eczema 2 Flashcards
Nucleotides are the subunits of _____ & ______
DNA & RNA
What did Hershey and Chase do
They used radioactive labeling to prove that DNA is responsible for heredity
What did Watson & Crick do
They proposed the double helix structure of DNA
Before we know the structure of DNA we thought Chromosomes contain ____ & _____
Dna & protein
Before we new the structure of DNA we knew:DNA had a _______backbone and DNA had _____________ attached to each sugar
sugar phosphate ; nitrogenous bases
The double helix model with the Xray diffraction pattern was generated by who? And what did it reveal?
Rosalind Franklin; revealed that DNA was a long thin helical molecule
The Watson and Crick Model said what 4 things
sugar phosphate backbone is on the outside
Bases are on the inside
Strands run antiparallel to each other
10 Nucleotide pairs per complete turn
Watson and Crick model was supported by what
Chargaff’s rules A=T and G=C
Nucleotides have chemically distinct ____
sides
What are the 4 nucleotide building blocks of DNA and what are the Purines, what are the pyrimadines?
A,T,G,C
PURINES: A, G
PYRIMADINES: T, C
What links nucleotide subunits within the DNA strand?
Phosphodiester bonds
5’ carbon of the sugar has a _________
phosphate group
3’ Carbon of sugar has a ______
OH
What holds the strands of the double helix together
hydrogen bonds
What forms as DNA strands twist around each other
major and minor grooves
The structure of DNA provides a machanism for _______
heredity
Segment of DNA that directs the production of a particular protein or functional RNA molecule
Gene
DNA is packaged into
chromosomes
DNA bound to protein
Chromatin
Condensed chromatin fibers
Chromosome
How are abnormal chromosomes detected
karyotyping
Organize and carry genetic info
chromosomes
The total genetic information carried by all the chromosomes of a cell or organism
Genome
T/F: The total genetic information carried by all the chromosomes of a cell or organism is called the genome
true
T/F: If the genome sizes are similar (between 2 species), their chromosome numbers must be similar
false
The ordered series of events by which a cell duplicates its contents and divides into two
cell cyle
Specialized DNA sequences are required for _________ & ___________
DNA replication; Chromosome segregation
The site where DNA replication begins
Replication origin
T/F: There is 1 replication origin in eukaryotic cells
False, there are multiple
The ends of a chromosome are called what
Telomeres
Telomeres contain _______________ & ___________
repeated nucleotide sequences; protective caps
What allows the duplicated chromosomes to be separated?
the centromere
The identical duplicated DNA molecule is called what
chromatid
The process where chromosomes are replicated, seperated and then partitioned into 2 daughter cells
cell cycle
Describe the chromosomes in interphase
they’re long and thin. They are organized within the nucleus in chromosome regions/territories which keeps the strands from getting tangled
Chromosome regions attach to sites on the________. Which is formed as a network of __________ made from ___________
nuclear envelope/ nuclear lamina; intermediate filaments; nuclear lamins
The large structure within the nucleus is called what
nucleolus
The nucleolus is the site of ______________ and ___________ assembly.
Ribosomal RNA transcription; ribosomal unit assembly
What can produce large biochemical subcompartments in cells?
weak interactions between macromolecules
What can produce large biochemical subcompartments in cells
weak interactions between macromolecules
For eukaryotes DNA must fit in the ______
nucleus
The levels of chromosome condensation depend on 3 things
stage of the cell cycle
whether active/ inactive gene
proteins the coil and fold DNA (like histones)
The complex of DNA and proteins that make up the chromosomes in a eukaryotic cell
chromatin
The structural unit of the eukaryotic chromosome. It’s composed of short length of DNA wrapped around an octameric core of histone proteins.
Nucleosome
The basic unit of eukaryotic chromatin structure
nucleosome
What is a nucleosome made of (2 general things)
Core particle (histone octamers)
Linker DNA
The small basic proteins with high proportion of positively charged amino acids (lysine and arginine)
Histones
_______ has N-terminal tails that can be modified. They package/condense DNA
histones
How many main types of histones are there
5
What does the positive charge of the Histone’s amino acids help do
bind to negatively charged DNA
Which of the 5 types of histone helps pull adjacent nucleosomes together?
H1
Chromatin loops are established by what
nonhistone proteins
Changes in nucleosome structure allows access to
DNA
___________DNA is less tightly packaged than inactive DNA
Transcriptionally active (Euchromatin)
Chromatin remodeling complexes interact with _______ & ______
histones; DNA
T/F: Chromatin remodeling complexes are highly regulated
true
ATP dependent enzymes that change the position of DNA wrapped around nucelosomes
chromatin remodeling complexes
Uses the energy of ATP hydrolysis to move nucleosomes to hence allow access to the tightly bound chromosome
chromatin remodeling complexes
Whats is another word for active (turned on) Chromatin?
Euchromatin (transcriptionally active, and hence looser)
What is another word for inactive (turned off) Chromatin? What process does this inhibit?
Heterochromatin (transcriptionally inactive, and hence densely coiled);
prevents transcription
In its default state, the tight coiling that characterizes chromatin structure limits the access of RNA polymerase and ___________ to eukaryotic DNA. Therefore, a cell’s chromatin must “open” in order for gene expression to take place. This process of “opening” is called __________, and it’s vital for the proper functioning of eukaryotic cells.
transcription factors; chromatin remodeling
A open/active chromatin (genes are switched on) has what kind of histones?
acetylated histones
A closed/inactive chromatin (genes are switched off) has what kind of histones?
deacytlated histones
What does histone modification do?
regulates transcriptional activity
Histone tail can be modified by the addition or removal of (list 3)
methyl, acetyl, phosphate, or other groups
T/F: Histone tail modification is irreversible
False, its reversible
Histone methylation leads to ________
tighter packing (gene repressed)
Histone acetylation leads to ________
looser packing (leads to gene expression)
T/F: Interphase chromosomes are uniformly packed
False, they contain both highly condensed and more extended forms of chromatin
Highly compacted chromatin
heterochromatin
more loosely packed, diffused chromatin
Euchromatin
What is the purpose of different cell types having different regions of chromosomes be more condensed or more extended?
it allows Cell type specific gene expression
T/F: During cell division ALL the chromatin becomes highly compacted
true
A chromosome is made of 2 identical sister ________
chromatids
What are the 2 types of heterochromatin?
Facultative & constitutive
Whats the difference between Facultative Heterochromatin and Constitutive Heterochromatin?
Facultative Heterochromatin can be converted to euchromatin
Constitutive Heterochromatin is permanently compact.
Constitutive Heterochromatin serves ________ functions within chromosomes and does NOT contain _______.
structural; genes
!What allows heterochromatin to form and spread? When does the spread stop?
Heterochromatin specific histone modifications
Ex. methylation of lysine 9 in H3 tail;
Stops once it reaches the Barrier DNA sequence
Barrier DNA sequence may contain ____________ for histone acetyltransferases
binding sites
!Sometimes genes located near ________ chromatin can get accidentally packaged into ________chromatin which prevents ____________. Ex) B-globin gene
Constitutive chromatin; Heterochromatin ;gene expression
!One of the 2 X chromosomes is inactivated by ________________ in the cells of mammalian females.
heterochromatin formation
!What are 2 types of Constitutive heterochromatin?
Centromeres and Telomeres
The centromere is bound by a complex of proteins called the what
kinetochore
What is the function of the centromere?
maintains sister chromatid cohesion during mitosis and meiosis
What protects chromosome ends from degradation during each round of DNA replication?
telomeres
What are the 2 purines and what are the 2 pyrimidines?
Purines- A & G
Pyrimidines- CUT cytosine, uracil thymine
T/F: Which of the following is NOT true of the N-terminal “tail” of histones binds to DNA in a sequence-specific manner
XXXXX ignore this Qxxxxxxx
false
The core histones’ long, extended tail at the N-terminus can be modified, it also helps DNA pack tightly and it extends
out of the _____________.
out of the nucleosome core.
Stepwise condensation of linear DNA happens in five different packing processes. Which process has a direct requirement for histone H1?
formation of the 30-nm fiber
T/F: Histones are highly evolutionarily conserved
true
Genes that are being transcribed are thought to be packaged in a _________ (more/less) condensed type of euchromatin.
less
Nucleosome core particles are separated from each other by stretches of ________ DNA.
linker
A string of nucleosomes coils up with the help of
_________ to form the more compact structure of the 30-nm fiber. A zigzag model describes the structure of the 30-
nm fiber. The 30-nm chromatin fiber is further compacted by the formation of ______that emanate from a central axis
histone H1; loops
Heterochromatin is highly ________.
Constitutive heterochromatin plays a(n) ________ role and Facultative heterochromatin functions in ________.
compact; structural; regulating gene expression
Cells must be able to _________ reproduce, or replicate, their genetic material at each cell division.
accurately
What enables DNA replication
base pairing
The cluster of proteins involved in DNA replication
Replication machine
The nucleotide sequence at which DNA replication is initiated. It attracts initiator proteins that pry DNA apart.
Replication Origin
Replication origin is rich with what bases
A and T
How many replication forks form at the replication origin?
2
The group of proteins that carry out replication. They’re attracted to origin of replication by initiator proteins.
Replication machine
This complex sits on the origin of replication throughout cell cycle
origin recognition complex
Replication machines (rapid) assemble at each replication fork. They replicate in which direction(s)
bidirectionally
What important enzyme does the Replication machine contain?
DNA polymerase
DNA polymerase can copy DNA molecules. Incoming nucleotides are added to the ________ end of the growing DNA chain. Therefore, elongation occurs in the __________ direction.
3′ hydroxyl; 5′ to 3′ direction
DNA Polymerase synthesizes DNA using the _______ strand as a template.
parental
What 3 things does DNA polymerase need?
- Template DNA
- Primer
- Deoxyribonucleoside Triphosphate (dNTP) bases
Due to complimentary base pairing, the incoming dNTP depends on the ______ in the template strand
base
Name the 4 dNTP bases
dATP, dTTP, dGTP, dCTP
What bond is formed between the phosphate group on the 5’-carbon of the incoming dNTP and the hydroxyl group of the 3’-carbon of the nucleotide on the growing chain?
The energy for this reaction comes from removing a what?
phosphodiester bond;
pyrophosphate
What is DNA polymerase’s role during the linking of the incoming 5′ phosphate with the 3′ hydroxyl group of the end nucleotide?
it catalyzes the reaction, it guides and positions the incoming nucleoside triphosphate to the template strand
The replication fork is _____________(symmetrical/asymetrical)
asymetrical
T/F: Only one parental strand needs to be replicated
Do Parental strands run in opposite directions (antiparallel)?
false; yes
The “_______strand” is synthesized continuously toward the replication fork. The “_______strand” is synthesized in the direction away from the replication fork.
leading ; lagging
Overall DNA is synthesized as _________ segments
discontinuous
Although mistakes are rare, DNA polymerase is able to _____________
self correct/ proofread
If the DNA polymerase added the wrong nucleotide during replication how does it correct the mismatch?
The new strand is moved to the editing (E) site. The mismatched nucleotide is cut from the new strand and replaced with the correct match.
T/F: DNA polymerase undergoes small structural rearrangement that allows it to catalyze the reaction.
true
The energy required for DNA polymerase’s proofreading comes from the hydrolysis of what?
of dNTP’s high-energy bond
T/F: If strands grew in the 3’-to-5’ direction, DNA polymerase’s removal of an incorrect nucleotide leaves the new stand without a high-energy bond to fuel the reaction
true
DNA polymerase can add nucleotides only to the ___ end of an existing nucleotide chain
3′
Short lengths of RNA act as _____ for DNA synthesis
primers
RNA primers are synthesized by _______ using a single DNA strand as the template
primase
Primase uses ________________ rather than deoxyribonucleoside triphosphate
ribonucleoside triphosphate
What starts the leading & lagging strand’s synthesis?
How many primers does leading strand synthesis need and how many does lagging strand synthesis need?
DNA polymerase;
Leading strand needs 1 primer
Lagging strand requires multiple primers
Why does the lagging strand require multiple primers?
since DNA polymerase is making Okazaki fragments, so at the start of each, there needs to be a primer
They keep polymerase attached to template DNA
Sliding clamp proteins
They hydrolysis the ATP to get the sliding clamp around the DNA
Clamp loaders
