CBSE(NCERT) GRADE 12 BIOLOGY 2024 SET3

Study the pedigree chart of a family showing the inheritance pattern of a certain disorder. Select the option that correctly identifies the nature of the trait depicted in the pedigree chart.

Which one of the following statements is correct in the context of observing DNA separation by agarose gel electrophoresis ?

A phenomenon where a male insect mistakenly identified the patterns of a orchid flower as the female insect partner, and tries to copulate and thereby pollinates the flower is said to be :

Observe the schematic representation of assisted reproductive technology given below : Identify the most appropriate technique depicted in the above diagram.

The source of ‘Smack’ is :

The first antibiotic was discovered accidentally by A while working on B. ‘A’ and ‘B’ are

If the sequence of nitrogen bases of the coding strand in a transcription unit is 5' – ATGAATG – 3', the sequence of bases in its RNA transcript would be

Match the following genes of the lac operon listed in column ‘A’ with their respective products listed in column ‘B’ : A Gene B Products a. ‘i’ gene (i) β-galactosidase b. ‘z’ gene (ii) lac permease c. ‘a’ gene (iii) repressor d. ‘y’ gene (iv) transacetylase Select the correct option : Options : a b c d

The human chromosome with the highest and least number of genes in them are respectively :

Assertion (A) : In birds the sex of the offspring is determined by males. Reason (R) : Males are homogametic while females are heterogametic.

Assertion (A) : X is a syndrome, which is caused by HIV. Reason (R) : HIV is a virus whose genetic material is DNA that ...

If the base adenine constitutes 31% of an isolated DNA fragment, then write what will be the expected percentage of the base cytosine in it. Explain how did you arrive at the answer given.

Observe the population growth curve and answer the questions given below: (a) State the conditions under which growth curve ‘A’ and growth curve ‘B’ plotted in the graph are possible. (b) Mention what does ‘K’ in the graph represent.

5' – G A A T T C – 3' 3' – C T T A A G – 5' (a) Name the restriction enzyme that recognises the given specific sequence of bases. What are such sequence of bases referred to as? (b) What are the arrows in the given figure indicating? Write the result obtained thereafter.

List the events that reduce the Biochemical Oxygen Demand (BOD) of a primary effluent during sewage treatment.

(a) “Farmers prefer apomictic seeds to hybrid seeds.” Justify giving two reasons. OR (b) Mention one advantage and one disadvantage of amniocentesis.

Explain the processing of heterogeneous nuclear RNA (hnRNA) into a fully functional mRNA in eukaryotes. Where does this processing occur in the cell?

(a) “Mother’s milk is considered very essential for the new born infant.” Justify. (b) What is a ‘vaccine’? Explain the principle on which it works.

(a) Tropical regions harbour more species than the temperate regions. How have biologists tried to explain this in their own ways? Explain. OR (b) (i) What does an ecological pyramid represent? (ii) The Ecological pyramids may have an ‘upright’ or an ‘inverted’ shape. Justify with the help of suitable examples.

State why plant breeders are interested in artificial hybridisation programme. How do they carry out this process?

Name the hormones and their source organ, which are responsible for menstrual cycle at puberty.

(a) What are transgenic animals? (b) Name the transgenic animal having the largest number amongst all the existing transgenic animals. (c) State any 3 reasons for which these types of animals are being produced.

For successful pregnancy, at what phase of the menstrual cycle an early embryo (upto 3 blastomeres) should be implanted in the uterus (IUT) of a human female who has opted for Assisted Reproductive Technology (ART)? Support your answer with a reason.

(a) Construct a pyramid of biomass in sea with phytoplankton and fishes. Explain giving reasons about the characteristic of the constructed pyramid. (b) In which condition will the pyramid remain always upright?

Name the hormone and its source organ responsible for the events occurring during proliferative phase of menstrual cycle. Explain the event.

(a) Why does DNA replication occur within a replication fork and not in its entire length simultaneously? (b) “DNA replication is continuous and discontinuous on the two strands within the replication fork.” Explain with the help of a schematic representation.

In a normal human female, why does menstruation only occur if the released ovum is not fertilised? Explain.

In a human female, the reproductive phase starts on the onset of puberty and ceases around middle age of the female. Study the graph given below regarding menstrual cycle and answer the questions that follow: (a) Name the hormones and their source organ, which are responsible for menstrual cycle at puberty. (b) For successful pregnancy, at what phase of the menstrual cycle an early embryo (upto 3 blastomeres) should be implanted in the Uterus (IUT) of a

Explain the events which occur within a female Anopheles mosquito after it has sucked blood from a malaria patient.

Draw a diagram of a human sperm. Label any four parts and write their functions.

In a human female, probability of an ovum to get fertilized by more than one sperm is impossible. Give reason.

(c) Name a species of mosquito other than female Anopheles and the disease, for which it carries the pathogen.

With the help of labelled diagram only, show the different stages of embryo development in a dicot plant.

(a) (i) Draw a schematic diagram of the cloning vector pBR 322 and label (1) Bam HI site (2) gene for ampicillin resistance (3) ‘ori’ (4) ‘rop’ gene. (ii) State the role of ‘rop’ gene. (iii) A cloning vector does not have a selectable marker. How will it affect the process of cloning ? (iv) Why is insertional inactivation preferred over the use of selectable markers in cloning vectors ? 5 OR (b) (i) Name the nematode (scientific name) that infects the roots of tobacco plant and reduces its yield. (ii) Name the vector that is used to introduce nematode-specific genes into the host plant (tobacco). (iii) How do sense and anti-sense RNAs function ? (iv) Why could parasite not survive in a transgenic tobacco plant ? 5

Endosperm development precedes embryo development. Justify.

(a) Work out a dihybrid cross upto $F_2$ generation between pea plants bearing violet coloured axial flowers and white coloured terminal flowers using Punnet’s square. Give their $F_2$ phenotypic ratio. State the Mendel’s law of inheritance that was derived from such a cross. 5 OR (b) Explain the process of transcription in prokaryotes. How is it different from transcription in eukaryotes ? 5