DNA: The Blueprint of Life
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Presentation Transcript
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 BiologyUnit 6-DNA Structure and Replication
Matthias Schleiden1804–1881 • 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 Schwann1810–1882 • 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) Virchow1821–1902 • 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
1877–1955 Frederick Griffith & Oswald Avery 1879–1941 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
(1952) Rosalind Franklin - X-ray photo of DNA.
1927–2003 Alfred Hershey & Martha Chase 1908–1977 Conducted experiments (the “Hershey-Chase” experiments) to confirm the transformation principle; determined that DNA is the genetic molecule of inheritance not proteins.
Erwin Chargaff1905–2002 • Adenine and Thymine always join together • A T • Cytosine and Guanine always join together • C G
1916–2004 James Watson &Francis Crick 1928 - living Discovered the double-helix structure of DNA (with the help of previous X-ray diffraction experiments by Rosalind Franklin and Maurice Wilkins). animation
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.
The Double Helix Molecule • The DNA double helix has two strands twisted together.
DNA • DNA is often called the blueprint of life. • In simple terms, DNA contains the instructions for making proteins within the cell.
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.
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
Phosphate Group O O=P-O O 5 CH2 O N Nitrogenous base (A, G, C, or T) C1 C4 Sugar (deoxyribose) C3 C2 DNA Nucleotide
One Strand of DNA phosphate • The backbone of the molecule is alternating phosphates and deoxyribose sugar • The teeth are nitrogenousbases. deoxyribose bases
Nucleotides Nitrogenous base One deoxyribose together with its phosphate and base make a nucleotide. Phosphate Deoxyribose
One Strand of DNA nucleotide • One strand of DNA is a polymer of nucleotides. • One strand of DNA has many millions of nucleotides.
Four nitrogenous bases • Cytosine C • Thymine T • Adenine A • Guanine G DNA has four different bases:
N N C N C C C N N C Two Kinds of Bases in DNA • Pyrimidines are single ring bases. • Purines are double ring bases. N N C O C C N C
N O N N C C O C C O C C C N C N C thymine cytosine Thymine and Cytosine are pyrimidines • Thymine and cytosine each have one ring of carbon and nitrogen atoms.
O N N N C C N C C C C N N N C N C C Guanine Adenine C N N Adenine and Guanine are purines • Adenine and guanine each have two rings of carbon and nitrogen atoms.
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?
O N C N N C C C N N C N N C O C C N C 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
O N C O C C C N C N N C C C N N C C N Hydrogen Bonds, cont. • When making hydrogen bonds, cytosine always pairs up with guanine • Adenine always pairs up with thymine • Adenine is bonded to thymine here
The earth is 150 billion m or 93 million miles from the sun. DNA by the Numbers • 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.
“Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone DNA Double Helix
5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 2 1 3 5 O P P T A 3 5 O O 5 P P 3 DNA Double Helix
A or G T or C Nitrogenous Bases • PURINES 1. Adenine (A) 2. Guanine (G) • PYRIMIDINES 3. Thymine (T) 4. Cytosine (C)
C T A G Chargaff’s Rule • Adeninemust pair with Thymine • Guanine must pair with Cytosine • Their amounts in a given DNA molecule will be about the same.
H-bonds G C A T BASE-PAIRINGS
Genetic Diversity… • Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.
The Code of Life… • 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 • 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 Template Parental DNA New DNA DNA Replication 1.Watson and Crick showed: the two strands of the parental moleculeseparate, and each functions as a template for synthesis of a new complementary strand. .
