DNA Characteristics of DNA 1 2 3 Supplies

DNA

Characteristics of DNA 1. 2. 3. 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 l l Is a nucleic acid that is double stranded Made up of subunits called nucleotides

A nucleotide consists of 3 parts: 1. 2. 3. Phosphate Sugar Nitrogen base: adenine (A), guanine (G), thymine (T), cytosine (C)

Section 12 -1 Structure of DNA 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 l The “Double Helix” looks like a twisted ladder l l l 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 l Def: Ability of DNA to make an exact copy or a new strand of DNA from an old one

The Steps in Replication 1. 2. 3. 4. 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 l Tight coils and supercoils of DNA and protein

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

Protein Synthesis

Genetics: The Science of Heredity 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

Genetics: The Science of Heredity 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

Genetics: The Science of Heredity 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

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

Genetics: The Science of Heredity DNA vs RNA

Genetics: The Science of Heredity 2 Types of RNA m. RNA: messenger RNA Copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm 1. t. RNA: transfer RNA Picks up and transfers amino acids in the cytoplasm to the ribosome and adds them to the growing proteins

Genetics: The Science of Heredity - 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.

Genetics: The Science of Heredity - 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.

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

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

Genetics: The Science of Heredity 1. 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