The best and most correct answer among the choices provided by your question is the third choice or letter C.
Human activity is the primary cause of the rapid rise in loss of biodiversity.
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That should be the cell membrane. The cell membrane acts as a filter in and out.
Placenta Previa
Placenta Previa is a disorder
that arises from the implantation and development of the placenta in the lower segment
of the uterine. The cause of this disorder is unknown. The three types of placenta
previa are complete, partial and marginal previa. The most common symptom of placenta
previa is painless bleeding during the third trimester.
hot pink......................................
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.
