The Structure of DNA and RNA All life on earth uses a chemical called DNA to carry its genetic code or blueprint. In this lesson we be examining the structure of this unique molecule. {Point out the alligator’s eyes in the first picture.} By the way, can you make out what this is? *************************************************************** [The goal of this presentation is to introduce high school biology students to the chemical structure of DNA. It is meant to be presented in the classroom while accompanying the teacher’s lecture, under the control of the teacher.]

What is genetics and Why do we study it? Genetics is the study of heredity and the variation of inherited characteristics. Reasons to study genetics: its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops. About better food crops, this area is controversial. There is a Dr. Charles Arntzen who is working on bioengineering foods with vaccines in them. People in poor countries could be immunized against diseases just by eating a banana, for instance.

There are 2 types of nucleic acids -DNA -RNA

DNA DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell. (Proteins made by ribosomes!) Why is DNA called the blueprint of life? Remember all cells have ribosomes even bacteria

RNA present in all living cells Its role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins

What are nucleic acids made of? Nucleic acids (a macromolecule) are made up of long chains of monomers called nucleotides Each nucleotide is made up of 3 parts a phosphate group (PO4) a sugar (deoxyribose or ribose) a nitrogenous base (GCAT or U)

bond bond P base Sugar Nucleotides A phosphate group bonded to one of the 2 sugars that is bonded to one of the nitrogenous bases DRAW THE NUCLEOTIDE bond bond base P phosphate Sugar It is the phosphate group which gives DNA its acidic properties

The different sugars Ribose (RNA) is a 5 carbon ring sugar (C5H10O5 ) Deoxyribose (DNA) is also a 5 carbon sugar, but lacks one oxygen atom C5H10O4 monosaccharide sugars have C:H:O ratio of 1:2:1 sugars typically end in -ose

Quick check What are the 2 types of nucleic acids? What are nucleic acids made of? What are the 3 parts of a nucleotide?? What are the 2 types of sugars?

Our genes are on our chromosomes. Where is DNA found? Our genes are on our chromosomes. floats in the cytoplasm of all prokaryotic cells {Ask students where the chromosomes are in this picture. Or ask them where the DNA is. Remind them that the mitochondria also have DNA.}

The Shape of the Molecule DNA is a very long polymer. The basic shape is like a twisted ladder or zipper. This is called a double helix. {Show students a model of the double helix. Explain what a spiral is and a helix is.}

One Strand of DNA nucleotide One strand of DNA is a polymer (multitude) of nucleotides. The backbone of the molecule is alternating phosphates and deoxyribose sugar The teeth are nitrogenous bases.

Remeber Each DNA nucleotide is made up of… 3 Remeber Each DNA nucleotide is made up of… a phosphate group a sugar deoxyribose A nitrogenous base G or C or A or T base PO4

The nitrogenous bases of DNA and RNA are 5 The nitrogenous bases of DNA and RNA are Guanine G Cytosine C Adenine A Thymine (DNA only) T Uracil (RNA only) U

The bases always pair up in the same way 10 The bases always pair up in the same way Guanine always bonds with Cytosine and C with G Cytosine Guanine Adenine forms a bond with Thymine and T with A Adenine Thymine https://www.youtube.com/watch?v=zR_wCYmjdkg 23 seconds Remember: Gangster CAT has DNA Soulja Boy likes RNA…why??

Quick check What are the 2 sugars found in nucleic acids? How many nucleotide bases are there? Name one possible base. Which base is only found in DNA? RNA?

Chargraff’s Rule: Adenine and Thymine always join together Cytosine and Guanine always join together

What conclusions can you make? Chargaff’s Rule What conclusions can you make? Organism %A %T %G %C Mycobacterium tuberculosis 15.1 14.6 34.9 35.4 Yeast 31.3 32.9 18.7 17.1 Wheat 27.3 27.1 22.7 22.8 Sea Urchin 32.8 32.1 17.7 17.3 Marine Crab 47.3 2.7 Turtle 29.7 27.9 22.0 21.3 Rat 28.6 28.4 21.4 21.5 Human 30.9 29.4 19.9 19.8

Over View of DNA vs. RNA RNA DNA Made of nucleotide subunits chained together Single strand of nucleotides Double strand of nucleotides 5 carbon sugar, ribose 5 carbon sugar, deoxyribose Nucleotide bases G, C, A, U (uracil) Nucleotide bases G, C, A, T (thymine)

Go to next blank ION page. Turn it sideways Set up a double bubble map for DNA and RNA DNA RNA

Double Bubble DNA RNA

DNA Replication and Protein synthesis

DNA Review Deoxyribonucleic Acid – composed of building blocks called nucleotides Phosphate Sugar (deoxyribose) Nitrogen bases Adenine – Thymine Guanine – Cytosine Right hand twist Double stranded http://accessexcellence.org/RC/VL/GG/index.html#Anchor-From-14210

Quick review Chromosomes: Tightly coiled strands of DNA Each chromosome contains genes Characteristics/traits passed down through generations The genes on a chromosome produce proteins This is how you see a trait!

What’s in a gene? sequences of nucleotide bases; passed down from parent to offspring These Genes code for polypeptides (proteins) All cells require proteins to function, thus they have many genes!

More about Proteins! Proteins are made of amino acids linked together by peptide bonds 20 different amino acids exist Amino acid chains are called polypeptides

From DNA to Proteins The major steps: Replication of DNA Transcribe to RNA Translate to Protein DNA is found in the nucleus of a cell RNA and proteins are found outside of the nucleus How does this happen?

Pathway to Making a Protein DNA mRNA tRNA (ribosomes) Protein

DNA  RNA  Protein Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein Nuclear membrane Transcription RNA Processing Translation DNA Pre-mRNA mRNA Ribosome Protein Eukaryotic Cell

16 Step 1: replication process of producing two identical replicas from one original DNA molecule First unzip Next copy Finally 2 identical strands

The strands separate 17 PO4 PO4

18 Each strand builds up its partner by adding the appropriate nucleotides PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 The nucleotides are present in the nucleoplasm. The nuclear equivalent of cytoplasm PO4 PO4 PO4 PO4 PO4

Review What is the copying of DNA into 2 strands called? How much of the strand created is new material?

Steps 2 and 3 Protein synthesis 2 main steps process by which the genetic code puts together proteins in the ribosomes 2 main steps Transcription Translation

Step 2: Transcription Double stranded DNA is unzipped One side is the template (pattern) and the other builds the mRNA mRNA= messenger RNA Carries genetic info to ribosmes This process happens in the nucleus

In-between Steps 2 and 3 Once the mRNA has been created it leaves the nucleus and heads to a ribosome

Step 3: Translation Now the mRNA is in the cytoplasm traveling to the ribosome Once there, it binds to a ribosome

The bases of the mRNA strand are read in sets of 3 Step 3: Translation The bases of the mRNA strand are read in sets of 3 A set of three is known as a codon/triplet Each codon will specify 1 of the 20 different amino acids

Step 3: Translation Once bound to the ribosome tRNA reads the codons on mRNA and transports the tRNA=transfer RNA The anticodons are connected to a specific amino acid

Step 3: Translation The ribosome connects the amino acids together into a chain called a polypeptide chain Polypeptides chains are just amino acids linked together. This is what makes a protein!

POP QUIZ!!!!!! Take out 1 sheet of paper Write your name Number 1-6

Question 1 Which of the following are components of nucleotides? (a) deoxyribose (b) amino acids (c) phosphate (d) enzymes (e) organic bases

Question 2 Which of the following represent a correct pairing of bases? (a) adenine with thymine (b) adenine with guanine (c) thymine with adenine (d) guanine with cytosine (e) thymine with thymine

Question 3 DNA molecules are formed from (a) organic bases (b) amino acids (c) deoxyribose (d) nucleotides

Question 4 Which of the following are nucleotide bases? (a) Valine (b) Guanine (c) Thymine (d) Serine

Question 5 Replication of DNA occurs (a) During cell division (b) before cell division (c) at any time

Question 6 A codon/triplet codes for (a) a protein (b) an amino acid (c) an enzyme (d) an organic base