide.
  2. Ribosomal RNAs bind with tRNA to catalyse the formation of phosphodiester bonds.
  3. Genomic RNA is always single stranded.
  4. Synthesis of rRNA occurs in cytoplasm by RNA polymerase III
  1. In studying a virus, you find the following proportions of nitrogenous bases present: adenine 23%, guanine 37%, cytosine 23% uracil 17%. Which of the following statement(s) regarding this virus is/are correct?
  1. It probably uses RNA as its genetic material.
  2. The genetic material of this virus is probably single stranded.
  3. Base pairing rules in virus in this virus include adenine: cytosine.
  1. I only
  2. I and II only
  3. II and III only
  4. All of these.
→
Read the following and answer any four questions from (i) to (v) given below:

Oral administration of small doses of hormones is contraceptive method used by the females. They are used in the form of tablets and hence called the pills. The oral pills are two types; mini pills and combined pills.

  1. Mini pills contain:
  1. Estrogen only.
  2. Progestin only.
  3. Combination of progesterone-estrogen.
  4. Inhibin.
  1. How do hormonal pills prevent pregnancy?
  1. By phagocytosing the sperms.
  2. By inhibiting ovulation.
  3. By preventing sperms from entering the vagina.
  4. All of these.
  1. Pill containing non-steroidal preparation, centchroman is:
  1. Mala D.
  2. Mala N.
  3. I-Pill.
  4. Saheli.
  1. Which among the following is incorrect for oral contraceptives?
  1. Oral pills alter the uterine endometrium and make it unsuitable for implantation.
  2. Oral pills have to be taken daily for 7 days starting within first five days of menstrual cycle.
  3. Oral pills increase the risk of intravascular clotting.
  4. Oral pills contain either progestin alone or combination of progestogen and estrogen.
  1. Assertion: Mala D, a combined contraceptive pill, have to be taken daily without a break.

Reason: Mala D contains synthetic progesterone and estrogen.

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
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Read the following and answer any four questions from (i) to (v) given below:

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids found in the living systems. DNA acts as the genetic material in most of the organisms. Although, RNA also acts as a genetic material in some organisms.

  1. In which of the following organisms, RNA acts as a genetic material?
  1. Escherichia coli
  2. $\text{Q}\beta$ Bacteriophage
  3. Tobacco Mosaic viruses
  4. Both (b) and (c)
  1. What is the reason for the additional stability of DNA in comparison to RNA?
  1. Presence of thymine
  2. Presence of uracil
  3. Presence of OH group
  4. Presence of deoxyribose sugar
  1. Which of the following criteria a molecule must fulfill to act as a genetic material?
  1. It should be able to generate its replica.
  2. It should be stable chemically and structurally.
  3. It should be able to express itself in the form of Mendelian character.
  4. All of these
  1. Assertion: RNA is liable and easily degradable.

Reason: The 2'- OH group present at every nucleotide in RNA is a reactive group

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
  1. Read the given statement and select the option that correctly fill in the blanks. Pyrimidines present in DNA are (i) and (ii) while pyrimidines present in RNA are (iii) and (iv).
  1. (i)-Adenine (iii)-Guanine (iii)-Cytosine, (iv)-Thymine
  2. (i)-Cytosine (iii)Thymine (iii)-Cytosine, (iv)-Uracil
  3. (i)-Cytosine (iii)-Uracil (iii)-Adenine, (iv)-Guanine
  4. (i)-Cytosine (iii)-Uracil (iii)-Cytosine, (iv)-Thymine
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How interesingly Gene is amplified by using PCR? Explain with diagram.
→
Explain Species-Area relationships graph.
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