Answer:
Fraternal twins are “dizygotic,” meaning that they developed from two different eggs fertilized by two different sperm cells, while identical twins are “monozygotic” i.e., they developed from a single fertilized egg that split.
Explanation:
The three mechanisms which regulate the heart are endocrine, cardiovascular and Sinoatrial nodes.
The endocrine system consists of the glands and hormones of the human body. The cardiovascular system is the organ system which is responsible for the circulation of the blood around the body and the oxygenation of the body's tissues. The sinoatrial node (SA node) generates the electrical impulses and is considered the natural pacemaker of the heart.
WATER
Solids will usually sink when placed in their own liquids with the exception of water
Explanation:
Ice (the solid form of water) floats on water that is cooler than 4 degrees centigrade. This is unlike any other material and this phenomenon has been referred to as the ‘water anomaly’.
Most substances will sink in their own liquid because the solid form is denser than the amount of their own liquid that they displace when immersed. This is because the particles in the solid are closely packed together hence there are more particles per volume than in the liquid form.
Water however, expands at temperatures below 4 degrees and hence ice is less dense than water at 4 degrees and below. The particles in ice are farther apart than particles of water at 4 degrees and below. There is, therefore, more particles per volume in the liquid form of water than in ice – making ice less dense.
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The process of turning off and on of genes is known as gene regulation.
Explanation:
When the gene is turned on, it instructs the cells to construct a particular protein. The proteins are the molecules that build your body with collagen, tendons, and bones or keratin in your hair.
The gene regulatory proteins allow the individual genes of an organism to be turned on or off . in different cell types there are different selections of gene regulatory proteins. The patterns of the gene expression gives each cell its unique characteristics.
Each cell produces or turns on only a fraction of its genes. the remaining genes are repressed or turned off. this process is known as gene regulation. The signals from the environment or from other cells activate proteins called transcription factors.
