DNAStructure and Function

WHAT IS DNA?

DNA stands for DeoxyriboNucleic Acid

The main job of DNA is

to make PROTEINS

Function of DNA

DNA contains genes that codes for all of our traitsIt is your genetic material or “program” or “blueprint” DNA is what makes you function and be who you are today

Passed from cell to cell

Location of DNADNA is found in the nucleus of the cell for eukaryotes

DNA is found in the cytoplasm for prokaryotes (ex: bacteria)

Our genes are on our chromosomes.Chromosomes are made up of a chemical called DNA

Building Blocks of DNA

Each nucleotide consists ofDeoxyribose (5-carbon sugar) Phosphate groupA nitrogen-containing base (A, G, T, C)

Nucleotide Structure

CH2

O

CC

C C

Sugar(deoxyribose)

NNitrogenous base (A, G, C, or T)

O=P-O O

Phosphate Group

Nitrogen Bases

Adenine (A)Guanine (G)Thymine (T)Cytosine (C)

A or G

T or C

Structure of DNA

Double Helix: Watson-Crick ModelStrands are held together by hydrogen bonds between bases

The sides are a sugar-phosphate backbone, while the “rungs” of the ladder are the bases.

The DNA strands run in opposite directions

Base-Pairing Rules

Adenine (A) pairs with Thymine (T)Cytosine (C) pairs with Guanine (G)

There are two classes of nitrogen bases called purines (double-ringed structures) and pyrimidines (single-ringed structures). The four bases in DNA's alphabet are:

adenine (A) - a purine cytosine(C) - a pyrimidine guanine (G) - a purine thymine (T) - a pyrimidine

DNA COPY PRACTICE

Make a copy of the following DNA Sequence:

DNA (Original): C G G T A

COPY: G C C A T

DNA(Original): A T C G C G A A

COPY: T A G C G C T T

Chargaff’s RuleA = T C = GA+T+C+G = 100

For example: The DNA is made up of 15% Adenine. Figure out the amount of the other nitrogen bases.

Adenine = Thymine Thymine = 15(a)G+C+15+15=100 (b)100-15-15=G+C (c)100-30 = 70G+C = 70 and Guanine =CytosineG= 35 and C=35Therefore: A=15%, T=15%, G=35%, C=35%

Practice ProblemThe DNA is made up of 30% Cytosine, figure out the amount of the other nitrogen bases.

Cytosine = Guanine G=3030+30+A+T=100 A+T= 100-30-30T+A=40A=20, T=20Therefore: G=30, C=30, A=20, T=20