Answer:
Directional Selection
Explanation:
The type of natural selection that favors one of the extreme phenotypes over the intermediate and another extreme phenotype is called directional selection. Here, the extreme phenotype exhibits better survival and reproductive fitness over the other phenotypic ranges.
In the given example, the frequency of the heat-tolerant allele in microbes is shown to increase under the conditions of higher temperatures of the water of the springs in which they live.
When the temperature of spring water is increased, the frequency of the heat-tolerant allele is reduced and is increased again upon an increase in water temperature.
Since the natural selection favors the extreme phenotype (microbes with heat tolerance) when the spring water exhibits higher temperatures, it is directional selection.
Answer:
The correct answer will be option-B.
Explanation:
Meiosis is a type of cell division which proceeds in two stages: meiosis I and meiosis II and result in the formation of four daughter cells.
The meiosis I is known as the reductional division as two daughter cells are formed with reduced ploidy level that is haploid cells from diploid cells. The cells formed contains chromosomes with two chromatids as the DNA amount gets doubled after the DNA synthesis.
Thus, Option-B is the correct answer.
Answer:
(D) 64
Explanation:
We have given number of chromosome pair that is haploid number = 6
We have to calculate the number of possible gamete in absence of recombination
The number of garnets is given by 
where n is haploid number
In question we have given haploid number, that is n=6
So the number of gametes without recombination 
So option (d) is the correct answer
Answer: Colon cancer
Explanation:
All cancers, but especially colon and rectal cancers, commonly referred to as colorectal cancer (CRC), have hereditary factors that potentially increase one’s risk.
Genetic testing is determine if there is an increased risk of colon cancer. Apolipoprotein E (apoE) plays a major role in the metabolism of bile acids, cholesterol and triglycerides, and has recently been proposed as being involved in the carcinogenic process. Given the potential role of bile acids in colorectal cancer etiology, it is reasonable that colorectal cancer risk might be modified by apoE genotype. The absence of an e3 apoE allele significantly increased the risk of colon cancer especially for individuals above 50years.
