Download App

Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance4 Marks
Question
Explain with diagram - Hershey and Chase experiment.###On the basis of experimental proof explain the diagram that DNA is genetic material.###How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
✓

Answer

→ The unequivocal proof that DNA is the genetic material came from the experiments of Alfred Hershey and Martha Chase (1952). They worked with viruses that infect bacteria called bacteriophages.
→ The bacteriophage attaches to the bacteria and its genetic material then enters the bacterial cell.
→ The bacterial cell treats the viral genetic material as if it was its own and subsequently manufactures more virus particles.
→ Hershey and Chase worked to discover whether it was protein or DNA from the viruses that entered the bacteria.
→ They grew some viruses on a medium that contained radioactive phosphorus and some others on medium that contained radioactive sulfur.
→ Viruses grown in the presence of radioactive phosphorus contained radioactive DNA but not radioactive protein because DNA contains phosphorus but protein does not.
→ Similarly, viruses grown on radioactive sulfur contained radioactive protein but not radioactive DNA because DNA does not contain sulfur.
→ Radioactive phages were allowed to attach to E.coli bacteria.
→ Then, as the infection proceeded, the viral coats were removed from the bacteria by agitating them in a blender.
→ The virus particles were separated from the bacteria by spinning them in a centrifuge.
→ Bacteria which was infected with viruses that had radioactive DNA were radioactive, indicating that DNA was the material that passed from the virus to the bacteria.
→ Bacteria that were infected with viruses that had radioactive proteins were not radioactive.
→ This indicates that proteins did not enter the bacteria from the viruses.
→ DNA is therefore the genetic material that is passed from virus to bacteria.
Image

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Case study (4 Marks)" from Molecular Basis of Inheritance→Molecular Basis of Inheritance — all question types→BIOLOGY STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

​​​​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.
→
Explain exponential growth equation with well labeled diagram.###Explain exponential growth.
→
Read the following and answer any four questions from (i) to (v) given below:
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
  1. The given diagram shows microsporangium of a mature anther. Identify A, B and C.
(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.
→
Assuming that within a population of beetles where Hardy Weinberg conditions are met, the colour black $(B)$ is dominant over the colour red $(b). 40\%$ of all beetles are red $(bb).$
Given this information, answer the questions below:
$A.$ What is the frequency of red beetles?
$B.$ Calculate is the percentage of beetles in the population that are heterozygous.
$C.$ What is the frequency of homozygous dominant individuals?
$OR$
$D.$ Assuming that Hardy Wienberg conditions are met in the beetle population consisting of $1500$ beetles. How many beetles would you expect to be black and red in colour respectively?
→
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.
→
Explain loss of biodiversity.
→
Read the following and answer any four questions from (i) to (v) given below:
The pollen grains or microspores are the male reproductive bodies of a flower and are contained in the pollen sac or microsporangia. Each pollen grain consists of a single microscopic cell, possessing two coats: the exine and the in tine. The exine of a pollen grain is made of chemically stable material. Because of this, pollen grains are often very well preserved for thousands of years in soil and sediments.
  1. One of the most resistant biological material present in the exine of pollen grain is:
  1. Pectocellulose.
  2. Sporopollenin.
  3. Suberin.
  4. Cellulose.
  1. The exine possesses one or more thin places known as:
  1. Raphe.
  2. Germ pores.
  3. Hilum.
  4. Endothecium.
  1. What is the function of germ pore?
  1. Emergence of radicle.
  2. Absorption of water for seed germination.
  3. Initiation of pollen tube.
  4. All of these.
  1. What is the key advantage to the plant for having such strong pollen grain walls?
  1. It protects the vital genetic material in the pollen grain.
  2. It allows pollen to serve as a valuable fossil record for the study of ancient plants.
  3. It prevents the pollen tube from growing out before the pollen grain reaches the stigma of a compatible species.
  4. It gives weight to the pollen grain, allowing it to cling better to the body surfaces of insect pollinators.
  1. The number of germ pores in dicots and monocots respectively are:
  1. One and three.
  2. Three and two.
  3. Two and three.
  4. Three and one.
→
Read the following and answer any four questions from (i) to (v) given below:
The given graphs show fluctuations in blood sugar of person X and Y during a 24 hour time period.

Based on the above information, answer the following questions.
  1. Which of the following holds true for person X?
  1. Person X is suffering from type I diabetes.
  2. Person X shows severe insulin deficiency and beta cell depletion.
  3. Person X is normal and shows good control of blood sugar level.
  4. Person X is subjected to excessive urination and abnormal thrust.
  1. The given graph indicates that person Y is suffering from.
  1. Diabetes
  2. Hypertension
  3. Atherosclerosis
  4. Rheumatic heart disease.
  1. Which of the following conditions are common in person Y?
  1. Excretion of glucose in urine and excessive urination.
  2. Polydipsia and mild beta cell depletion.
  3. Progressive erosion of articular cartilage at synovial joint.
  4. Both (a) and (b).
  1. A person suffering from diabetes mellitus becomes weak because.
  1. The cells are unable to utilise glucose and other carbohydrates for energy production.
  2. Degradation of fat increases production of toxic ketone bodies.
  3. Cells utilise proteins for obtaining energy
  4. All of these.
  1. Assertion: Type I diabetes involves failure of insulin to facilitate the movement of glucose into cells.
Reason: Type II diabetes is caused by failure of beta cells to produce adequate amount of insulin due to beta cell depletion.
  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.
→
Give a detailed description of human male reproductive system. (Diagram required)
→
Explain bioreactor with diagram.
→