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Chapter 3- Sec 1 What is DNA?. Life Science. DNA. What does DNA stand for? Deoxyribonucleic Acid !!! De/oxy/ribo/nucleic Acid Deoxyribonucleic Acid , or DNA, is a code that contains information that an organism needs to grow and function. Discovering DNA.
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Chapter 3- Sec 1What is DNA? Life Science
DNA • What does DNA stand for? • Deoxyribonucleic Acid !!! • De/oxy/ribo/nucleic Acid • Deoxyribonucleic Acid, or DNA, is a code that contains information that an organism needs to grow and function.
Discovering DNA • In 1952, Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form. • Used X-Rays
In 1953, James Watson and Francis Crick created an accurate model of DNA. • Model was similar to a ladder • The structure of DNA is similar to a twisted ladder. Crick Thieves? Watson
The structure of DNA is a similar to a twisted ladder (double helix)…
DNA Structure • The structure of the “Ladder”… • The sides of the ladder are made up of Deoxyribose (sugar) and Phosphate. • The rungs (or steps) of the ladder are made up of nitrogen bases (ATCG).
The steps of the ladder are made of pairs of smaller molecules called Nitrogen Bases. • These bases “fit together” in the combination: • Adenine fits with Thymine • Cytosine fits with Guanine • Connected by a Hydrogen bond
Joined nucleotides PO4 PO4 PO4 PO4 sugar-phosphate backbone + bases 7 A molecule of DNA is formed by millions of nucleotides joined together in a long chain
DNA Replication • When a cell divides, the DNA “code” is copied (or duplicated) and passed to the new cells. • The DNA duplicates itself by unwinding and separating the bases forming 2 strands.
http://www.hhmi.org/biointeractive/media/DNAi_replication_vo1-lg.movhttp://www.hhmi.org/biointeractive/media/DNAi_replication_vo1-lg.mov
DNA makes up chromosomes • Each chromosome is composed of a long strand of DNA wrapped around. • Human Body cells have 46 chromosomes or 23 pairs. <stop here>
How many chromosomes are in other living things? • Toucan – 104 • Goldfish – 94 • Dogs – 78 chromosomes • Horse- 64 • Banana- 22 chromosomes • Jack Jumper Ant- only 2 chromosomes!