SAM Biology M1: DNA

Topics: DNA, RNA, Base pair Pages: 2 (394 words) Published: August 20, 2014
M1: DNA
DNA
-DNA are the chemical unit for genetic information in most organisms. -DNA are informational macromolecules that are used to store hereditary information that determines functional and structural characteristics of organisms. -In eukaryotes, the linear DNA is found primarily in the nucleus of cells. -In prokaryotes (e.g. bacteria), there is one circular loop of double-stranded DNA in cytoplasm.

General Structure of DNA
-The structure of DNA as a double helix made up of a sequence of complementary bases joined by weak bonds. The bases are attached to a sugar phosphate backbone -A DNA molecule is made up of subunits / monomers called DNA nucleotides. -There are 2 types of DNA nucleotides, purines and pyrimidines. -Purines are double ringed structure: Adenine and Guanine.

-Pyrimidines are single ringed structures: Thymine, Cytosine and Uracil. -The DNA nucleotides joined to form two DNA polynucleotide strands. -The 2 strands are anti-parallel.
-Within a single strand, nucleotides are joined together by strong phosphodiester bonds.

-Each strand has alternating sugar-phosphate backbone with nitrogenous bases attached to the sugar molecule. -Complementary base pairs are formed between bases on the two strands. The complementary bases are joined by weak hydrogen bonds. -The DNA molecule has a diameter of 2 nm and makes one turn every 10 nucleotides or 3.4nm. -Genetic information is encoded in the sequence of bases along the strands.

Complementary Base Pairing Rule
-Cytosine always pairs with Guanine.
-Adenine always pairs with Thymine.

Chargaff’s Rule
-Each species has identical amounts of Adenine and Thymine bases in their DNA, and also identical amounts of Guanine and Cytosine, A = T; G = C. -A + G = T + C

RNA (Ribonucleic Acid)
-It is a single stranded molecule.
-It can be found in nucleus as well as cytoplasm.
-There are three types of RNA: mRNA, tRNA, and rRNA
-The RNA molecule...
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