Ch. 5: DNA and Modern Genetics!! “The Molecule of Life”

Do Now!!  What is DNA? Why is it important? List three places in the body where you can find DNA.

Objectives To explain the structure of DNA To identify the different types of bases how they pair up To list the scientists involved in discovering DNA

So what is DNA? A molecule that stores information What do the letters stand for? DEOXYRIBONUCLEIC ACID Where is it found? In the nucleus (or nuclear region in prokaryotes) What is it used for? Blueprints of your genes/traits To make proteins!

What is DNA Made of? Repeating units of nucleotides Nucleotides are made of 3 components: 5 carbon sugar (Deoxyribose) Phosphate Group Nitrogenous base

Nitrogenous Bases Purines Have 2 rings (double ring structure) Adenine (A) Guanine (G) Pyrimidines Have 1 ring (single ring structure) Thymine (T) Cytosine (C) Uracil (U) instead of Thymine in RNA

Nitrogenous Bases

Chargaff’s Rule Erwin Chargaff Discovered that A pairs with T and C pairs with G. Chargaff’s rule: A=T, C=G Amounts vary between species

What is the complimentary sequence?? ATGCTAATTCGCATCG

Do Now!  TGACCAGTTTAGCTAGGGC What makes up a nucleotide? What is the difference between a purine and a pyrimidine? Identify the purines and pyrimidines we talked about! Please write the complementary sequence: TGACCAGTTTAGCTAGGGC

Objectives To identify the scientists who contributed to the discovery of DNA To define the structure of DNA To complete a DNA structure worksheet

Rosalind Franklin Used X-ray diffraction to determine shape of DNA X-rays aimed at molecule, bounce off electrons Determines the molecule’s shape

Rosalind Franklin Took now famous photo 51 Data indicated that DNA was a double helix shape Helped Watson and Crick solve the structure of DNA

Watson and Crick Built a model of the double helix DNA molecule: two outside strands consist of alternating sugar and phosphate molecules thymine and adenine bases pair to each other by two hydrogen bonds cytosine and guanine bases pair to each other by three hydrogen bonds *Go back to your DNA sequence!

DNA Structure DNA looks like a twisted ladder! Rails: alternating deoxyribose sugars and phosphates Rungs (steps): base pairs (C-G, A-T) bonded by hydrogen bonds

Do Now!  Label the parts of the DNA! C D

Objectives To review DNA structure To define DNA replication To identify the steps of DNA replication

DNA Replication Allows cells to get an exact copy of DNA. Replication: Parent strands separate, serve as templates Daughter DNA produced (have one DNA strand from parent and one new strand)

Steps to Replication 1- The two DNA strands unwind and separate: Helicase- enzyme that separates the DNA molecule

Steps to Replication 2- Nucleotides match up base by base with the nucleotides on each TEMPLATE DNA strand: All of the C’s pair with the G’s and all of the A’s pair with the T’s. DNA Polymerase: enzyme that creates new DNA by assembling nucleotides

Steps to Replication 3- Each new daughter DNA molecule has one strand of new DNA and one from the original parent strand.

Replication Animation! http://highered.mheducation.com/sites/0072943696/student_v iew0/chapter3/animation__dna_replication__quiz_1_.html

Do Now!!  Please complete the worksheet in front of you!

Objectives To define RNA To identify the different types of RNA To define transcription and translation

So why do we NEED DNA??

We need to make RNA to make proteins!! What is RNA? Ribonucleic Acid How is it different from DNA? Single stranded Indefinite shape Uses “uracil” Contains Ribose

Types of RNA 1. Messenger RNA (mRNA): Linear Located in both the nucleus and the cytoplasm Brings genetic code from DNA to the ribosome to make protein (in cytoplasm) Contains codons (every 3 letters, ex. AUG is 1 codon)

Types of RNA 2. Ribosomal (rRNA): Located within the ribosome Helps make the structure of the ribosome

Types of RNA 3. Transfer (tRNA) Located in the cytoplasm Clover-like loop structure Brings amino acids (attached to top of tRNA) to ribosome to help build proteins Contains anticodon (3 letter sequence at bottom of tRNA, complements codon)

The Central Dogma! DNA RNA Protein Transcription: Occurs in nucleus Create (transcribe) mRNA from DNA template Translation: Occurs in cytoplasm Takes mRNA and makes proteins with the help of tRNA and ribosomes.

Do Now!!  Please take out your worksheet from last class and finish!

Objectives To identify the steps of transcription. To understand the process of transcription and how mRNA is made.

Transcription Gene: a distinct sequence of nucleotides Determines your traits Only individual genes are transcribed, not a whole DNA molecule Occurs in the nucleus Produces mRNA

Transcription Step 1: DNA molecule unwinds and separates just like in replication: RNA polymerase: enzyme that unwinds the DNA and assembles new nucleotides (makes RNA strand).

Transcription Step 2: RNA nucleotides match up with their complimentary bases on the DNA template strand: RNA polymerase assembles these nucleotides Creates a single stranded mRNA molecule Practice: Write the complimentary mRNA strand from this DNA ATCGATGGCAAGCTA

Transcription Step 3: mRNA detaches once entire gene is done and DNA rewinds: mRNA strand leaves nucleus through pores Goes to cytoplasm to help ribosomes make proteins *Delivers directions from DNA for how to make proteins *Many copies of RNA can be made from the same gene in a short period of time.

Transcription Video http://www.dnalc.org/resources/3d/12-transcription-basic.html

Do Now!!  With a partner, please complete the worksheet in front of you!

Do Now!!  What is the “Central Dogma”? What is transcription? Please transcribe the DNA sequence below: T A C C G A A T C G T A C G G A C T

Objectives To define translation To identify the steps of translation To practice building amino acid sequences to form proteins

Translation What happens in the steps before translation? What happens in translation? Where does this happen?

Translation Step 1: Translation begins when a ribosome attaches to the beginning of an mRNA molecule. *Translation MUST START AT THE LETTERS “AUG”: This is the START codon * Every 3 letters on the mRNA is called a “Codon” that codes for a specific amino acid.

CODON BINGO!!

Do Now!!  A U G C G G C U A A U U What is translation? Where does translation take place? Write the amino acid sequence this mRNA strand would form: A U G C G G C U A A U U

Objectives To identify the steps of translation To practice the process of protein synthesis

Translation Step 2: A tRNA molecule carrying an amino acid matches up to a complementary codon in the mRNA on the ribosome: *tRNA molecules contain “Anticodons” which are 3 bases on bottom of tRNA Anticodons compliment codons on mRNA

Translation Step 3: The ribosome attaches one amino acid to another as it moves along the mRNA molecule. Amino acids are attached by PEPTIDE BONDS.

Translation Step 4: The tRNA molecules are released after the amino acids they carry are attached to the growing chain of amino acids. Return to cytoplasm to pick up another amino acid

Translation Step 5: The ribosome completes the translation when it reaches a stop codon: The newly made protein is then released.

Do Now!!  Please complete the worksheet in front of you!

Objectives To define genetic mutation To identify the different types of genetic mutations

What is a mutation? Mutation: a permanent change in a cell’s DNA Errors can occur when DNA is copied UV light, X-rays, chemicals, etc. can cause mutations in DNA

Types of mutations Substitution – Exchanges one base for another. Normal: ACAGAG Mutated: ACAGGG Insertion – Extra base pairs are inserted. Normal: AATGAG Mutated: AATGTGGAG

Types of mutations (cont.) Deletion- Section of DNA is lost or deleted. Normal: CTGGAG Mutated: CT___AG Frameshift- Message is no longer read correctly. Normal: THE FAT CAT ATE THE BIG RAT Mutated: HEF ATC ATA TET HEB IGR AT

What happens when there is a mutation? Cells have different ways to repair mistakes: Proofreading enzymes can correct mismatched base pairs EX: DNA polymerase, exonuclease

Do Now!!  What are the three kinds of mutations? What is a frameshift? Are all mutations bad?

Objectives To discuss the effects of genetic mutations on protein synthesis To complete a review protein synthesis worksheet To simulate genetic mutations in a lab activity

Mutations can have different effects The mutation has no effect: Amino acids have more than 1 code The effect of a mutation is minor: Could affect skin/eye/hair pigmentation The effect of a mutation is great: Genetic disorder/disease

Genetic disorders Sometimes passed from parents to offspring: Sickle Cell Anemia Cystic Fibrosis (CF) Hemophilia Tay- Sachs Disease Huntington’s Disease (HD) Cancer

Sickle cell anemia Mutation occurs on gene that codes for hemoglobin: Hemoglobin – a protein that carries oxygen in red blood cells Substitution mutation causes 1 amino acid to be replaced with another