Answer:
The correct answer is option d.
Explanation:
Based on the given question, the genotype of the male parent is aa, the genotype of the female parent is Aa, and the genotype of the offspring is AAa, showing trisomy characteristics. In the given case, the existence of two A chromosomes shows that the chromosomes non-disjunction at the time of gametogenesis have taken place in the female as she is the only one possessing A allele. Hence, it can be concluded that the disjunction is maternal in characteristic.
The duplication of chromosomes takes place at the time of the S-phase of meiosis. Thus, after going through S-phase, the karyotype of the cell will be AAaa (maternal gametogenesis), this set of the chromosome is termed as homologous pair, and the pair of AA or aa is termed as sister chromatids.
The meiotic disjunction takes place in two phases. First, in meiosis I disjunction, in this separation of homologous chromosomes takes place, that is, the maternal cell AAaa get differentiated into aa and AA daughter cells. Secondly, in meiosis II disjunction, the separation of sister chromatids takes place into two independent chromosomes, that is, the formation of two cells each comprising chromosome A from the AA cell and the formation of two cells each with chromosome a from the aa cell.
Thus, the phenomenon of non-disjunction would have taken place at the time of meiosis II in the case of a female gamete to exhibit two A chromosomes. Hence, the correct answer is option d.
The answer is A:<span> Metamorphic rocks</span><span> may display two different grain sizes.</span> :)
Answer:
Answered below.
Explanation:
The fossil records are beneficial in giving us. wide range of knowledge about fossils but sometimes these records are flawed, in that they are incomplete or misleading.
Many of the fossil records available are incomplete because some animals tend to decay within a short period of time due to their soft tissue. Also some are destroyed due to the movement of tectonic plates over time.
Another flaw scientists encounter is that there are no fossils which illustrate or represent the orderly transition from one organism to another. Fossils generally do not support the Darwinian theory of evolution as no evidence is found of ordered, sequential transition from simple to complex life forms as postulated.
These flaws are significant because they influence our knowledge and understanding of life forms and evolution.
Answer:
Schwann cells or neurilemma cells are the cells which form the myelin sheath around neuronal axons in the peripheral nervous system (PNS) only.
Neurilemma is the collective term used for cytoplasm and nuclei present around the myelin sheath which helps in the regeneration process of nerves.
A Schwann cell surrounds the axon, invaginate it and the plasmalemma of the Schwann cells joins and from a double membrane structure called mesaxon. This mesaxon starts wrapping the axon in spiral fashion and cytoplasm start condensing into the compact myelin sheath.
In the process of the nitrogen cycle. <span>
The nitrogen cycle is a biogeochemical succession process of nitrogen that involves: fixation, ammonification, nitrification, and denitrification. Like any other biogeochemical cycles. This process undergoes and affects the biological, geometrical and chemical aspects in the ecosystem and the abiotic and biotic community. Hence, the nitrogen cycle leads the abiotic component –nitrogen- to contribute to the biotic community, decomposition and primal production. Further, it becomes an essential part of the environment because some life components are contains it, similarly, amino acids, nucleic acids in RNA and DNA. </span><span> </span>
