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Direction : Study the following questions carefully and choose the right answer.
» Explain it
A
DNA Deoxyribo nucleic acid is a macromolecule having double stranded structure in which many nucleotides are present. It is mainly found in nucleus. In smaller amount it is also found in mitochondria and chloroplast. It contains the base adenine, thymine and cytosine and guanine. 

Hence, option A is correct.
 
» Explain it
E
Mutation is a sudden and permanent change in the gene mostly due to environmental (external) reasons such as ultraviolet radiation from the sun. It is heritable from one generation to another. A gene mutation is a permanent alteration in the DNA sequence that makes up a gene.

Hence, option E is correct.
 
» Explain it
B
In human male sex chromosome is XY where as in female sex chromosome is XX. When a male gamete (sperm) carrying X chromosome fertilize an ova, the zygote develop into female where as sperm carrying Y chromosome fertilizes an egg to develop zygote into male. Female chromosome is X in both the cases.

Hence, option B is correct.
 
4
This genetic disorder occurs due to an additional chromosome added to 21st autosomal chromosome and result into mental retardness, eyes protruded an irregular physical structure. Which of the following is this?
» Explain it
C
In human, each cell contains 46 chromosomes. Any addition or deletion in the number of sex chromosome or autosome causes genetic disorder. Down’s syndrome is one of them. When an extra chromosome is added to autosomal chromosome this leads to Down’s syndrome. The person is mentally retarded, eyes protruded an irregular physical structure.

Hence, option C is correct.
 
5
Which of the following is not an algae?
» Explain it
E
Algae belong to cryptogames (plant without seed). It has chlorophyll. Common examples of algae are- Porphyra , Ulva, Surgassum, Anabina, Fucus, Belonia etc.Ferns are not algae.

Hence, option E is correct.