Molecular Genetics

DNA Review! Has shape of helix or corkscrew Is about 2 nm in diameter 2m of it in a nucleus!! Makes a complete helical turn ever (3.4 nm) every 10 base pairs

DNA is Supercoiled: A strand of DNA in prokaryotic cells coils into a closed loop, then twists on itself like a necklace that is coiled into a series of small loops. HISTONES are base proteins that DNA wraps around, that form the core of NUCLEOSOMES. Page: 230 textbook

Scowqo

Three main components deoxyribose sugar a phosphate group (same as RNA) nitrogenous base ▫adenine ▫guanine ▫thymine ▫cytosine

DNA is composed of many nucleotides held together by phosphodiester bonds (therefore it is a polymer) A phosphodiester bond is a covalent bond that holds a DNA strand together by joining a phosphate group at position 5 in the pentose sugar of one nucleotide to the hydroxyl group at position 3 in the pentose sugar of the next nucleotide Backbone of DNA is: Sugar – Phosphate – Sugar - Phosphate

Structure of deoxyribose A sugar derived from ribose by replacing a hydroxyl group with hydrogen.

The Double Helix DNA consists of two antiparallel strands of nucleotides Bases of one strand are paired with bases in the other strand Nitrogenous base pairs are arranged above each other, perpendicular to the axis of the molecule A Purine always bonded to a Pyrimidine ▫Adenine with Thymine ▫Guanine with Cytosine  Termed Complimentary Base Pairing  Fundamental to the storage and transfer of genetic information

Because I’m all about that Base….

Purines – A & G Pyrimidines – T & C (also U in RNA) bases are bonded together by hydrogen bonds right-handed helix (clockwise turn) makes complete turn every 10 nucleotides

Two strands of DNA run antiparallel Directionality of DNA: refers the end-to-end chemical orientation of a single strand of nucleic acid. One strand runs in the 5 ’ to 3 ’ direction while the other strand runs in the 3 ’ to 5 ’. The 3 ’ end terminates with the hydroxyl group of the deoxyribose sugar. The 5 ’ end terminates with a phosphate group The 5′ is upstream; the 3′ is downstream. DNA and RNA are synthesized in the 5′ to 3′ direction

Finding the code... 5 ’ - ATGCCGTTA - 3 ’ 3 ’ - TACGGCAAT - 5’ By convention, only the 5’ to 3’ strand is written since the complementary strand can easily be deduced... Try this one... 5 ’ - TGGACGCTT - 3 ’

Homework... Complete your worksheet mqYhttps:// mqY What are your thoughts? Research some controversial topics on bioengineering or GMO’s and be ready to discuss Monday.