Bio Boarding
Unit 2 Review/ Notes
DNA
Draw a nucleotide
Include: Phosphate, Sugar, and Nitrogen base!
What are the building blocks of DNA
and RNA?
Nucleotides!!!
What are the four DNA bases?
Adenine
Guanine
Thymine
Cytosine
Which bases pair with which?
What are these base pairings referred to as?
Complimentary base pairs
How many Hydrogen Bonds do A&T
have between them? C&G?
A&T = 2 h-bonds
C&G = 3 h-bonds
Which bases have
stronger Hydrogen
bonding between
them?
C&G!!!
If DNA is a ladder, what are the sides?
Alternating Sugar and Phosphate molecules!
What are the rungs?
Nitrogen bases!
Which fragment is the smallest?
What does the BRCA gene do?
Regulate cell cycle (it’s a tumor
suppressor gene)
What would happen if the BRCA
gene was missing?
Increased risk for person to get
cancer
An example of a carcinogen is cigarette
smoke. Why are carcinogens bad for
us?
Carcinogens are chemicals that cause mutations
that lead to cancer
Mitosis
Why do we need mitosis? (why do we
need our body cells to divide?)
• Growth
• Repair damaged cells
• Replace old cells
Draw the phases of Mitosis in order!
During prophase, what happens so we
can see the DNA?
DNA coils or condenses into chromosomes
What pulls the sister chromatids apart
during anaphase?
Spindle fibers!
What would happen if one broke during
mitosis?
DNA wouldn’t be evenly distributed between
daughter cells…one would have too much one
would have too little
What is the longest phase of the cell
cycle?
Interphase – where the cell is hanging out and
doing its job!
What happens at each checkpoint?
G1 checkpoint: Checks for damaged
DNA before Synthesis phase (doesn’t
want to copy bad DNA!)
G2 checkpoint: (after DNA is copied)
Prevents mutated DNA from going
into mitosis
Mitosis checkpoint: Checks spindle
fibers from metaphase to anaphase.
Makes sure the right amount of DNA
gets to each cell!
PCR
What is PCR?
Polymerase chain reaction and it’s used to make
copies of DNA (like a DNA photocopier)
Think about why we would need to be able to
do this…
What is the purpose of the helicase
enzyme?
Break H-Bonds to “unzip” the DNA
How would you describe the
difference between the DNA in bands
A and B?
Gene B is the same as
A, but there are
more copies of the
gene in band B
making it show up
as a thicker and
brighter band!
What are the enzymes that perform
DNA replication and what are their
roles?
Helicase – breaks hydrogen bonds
between base pairs to unzip DNA
DNA Polymerase – adds new
nucleotides to a strand of DNA
Ligase – reforms sugar & phosphate
backbone