Cycle 3 Flashcards
Each nucleotide consists of the five-carbon ______, a _______ group, and one of the four _________
sugar deoxyribose, phosphate, nitrogenous bases
Two of the bases, adenine, and guanine are _____, nitrogenous bases built from a pair of fused rings of carbon and nitrogen atoms
purines
The other two bases, thymine and cytosine, are ______, built from a single carbon ring
pyrimidines
Number of ____ = number of ______ (the amount of adenine = thymine, the amount of guanine = cytosine)
purines, pyrimidines
DNA polymerase on template strands is assembled in what direction
Assembled 5’ to 3’
The direction of movement of DNA polymerase on template strands
Moves ______
3’ to 5’
______The process of DNA replication in which the two parental strands separate and each serves as a template for the synthesis of new progeny double-stranded DNA molecule
Semi-conservative
______: A DNA strand assembled in the direction of DNA unwinding
Leading strand
______: A DNA strand assembled discontinuously in the direction opposite to DNA unwinding
Lagging strand
Unwinds DNA helix
Helicase
Avoids twisting the DNA ahead of replication form (in circular DNA) by cutting the DNA, turning the DNA on one side of the break in the direction opposite to that of the twisting force, and rejoining the two strands again
Topoisomerase
Stabilizes single-stranded DNA and prevent the two strands at the replication form from reforming double-stranded DNA
Single-stranded binding proteins
Synthesizes RNA primer in the 5’ to 3’ direction to initiate a new DNA strand
Primase
-Main replication enzyme in E.Coli
-Extends the RNA primer by adding DNA nucleotides to it
DNA polymerase 3
At the one end, a phosphate group is bound to the ___ carbon of deoxyribose sugar whereas at the other end, a hydroxyl group is bonded to the ___ carbon of deoxyribose sugar
5’, 3’
DNA strands grow in a ____ direction
5’ to 3’
An unwound and open region of a DNA helix where DNA replication occurs
Replication bubble
A bubble consists of two _______ replicating in opposite directions
replication forks
______ gives you information when characterizing the genome
Karyotype
In karyotype, scientists take chromosomes during _____, take them out of the cell, and line them up from _____ to ______
metaphase, largest to smallest
Humans have __ sets of __ chromosomes
2 sets of 23 chromosomes
T/F: The number of chromosomes and their length vary between species
TRUE
Each set has to have _____ chromosomes and would be different numbers on the karyotype
unique
Sunflower would be a tetraploid as it has _n
4n (4 sets of unique chromosomes)
Most plants are _____
polyploidy
Why study or quantify the genome?
Genome codes for what is going to happen in the cell
Basic comparisons between species
Insight into the evolution, function, and “complexity” of an organism
Genome size does ___ relate to how complex an organism is
not
A genome is all of the DNA in ____ COPY of an organism’s chromosomes
ONE (in one set)
Chromatids are identical DNA molecules attached at their _____
centromeres
IN G: DNA is a
double helix
It has polarity (one end is 5’ other is 3’)
Antiparallel
IN S: Replicate, now have
two helices
T/F Regardless of replication or division, the chromosome number is still the same
TRUE
_____ = number of unique nuclear chromosomes present in an organism
n-value
________ (ploidy) tells us the number of unique sets that are present in an organism
The coefficient of n
_____ represents the amount of DNA in one set of an organism’s nuclear chromosomes: genome size
C-value
C Value:
Quantity of base pairs or mass (______)
picograms
The_______ tells us how many times the entire genome is present in a cell (copies of the genome)
coefficient of C
____ of species remains constant
C Value
_____ is changing
Copy #
_____ DOES NOT CHANGE DURING THE CELL CYCLE
PLOIDY
___ implies nothing about C
n
One of the two identical halves of a duplicated chromosome
Chromatid
_____: The region where two chromatids are attached
Centromere
______: Protective caps at the ends of chromosomes
Telomeres
__: The number of unique sets of chromosomes in a cell.
n
For humans, n=
23
___: The amount of DNA in a cell, often expressed in terms of mass or the number of DNA molecules
C
S phase: DNA replicates, so it remains __n but the C value doubles to _C
2n, 4C
_______: Results in gametes with 2n, which can lead to polyploid offspring if fertilization occurs
Tetraplidu (4n)
G1 phase: __n and __C
2n and 2C
G2 phase: The cell is __n and __C (since the DNA has replicated, but chromosomes have not yet divided)
2n and 4C
_______: Produces gametes with uneven chromosome distribution, leading to infertility or inviability due to imbalance
Triploidy (3n)
After mitosis (M phase): Back to __n and __C (each daughter cell gets one set of chromosomes)
2n and 2C
_______: Standards meiosis involves halving the chromosome number to produce haploid (n) gametes
Diploidy (2n)
_________ refers to the observation that the genome size (C-value) does not correlate with organisms complexity
The C-value paradox
DNA is a ______ molecule that forms a helical structure
double-stranded
______: The building blocks of DNA, consisting of a sugar (deoxyribose). A phosphate group, and a nitrogenous base (Adenine, Thymine, Cytosine, or Guanine)
Nucleotides
The two strands of DNA run in ______ directions (5’ to 3’ and 3’ to 5’)
opposite (Antiparallel strands)
Mechanisms that ensure the inheritance of sameness: (3)
-Semi-conservative replication
-Proofreading by DNA polymerase
-Mismatch repair
_______: The unwound section of DNA where replication occurs
Replication bubble
______: Synthesized continuously in the 5’ to 3’ direction, toward the replication fork
Leading strand
A pairs with T via two ______, and G pairs with C via three ______
hydrogen bonds
________: Synthesizes discontinuously in short fragments called Okazi fragments, away from the replication fork, and later joined by DNA ligase
Lagging strand
_____: Short RNA primers are placed on the lagging strand (and once on the leading strand) to provide a starting point for DNA polymerase
Primers
_______: A state in which a cell can no longer divide but remains metabolically active. This is often a response to DNA damage or the shortening of telomeres
Cell senescence
_______: The maximum number of times a normal somatic cell can divide before reaching senescence, typically around 40-60 divisions in humans
Hayflick limit
Cells reach senescence due to the progressive shortening of _______ with each replication cycle, which acts as a biological clock for cell division
telomeres
Telomeres consist of repetitive nucleotide sequences, particularly ______ in vertebrates, repeated thousands of times at the ends of chromosomes
TTAGGG
These TTAGGG sequences protect the end of ______ from degradation and prevent them from _____ with other chromosomes
chromosomes, fusing
Why chromosomes shorten at each replication: DNA polymerase can only add nucleotides in the 5’ to 3’ direction, which creates an issue for the _____ strand.
lagging
After removing RNA primers at the ends of chromosomes, there is no way to replace them with DNA, resulting in:
a small amount of DNA loss at each replication cycle
_______: An enzyme that adds telomeric sequences (TTAGGG) to the ends of chromosomes, compensating for the DNA loss during replication
Telomerase
Telomerase contains an ___ template that is complete to the telomeric sequence and acts as a reverse transcriptase to extend the telomeres
RNA
Telomerase is most active in ____ cells, stem cells, and some ____ cells, allowing them to divide indefinitely without undergoing senescence
germ, cancer
We inheritance sameness, meaning daughter cells look close to identical because of the way DNA replication occurs in the __ phase
S
A distinct 3’ and 5’ end on each confers _____ (positional) on DNA backbones
polarity
For a cell to divide, has to replicate its ______
genome
________ has very high accuracy overall but is going to make some mistake
DNA polymerase
DNA replication and cell mitosis : Inheritance of ______
sameness
DNA polymerase needs preexisting ______ (RNA or DNA)
nucleotide
3’ has a free ________ group
This is the group DNA polymerase needs to extend the strand
hydroxyl (OH)
5’ has free ______
Cannot be extended by DNA polymerase
phosphate
RNA has ___ DNA has T
U
Two strands of double helix run _______
antiparallel
Replication is ___-conservative
semi
1 target of chemotherapy is the __ phase
One inhibits topoisomerase or bases
S
Adult ____cells in the body have telomerase (lower levels)
stem
DNA unwinds and each strand acts as a ____ for the synthesis of a new, complimentary, antiparallel strand
template
What about the LAST bubble on the end of a chromosome? The _____ strand has copied over every single base in the template strand
But ______ still needs to copy all that over because it’s going to be removed by polymerase one
leading, lagging
The_______ is what DNA polymerase reads off of
template strand
_____ replicate one strand continuously, and one discontinuously (leading vs lagging)
Replisomes
Replication “bubble” arises from two “____” created at one “origin”
forks
Each time cell replicates, it loses some _____
telomerase
______ protect you from losing sequences of genes
Telomeres
In senescence cell can: remain in G1 and G0 and function, remain and not function, or ______
apoptosis
It didn’t get filled up and will always be shorter because it needs more template and primer, doesn’t know what to do at end
That is why ______ comes to an end and extends
telomerase
Eventually reaches critical length (reaches _______ ______)
hayflick limit
Once it gets there, cell ______, meaning it will no longer replicate
senescence
HOWEVER: telomerase helps maintain telomere length, Does not prevent it from shortening, just _______ it
extends
Primers closer to ____
ORI
T/F Male germ cells do not, but female oocytes do have telomerase
FALSE: Male germ cells do, but female oocytes do not
_____ cells need telomerase to grow
Cancer
Telomerase is an ____-dependent DNA polymerase
RNA
List of mechanisms to ensure Inheritance of sameness: (3)
-Complimentary base pairing- A must match with T and C must match with G
-Semi-conservative mode of replication- DNA synthesis relies on a pre-existing template so each copy MUTS be made to match the existing template
-Proofreading - 3’ to 5’ exonuclease activity of DNA polymerase 3 that corrects errors made during replication
Gene not activated in _____ cells, but cancer would turn it on
somatic
Lots of telomerase During_______ ________ (very active in embryogenesis)
embryonic development
