DNA The molecule of heredity.

• The molecules of DNA is the information for life (determine an organism’s traits)

• DNA achieves its control by determining the structure of proteins.

DNA

•Deoxyribonucleic Acid

• nucleotides are the building blocks of nucleic acid

The Structure of Nucleotide

• DNA is made of repeating subunits called nucleotides.

• Nucleotide – – Simple sugar– Phosphate group – Nitrogenous base

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Phosphate group

Sugar

Nitrogenous base

•The simple sugar in DNA is called deoxyribose which gives DNA its name

• In DNA, there are four possible nitrogenous bases:

–adenine (A)

–guanine (G)

–cytosine (C)

–thymine (T).

•Nucleotides join together to form long chains

–the phosphate group of one nucleotide bonds to the sugar of an adjacent nucleotide(they form the backbone of the chain)

•the nitrogenous bases stick out like the teeth of a zipper.

• The DNA molecule is a double helix. It contains two strands of nucleotides, in a spiral shape– Sugar- phosphate chains on the outside

with the nucleotides in the inside.– The nucleotides held together by H bonds

between A and T, and also between G and C. (Base Pairs)

•The sequence of nucleotides on one strand is matched perfectly to a complementary sequence on the other strand.

•In DNA, the amount of A = amount of T, and the amount of G = amount of C.

The importance of nucleotide sequences

• The sequence of nucleotides forms the unique genetic information of an organism.

• The closer the relationship is between organisms, the more similar their DNA nucleotide sequences will be.

DNA Replication

Process where DNA copies itself

• Separation of strands – bonds are broken

between complementary base pairs

• base pairing– The bases of free

nucleotides pair with the bases of the original DNA strands

– Each strand builds a complementary strand

• Results of DNA replication– 2 DNA molecules– Each consists of an original strand of

nucleotides and a new strand

• Errors sometime do occur

• The wrong nucleotide is added to the new strand

• A protein (enzyme) that proofreads the new DNA strand and corrects the mistake

• http://www.lewport.wnyric.org/JWANAMAKER/animations/DNA%20Replication%20-%20long%20.html

• http://science.nhmccd.edu/biol/bio1int.htm