Variation and its type - class-X

Mutations, recombinations and deletions all are the sources of genetic variation. A Mutation occurs when a DNA gene is damaged or changed in such a way as to alter the genetic message carried by that gene. Recombination involves the exchange of genetic material either between multiple chromosomes or between different regions of the same chromosome. Deletion is a mutation in which a part of a chromosome or a DNA sequence is missing. 

Variations can be defined as the difference in characters among the individuals of same species, it gets affected by internal changes, environmental changes, hybridization etc.

The genetic material in prokaryotes is not confined into a nucleus and they do not have a nuclear membrane and the genetic material is present in the form of chromatin and cytoplasm and there is no chance of crossing over during meiosis and no fertilization but random mutations do arise in them and it results change in the genetic material.

A.Somatogenic variation – These are acquired variations and non inheritable in nature. Eg:phenotypic plasticiy.

B.Discontinuous variations – These are responsible for the formation of a new species and the organism, thus, formed is called mutant. Eg:Mutations.

C.Continuous variations – These are fluctuating variations and cannot give rise to new species. Eg:Human height.

So,
the correct option is ‘Continuous variations’.

Primary source of allelic variation is recombination. Recombination is the natural process of breaking and rejoining DNA strands to produce new combinations of genes and, thus, generate genetic variation. This is the phenomenon that occurs during meiosis I.

The process of forming new allelic combination in offspring by exchanges between genetic materials of parents is called Recombination.

Variation is a change or slight difference in condition, amount, or level, typically within certain limits appear in the progeny compared with parents.

Recombination and variations appear in sexually reproducing organisms during meiosis and fertilization.

So,
the correct option is ‘Meiosis and fertilization’.

• Physiological variation is related to the differences in the ways individuals of the same species react to conditions in their environment because of difference in their functioning of the body. Production of insulin is an example of physiological variation.
• So, the correct option is 'Physiological variation'

Evolution is dependent on the natural selection , genetic drift , gene flow , mutation are the main factors responsible for evolution .

Scarred eyebrow is an acquired trait which is never passed on to the offspring because scarring does not change the genes of the reproductive cells of the parent.

Genetic variability is the change in the sequence of the gens due to mutations. These mutations has led to new species generation. The so evolved species are selected in the environment based on natural selection

For a genotype AaBbCc, the number of different gametes produced is 2^n, where n is the number of heterozygous gene pairs. Here, n=3, so 2^3 = 8.

Variation is a change or slight difference in condition, amount, or level, typically within certain limits appear in the progeny compared with parents. Variations appear in sexually reproducing organisms during meiosis and fertilization and also by mutations. So, the correct option is ‘Mutation’.

Sexual reproduction involves gamete formation and fertilisation. During fertilisation, 1 gamete from each parent combines to form a zygote. Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote and ultimately within the organism.

In the living organisms, variation due to environment, not transmitted from generation to generation. so these are temporary, where as variations due to mutations are transmitted from generation to generation, so they are permanent. 

So, the correct option is 'Environmental variations'.

• Point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a sequence of DNA or RNA. Each triplet codon corresponds to an amino acid when translated to protein. When one of these codons is changed by a point mutation, the corresponding amino acid of the protein is changed.
  
• Chromosomal mutation is presence or absence of one or more set of chromosomes in a cell or a structural abnormality in the normal set of chromosomes.
  
• Somatic mutation is the occurrence of a mutation in the somatic cells (cells other than sperm and egg) of the organism. These are frequently caused by environmental factors like exposure to UV rays or to certain chemicals. 
  
• Gene mutation is a permanent alteration in the DNA sequence that makes up a gene. They are of two types: Hereditary mutations (inherited from parents) and Acquired mutation (occur at some time during a person's life).
  

Sexual reproduction results in more variation than the asexual reproduction. During sexual reproduction, there are chances of errors occurring during DNA copying. Crossing over also takes place during sexual reproduction. All these ultimately result in the variation. This variation helps survival in species and also supports diversity in the course of evolution.

Total of specialized protoplasm other than germplasm in individual body or protoplasm of somatic cells is termed as somatoplasm. Germplasm is protoplasm of germ cells (egg and sperm cells) or any living tissues with the capability of generating new organisms. The germplasm is inherited from parents to offspring along with gametes; thus any mutation in germplasm is passed to progeny which is a requisite for successful mutation; option B is correct. Since somatoplasm is not passed to offspring, any mutation in it affects that individual only and is not passed to offspring which makes option A incorrect. The liquid phase of cell nucleus which harbours the nucleolus and chromatin and other structures is called as karyolymph. Similarly, the mutation in zygote affects single individual that develops from that zygote. Option C is incorrect. The granular endoplasmic reticulum that has studded ribosomes on its surface is called as ergastoplasm which is not inherited to offspring and thus is not suitable for successful mutation; option D is incorrect. Correct option B is correct. 

A sudden, inheritable, discontinuous variation due to change in chromosomes and genes is called Mutation. It is hereditary. Mutations in somatic cells are not hereditary.

So,
the correct option is ‘somatic’.

Somaclonal variations are genetic variations observed in plants regenerated from tissue culture.