DNA Structure and Replication

Honors Biology2013

DNA

• Deoxyribonucleic acid– Genes are composed of this material– Instructions for the cell on how to make proteins– Double helix structure ( figured out by James

Watson and Francis Crick through Rosalind Franklin’s x-ray crystallography)

– Nucleic acid• What are the monomers of nucleic acids???

DNA

• Deoxyribonucleic acid– Genes are composed of this material– Instructions for the cell on how to make proteins– Double helix structure ( figured out by James

Watson and Francis Crick through Rosalind Franklin’s x-ray crystallography)

– Nucleic acid• What are the monomers of nucleic acids???

• Nucleotides!

DNA

• DNA is made up of nucleotides– A nucleotide consists of 3 parts• A 5 carbon sugar (deoxyribose)• A phosphate group• A nitrogenous base

– Two types» Purines (adenine and guanine) have two rings» Pyrimadines (thymine and cytosine) have one ring

DNA

• DNA has two sugar-phosphate strands that are the backbone and the nitrogenous bases make up the “rungs” of the ladder

DNA

• Chargaff’s Rule- there are similar percentages of adenine and thymine, and cytosine and guanine.

• This is because adenine binds to thymine and cytosine binds to guanine through hydrogen bonding---This is called base-pairing.

• Adenine to Thymine has 2 hydrogen bonds between them

• Cytosine to Guanine has 3 hydrogen bonds between them.

What would be the order of the other side of this DNA molecule??

AAGCTACC

A-TA-TG-CC-GT-AA-TC-GC-G

DNA

• The order of nitrogenous bases in DNA determines the order of amino acids in a protein.

DNA Replication

• Prokaryotic DNA is found in their cytoplasm• Eukaryotic DNA is found in the nucleaus of the

cell.• When a cell divides, it must make an exact

copy of its DNA so both cells have complete sets.

• This happens in the S phase of interphase of the cell cycle.

DNA Replication

• During replication, DNA double helix is separated.

• Each strand acts as a template and produces two new complementary strands.

DNA Replication

• Replication begins at sites on the DNA molecule called origins of replication.

• Helicase unwinds the DNA molecule to produce two separate strands.

• Primase makes a short strand of RNA that is used to start synthesis of the complementary strand.

• DNA polymerase adds new nucleotides to the new strand.

• Nuclease checks and repairs the DNA for damage or mutations.

DNA Replication videos

http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter3/animation__dna_replication__quiz_1_.htmlhttp://www.dnatube.com/video/335/Animated-DNA-Replication