<u>Answer</u>: option B they have a random gene mutation that affects their fur colour.
<u>Explanation</u> :-
- <em>Variation</em> is the phenomena which occurs in all populations.
- These variations result in slight differences in the phenotypes of individuals .
- These variations only arise due to <em>random mutations </em>that arise in the individuals’ genome and then can be inherited by their offspring.
- There is always a probability of one particular trait to make the individuals survive better in the environment as compared to other trait.
- The individuals having the trait that helps them to survive better in the environment tend to survive more and leave more progeny. This is termed as <em>survival of the fittest</em>.
- Thus, according to the question it can be inferred that the dark fur colour arose due to a <em>random mutation </em>since it is the only source of variation. Since, in the given environmental conditions the mice having the dark fur colour were less susceptible to the predators they are better fitted to survive.
- The dark brown fur coat mice, survive better, leave more progeny and hence, increase their population with time. However, the orginal source of origin of this trait was a random mutation. Had this mutation not occured, the dark coloured fur mice would not have been there.
So, a <em>random gene mutation affecting the fur colour made the dark coloured mice first appear in the population.</em>
Answer: when one is lost, one is formed
The type of inversion is Paracentric inversion.
There are two types of inversion at the chromosome level, depending on the centromere:
Paracentric inversions:
the centromere is not included in the inversion.
Pericentric inversions:
The centromere is included in the inversion which can transform a metacentric chromosome into an acrocentric chromosome.
the structure that will form during synapsis is inversion loop.
These inversions are balanced rearrangements but at the moment of meiosis they cause difficulties in pairing. There is most often formation of a pairing loop. The occurrence of recombination in the inverted segment causes the formation of abnormal gametes by duplication / impairment.
