DNA

Characteristics of DNA Supplies instructions for cell processes, like how to make proteins Can be copied each time a cell divides It is the “blueprint of life”, every living thing has DNA

DNA Structure Is a nucleic acid that is double stranded Made up of subunits called nucleotides

A nucleotide consists of 3 parts: Phosphate Sugar Nitrogen base: adenine (A), guanine (G), thymine (T), cytosine (C)

Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Section 12-1 Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Scientific Contributions Watson and Crick: made a model of DNA structure in 1953 The “Double Helix” looks like a twisted ladder Sides of the ladder are alternating sugar and phosphate units Rungs are the bases held together by hydrogen bonds A always pairs with T and C always pairs with G

DNA Replication Def: Ability of DNA to make an exact copy or a new strand of DNA from an old one

The Steps in Replication Start with a DNA molecule Hydrogen bonds break and the strands separate (unzip) Add matching nucleotides The result: 2 identical DNA molecules ½ old strand, ½ new strand

Drawing DNA Replication: Step 1

Drawing DNA Replication: Steps 2 and 3

Drawing DNA Replication: Step 4

DNA Replication:

Chromosomes Tight coils and supercoils of DNA and protein

Section 12-2 Chromosome Nucleosome DNA double helix Coils Supercoils Histones

Protein Synthesis

Genes and the Genetic Code Gene: a segment of DNA on a chromosomes that codes for a specific trait Genetic Code: formed by the order of nitrogen bases along a gene that specifies what type of protein will be produced

How cells make proteins A cell uses the coded information from a segment of DNA (gene) to make a specific protein Why make proteins? Proteins determine your traits, hair color, eye color, tongue rolling ability, etc. Things that are not traits: athletic ability

What Protein Synthesis involves: DNA found in the nucleus Ribosome: where the proteins are made RNA (see below) Amino acids: these are the building blocks of proteins

RNA Similar to DNA Structure of RNA: Sugar is different Single-stranded Uracil replaces thymine Still has cytosine (C), guanine (G), and adenine (A)

DNA vs RNA

2 Types of RNA mRNA: messenger RNA Copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm tRNA: transfer RNA Picks up and transfers amino acids in the cytoplasm to the ribosome and adds them to the growing proteins

How Cells Make Proteins - The DNA Connection How Cells Make Proteins During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein.

Mutations - The DNA Connection Mutations can cause a cell to produce an incorrect protein during protein synthesis. As a result, the organism’s trait, or phenotype, may be different from what it normally would have been.

So, what’s the big deal? most of the time they are fixed by our bodies Mutations happen all the time most of the time they are fixed by our bodies

If they are not fixed, 3 things could happen: 1. Absolutely nothing: occurs most of the time 2. A small change: like having 2 different color eyes a change that does not effect the way you live

has a big effect on how you live 3. A BIG change: (can be good or bad) like getting a disease or being able to blend in to your environment better has a big effect on how you live