DNA Structure and Replication Flashcards
Concept 1 (25 cards)
Nucleic Acids
macromolecule that holds our genetic material
Genes
sections of DNA that serve as instructions for making proteins (located on ribosome)
Proteins carry out all _____ activity
cellular
Two types of Nucleic Acids:
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
Nucleotides
monomer of Nucleic acids
3 parts of a nucleotide
-Phosphate
-Sugar (DNA/RNA)
-Nitrogen Base (Adenine, Guanine, Cytosine, Thymine (DNA only), Uracil (RNA only)
DNA structure
Double helix:
-Sugar/ phosphate form “sugar-phosphate backbone”
-Nitrogen bases bond in middle with weak hydrogen bonds
-All other bonds are strong covalent
DNA Structure was discovered by:
James Watson and Francis Crick in 1953
Nitrogen Bases (2 Types)
-weak hydrogen bond to their Complementary Base Pair
-A with T (double bond)
-C with G (triple bond)
Purines
Adenine, Guanine
Pyrimidines
Cytosine, Thymine
DNA is ____parallel
Antiparallel
Antiparallel
the strands run in opposite directions (antiparallel) directions
-1st strand in 5’ to 3’ direction
2nd strand in 3’ to 5’ direction
-Phosphate end is the 5’ end
-Deoxyribose sugar is the 3’ end
RNA Structure
single strand of nucleotides with exposed bases
-RNA bases bond with DNA bases
-A binds with U
-C binds with G
DNA Replication
when cell is ready to divide, it needs to copy its DNA
-happens in nucleus
-during S phase of Interphase
Step 1: DNA Replication
Enzyme Helicase unzips the DNA into 2 strands
-several “Origins of Replication” will be unzipped at once
Step 2: DNA Replication
Enzyme DNA Polymerase adds complementary nucleotides to the template strands (A-T, C-G)
-Only adds nucleotides to the free 3’ end of strand. This forms new DNA in the 5’-3’ direction ONLY
What does Enzyme PRIMASE do in Step 2 of DNA Replication
-required for synthesis
-like a “key” for car ignition
-makes RNA primers
What does enzyme DNA POLYMERASE do in Step 2 of DNA Replication
1: adds nucleotides to RNA primer- makes polynucleotides
2: removes RNA primer and replaces it with DNA
3: Proofreads the strand before backbone is finished
What does Enzyme DNA LIGASE do in Step 2 of DNA Replication
-“seals” gaps in DNA (okazaki fragments)
-connects DNA by making phosphodiester bonds
Leading Strand
-made toward Replication fork (in 5’-3’ direction from 3’-5’ strand
-needs ONE RNA primer
-made continuously
Lagging Strand
-made away from Replication fork
-made discontinuously (makes Okazaki fragments)
-needs MANY RNA primers
Step 3: DNA Replication
Two identical DNA molecules formed, with one “old” strand and one “new” strand. (Semi-Conservative Replication)
Semi-Conservative Replication
each parent strand is now a template that determines the order of the new bases
-forms “complementary” strand to original strand
-new double helix is a combo of one “old” and one “new” strand
