Biology Questions

The term 'Vector' in recombinant DNA methods, refers to a plasmid or other agent used to transfer DNA into a living cell.

The receptor molecules, which receive signals from outside the cell, passing the signal to the inside.

In order for a nerve cell, or any cell, to perceive its environment, it needs a sensory apparatus. And for an individual cell, most of that sensation is derived at the cell surface. So, it expresses on its cell surface proteins that span across the membrane.

In the outside world, these proteins can act to receive signals, catching molecules on the outside and then as the molecule passes to the inside of the cell, they can send signals like alarm signals that can tell the cell that a particular molecule is outside.

Hence, here B is the receptor cell.

Meiosis ::

Meiosis is a type of cell division that reduces the chromosome number by half in daughter cells, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them.

Why it is called as Reduction Division ::

1. As the Meiosis division process involves in reduction of chromosome number in the daughter cells to half the number in the parent cell, this process is called Reduction Division.
Meiosis creates gametes (egg and sperm cells).

2. The resulting gametes have 23 new chromosomes, one member of each of the 23 pairs, representing unique combinations of the original maternal and paternal copies.

We know that, the nucleotide in DNA is of the form deoxyribose + phosphate group + polymerase.

Hence, Deoxyribose + Phosphate Group + Thymine is the only option in that form of nucleotide in DNA.

Heritable variation is one of the four most important factors that affect whether natural selection can occur. These factors include

1) Heritable variation

2) Descent with modification

3) Struggle for survival, and necessarily if the others are satisfied

4) Survival of the fittest.

Heritable variation allows for possibly beneficial, negative, or even neutral mutations to get filtered during each generation by natural selection--weeding out negative mutations, passing on positive and neutral ones. Without heritable variation, species would quickly fall victim to parasites who take advantage of identical genetic material in a population and evolution would not occur.

Variation is the raw material of evolution.