DNA STRUCTURE AND FUNCTION CHAPTER 10 DNA STRUCTURE AND FUNCTION

DNA-DeoxyriboNucleic Acid Found in the nucleus of eukaryotic cells Stores hereditary information Serves as the “blueprint for making proteins Gene- a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color, etc.),

DNA-DeoxyriboNucleic Acid Composed of many repeating nucleotides Each nucleotides has 3 parts: A simple sugar called A phosphate group A nitrogen base

TWO types of Nitrogen bases: Purines-double ringed Adenine (A) Guanine (G) Pyrimidine-single ringed Cytosine (C) Thymine (T

James Watson & Frances Crick Described the structure of DNA as a: Double helix -two strands wound around each other like a twisted ladder.

The backbone consists of alternating deoxyribose and phosphate groups. The phosphate group bonded to the 5’ carbon atom of one deoxyribose is covalently bonded to the 3’ carbon of the next. The two strands are antiparallel; that is one strand runs 5’ to 3’ while the other runs 3’ to 5’.

Complimentary base pairing: Each nitrogen base forms hydrogen bonds with the one directly opposite it, forming base pairs (also called nucleotide pairs). Complimentary base pairing: Adenine pairs with thymine. (A-T) Guanine pairs with cytosine. (G-C)

The sequence of nucleotides will determine the genetic information unique to an organism. Endless combinations result in different traits, appearances, and functions of the organism.

DNA REPLICATION Is the process where DNA makes a copy of itself. Functions of DNA replication: Cells divide for an organism to grow or reproduce. Every new cell needs a copy of the DNA or instructions to know how to be a cell. DNA replicates right before a cell divides during interphase. One half of the old strand is always kept in the new strand. (semi-conservative)

Steps to DNA replication Step 1: an enzyme “unzips” or separates the DNA double helix. Step 2: free floating nucleotides pair up with the complementary bases on each of the original DNA strands Step 3: two DNA molecules form that are identical to the original DNA molecule.