Answer:
The two strands of the parent DNA are separated, and two daughter DNA strands are formed.
Explanation:
DNA replication is a complex process which replicates or produces new DNA molecule from the parent DNA molecule mediated by enzymes and ATP.
The mechanism of DNA replication is known as the semi-conservative mode in which one new strand of DNA is synthesized complementary to the one strand of DNA. To form a new DNA molecule both the strand of the DNA gets separated and then a new daughter strand is formed complementary to each parent strand.
Thus, the selected option is correct.
Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
New cells are typically produced during cell division. Cell division is a complex process that is regulated and checked at many points. Due to varying factors, the cell regulation mechanism may become non functional and this usually result in abnormal cell growth and division.
An abnormal cell growth may be cancerous or non cancerous. The best thing to do when one notices an abnormal growth in his body is to go and see the doctor. The doctors will administer appropriate test in order to determine the type of tumor that is present. If the tumor is non cancerous it will be removed by minor surgery. In case the tumor is cancerous, appropriate treatments will depending on the part of the body where it is found, the stage of growth and nature of the cancerous cells.
