Ask Me Everything3

Blasts from the past

What is DNA?

The nucleus of a body celi contains the instructions to make the proteins that determine how that celi functions and what your body looks like. These instructions, or genes, are carried on structures called chromosomes, which are madę from deoxyribonucleic acid, or DNA.

1866

German priest and scientist Gregor Mendel publishes his results of experiments on the laws of inheritance, confirming that genes come in pairs, with one inherited from each parent

1869

Swiss biologist Johannes Friedrich Miescher identifies a substance in the nucleus of white blood cells, which is later called deoxyribonucleic acid (DNA)

1910

U.S. scientist Thomas Hunt Morgan studies genetic variations in fruit flies and confirms that genes are carried on chromosomes

1944

Canadian and American scientists Oswald Avery,

Colin MacLeod, and Maclyn McCarty prove that genes are madę of DNA

1952

British physicist Rosalind Franklin produces an image of a DNA molecule using x-ray diffraction

1953

Briton Francis Crick and American James Watson use Franklin’s DNA image and earlier research to figurę out the double helix structure of DNA

1972

U.S. scientist Paul Berg successfully cuts and splices DNA to create the first genetically engineered strand of DNA

1984

Danish scientist Steen Willadsen sucessfully clones a sheep from embryo cells

2003

The international Fluman Genome Project team announce the completion of the human genome sequence

2009

A German Shepherd search and rescue police dog, who rescued the last person alive following the attacks in New York on 9/11, is cloned to create five puppies

Counting

chromosomes

Each body celi has 46 chromosomes in 23 pairs. One chromosome from each pair is inherited from your mother and one from your father. One pair of chromosomes determines your gender. Two “X”s makes a girl, and "XY” makes a boy.

Tell me morę:

DNA structure

h DNA is shaped like a * double helix, or twisted ladder, madę up of two linked strands.

■ The two DNA strands are joined by “rungs” madę up of paired Chemicals, called bases, that provide the “letters” of the instructions in genes.

■ There are four bases: adenine (A),

thymine (T), guanine (G), and cytosine (C).

■ A is always paired with a T and every C with a G.

(c) 2011 Dorling Kindersley. Ali

i the DNA lust °^ne T

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Cytosine (C)

Adenine (A)

Guanine (G)

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Thymine (T)

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