Biology Questions

If you were to produce a protein in bacterial cloning systems, you would not get the same post transcriptional and post translational modifications because the prokaryotic and eukaryotic systems work differently on the modifications.

Thus human recombinant protein genes are usually cloned in yeast cells. Also since they have a short generation time, they can be easily culture.

A tetrad is best described by Four chromatids. It is formed from two homologous chromosomes, each consisting of two chromatids in the first stage of meiosis called prophase1.

In flowering plants one sperm nucleus fertilizes the egg and the other sperm nucleus fuses with two other nuclei found within the ovule, thus forming triploid endosperm.

Hence, double fertilization is unique to flowering plants.

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.