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Powerpoint #1 Chapter 12 DNA Structure

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The building blocks of nucleic acids are nucleotides. One Nucleotide

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Nitrogen Base

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DNA is found in the nucleus of the cell

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DNAs function is to store and transmit genetic information.

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How did scientists determine the structure of DNA?

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A little background in what was discovered so far 1940s Oswald Avery and others determined that DNA stores and transmits genetic information

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1950 - Erwin Chargaff Noticed a pattern: Comparing ANY sample of DNA he discovered that the percentages of the nitrogen bases guanine(G) and cytosine(C) are equal. The same is true for the percentages of adenine(A) and thymine(T). CHARGAFFS RULE # A = # T # G = # C

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1951 The Structure (shape) of DNA It was a RACE - lots of competition USA Linus Pauling (Nobel prize - chemical bonds) London, England Rosalind Franklin and Maurice Wilkins were photographing the DNA molecule. England Cambridge University, James Watson and Francis Crick build models

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1952 - Rosalind Franklin X-ray crystallography Shine X-rays on crystalized DNA, bounce off see an image. Clues Order/pattern Equal width Born:1920 Died:1958 (Age 37)

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X-Ray crystallography

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1953 Watson and Crick With Franklin's and many other scientists data, Watson and Crick were soon able to determine the structure of DNA. On March 18, 1953, Watson and Crick published the first accurate model of the DNA molecule. DNA DOUBLE HELIX

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1960 Watson, Crick, and Wilkins received the Nobel prize for their work. Watson & Crick accepting Nobel Prize Franklin had died of cancer in 1958, at age 37. Would you award her a Nobel Prize?

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The four different nitrogen bases in DNA (for different types of DNA nucleotides) are: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T)

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A always pairs with T G always pairs with C The bases that pair with each other are called complimentary

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The code is read 3 bases at a time (4x4x4=64) and can be thousands or millions of base pairs long. (64 x 64 x 64 x 64.)

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A single DNA molecule may contain thousands of nucleotides (bases). The order of the nucleotides (bases) in a DNA is a code that provides instructions for making proteins.

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A segment of DNA that codes for a specific protein is called a gene. Genes code for traits such as: Hair color Eye Color How many fingers you have Skin color Enzymes to break down the food that you eat

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In your cells, DNA wraps up tightly around proteins called histones to produce a substance called chromatin which condenses during cell division (mitosis) to form structures called chromosomes

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Bases are either: Purines (A & G) a nine-member, 4 nitrogen molecule Pyrimidines (T & C) a six-member, 2 nitrogen molecule

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The bases hydrogen bond to each other at the locations to the right. Look for these donors and acceptors to determine where bonds are located

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G & C bond in three locations A & T bond in two locations

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Backbone made of sugar and phosphate Base Pairs: Adenine, Guanine, Cytosine, Thymine 1 Nucleotide