DNA These “genes” never go out of style!! Ms. Kooiman La Serna High School

Chapter 12-1 Vocabulary Nucleus Structure found at the center of eukaryotic cells. Contains genetic information. DNA Deoxyribonucleic acid Chromosomes Threadlike structures found within the nucleus containing genetic information passed on from one generation to the next. Chromatid Tightly coiled or condensed DNA wrapped around proteins. Centromere Area where chromatids of a chromosome are attached. Gene Sequence of DNA located on the chromosomes. A set of codes that determine which protein will be made.

Scientific History 1928 – Griffith and Transformation 1928 – Griffith and Transformation – –The early experiments told scientists that cells contain some substance that allows traits to be passed from one generation to the next 1944 – Avery and DNA 1944 – Avery and DNA –Later experiments showed that substance was DNA

Scientific History 1952 – Hershey-Chase Experiment 1952 – Hershey-Chase Experiment 1952 – Rosalind Franklin 1952 – Rosalind Franklin 1953 – James Watson and Francis Crick 1953 – James Watson and Francis Crick –Experiments beginning in the 1950’s focused on the structure of DNA 2000 – Human Genome Project 2000 – Human Genome Project –Research still continues today to further understand and map out the each gene found on the human genome!

DNA Structure DNA - Deoxyribonucleic acid DNA - Deoxyribonucleic acid A molecule that enables organisms to reproduce their genetic information to the next generation. A molecule that enables organisms to reproduce their genetic information to the next generation. Contains thousands of genes (unit of inheritance) Contains thousands of genes (unit of inheritance) DNA contains information which is translated into proteins that carry out most biological functions. DNA contains information which is translated into proteins that carry out most biological functions.

DNA Structure DNA is a macromolecule DNA is a macromolecule –Nucleic Acid – made up of long chains of nucleotides –Nucleotides are made of 3 parts  Sugar (5 carbon deoxyribose)  Phosphate group  Nitrogen base

DNA Structure cont….. Nucleotides can have four different nitrogen bases C = Cytosine T = Thymine A = Adenine G = Guanine

DNA Structure cont….. Nucleotides are held together with a phosphate-sugar backbone Nucleotides are held together with a phosphate-sugar backbone

DNA Structure cont….. DNA is double-stranded DNA is double-stranded Nitrogen bases link up and attach with hydrogen bonds Nitrogen bases link up and attach with hydrogen bonds

Chargaff’s Rules Adenine = Thymine and Cytosine =Guanine So…..when 2 strands of DNA bond A pairs with T and C pairs with G These are called “complimentary base pairs”

The Double Helix DNA has a “Double Helix” structure DNA has a “Double Helix” structure –Two strands wrap together like a twisted ladder or winding staircase

The Double Helix

Rosalind Franklin  Used X-ray diffraction to help find the structure of DNA  Purified large amounts of DNA and stretched the out the parallel strands  Aimed a powerful X-ray beam and recorded the pattern on film  See example of data below…. Major contribution…….X-ray showed the helical structure of DNA!!

Dr. Franklin was educated as a physical chemist. She made major research breakthroughs in the understanding of the double-helix structure of DNA (deoxyribonucleic acid), the building block of life or the genetic material of living organisms. Apparently without her knowledge or permission, Maurice Wilkins shared some of Dr. Franklin’s data with James Watson and Francis Crick. Watson, Crick and Wilkins later shared the Nobel Prize for Physiology or Medicine in 1962 for their discovery of the structure of DNA. Although this discovery was due in part to Dr. Franklin’s work, she never received any of the credit. Watson, Crick and Wilkins Rosalind Elise Franklin Rosalind Elise Franklin, Ph.D.,

Francis Crick and James Watson Were also working on finding the structure of DNA through cardboard models Were also working on finding the structure of DNA through cardboard models 1953, given Franklin’s X-ray information 1953, given Franklin’s X-ray information Published findings in a historic one-page paper explaining that DNA was a double-helix in which two strands of DNA were wound around each other. Published findings in a historic one-page paper explaining that DNA was a double-helix in which two strands of DNA were wound around each other. Once this was discovered they explained the base-pairing which explained Chargaff’s rules!! Once this was discovered they explained the base-pairing which explained Chargaff’s rules!!

DNA Summary Many scientists worked for many years to determine the structure of DNA, this is what they found Many scientists worked for many years to determine the structure of DNA, this is what they found –DNA is a made up of nucleotides –Nucleotides are connected by a phosphate- sugar backbone –DNA is double-stranded helix –Complimentary nitrogen bases bond to link two strands of DNA