chapter 3- sec 1 what is dna? life science. dna what does dna stand for? deoxyribonucleic acid !!!...

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.

Thieves?

Watson

Crick

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

A molecule of DNA is formed by millions of nucleotides joined together in a long chain

PO4

PO4

PO4

PO4

sugar-phosphate backbone

+ bases

Joined nucleotides 7

What does ATCG stand for???

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.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.

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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!