Biology Test 17

According to Darwin's concept of natural selection, the organisms, which are provided with favourable variations, would survive because they are fittest to face their surroundings, while the organisms which are unfit for surrounding variations, are destroyed. Prevalence of pesticide resistance insects is due to the adaptability of these insects for the changes in environment (due to the use of pesticides).

The Hardy-Weinberg equilibrium is a principle stating that the genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors. When mating is random in a large population with no disruptive circumstances, the law predicts that both genotype and allele frequencies will remain constant because they are in equilibrium. This law was based on random mating but no mutation, no gene flow and no genetic drift.

Germplasm theory was proposed by Weismann (1885). According to which only germplasm goes to next generation whereas the somatoplasm dies with each generation and does not influence the germplasm.

The correct sequence of stages in the evolutions of the modern man (Homo sapiens) is Australopithecus→Homo erectus → Neanderthal man → Cro-magnon man→ Modern man.

Genetic linkage describes the way in which two genes that are located close to each other on a same chromosome are often inherited together.

When two genes are close together on the same chromosome, they do not assort independently and are said to be linked. They tend to get inherited together. They are tightly bonded to fail break.

As all the female offspring get their normal X-chromosome from the father, none of them would be colourblind. All the male offspring would be colourblind as they get their X-chromosome with the recessive allele from their mother.

The theory of genic balance given by Calvin Bridges (1926) states that instead of XY chromsomes, sex is determined by the genic balance or ratio between X-chromosomes and autosome genomes.