His immune system is using the first line of defense. His body is using purging methods that is caused by irritation of the hairs in his nose. This defense system<span> uses physical and chemical barriers that are prepared to defend the body from infection.</span>
The use of alcohol, tobacco and drugs can contribute to all of the following like, increased possibility of miscarriage, premature delivery, low birth weight except delayed labor. It is impossible that a mother can have delayed labor because first using this kind of drugs can give you miscarriage.
The actual answer is D because risk factors are anything that increases the risk of someone getting sick or disease
Please mark as Brainly
Answer:
D. Yes, two hydrogen bonds could form between thymine and cytosine.
Explanation:
A hydrogen bond (often informally abbreviated H -bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative atom or group, particularly the second-row elements nitrogen (N), oxygen (O), or fluorine (F)—the hydrogen bond donor (Dn)—and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac).
The formation of stable hydrogen bonds depends on the distance between two strands, the size of the bases and geometry of each base. Stable pairings occur between guanine and cytosine and between adenine and thymine (or adenine and uracil in RNA).
One hydrogen bond could form between the C4 carbonyl group on thymine (a hydrogen bond acceptor) and the C4 amino group on cytosine (a hydrogen bond donor). Another hydrogen bond could form between N3 of thymine (a hydrogen bond donor) and the N3 of cytosine (a hydrogen bond acceptor). Note that the C2 carbonyl groups found on both bases are both hydrogen bond acceptors and therefore a hydrogen bond cannot be formed between them.
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