Internal and external hydrogen bonds stabilize the DNA molecule. The two strands of DNA stay together by H bonds that occur between complementary nucleotide base pairs. Two hydrogen bonds occur between the adenosine and the thymine base pairs, and between the cytosine and the guanine there are three.he two DNA strands are held together by interchain hydrogen bonds. H-bonds pair the bases in one chain to the complementary bases in the other chain. (A/T and G/C).
What are circadian rhythms? Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment. They are found in most living things, including animals, plants and many tiny microbes. The study of circadian rhythms is called chronobiology.
The most obvious is our sleep cycle, with activity during the day, followed by sleep during the night. Circadian rhythms have also been demonstrated in humans for changes in body temperature, heart rate, alertness, and physical performance in sports. In this human biology science fair project, you will investigate human circadian rhythms by measuring body temperature and reaction time at different times of day.