Exam 4 Flashcards
What type of sugar is deoxyribose?
a pentose sugar
In 1950, Erwin Chargoff reported that DNA composition varies from one species to the next.
True or False
true
Nucleic acids are polymers specialized for what three things?
- storage
- transmission
- use of genetic information
What is the monomer of nucleic acids?
nucleotides
Are pyrimidines single rings or double rings?
single rings
Which nitrogen bases are purines ?
adenine and guanine
Are Purines single rings or double rings?
double rings
What is the name of the rule that states that in any species there is an equal number of A and T bases, and an equal number of G and C bases?
Chargaff’s rule
Pairing a purine with a pyrimidine results in a uniform width.
true or false?
true
What three things together build a nucleotide?
pentose sugar+ N-containing base+ phosphate group
What two pyrimidines are used in DNA ?
- Thymine
* Cytosine
What did James Watson and Francis Crick (the buttheads) do?
Introduced an elegant double-helical model
Stole the information from Rosalind Franklin
Who was responsible for taking DNA and crystalizing it to take an x-ray photograph?
Rosalind Franklin
How did Rosalind Franklin determine that DNA was a double helix?
By MEASURING the xray crystallography that she had taken of DNA
The Watson-Crick model helped explain Chargoff’s rule. true or false?
true
Why can A not pair with C and G not pair with T?
Because of the amount of hydrogen bonds needed
What does anti-paralell mean?
the two strands going in opposite directions, like two roads going in opposite directions
The two strands of DNA are _____________, so each strand acts as a template for building a new strand in replication.
complementary
In DNA replication, what does the enzyme helicase unwind?
the parent molecule
Once the parent molecule unwinds, the two new daughter strands are built based on what?
base pairing rules
What does a daughter DNA molecule consist of?
One parental strand and one new strand
The new cell that will be made needs a copy of what?
the entire DNA
What is a template?
An existing DNA strand that we can use to copy from or build off of
What type of bond holds the two strands together?
Hydrogen bonds
What Model predicts that when a double helix replicates, each daughter molecule will have one old strand “conserved” from the parent molecule and one newly made strand?
Semiconservative Model
Is DNA synthesis anabolic or catabolic?
anabolic
What four things will the cell need to do DNA replication?
- Energy
- Template
- Enzymes
- Nucleotides (4 Nitrogen bases)
How many strands of DNA are there that must be copied?
48 strands, 24 pairs
DNA is short and thick.
True or False?
Fasle, DNA is very thin and incredibly long
Does DNA synthesis require ATP (Energy)?
Yes, it’s anabolic, it needs energy to build
Name the 4 nitrogen bases used to construct DNA
- Adenine
- Thymine
- Cytosine
- Guanine
Of the 4 bases, which ones are double rings?
Adenine and Guanine
What monomer is used to build into polymers in DNA replication?
Nucleotides
What is copulation?
the act of intercourse to introduce an egg cell to a sperm cell
DNA replication takes one strand and makes it into ___ _______.
two strands
In cells produced by mitosis, are all chromosomes alone or in pairs?
all chromosomes are in pairs
How many PAIRS of chromosomes are found in humans?
23 pairs
Are egg and sperm cells functional without fertilization (without eachother)?
no, they are not functional alone
When DNA first replicates, the two inner strands are still what?
Still attached to eachother, stuck together
During DNA replication, they speak of a “narrow waist” where there is a pinching of the two sister chromatids together, what is this area called?
centromer(e)
Where does the new strand replicate, on the outside or inside?
on the inside
What is the function of mitosis?
to pull apart the chromatids and allow them to complete and become two chromosomes.
If in Mitosis all chromosomes are in pairs, (one from mom, one from dad), what happens with Meiosis?
Meiosis= 1/2 of each chromosome pair
Which helps you repair, mitosis or meiosis?
Mitosis
What is made up of DNA and histone proteins?
Chromatin
Where are eggs and sperm produced?
in the ovaries and testes
How is asexual reproduction in humans done efficiently?
mitosis
How is asexual reproduction in bacteria done efficiently?
binary fission
Asexual reproduction means to what?
clone
Sexual reproduction is done through _______.
meiosis
egg and sperm
Is DNA replication part of interphase or mitosis?
DNA replication is part of interphase
In which part of the stages of mitosis is most of the work done?
prophase/prometaphase
Once the chromosomes look like X’s , they have been replicated (s phase) and are ready (for G2) and are ready for mitosis.
true or false?
true
The centrioles grow microtubules and attach to the chromosome at what part?
the centromer
What protein by the centromer can the microtubules attach to?
kinetochore
In what part of Interphase does DNA replicate?
S phase
In prophase, prophase I, and prophase II, chromatin is condensing into ___________.
Chromosomes
In Prophase (during mitosis), the nuclear envelope and the nucleolus are doing what?
breaking down
Does a replication of centrioles happen during mitosis?
yes
What does Helicase do?
unwinds the parent double helix at replication forks
What does a single-strand binding protein do?
Binds to and stabilizes single-stranded DNA
Which enzyme relieves “overwinding” strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
Topoisomerase
What is primase for?
synthesizing RNA Primer at 5’ end of leading strand and of each Okazaki fragment of lagging strand
What makes new DNA strands by covalently adding nucleotides to the 3’ end of pre-existing DNA strand or RNA primer
DNA pol III
What enzyme removes RNA nucleotides of primer and replaces them with DNA nucleotides?
DNA polymerase I
Which enzyme is responsible for joining the 3’ end of DNA that replaces primer to the rest of the leading strand and joins Okazaki fragments of the lagging strand?
DNA ligase (hint: ligands join things together)
Which enzyme works first, DNA pol I or DNA pol III?
DNA polymerase III
Replication begins at particular sites called what?
Origins of replication
What happens to the two DNA strands at the origin of replication?
the two DNA strands are separated, opening up a replication “bubble”
Where do origins of replication usually begin?
Where there are multiple A-T sequences in a row together.
Why are A-T sequences a good place for an origin of replication?
Because they are easier to break apart since A-T only have 2 hydrogen bonds
Are there multiple origins of replication or just one?
multiple, this helps it to happen quicker
A eukaryotic chromosome may have hundreds or even thousands of origins of replication.
true or false?
true
Replication proceeds in which direction from each origin, until the entire molecule is copied?
in both directions
The Daughter strand is the ___ strand while the Parental Strand is the ___ strand
new, old
Which strand is the template?
The parental strand
RNA can complimentary base-pair with DNA.
true or false?
true
DNA polymerases can only ADD nucleotides to the 3’ end, they cannot do what?
initiate synthesis of a polynucleotide
they cannot start until a primer is added
We can only add new nucleotides to a 3’ end becuase of the _____ of the enzyme.
shape
Which enzyme can start an RNA chain from scratch and add RNA nucleotides one at a time to the parental DNA template?
primase
When they refer to the RNA primer as short, how many nucleotides long is it?
5-10 nucleotides long
5’ and 3’ has to do with the orientation of what?
the carbons
The 3’ end is continuous, while the bottom strand (lagging strand) has to wait for what?
- for it to unwind
- wait for a primer
- then add nucleotides
At the end of each replication bubble is a replication ____. A y-shaped region where new DNA strands are __________.
fork
elongating
Does helicase untwist the double helix behind or ahead of the fork
ahead of the fork
Does topoisomerase correct “overwinding” behind or ahead of the fork?
ahead of the fork
What two things do most DNA polymerase require?
a primer
a DNA template strand
What is the rate of elongation in bacteria and the rate of elongation in human cells?
bacteria= 500 nucleotides per second humans= 50 nucleotides per second
DNA polymerases add nucleotides only to the free 3’ end, therefore a new DNA strand can elongate only in the _’ to _’ direction
5’ to 3’
To elongate the lagging strand, DNA polymerase must work in what direction?
in the direction away from the replication fork
The lagging strand is synthesized as a series of segments called what?
Okazaki fragments
Okazaki fragments are joined together by what enzyme?
DNA Ligase
The lagging strand can’t add nucleotides continuously, it can only add to a 3’ end so it has to wait for what to happen before it can add a primer?
for helicase to unwind it
What does DNA Polymerase I do to the RNA Primer?
It cuts out the RNA primer and replaces the RNA with DNA nucleotides
Ligase comes in after DNA Polymerase I and does what?
Connects it together so that we have a continuous strand of DNA
What does a DNA Polymerase proofreader do?
Goes down the newly made DNA strand, finds mistakes, cuts them out and replaces any incorrect nucleotides
What happens if a proofreader misses a mistake?
a mutation occurs
What do SOS enzymes do?
repair
What is another name for a mutagenic agent?
a carcinogen
What happens in nucleotide excision repair?
a nuclease cuts out incorrect nucleotide and replaces damaged stretches of DNA
Base pairs code for amino acids.
true or false?
true
When is the only time that mutations can happen?
When DNA is replicating
What is Nuclease
an SOS repair enzyme
When is the only time that a mutation that occurs can effect your offspring?
If the mutation happens while making an Egg or a Sperm
Why do humans evolve so slowly?
they have a low reproduction rate
What are the chances that a mutation can occur?
10^6 or 1 in a million
Cancer is a mistake in DNA replication.
true or false?
true
How many errors occured for someone that gets sickle-cell anemia?
only one error
What does sickle-cell anemia protect from?
malaria
If there were no errors possible, we would never get cancer, but we would also never do what?
evolve
The chromosomes of prokaryotes are what shape?
circular
As DNA replicates, it gets _______.
shorter
Once you cut out the primer at the end, you cannot complete it. During the next round of replication, it will get ___ ___.
cut off
What are the ends of DNA that don’t code for anything called?
telomers
Define Biological age
how many times your cells have divided
Define Chronological age
Age you are in numbers
Telomeres do not prevent the shortening of DNA molecules, but what do they do?
postpone the erosion of genes near the ends of DNA
It has been proposed that the shortening of telomeres is connected to what?
aging
define apoptosis
cell death
Each time DNA replicates, _______ gets cut off
telomer
What is the name of the enzyme that catalyzes the lengthening of telomeres in germ cells?
telomerase
define gametes
egg and sperm cells when they come together
what is another name for germ cell?
stem cell
As we age, what happens to the stem cells ability to produce new cells?
it goes down
Without telomerase, you lose the telomer, and what happend to the cell?
it dies
There is evidence of telomerase activity in cancer cells, which makes the cancer cells somewhat ________.
immortal
What helps condense DNA during cell division?
histone protein
Do normal cells have telomerase? If so when?
yes, but it turns off after gestational period
What is Cancer?
uncontrolled cell division
cells get stuck in a part of the cell cycle
What does cigarette smoke do to the rates of mitosis?
speeds it up
Name some things that can speed up your biological time clock?
- cigarette smoke
- UV exposure
- substance abuse
- life style choices
What best distinguishes living things from non-living things?
the ability of organisms to reproduce
also metabolism
Mitosis is cell division that takes place in what type of cells?
somatic cells
Meiosis produces non-identical daughter cells.
true or false
true
What happens when unicellular organisms do cell division?
division of one cell reproduces the entire organism
What three things does cell division in multicellular organisms result in?
- Production of gametes (egg and sperm)
- Growth
- Repair
Name the two types of cell division in eukaryotes
Mitosis and Meiosis
define genome
all the DNA in a cell
A genome can consist of a single DNA molecule or a number of DNA molecules. Which is common in prokaryotes and which is common in eukaryotes?
single=prokaryotes
multiple=eukaryotes
What are DNA molecules in a cell packaged into?
chromosomes
A Somatic cell is a non-reproductive cell.
true or false?
true (non-sexual)
Is a Gamete a reproductive cell or a non-reproductive cell?
a reproductive cell (sexual)
Gametes have half as many chromosomes as Somatic Cells.
true or false?
true
In Mitosis, Each duplicated Chromosome has __ sister chromatids, which separate during cell division.
2
What is the part of the duplicated chromosome where the two chromatids are most closely attached called
centromere (the waist)
Eukaryotic cell division consists of 2 parts, what are they?
Mitosis, and Cytokinesis
In cytokinesis when the contents of the cytoplasm are divided between the two new cells, is this an equal division?
No
The Mitotic (M) phase consists of what 2 things?
Mitosis and cytokinesis
Where does the cell “do it’s job”?
Interphase
Where does about 90% of the cell cycle take place?
Interphase
Interphase can be divided into 3 subphases, name them
G1
S Phase
G2
The cell grows in all three subphases of interphase, but in which phase are the chromosomes duplicated and DNA replicated
s phase
In which subphase of interphase does the cell grow into its adult characteristics?
G1
Name the phases of mitosis
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
- cytokinesis
In which phase do the microtubules pull apart the sister chromatids?
Anaphase and Anaphase II
Once sister chromatids are pulled apart they are no longer chromatids they are ___________.
chromosomes
In animal cells, cytokinesis occurs by a process known as ________.
cleavage, forming a cleavage furrow
What is the cleavage furrow made of?
microfilaments
A cell plate will eventually modify into what?
a cell wall
What major thing happens in metaphase?
microtubules attach at kinetochore and move the chromosomes to the middle (metaphase plate)
What is the name of the complex of DNA and protein, that eukaryotic cells have, that condenses during cell division?
chromatin
How many sets of chromosomes do somatic cells have?
2 sets
In comparison to somatic cells, how many chromosomes do gametes have?
1/2 as many
Each duplicated chromosome in eukaryotic cells, have 2 ______ __________, which separate during cell division
2 sister chromatids
define cytokinesis
the division of the cytoplasm
What type of cell division are gametes produced in?
meiosis
Meiosis yields nonidentical daughter cells. How many sets of chromosomes do these cells have?
only one set, half as many as the parent cell
What Phase of mitosis does cytokinesis take place during?
Telophase
What is the acronym that Mary used to help us remember the stages of mitosis?
PMAT
Can plant cells have more than one nucleolus?
yes
How big are the two new cells that have just been divided in telophase/cytokinesis?
half the size of the original cell
Where do the two new cells that have just been separated in telophase/cytokinesis need to go next?
Back into interphase to grow up
What happens to the chromatin in Prophase, Prophase I, and Prophase II ?
It begins condensing into chromosomes
During which phase of mitosis have the centrioles /centrosome replicated and gone to separate sides of the cell?
prophase/prometaphase
What do the microtubules of the mitotic spindle do?
They pull and push sister chromatids apart toward opposite spindle poles
What are aster, where are they found?
aster are microtubules emanating (sticking out of) the centrosomes
During which phase do the microtubules attach to the kinetochore and move the chromosomes to the middle?
Metaphase
What builds the mitotic spindle?
centrosomes
In anaphase, what do the microtubules attached to the kinetochore do to pull the sister chromatids apart and toward the opposite poles of the cell?
contract and shorten
In animal cells, cytokinesis occurs by the forming of a cleavage furrow that divides the cell into two parts, what is formed in plant cells that has a similar job?
cell plate
What is a homologous pair?
Both chromosomes of each pair carry genes controlling the same inherited characteristics
A genes specific location along the length of a chromosome is called what?
locus
When you say a cell is 2n it means it’s what?
diploid, it has only 2 sets of information
