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 6(i) to 6(v) given below:
Rama lives in a society where a robbery occurred last night. Robbers came into the flat and murdered the old lady residing there. Police came and restricted the entry into the flat. They took samples from the room, where the dead body was found. While examining, they found that there is some blood and tissue in the nails of old lady. According to their observation, police filtered out their inspection to three suspects viz. servant, cook and milkman. Finally after two days of robbery, police caught the criminal. It was the old lady's cook. Rama was amazed to see that how quickly police completed and shut the case. She asked the inspector that how they did it? The police man told her that it become possible due to the sample collected from the victim, that lead them to the criminal. TI1e sample taken from nail scraping was amplified using PCR and then tested.
  1. What technique was used by the police to identify the criminal?
  1. DNA fingerprinting.
  2. Gel electrophoresis.
  3. Molecular diagnosis.
  4. Clonning.
  1. In PCR, the temperature used to denature the DNA is about:
  1. 76º
  2. 25º
  3. 95º
  4. 40º
  1. Which of the following statements regarding PCR is correct?
  1. Taq polymerase, which is isolated from bacterium Thermus aquaticus is stable at low temperature only.
  2. With the help of DNA ligase, the complementary sticky ends of the DNA are joined to produce a rDNA.
  3. Since the sequence of primers are complementary to 5' end of the template DNA, they anneal to it.
  4. DNA purified from the cell is precipitated by adding hot ethanol.
  1. Taq polymerase synthesises DNA region between the primers using:
  1. $Mg^{2+}$
  2. dNTPs
  3. DNA ligase
  4. Both (a) and (b).
  1. Given below are steps of polymerase chain reaction.


Select the option that correctly mention the sequence in which they occur.
  1. (ii) → (iii) → (i)
  2. (i) → (ii) → (iii)
  3. (iii) → (i) → (ii)
  4. (ii) → (i) → (iii)
→
Read the following and answer any four questions from (i) to (v) given below:
The process of translation requires transfer of genetic information from a polymer of nucleotides to synthesise a polymer of amino acids. The relationship between the sequence of amino acids in a polypeptide and nucleotide sequence of DNA or mRNA is called genetic code. George Gamow suggested that in order to code for all the 20 amino acids, code should be made up of three nucleotides.
  1. What is a codon?
  1. A length of DNA which codes for a particular protein.
  2. A part of the tRNA molecule to which a specific amino acid is attached.
  3. A part of the tRNA molecule which recognises the triplet code on the messenger RNA.
  4. A part of the messenger RNA molecule that has a sequence of bases coding for an amino acid.
  1. Three consecutive bases in the DNA molecule provide the code for each amino acid in a protein molecule. What is the maximum number of different triplets that could occurs?
  1. 16
  2. 20
  3. 24
  4. 64
  1. Listed below are some amino acids and their corresponding mRNA triplets.
Amino acid
mRNA triplet
Phenylalanine
UUU
Lysine
AAG
Arginine
CGA
Alanine
GCA
Which DNA sequence would be needed to produce the following polypeptide sequence? Alanine-Arginine-Lysine-Phenylalanine
  1. $\text{CGT}\ \ \ \text{GCT}\ \ \ \text{TTC}\ \ \ \text{AAA}$
  2. $\text{CGT}\ \ \ \text{GCT}\ \ \ \text{TTC}\ \ \ \text{TTT}$
  3. $\text{CGU}\ \ \ \text{GCU}\ \ \ \text{UUC}\ \ \ \text{AAA}$
  4. $\text{CGU}\ \ \ \text{GCU}\ \ \ \text{UUC}\ \ \ \text{TTT}$
  1. Identify the non-sense codons among the following.
  1. AUG
  2. GUG
  3. UAA
  4. UGG
  1. A polypeptide is made using synthetic mRNA molecules as shown.
Synthetic mRNA used
Polypeptide produced
UUUAAAUUUAAA
Phenylalanine-Iysine-phenylalanine-Iysine
What are the DNA codes for the amino acids phenylalanine and lysine?
S.no
Phenylalanine
Lysine
(a)
AAA
TTT
(b)
AAA
UUU
(c)
GGG
CCC
(d)
TTT
GGG
→
Describe pregnancy and embryonic development.
→
Read the following and answer any four questions from (i) to (v) given below:
Organism P has thick lips and tongue so that it can easily feed on the commonly available spiny plants. Organism Q has thick layer of insulating fat under the skin. It was strong hooves to walk steadily on steep surfaces and lives in burrows during winters. Organism R has bright colours and sticky pads on its fingers and toes. It lives on trees.
  1. Which of the following is correct habitat for organisms P regarding its adaptation?
  1. Grassland biome.
  2. Desert biome.
  3. Tropical rainforest.
  4. Tropical deciduous forest.
  1. Which of the following is correct match regarding organism Q and its habitat?
  1. Tundra - Polar bear.
  2. Tropical rain forest - Deer.
  3. Grassland - Bighorn sheep.
  4. Desert - Camel.
  1. Which of the following is incorrect regarding organisms R's habitat?
  1. The vegetation shows stratification.
  2. Epiphytic growth is rich.
  3. Standing crop is highest.
  4. Deep rooted shrubs are common due to abundant sunlight.
  1. The dominant plants in habitat where P lives could be:
  1. Opuntia
  2. Nymphaea
  3. Deodar
  4. both (a) and (c).
  1. Organisms P, Q and R respectively most likely occur in:
  1. F, B and A.
  2. C, A, E.
  3. A, F and C.
  4. B, D and A.
→
Write a short note on transcription unit.### Explain : Transcription unit
→
Read the following and answer any four questions from (i) to (v) given below:
Wetlands are called Ramsar sites because the first international convention on their conservation was held in Ramsar in Iran in 1971. Wetlands or Ramsar sites are low lying marshy areas which get filled up during rains due to runoff and overflow from other water bodies. They are often considered to be waste lands which are used as dumping areas and filled up to recover land for various constructions activities. As a result, a large number of wetlands have disappeared.
  1. Select the incorrect match of wetland and its location.
 
Wetland
Location
(a)
Harike
Punjab
(b)
Chandra Tai
H.P.
(c)
Bhoj
M.P.
(d)
Ashtamudi
Odisha
  1. Migratory bird flamingo breeds in which of the following wetlands?
  1. Bhitarkanika Mangroves.
  2. Rann of Kutch.
  3. Harike.
  4. Chandra Tal.
  1. Which of the following is not an importance of wetlands?
  1. They are an important source of recharging groundwater.
  2. They provide protection from floods.
  3. They are good source of siltation and purification of water.
  4. None of these.
  1. Which of the following wetland ecosystem is highly acidic and has a accumulation of decomposed plants known as peat?
  1. Bog
  2. Mangrove
  3. Estuary
  4. Watershed
  1. The mangroves of Bhitarkanika are famous for:
  1. Rare migratory waterbirds.
  2. Nesting sites for endangered olive ridley turtles.
  3. Prawn cultivation.
  4. All of these.
→
Read the following text carefully and answer the questions that follow:
A healthy immune system defends the body against disease and infection. But if the immune system malfunctions, it mistakenly attacks healthy cells, tissues, and organs. Called autoimmune disease, these attacks can affect any part of the body, weakening bodily function and even turning life-threatening.
Image
i. Why are autoimmune diseases called degenerative diseases? (1)
ii. Name the autoimmune disease of body muscles. (1)
iii. Which types of immunity is provided by T-lymphocytes? (2)
OR
Which immune cells form humoral immune system? (2)
→
Read the following and answer any four questions from (i) to (v) given below:
The DNA, which is transferred from one organism into another by joining it with the vehicle DNA is called passenger or foreign DNA. Generally three types of passenger DNAs are used. These are complementary DNA (cDNA), synthetic DNA (sDNA) and random DNA. Complementary DNA (cDNA) is synthesized on RNA template (usually mRNA) with the help of reverse transcriptase. Synthetic DNA (sDNA) is synthesized on DNA template or without a template. Random DNA are small fragments fanned by breaking a chromosome of an organism in the presence of restriction endonucleases.
  1. Reverse transcriptase enzyme was discovered by:
  1. Temin and Baltimore.
  2. Cohen and Boyer.
  3. Arber and Nathan.
  4. Paul Berg.
  1. During cDNA formation, what would happen if DNA formed by reverse transcriptase is not treated with the alkali?
  1. cDNA will not be digested.
  2. mRNA will not be digested.
  3. Hydrogen bonds will not form between base pairs.
  4. rnRNA will not be formed.
  1. Enzyme that helps in the formation of double stranded cDNA is:
  1. DNA synthetase
  2. Ligase
  3. DNA polymerase
  4. Helicase.
  1. DNA polymerase can be obtained form:
  1. Retrovirus.
  2. Agrobacteriurn.
  3. Tobacco mosaic virus.
  4. Thermus aquaticus.
  1. DNA synthesised without a template is referred to as:
  1. Complementary DNA.
  2. Random DNA.
  3. Synthetic DNA.
  4. Z-DNA..
→
Read the following and answer any four questions from (i) to (v) given below:
Human male reproductive system comprises of a pair of testes, primary sex organs associated with formation of gametes and production of sex hormone. Study the given figure of human male reproductive system and answer the following questions.
  1. Which of the following is correct for labelled part P?
  1. P is rete testis which transports sperms to outside.
  2. P is epididymis which secretes fluid that nourish the sperms.
  3. P is epididymis that carry sperms and secretion of seminal vesicles.
  4. P is rete testis, which lies along inner side of each testis and stores the sperms.
  1. Identify the correctly matched pair.
  1. Q - Vasa efferentia.
  2. R - Ejaculatory duct.
  3. S - Seminal vesicle.
  4. T - Cowper's gland.
  1. Which statement is incorrect for Q?
  1. It carries spermatozoa from epididymis to ejaculatory duct.
  2. Q are only 2 in number.
  3. It arises from rete testis.
  4. It constitutes male sex accessory duct.
  1. Which structure passes through the prostate gland and carries sperms and secretion of seminal vesicle?
  1. P.
  2. T.
  3. S.
  4. R.
  1. Assertion: Mucus present in secretion of bulbourethral gland decreases the number of sperms damaged during ejaculation.
Reason: Mucus lubricates the end of penis and lining of the urethra.
  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.
→
Read the following and answer any four questions from (i) to (v) given below:
DNA fingerprinting is a technique of determining nucleotide sequences of certain areas of DNA which are unique to each individual. Each person has a unique DNA fingerprint. Each fingerprint is the same for every cell, tissue and organ of a person. DNA fingerprinting is the basis of paternity testing in case of disputes.
  1. The technique developed to identify a person with the help of DNA restriction analysis is known as.
  1. DNA profiting
  2. DNA fingerprinting
  3. RFLP
  4. Both (a) and (b).
  1. For DNA fingerprinting, DNA is obtained from.
  1. Blood
  2. Hair root cells
  3. Semen
  4. All of these
  1. During DNA fingerprinting, the radioactive probes.
  1. Hybridise with DNA sample to form double stranded structure
  2. Egrade the DNA
  3. Create positive charge on DNA
  4. Cut the DNA sample at various sites.
  1. In India, DNA fingerprinting technique was developed by?
  1. Dr. Lalji Singh
  2. Alec Jeffreys
  3. Dr. Khorana
  4. None of these.
  1. Which of the following is true about DNA fingerprinting?
  1. VNTR is used as probe.
  2. DNA samples are loaded on agarose gel electrophoresis.
  3. It is based on identification of nucleotide sequence present on the DNA molecule.
  4. All of these
→