Explanation:
In humans, sex is determined by the father.
The mother produces only one kind of gamete - having X-chromosome only.
The father produces two kinds of gametes - where one contains the X chromosome and another one contains the Y chromosome.
During fertilization, if the X chromosome of the father fuses with the ovum of the mother, which contains an X chromosome, it becomes a girl child.If the Y chromosome of the father fuses with the ovum containing X in the mother, it results in a boy.
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$R$ - The lower the $BOD$ of water, lower is its polluting potentials.
$I.$ DNA being a hydrophilic molecule cannot pass through cell membranes
$II.$ Agrobacteriumtumefaciens delivers a piece of $DNA$ known as $'Z-DNA'$ in the Tiplasmid which transforms normal plant cells into tumour cells to produce chemical against pathogens
$III.$ Retrovirus, adenovirus, papillomavirus are also now used as cloning vectors in animal because of their ability to transform normal cells into cancerous cell.
$IV.$ In genetic engineering, $DNA$ from different sources are cut with the same restriction enzymes so that both $DNA$ fragments have same kind of sticky ends
Choose the correct option
$R$ : The linking of antibiotic resistance gene with plasmid vector became possible by enzyme $DNA$ ligase.