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Biology 311C Lecture 8

Biology 311C Lecture 8 - •*The reaction that links two...

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September 12, 2011 Biology 311C Lecture 8 Nucleic Acids The amino acid sequence of a polypeptide (like the beta subunit of hemoglobin) is programmed by a unit of inheritance called a gene. Genes are made of DNA, a nucleic acid made of monomers called nucleotides. Nucleic acids store, transmit, and help express hereditary information. The human genome is the total number of genes we find in our genetic information. There are about 25,000 genes. DNA goes to RNA (transcription) and from RNA to cytoplasm (translation). Synthesis of a protein then happens when the mRNA is read and the product is a polypeptide. The DNA is in the nucleus because it is protected. RNA is a copy of the RNA and moves into the cytoplasm. DNA stands for deoxyribose nucleic acid. RNA stands for ribose nucleic acid. The 2’ carbon distinguishes RNA from DNA. If there is a hydroxyl, it’s ribose. If it’s just a hydrogen, it’s in deoxyribose. In the 5’ group, that is where we find the phosphate group in the nucleotide.
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Unformatted text preview: • **The reaction that links two nucleotides together is dehydration; the bond formed is called a phosphodiester, and includes a P atom. • In RNA, the 5’ end has a phosphate group and in the opposite end (3’), there is a hydroxyl group. • 3’ and 5’ carbons are joined by phosphodiester linkage. • RNA molecules usually exist as single polynucleotide chains. • DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix. • In the DNA double helix, the two backbones run in opposite 5’ -> 3’ directions from each other, an arrangement referred to as antiparallel. • Hydrogen bonds form between bases in adenine (A) always with thymine (T), and guanine (G) always with cytosine (C) which is called complementary base pairing. • Sugar-phosphates make up the backbones. The base pair is joined by hydrogen bonding....
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