THE GENETIC MATERIAL OF LIFE UNIT 3 DNA THE GENETIC MATERIAL OF LIFE UNIT 3

What is DNA? Stands for: DeoxyriboNucleic Acid Molecule that stores genetic information in all organisms DNA is stored in the nucleus of your cells

Fun DNA Facts! DNA is too small to see, but under a microscope it looks like a twisted up ladder! DNA stands for: D: Deoxyribose N: Nucleic A: Acid Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!!

Structure of dna

DNA Structure DNA is a long chain made up of units called nucleotides Each nucleotide has three parts: Phosphate group (one phosphorus/3 oxygens) Deoxyribose (ring-shaped sugar) Nitrogen-containing base There are only four types of nucleotides—based on what type of nitrogen base they have

Structure of Nucleotides Phosphate group Nitrogen Base: Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Deoxyribose

The letter refers to the DNA bases as well as the nucleotide One molecule of DNA contains BILLIONS of nucleotides, but there are only 4 types: Adenine (A) Guanine (G) Thymine (T) Cytosine (C) The letter refers to the DNA bases as well as the nucleotide

Base Pairing DNA is a double helix structure—this means that there are two strands of DNA that wind together like a twisted ladder The strands are bonded together at the bases

The bases always pair up in the same way based on base pairing rules: Adenine bonds with Thymine Adenine Thymine Cytosine bonds with Guanine Cytosine Guanine

Pairing up PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4

THE DOUBLE HELIX bases sugar-phosphate chain

The structure of DNA consists of two strands wrapped around each other in a double helix

So if one strand is… what is the other strand, based on base pairing rules? C G - T - A - G - C

Try it out… DNA structure worksheet! See it DNA structure in action: http://youtu.be/zwibgNGe4aY Build a virtual DNA strand: http://learn.genetics.utah.edu/content/molecules/builddna/ DNA candy model!

DNA Replication

DNA Replication Before a cell divides, it must make a copy of its DNA

(A mistake is called a mutation) The steps of DNA Replication: DNA is unwound DNA polymerase adds nucleotides, according to base pair rules The strand is proofread as nucleotides are added, and mistakes can be fixed if the wrong base was added (A mistake is called a mutation) DNA polymerase continues adding nucleotides until a STOP signal is reached

DNA Replication in action

Try it out! Make sure to click on DNA Replication NOT protein synthesis because we have not learned about protein synthesis yet! DNA Paperclip Replication Activity

Transcription

RNA (this molecule is used during transcription) RNA: RiboNucleic Acid Chain of nucleotides made of: Sugar Phosphate group Nitrogen-containing base It’s a temporary copy of DNA that is used and then destroyed

DNA vs. RNA DNA RNA Its sugar is deoxyribose Both have a sugar, phosphate, & base DNA RNA Its sugar is deoxyribose Bases are: Adenine, Thymine, Guanine, Cytosine Double strand of nucleotides Its sugar is ribose (has one extra oxygen) Bases are: Adenine, Uracil, Guanine, Cytosine (uracil pairs w/ adenine) Single strand of nucleotides

Transcription Copying a sequence of DNA to make a complementary strand of RNA This is catalyzed (allowed to happen) by RNA polymerase

Basic steps of Transcription in Cells DNA strands unwind RNA polymerase copies one strand of DNA and creates a complementary strand of RNA nucleotides (known as mRNA) Once the gene has been copied, mRNA detaches from DNA mRNA moves out of the nucleus and into the cytoplasm

Step 1 Step 2 Step 3 transcription complex start site nucleotides DNA RNA copying RNA Step 3

Types of RNA Three types of RNA are formed during transcription, they will be used in translation: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

Watch transcription in action http://study.com/academy/lesson/transcription-of-messenger-rna-mrna-from-dna.html

translation

Translation Process that converts (translates) mRNA into a protein —called protein synthesis mRNA is a message that codes for a protein when it attaches to a ribosome in the cytoplasm of the cell Each combination of 3 nucleotides (known as a codon) on the mRNA codes for an amino acid —groups of amino acids become proteins in the cell

Steps of Translation mRNA moves out of nucleus and into the cytoplasm mRNA attaches to ribosome Transfer RNA (tRNA) decodes the mRNA into amino acids, which link together into proteins Protein (chain of amino acids) detaches from ribosome and goes off to work in the cell

Check it out… Go to the following website to see translation (also called PROTEIN SYNTHESIS) in action http://www.pbslearningmedia.org/resource/tdc02.sci.life.gen.proteinsynth/from-dna-to-protein/ http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html Make sure to click on Protein Synthesis!!

Genetic Code tRNA matches each codon in mRNA to three nucleotide bases called anticodons on tRNA This anticodon has a specific amino acid attached that will eventually form a chain of amino acids to make a protein : There are 64 possible 3 letter combinations BUT only 20 amino acids…. SO, some Codons code for more than one amino acid

Codon   Anticodon

Different codons code for different amino acids!!!

Transcription vs. Translation Review Process by which genetic information encoded in DNA is copied onto messenger RNA Occurs in the nucleus DNA mRNA Translation Process by which information encoded in mRNA is used to assemble a protein at a ribosome Occurs on a Ribosome mRNA protein

Mutations

Mutation A Mutation is a change in an organism’s DNA It’s a mistake made during replication or transcription Can be: Harmful: diseases, disorders or deformities Helpful: help the organism to survive Neutral: organism is unaffected

Passing on Mutations If a mutation occurs in a sperm or egg cell, the mutation IS PASSED on to offspring If a mutation occurs in a body cell, it only affects the organism and IS NOT PASSED on to offspring

Causes of Mutations During DNA Replication: Base-pairing mistakes can happen but most are fixed Exposure to powerful Chemicals: Cigarette smoke, smokeless tobacco, exhaust from burning petroleum fuels, pesticides, herbicides, alcohol, sawdust from CCA lumber, paints, mineral spirits & oils, asbestos, etc. Exposure to powerful radiation: Gamma Rays (nuclear fuel & bombs) X rays (at hospitals & dental offices) UV rays (from sunlight and tanning beds)

Sickle Cell Anemia

Point Mutations An alteration in DNA sequence caused by a single nucleotide base change, insertion, or deletion

Types of Mutations Insertion-- changes the number of DNA bases in a gene by adding a piece of DNA. The protein made by the gene may not function properly. Deletion-- changes the number of DNA bases by removing a piece of DNA. This could be removing a few base pairs within a gene or an entire gene/several neighboring genes. This may alter the function of the resulting protein(s). Duplication-- consists of a piece of DNA that is mistakenly copied one or more times. This may alter the function of the resulting protein.

What happens when a protein is altered due to a mutation? To function correctly, each cell depends on thousands of proteins to do their jobs in the right places at the right times. A mutation can cause the protein to malfunction or to be missing entirely. An altered protein can disrupt normal development or cause a medical condition. Examples: Breast Cancer, Down’s syndrome, Crohn’s disease, Hemophilia, Duchenne Muscular Dystrophy

What do you know? Mutations concept map