Chapter 14 DNA The Genetic Material Flashcards
Functions of DNA
-Long-term storage of genetic information
- Gene: Section of DNA with a specific function (look at notes)
-Chromosome: Long double helix of DNA organized around proteins
-Genome: All of the genetic material (chromosomes) in an organism
Nucleotide Composition
Nucleotide Base: Monomer of nucleic acids, Variants: A, T, C, or G
Components of a nucleotide: 5’ carbon of sugar, Phosphate group, Nitrogenous Base: Purine and Pyramidine
Primary Structure of DNA
The sequence of nucleotides, nucleotides linked by Covalent (phosphodiester) bonds
1. Phosphate group links 3’ carbon of sugar
2. Creates sugar-phosphate backbone
Directionality
5’—>3’
a. Nucleotide bases always added to 3’ end
Secondary Structure
Double helix of two DNA strands
Nucleotide Pairing
Base pairing: Apairs with T; C pairs with G
Called Chargaff’s rule
Antiparallel Configuration
-Strands in a double helix are complementary strands result from base pairing-if you know one, you know the other
- Strands are antiparallel- the run in opposite directions
Purpose of Replication
-To copy/synthesis to make
-Purpose: Prepare for cell division by making a copy of genome
Copied chromosomes
Held together by a centromere (revisit in cell division)
Polymerization Reaction
-Polymerization via dehydration reactions
-Requires Energy: Endergonic reaction, Anabolic reaction (look through notes)
Semi Conservative
Each new chromosome contains one original DNA strandand one new DNA strand
Origin of replication
Prokaryotes: One origin of replication
Eukaryotes: Many origins per chromosome
DNA unwinds from the origin of replication to form a
replication bubble
Two Key enzymes of the replisome
Primase and DNA polymerase
Primase
- Adds RNAprimers: Starting nucleotide sequence
- RNA primers give DNA polymerase a place to start
DNA Polymerase
a. Main replication enzymes
b. Adds nucleotides basses in 5’ to 3’ direction
c. That is, always add to 3’ OH
d. RNA primer provides starting 3’OH
DNA replication Direction
5’ to 3’ direction
Leading Strand
Built continuously towards replication fork
Lagging Strand
Built discontinuously (in sections) AWAY from the replication fork
Sections are called
Okazaki fragments
Linear chromosome replication issue
Unable to Synthesize lagging strand to the end
Solution to Issue
Add extra non-coding DNA (telomeres) to end
Telomeres added by
Enzyme telomerase
Telomere only occurs in
Gametes, stem cells, and Cancer cells
