Life’s Instruction Manual of What Genes are Made Of DNA Life’s Instruction Manual of What Genes are Made Of

DNA (Deoxyribonucleic Acid) DNA Video

The Genetic Book of Life Genome: Book Chromosome: Chapter DNA Strands: Sentences Genes: words Base pairs: letters

Important Scientists in Cellular Biology Unit 6-DNA Structure and Replication

Introduction to DNA

Matthias Schleiden 1804–1881 Contributed to cell theory (All living things are composed of cells.); worked with Theodor Schwann; studied plant tissues and determined that plants are made of cells; also realized the importance of the cell’s nucleus and felt it might relate to cell division

Theodor Schwann 1810–1882 Contributed to cell theory (All living things are composed of cells.); worked with Matthias Schleiden; discovered “Schwann cells” in the nervous system; studied animal cells/tissues especially muscular and nervous tissues; considered the founder of histology

Rudolf (Rudolph) Virchow 1821–1902 Contributed to cell theory (All cells arise from existing cells.); considered father of pathology; was an advocate for public health; applied cell theory to the spread of diseases in the human body

Frederick Griffith & Oswald Avery Griffith did experiments trying to find a vaccine for pneumonia; he discovered that when harmless bacteria and a virulent (actively poisonous) bacteria were mixed some of the harmless bacteria became virulent, he called this transformation; Avery continued Griffith’s experiments and tried to find out what substance caused the transformation, he determined it was DNA that caused the transformation 1879–1941 1877–1955

Rosalind Franklin - X-ray photo of DNA. (1952)

Alfred Hershey & Martha Chase Conducted experiments (the “Hershey-Chase” experiments) to confirm the transformation principle; determined that DNA is the genetic molecule of inheritance not proteins. 1927–2003 1908–1977

Erwin Chargaff 1905–2002 A T Cytosine and Guanine always join together Adenine and Thymine always join together A T Cytosine and Guanine always join together C G

James Watson & Francis Crick Discovered the double-helix structure of DNA (with the help of previous X-ray diffraction experiments by Rosalind Franklin and Maurice Wilkins). animation 1916–2004 1928 - living

Watson & Crick proposed… DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule” DNA had specific pairing between the nitrogen bases: ADENINE – THYMINE CYTOSINE - GUANINE

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.}

The Double Helix Molecule The DNA double helix has two strands twisted together. We will take apart the DNA molecule to see how it is put together. First, we will look at one strand.

DNA DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell. Why is DNA called the blueprint of life?

What can DNA do? 1. Can replicate before cell division. 2. Can direct protein synthesis. It tells the RIBOSOME to make a protein.

Why do we study DNA? We study DNA for many reasons, e.g., 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.

Genetic material of cells… GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT Called NUCLEIC ACIDS DNA is made up of repeating molecules called NUCLEOTIDES

DNA Nucleotide O O=P-O N CH2 O C1 C4 C3 C2 Phosphate Group Nitrogenous base (A, G, C, or T) CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose)

One Strand of DNA deoxyribose bases The backbone of the molecule is alternating phosphates and deoxyribose sugar The teeth are nitrogenous bases. phosphate deoxyribose {Point to the 3-D mode, if you have one, to show the parts as you discuss them.} bases

Nucleotides Nitrogenous base Phosphate Deoxyribose One deoxyribose together with its phosphate and base make a nucleotide. Nitrogenous base {Ask students where they have seen a similar molecule before in this class. Answer: ATP . Emphasize that nucleotides are the basic building blocks or units of a DNA molecule and that a single molecule has many millions of nucleotides.} Phosphate Deoxyribose

One Strand of DNA One strand of DNA is a polymer of nucleotides. One strand of DNA has many millions of nucleotides. {Point to the 3-D mode, if you have one, to show the parts as you discuss them.}

Four nitrogenous bases DNA has four different bases: Cytosine C Thymine T Adenine A Guanine G These four bases are abbreviated by using their respective first letters.

Two Kinds of Bases in DNA Pyrimidines are single ring bases. Purines are double ring bases. N C O C C N C C N

Thymine and Cytosine are pyrimidines Thymine and cytosine each have one ring of carbon and nitrogen atoms. C N O cytosine C N O thymine

Adenine and Guanine are purines Adenine and guanine each have two rings of carbon and nitrogen atoms. C N O Guanine C N Adenine

Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. The teeth are the nitrogenous bases but why do they stick together? {Point to the 3-D model to show the parts as you discuss them.}

Hydrogen Bonds The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. The bonds between cytosine and guanine are shown here with dotted lines C N O

Hydrogen Bonds, cont. O C N When making hydrogen bonds, cytosine always pairs up with guanine Adenine always pairs up with thymine Adenine is bonded to thymine here

DNA by the Numbers The earth is 150 billion m or 93 million miles from Each cell has about 2 m of DNA. The average human has 75 trillion cells. The average human has enough DNA to go from the earth to the sun more than 400 times. DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun. If you unravel all the DNA in the chromosomes of one of your cells, it would stretch out 2 meters. If you did this to the DNA in all your cells, it would stretch from here to sun more than 400 hundred times!

DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone

DNA Double Helix P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A

Nitrogenous Bases PURINES 1. Adenine (A) 2. Guanine (G) PYRIMIDINES 3. Thymine (T) 4. Cytosine (C) A or G T or C

Chargaff’s Rule Adenine must pair with Thymine Guanine must pair with Cytosine Their amounts in a given DNA molecule will be about the same. T A G C

BASE-PAIRINGS C G H-bonds T A

Genetic Diversity… Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

The Code of Life… A T C G T A T G C G G… The “code” of the chromosome is the SPECIFIC ORDER that bases occur. A T C G T A T G C G G…

DNA is wrapped tightly around histones and coiled tightly to form chromosomes

DNA Replication video DNA Replication Animation DNA Animation

DNA Replication A-T, G-C DNA must be copied The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing: A-T, G-C Each strand of the original DNA serves as a template for the new strand

DNA Replication 1. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand. . DNA Template New DNA Parental DNA

1. Why is replication necessary? 2. Describe how replication works. Replication Quiz 1. Why is replication necessary? 2. Describe how replication works. 3. Use the complementary rule to create the complementary strand: A---? G---? C---? T---?

Replication Quiz 1. Why is replication necessary? So both new cells will have the correct DNA 2. Describe how replication works. Enzymes unzip DNA and complementary nucleotides join each original strand. 3. Use the complementary rule to create the complementary strand: A---T G---C C---G T---A

Animation Time… DNA replication animation take 2 DNA Replication Process

(1961) Watson & Crick proposed… …DNA controlled cell function by serving as a template for PROTEIN structure. 3 Nucleotides = a triplet or CODON (which code for a specific AMINO ACID) See p.303 AMINO ACIDS are the building blocks of proteins.

DNA Transcription DNA can “unzip” itself and RNA nucleotides match up to the DNA strand. Both DNA & RNA are formed from NUCLEOTIDES and are called NUCLEIC acids. See p.301

We will discuss details of this on a later date DNA Translation The cell uses information from “messenger” RNA to produce proteins See p.304-305 We will discuss details of this on a later date

Transcription/Translation Quiz Why is transcription necessary? Describe transcription. Why is translation necessary? Describe translation. What are the main differences between DNA and RNA. Using the chart in your journal, identify the amino acids coded for by these codons: UGGCAGUGC

1. Why is transcription necessary? Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm. 2. Describe transcription. RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA. 3. Why is translation necessary? Translation assures that the right amino acids are joined together by peptides to form the correct protein.

4. Describe translation. The cell uses information from MRNA to produce proteins. 5. What are the main differences between DNA and RNA. DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil. Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGC tryptophan-glutamine-cysteine

(a library of about 1,000 books) AMAZING DNA FACTS… DNA from a single human cell extends in a single thread for almost 2 meters long!!! It contains information equal to some 600,000 printed pages of 500 words each!!! (a library of about 1,000 books)

LET’S REVIEW DNA… Summarize the relationship between genes & DNA. Describe the overall structure of the DNA molecule. What are the 4 kinds of bases?