(SBI4U1) DNA Structure and Replication Flashcards
What does DNA stand for?
Deoxyribonucleic Acid
Where is DNA found?
Nucleus
What does DNA do? (2)
Contains hereditary information
Provides instructions for making proteins
Why are proteins important?
Needed to carry cellular processes
What is the monomer that makes a DNA polymer?
Nucleotides
What are the three parts of a nucleotide?
Phosphate
Pentose/ribose sugar (deoxyribose)
Nitrogen base
What are the 4 nitrogen bases?
Adenine
Guanine
Thymine
Cytosine
Identify the nitrogen base: A
Adenine
Identify the nitrogen base: G
Guanine
Identify the nitrogen base: T
Thymine
Identify the nitrogen base: C
Cytosine
Which two nitrogen bases are double rings?
Adenine and Guanine
Which two nitrogen bases are single ring?
Thymine and Cytosine
What are double ring nitrogen bases called?
Purines
What are single ring nitrogen bases called?
Pyrimidines
What is the main structural component of the DNA double helix?
The sugar-phosphate backbone
The 2 sugar-phosphate backbones are bonded to each other through their ________ _____ using _________ _______
Nitrogen bases
Hydrogen Bonding
A purine always pairs up with what?
Pyrimidine
Adenine (A) always binds to:
Thymine (T)
Cytosine (C) always binds to:
Guanine (G)
DNA exhibits _______________ base pairing
Complementary
The 5’ end of one sugar is connected to the _’ end of the next sugar by a __________ group
3
Phosphate
The sequence/order of nitrogen bases is always read in the _’ to _’ direction
5’
3’
The 2 sugar-phosphate strands are “_______” relative to each other in order to keep the nitrogen bases line up
What is this called?
Flipped
Antiparallel strands
The sugar phosphate strand on the left side runs _’ to _’
5’
3’
What are the three main differences between DNA and RNA?
The sugar molecule of DNA is missing an oxygen from carbon 2
The nitrogenous base in RNA is Uracil instead of Thymine in DNA
DNA is double stranded, whereas RNA is single stranded
When cells divide, ___ needs to be copied
DNA
What enzymes make the new DNA?
DNA polymerases
What is needed by DNA polymerases to build new DNA? (2)
Template strand
Primer
What is a primer? (2)
Short strands of RNA
Starting point where new nucleotides are added to the growing strand
DNA polymerases synthesize DNA in what direction?
5’ to 3’ direction
On on half of the DNA, the new strand is made as a continuous piece called:
Leading strand
On the other half of the DNA, the new strand is made in small pieces called:
Lagging strand
What enzyme breaks the hydrogen bonds between nitrogen bases during DNA replication?
Helicase
What stabilizes the single strands of DNA so that they don’t rejoin?
Single Stranded Binding (SSB) Proteins
Primers are a ________ point where new nucleotides are added to the _______ strand
Starting
Growing
New nucleotides are added by:
DNA polymerase III
Which end does the DNA polymerase III adds nucleotides?
Only adds nucleotides to the 3’ end of an existing DNA strand
What provides a 3’ end for DNA polymerase III to add to?
RNA primer
DNA polymerase III adds nucleotides in what direction?
5’ to 3’
On which strand can DNA polymerase add nucleotides continuously?
Leading strand
What are the short DNA segments added on the lagging strand called?
Okazaki Fragments
Why is there short DNA segments on the lagging strand? (2)
DNA can only be added in the 5’ to 3’ direction
The newly forming lagging strand runs 3’ to 5’
The primers of the lagging stand are _______ by what?
Removed
DNA polymerase I
What are Okazaki fragments joined together by?
DNA ligase
Once all RNA primers are removed, new DNA is left with _____ _____ ________ ____ that are _______
Short single stranded ends
Removed
What are the short single stranded ends that are removed called?
Telomers
As ________ shorten, the cell ages and eventually dies
Telomers
Why are telomers removed?
They are removed because the ends are noncoding regions
Is DNA replication perfect?
No
What can catch errors in base pairing? How does it deal with errors?
DNA polymerase I
Remove incorrect bases
