DNA The Blueprint of Life

Nucleic Acids (Remember the macromolecules back in Chapter 2?) Nucleic Acids - store the genetic instructions for all life Two types of nucleic acids: RNA and DNA

DNA Stands for: Deoxyribonucleic Acid Type of sugar: Deoxyribose # of strands of nucleotides: 2 (Double Stranded) “double helix” Function: stores genetic material

2. A sugar (called deoxyribose) 3. A Nitrogen Base – There are 4! DNA is made up of small repeating units (monomers) called nucleotides. Nucleotide  has three parts: 1. A phosphate group 2. A sugar (called deoxyribose) 3. A Nitrogen Base – There are 4! Adenine “A” Thymine “T” Guanine “G” Cytosine “C”

DNA  Structure: Two strands of nucleotides bonded together at the nitrogen bases (with hydrogen bonds) and twisted. flat twisted What is DNA Made Of? DNA is made of four building blocks called nucleotide bases; adenine (A), thymine (T), guanine (G) and cytosine (C). Each strand of DNA is made up of long strings of these nucleotides arranged in a specific order. Two strands stick together and twist to form a helix.

Watson and Crick Are responsible for the 1st model of DNA and described its shape as a double helix (twisted ladder)

The two sides of the DNA ladder are made up of sugar and phosphate groups. The steps (center) of the DNA ladder are made up of base pairs : adenine+thymine or guanine+cytosine

Chargaff’s Rule = A (Adenine) bonds to T (Thymine) and C (Cytosine) binds with G (Guanine). Base pairs are weakly joined together by hydrogen bonds to form each step of the ladder.

The KEY!!!! The sequence (order) of the 4 base pairs determines the genetic instructions or ‘code’ for life.

DNA Replication – replica = copy creating two identical DNA molecules by copying the original DNA strand

DNA Replication Steps: DNA Polymerase DNA unwinds DNA unzips DNA polymerase (an enzyme) break the weak hydrogen bonds holding the base pairs together splitting the DNA ladder down the middle.

3. Enzymes hydrogen bond new nitrogen bases onto the original DNA ½ ladders using Chargaff’s base-pairing rule (A-T and G-C). 4. Finally, sugar and phosphate groups covalently bond to the new nitrogen bases and to each other to finish off the two new DNA strands.

Results: two identical DNA strands made up of ½ of the original strand and ½ of the new strand.

When does DNA copy itself? The cell replicates its DNA right before cell division. When two new cells are produced in cell division, each new cell needs its own copy of the DNA. (Identical Copy!) What happens to the Cell after DNA Replication? After DNA replication, the cell will divide in half (cell division) and give each new cell a copy of the DNA.

Chromosomes As humans, we have 46 chromosomes in each of our cells. Each chromosome has millions of base pairs storing the codes that make up our bodies. (The code depends on the sequence “order” of the bases.)

Chromosome  coiled DNA and protein “spacers” called histones. Histones keep the chromosome from getting tangled.

DUPLICATED CHROMOSOME A chromosome that has gone through DNA replication and has an identical “sister” DNA copy attached to it. We call each copy of this duplicated chromosome a sister chromatid.

RNA Stands for: Ribonucleic Acid Type of sugar: Ribose # of strands of nucleotides: 1 (single stranded) Function: Transfers genetic material