Answer:
Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation.
Explanation:
Homeostasis refer to the metabolic balance being maintained by several processes. It may include having a stable internal physiologic condition such as the blood ph or body temperature. Among the options, the best answer would be c. the villi of the small intestine would increase the absorption of nutrients from small intestine to the blood.
Answer:
spinal cord
Explanation:
Reflex actions are the involuntary action of the body in response to a signal or stimulus. The reflex action of body is controlled by spinal cord.
Reflex arc acts as a neural pathways that transmit impulse to the brain via spinal cord. Sensory neurons pass through synapse in the spinal cord which activate spinal motor neuron to act immediately without any delay.
Immediate taking off hand from hot oven is an example of reflex action, which is regulated by spinal cord.
Hence, the correct option is spinal cord.
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.
