Stem Cells. Hope this helps.
A DNA molecule consists of two stands of nucleotides that wind around each other like a twisted ladder with a phosphate and sugar backbone. The nitrogenous bases are divided into two groups called the pyrimidines and the purines. The pyrimidines include the thymine and cytosine, the purines are adenine and guanine. The nitrogenous bases in the double helix are bound together according to the base pairing rule. Adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C). The student either drew the base pairing showing adenine and thymine or guanine pairing with cytosine.
Answer: crossing over
during the process of fertilization, a sperm and egg join together to create a zygote. since a sperm had half the number of chromosomes and an egg has half the number of chromosomes, when they join together the zygote had a complete diploid set of chromosomes. the assortment of chromosomes and crossing over promotes genetic variation during the process of reproduction
Answer:
There is currently no consensus regarding the definition of life. One popular definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve.
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