Exam 2
What are nucletides made of?
-deoxyribose sugar -3 phosphate groups on the 5' carbon -nitrogenous base (A,T,G,C) on the 1' carbon -free -OH group on 3' carbon
How many amino acids are used to make proteins?
20 amino acids
primer
A short segment of DNA that acts as the starting point for a new strand; made by RNA primase
What is the source of energy for DNA synthesis
All 4 deoxynucleotides (dATP, dCTP, dGTP, dTTP)
How to coordinate rates of replication at the fork?
As each new primer for an Okazaki fragment is synthesized, the lagging strand forms a loop that persists until the new lagging strand encounters the previous Okazaki fragment.
Mitochondria contain their own double-stranded, circular DNA and replicate on their own. Why don't they suffer the same consequences as our cells in terms of limited division?
Because mitochondrial DNA is circular, it doesn't shorten when it replicates.
Which of the following is true regarding DNA replication?
Both strands get shortened at opposite ends during replication.
How does DNA Polymerase get started?
DNA Polymerase needs: Template strand Free 3' end of the new strand Four kinds of dNTPs Each DNA Polymerase complex contains a special RNA polymerase called Primase that makes short primers of RNA, 18-22 bases long. DNA polymerase then adds dNTPs to the 3' end of the RNA primer.
_____ requires both a template and a free 3′ end to elongate a nucleotide chain.
DNA polymerase
Why are primers needed for DNA replication?
DNA polymerase can only add nucleotides to an existing chain.
proofreading
DNA polymerase checks base pairs and corrects their errors
Which of the following statements is true regarding chromosome replication in eukaryotes?
During chromosome replication, multiple origins of replication form for all DNA in a cell.
In the absence of the enzyme primase, only the leading strand of DNA would be replicated. (True/False)
False; DNA polymerase always needs a primer, even on the leading strand
____ moves outward from the origin of replication and breaks hydrogen bonds between DNA nucleotides.
Helicase
hydrophobic amino acids
Hydrophobic amino acids tend to avoid water These will frequently be found folded into the interior of protein rings and CH3 at the tips
Imagine that a doctor is culturing cells from a malignant melanoma and from a normal skin sample. How would you expect these two cell populations to differ?
Malignant melanoma cells would have active telomerases that constantly replenish and lengthen telomeres
Who conducted classic experiments to determine that DNA replication is semi-conservative?
Mathew Meselson and Franklin Stahl; they did this by utilizing 2 forms of nitrogen to distinguish between the old (N-15) and new strand (N-14)
basic amino acids
Positively charged NH group
difference between prokaryotes and eukaryotes cell division
Prokaryotes: one circular chromosome one origin of replication Eukaryotes: several linear chromosomes tens of thousands of origins
What differentiates amino acids?
R group The peptide backbone is the same for all the amino acids (+H2N-CH-COO-)
_____ is the first enzyme to synthesize a nucleic acid at a replication fork. Please choose the correct answer from the following choices, and then select the submit answer button.
RNA primase
cysteine
SH group can form covalent 'disulfide bonds' with other cysteines
Which of the following statements is true regarding telomeres?
Telomeres can contain repeated base sequences.
template strand
The DNA strand that serves as a model for ordering the sequence of nucleotides in an mRNA transcript.
What would happen if telomerase stopped working in a cell in which it normally functions at high levels?
The cell would eventually die as the DNA continued to shorten
DNA polymerization
The enzyme DNA polymerase makes a copy of a strand of DNA by adding nucleotides to the 3' end of an adjacent but incomplete polynucleotide chain.
leading strand
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.
lagging strand
The strand that is synthesized in discontinuous smaller fragments using individual sections called Okazaki fragments
Why are telomeres a necessary component of linear chromosomes?
They maintain the length of a chromosome because DNA is shortened every time it is replicated.
what are the subgroups of hydrophilic amino acids?
Three sub-groups: Polar Basic Acidic
____ relieves the tension on the double helix during DNA replication. Please choose the correct answer from the following choices, and then select the submit answer button.
Topoisomerase
replication fork
a Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated
mutations
a random error in gene replication that leads to a change
replication bubble
an unwound and open region of a DNA helix where DNA replication occurs
Which of the following reasons explains why bacteria can continually divide?
because their DNA is circular so the DNA never shortens after replication
single strand binding proteins
bind to and stabilize single-stranded DNA
telomerase that is abnormally very active
cancer; increased and abnormal cell divisions for telomerase is reactivated
parts of an amino acid
central carbon amino group (NH2) R group carboxyl group hydrogen group
template strand: 5'-ATGC-3'
daughter strand: 3'-TACG-5'
variable group
different in every amino acids aka R group or side chain
telomere
each end of eukaryotic chromosome is capped by repeating sequence; contains RNA molecule complementary to telomere sequence
semiconservative replication
each new DNA molecule consists of one new strand and one old strand
origin of replication
each point at which DNA synthesis is initiated
DNA ligase
enzyme that ligates/joins the fragments together
The semiconservative model of DNA replication means that each DNA strand consists of some newly synthesized DNA and some parental DNA.
false
DNA polymerase is the enzyme that separates the two strands of DNA during DNA replication.
false; helicase
During DNA replication, the leading strand contains Okazaki fragments.
false; lagging strand
proline
forms a 'ring' with backbone - makes backbone less flexible
telomerase is fully active and does not decline
germ cells (egg/sperm) stem cells
Polar amino acids
have uncharged electronegative atoms (Polar covalent bonds) I and II OH O
The following enzymes play important roles in DNA replication: DNA polymerase, primase, ligase, helicase. In what order do they work during replication?
helicase, primase, DNA polymerase, ligase
telomerase that is inactive
in most cells in the adult body; telomerase shortening limits the number of mitotic division--> few cell divisions=aging and slower recovery rates
A eukaryotic chromosome has _____ origin(s) of replication, and a bacterial chromosome has ______ origin(s) of replication.
many, one
acidic carboxyl acid groups
negatively charged C / \\ O- O
The point at which DNA synthesis is initiated is called the:
origin of replication
How to replicate so much DNA?
origin->bubble->2 forks move away from origin New DNA synthesis occurs at replication forks Newly synthesized strands are of opposite polarity (anti-parallel)
DNA replication
process of duplicating a DNA molecule; similar process in all organisms
gylcine
second H atom - small, adds flexibility to protein backbone
helicase
separates the strands of parental double helix at replication fork
base pairing
the nearly perfect fit between A-T and G-C nucleotides
pKa
the pH at which an ionizable group is half ionized
What is the function of the enzyme DNA polymerase?
to synthesize a strand of DNA using DNA as a template
In circular DNA, the DNA molecule is not shortened during replication.
true
Synthesis of nucleic acids always occurs in the 5′ → 3′ direction.
true
stem cells
undifferentiated cells that can divide and give rise to cells that can develop into any one of the body's different cell types
Topoisomerase II
works upstream from the replication fork to relieve the stress on the double helix that results from its unwinding at the replication fork