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 body clock, or circadian clock, is an internal clock that keeps track of time. Circadian comes from circa-diem meaning around a day. So in a mouse for example it is about 23.5 hours and for a human its about 24.5 hours. If you are kept in constant darkness your body will still work to around a 24-hour cycle. It is not just being driven by light and dark. It is an intracellular clock so if you look in individual cells they are all able to keep time as well. If you put cells in a dish they will show 24-hour changes in gene expression.