Question of Exercise-5

Chromosomal Basis of Inheritance of Class 12

Question
The parallelism between factors and chromosome led to

Answer

Option 1 Cell theory

Option 2 Chromosome theory of heredity

Option 3 Pangenesis

Option 4 Mapping of genes

Frequently Asked Questions

Natural reservoir of phosphorus is

A: Animal bones

B: Rock

C: Fossils

D: Sea water

Solution:

Explanation:

Phosphorus is very important for the growth of plants and animals.

The chief reservoir of phosphorus is rock. 

It is obtained by the weathering of the rocks. 

The phosphorus enters into the biosphere, lithosphere and hydrosphere by phosphorus cycle.

Calcium along with phosphorus helps in formation of bone cells.

Fossils and seawater are the reservoir of carbon.

Final answer:

The correct answer is rock, i.e option (B).

Ubisch bodies are present in

A: Pollen tube

B: Pollen gain

C: Microspore

D: Tapetum

Solution:

Explanation:

Ubisch bodies are small, acellular bodies present in tapetum.

They help in the formation of the exine layer of pollen grains. 

During spore wall formation, ubisch bodies are found in the cytoplasm of the tapetum.

They are not found in the cytoplasm of pollen tube, pollen grain and microspore.

Final answer:

The correct answer is tapetum, i.e option (D).

Propagation of ginger is generally done using

A: Seed

B: Stem (rhizome)

C: Root

D: Leaf

Solution:

Explanation :- 

Vegetative propagation is a method of asexual mode of reproduction in which new plants are grown from the vegetative parts like roots, stems, leaf etc. 

Propagation of ginger is not performed by seed, root and Leaf. 

It is propagated through underground horizontal stems, i.e rhizomes.

Rhizomes have the ability to develop the root and shoot system of the new plant.

They also act as storage organs in plants.

Final answer :-

The correct answer is stem (rhizome), i.e option (B).

The phenotypic ratio in dihybrid cross is

A: 9 : 3 : 3 : 1

B: 9 : 2 : 2 : 1

C: 7 : 2 : 2 : 3

D: 5 : 3 : 3 : 2

Solution:

Explanation:

  • Dihybrid is a cross between two individuals differing in two traits/characters.
  • In Mendel's dihybrid cross, the parents are - plants with round yellow colored seeds (RRYY) and plants with green colored wrinkled seeds (rryy). 
  • The F1 progeny are round and yellow seeds (RrYy).
  • The F1 progeny is allowed to self-fertilize to produce F2 generation exhibiting 4 different phenotypes-Yellow round (9), yellow wrinkled (3), green round (3), and green wrinkled seed plants (1). 
  • The phenotypic ratio of the dihybrid cross is ratio 9:3:3:1( round yellow seeds: wrinkled yellow seeds: round green seeds: wrinkled green seeds).
  • The dihybrid cross is shown in the figure.

phenotypic ratio in dihybrid cross

Final Answer: Hence, the correct answer is (A)  9 : 3 : 3 : 1.

Define apomixis

Solution:

Explanation-

  1. Apo-means without and mixis means mixing- is a mode of reproduction in which no zygote formation takes place through gametic fusion. 
  2. Apomixis is a kind of asexual reproduction that mimics sexual reproduction.
  3. Some species of Asteraceae and grasses evolved a special mechanism of producing seeds without fertilization, called apomixis. 
  4. It is characterized by quick multiplication and producing genetically similar plants from a single parent. 
  5. Offspring produced by the asexual reproduction are genetically identical and are related to clones and each member is known as a ramet.
  6. Types of apomixis include- Diplospory, Adventive embryony, apospory. 

Final Answer-

Apomixis is a kind of asexual reproduction that mimics sexual reproduction. It is characterized by quick multiplication and producing genetically similar plants from a single parent. 

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