DNA structure and replication Flashcards
DNA monomers
nucleotides
3 parts of a nucleotide
(deoxyribose) sugar, phosphate group, nitrogenous base
shapes of the parts of nucleotides
sugar- central pentagon, phosphate group-circle, nitrogenous base- hexagon/shape with letter in it
4 types of nitrogenous bases
adenine(A),thymine(T),guanine(G), and cytosine (C)
what holds the 2 strands together
hydrogen bonds between nitrogenous bases
what part of the structure makes up the backbone
sugar and phosphate groups (covalently bonded)
what part of the structure makes up the interior
nitrogenous bases w/ hydrogen bonds between complementary bases
state the base pairing rule and why these bases pair up
Adenine pairs with thymine and guanine pairs with cytosine because pyrimidines (single ring T&C) pairs with a purine (double ring A&G) resulting in helix being 3 rings wide
Which scientists work helped confirm the above as the base pairs? Explain.
Watson and Crick’s discovery was based off of the work of Rosalind Franklin and Erin Chargaff
What is the purpose of DNA replication ?
purpose- to create exact copies of cell’s DNA before it divides which is crucial for growth and repair
Why is DNA replication necessary
if there is no DNA replication cells won’t have the necessary instructions to function properly
Where within a eukaryotic cell does it take place?
in the nucleus
Overall process of replication - describe the steps
- Helicase unzips the double helix in multiple places by breaking hydrogen bonds in both directions and exposes both strands, 2. Free floating nucleutides form hydrogen bonds w/ exposed bases on template strand, 3. DNA polymerase enzyme catalyzes the synthesis of DNA by covalently bonding the free floating nucleotides to each other in the new strand, 4. End result- 2 new identical DNA molecules
What is the difference between the leading and lagging strand?
Leading- built continuously in the 5’-3’ direction toward the replication fork, uses the 3’-5’ og strand as template, lagging- built in okazaki fragments that are added toward the fork, but built away from fork, uses Og 5’-3’ strand as template, fragments are joined together by ligase
Why is there a difference of leading and lagging?
The strands being antiparallel mean that the new strands must be antiparallel to them, resulting in difference in direction as it must always be built from 5’-3’
What is the end result of replication ?
2 new identical DNA molecules
Which enzymes are involved in rep and what do they do, be specific?
Helicase- unzips double helix in both directions, DNA polymerase- find and correct errors, catalyzes synthesis of DNA by covalently bonding the new nucleotides to each other in the new strand, ligase-joins okazaki fragments together
When within the cell cycle does replication take place ?
S phase of interphase
Why is it important that replication takes place at that time ( s phase)
Ensures that each new cell created during cell division receives a complete copy of genetic material for its function
