Random changes in allele frequency in a population are usually called genetic drift. The reason why this is the answer is because it is a very specific word which is used to describe exactly that - random changes in allele frequency.
All the other cases; answers, here aren't correct and don't apply.
Answer:
C) Through genomic imprinting, methylation regulates expression of the paternal copy of the gene in the brain.
Explanation:
The pattern of gene expression wherein either paternal or maternal gene is expressed in specific cells while the other one is prevented from expression is known as genomic imprinting.
In the given example, the maternal copy of the gene on chromosome 15 is expressed in brain cells while its paternal copy is not expressed in these cells. Hence, the pattern of expression of this gene is regulated through genome imprinting. One of the mechanism is methylation of cytidine residues of CpG islands of the DNA that are more frequently present within promoters of the genes.
When the cytidine residues of these sequences are methylated into 5-methylcytidine, the transcription factors do not bind to these promoters preventing the expression of these genes.
Hence, methylation of cytidine residue in CpG islands of the promoters of the gene present on chromosome 15 could have silenced its expression in brain cells.
Answer:
Water in the geosphere can be discharged into surface water, becoming part of the hydrosphere once again, or it could be drawn up into the roots of a plant and become part of the biosphere. Water in the biosphere can be released into the atmosphere through transpiration in plants, or respiration in animals.
The right answer is b. Tree.
Some plants (like trees) have evolved with different unusual nutritional adaptations over time. Heterotrophic plants are plants that use only or partly a source of organic carbon to grow, unlike the most common autotrophic plants, which use inorganic carbon and water to grow, often through the process of photosynthesis (photoautotrophic).
