DNA Flashcards
Function of DNA
DNA = Deoxyribonucleic Acid
Function : Carries genetic information
What are nucleotides?
Nitrogen containing organic substances that form the basis of the nucleic acids, DNA and RNA
What 3 groups do nucleotides contain?
A phosphate group (circle)
A pentose sugar (deoxyribose in DNA & ribose in RNA)
An organic base = a nitrogen containing base (Adenine,Thymine,Cytosine,Guanine)
What is the structure of DNA
- ## Polymer of deoxyribose-nucleotides
How are polynucleotides formed?
-Nucleotides join from a condensation reaction
-This forms phosphodiester bonds between the pentose sugar (deoxyribose) of one nucleotide and the phosphate group of the next
- Sugar phosphate backbone with the bases projecting outwards
What is a joined DNA strand?
Double stranded DNA molecule
Bases join to bases on opposite strand
Bases linked by hydrogen bonds
Strands in opposite directions
One nucleotide joined to an upside down nucleotide
What are the 4 nitrogen containing bases?
Adenine
Thymine
Cytosine
Guanine
Base Pairing
2 polynucleotide chains coil around eachother forming a double helix
- Held together by hydrogen bonds between opposite bases called base pairs
- Base pairs A-T , C-G
Hydrogen bonds of bases
Adenine and Thymine bond with 2 hydrogen bonds : A-T 2
Cytosine and Guanine bond with 3 hydrogen bonds :
What are the Monomer/Polymer of DNA?
Monomer - Nucleotide
Polymer - DNA
What are phosphodiester bonds/where are they found ?
Bonds between the pentose sugar of one nucleotide and the phosphate group of the next
What do phosphodiester bonds do?
They hold the sugar-phosphate backbone together
What are the structures of DNA?
Long
Helical
Double stranded
Hydrogen bonds
Sequences of bases
Sugar phosphate backbone
What is the function of DNA being long and helical?
Long = It can store lots of information
Helical = Compact
What is the function of DNA being double stranded?
- Protects the bases
- Increases stability
- Each strand acts as a template for DNA replication
What is the function of the sugar phosphate backbone and double helix?
Provides strength, stability and protects bases and weak hydrogen bonds
What is the function of sequences of bases?
Codes for specific amino acid sequences
- Unique to each organism
What is the function of hydrogen bonds?
Many hydrogen bonds make the molecule stable
Suitable in DNA replication as they are easily broke
What enzymes are needed in DNA replication
DNA Helicase
DNA Polymerase
What is the function of DNA helicase?
Unwinding DNA and breaking hydrogen bonds between bases
- This is so nucleotides can attach and each strand can act as a template
What is the function of DNA polymerase?
-Joins adjacent nucleotides
-Forms phosphodiester bonds along the sugar phosphate backbone
DNA Replication Steps
1) DNA helicase breaks hydrogen bonds between base pairs
- strands separate —> 2 templates
2) Free nucleotides attach to complementary bases on each template strand by hydrogen bonds
3) DNA polymerase joins the sugar phosphate backbone of the new strand
4) 2 identical DNA molecules are formed
- each new DNA molecule consists of 1
old + 1 new strand
