Studied by 247 people
What are nucleic acids?
polymers consisting of nucleotide monomers
What three things are nucleotides made of?
a phosphate group, a 5 carbon sugar, and a nitrigenous base
True of false: the nitrogenous base in a nucleotide is comparable to the r groups in amino acids
true
What are nucleotide monomers held together by
covalent bonds called phosphodiester bonds
Do nucleic acids have chemically distinct ends? If so, what are they?
yes, 5’ and 3’
What is complementary base pairing
hydrogen bond formation between nitrogenous bases
What is anti parallel arrangement
the orientation of the twiostrands of a molecule of dna
What is Chargaff’s rule?
Purines and Pyrimidines exist in a 1:1 ratio
DNA twists to form what?
forms an alpha helix with a major and a minor groove
How is DNA packaged within a cell?
into chromosomes
What is a chromosome made of?
chromatin
What are histones
DNA binding proteins
What is a nucleosome
DNA wrapped around a set of histones
What do genes provide?
information to build proteins
Where are genes present?
in all cells of an individual
How are genes inherited
from parent to offspring
Why is dna replication important
cells need to be able to copy their genetic material every time they divide
What occurs during DNA replication
1. DNA ‘unzips’
2. DNA unwinds
3. The original DNA strands function as templates for the addition of new, complementary nucleotides
4. Phosphodiester bonds link the nucleotides together
5. The process repeats until the entire molecule of DNA is copied
True or False: DNA replication is semi conservative
true
What is the Origin of replication (ORI)
the site where DNA starts
How many origins of replication do prokaryotes have
one
How many origins of replication do eukaryotes have
many
What is the function of Topoisomerase
inwinds dna, keeps a supercoil from forming
What is the function of DNA Helicase
separates the dna strands
What is the function of single stranded binding proteins
to stabilize the dna while it is unfolded and unattached
What is the function of primase
-adds RNA primer that tells DNA polymerase 3 where to attach
-connect okazaki fragments
-remove rna primer and replace it with dna
What is the function of DNA polymerase III
catalyzes formation of the new DNA strand using the original strand as its template
DNA Replication step 1
Enzymes unwind the double helix
DNA replication step 2
Proteins stabilize the unwound DNA
DNA replication step 3
The leading strand is synthesized continuously by DNA polymerase 3
DNA Replication step 4 (lagging strand)
The lagging strand is synthesized discontinuously. RNA primase synthesizes a short RNA primer primase, which is then extended by DNA polymerase 3
DNA replication step 5 (lagging strand)
DNA polymerase 1 removes the RNA primers and replaces it with DNA
DNA replication step 6 (lagging strand)
DNA ligase links the individual Okazaki fragments together to make a single long strand of DNA
Which way does the leading strand go?
5"‘ to 3’
Which way does the lagging strand go?
3’ to 5’
What is mismatch repair?
when an enzyme takes out and then replaces a single piece of dna
What is excision repair?
when an ezyme takes out an entire section of dna and then replaces it
What is the central dogma
the flow of information from DNA to proteins
Transcription describes…
the process of copying information exactly as it is written without modification
Transcription involves..
the enzume RNA polymerase catalyzing the formation of a molecule of mRNA using the template strand of DNA
RNA polymerase catalyzes the synthesis of a strand of what
mRNA with a 5’ to 3’ orientation
True or false: the mRNA product is complementary to the template strand
true
What role do hydrogen bonds play in transcription
stabilize the RNA nucleotides to the template strand
What controls whether a gene is transcribed or not
promoter regions in the DNA and transcription factors
What does transcription generate in eukaryotes
a primary mRNA transcript that is spliced to form the mature mRNA
True or false: RNA splicing occurs in both prokaryotes and eukaryotes
False, it only occurs in eukaryotes
In RNA splicing, what is taken out and what is kept to form a mature mRNA molecule
introns are removed, exons are kept and joined together
Which RNA protein complex completes splicing of the primary sequence
snRNP (snurp)= small nuclear ribonucleic protein
What must the snRNP’s be doing during splicing?
adding a 5’ methyl cap and a 3’ poly-A tail
What is protein synthesis
the story of how information encoded in a sequence of nucleotides is translated into a “different language”
The information in mRNA comes from what
the coding strand of DNA
What is mRNA organized into
units called codons
What are the three stop codons:?
UAA, UAG, UGA
When does protein synthesis happen?
When tRNAs bring amino acids to the ribosome
What is tRNA charging
when tRNA must be loaded with the appropriate amino acid before it can be used during translation
Does tRNA require atp
yes, it requires atp and enzymes called aminoacyl-tRNA synthetases
How many sites are there in translation? What are they called? In what order do they appear in?
3 sites, A, P, and E in that order
remember APE
What three steps is translation made up of
Initiation, elongation, and termination
What happens during initiation?
mRNA and ribosomes assemble (starts with the start codon AUG)
What two things happen during elongation?
Charged tRNA carrying an amino acid enters at the A site, and GTP is consumed when codon and anticodon are matched
What moves along the length of mRNA and tRNA to allow it to make the protein
ribosomes
What happens during termination?
it occurs when a stop codon is reached, release factors bind to the stop codon and break teh bond between the tRNA and the polypeptide
What are the three types of cell division
binary fission, mitosis, and meiosis
What is required before mitosis can happen?
replication of all the chromosomes
What is a karyotype
the genetic information in an organism
What happens in the first phase of mitosis
replicated DNA form chromosomes with two sister chromatids held together at the centromere
What are the 5 phases of mitosis (in order)
prophase, prometaphase, metaphase, anaphase, telophase&cytokinesis
What occurs during prophase?
chromatin condenses to form sister chromatids, the mitotic spindle begins to form
What happens during prometaphase
nuclear envelope breaks down, mitotic spindle fibers contact chromosomes at kinetochores and connect to centrosomes
What happens during metaphase
chromosomes complete migration to the middle of a cell (the metaphase plate)
What happens during anaphase
sister chromatids separate into daughter chromosomes which are pulled to opposite ends of a cell by spindle fibers
What happens during telophase
nuclear envelope reforms and chromosomes de condense
followed by cytokinesis
What phase do cells spend most of their life in
interphase
What is the cell cycle?
Interphase+M phase
What makes up interphase
G1 phase, S phase, and G2 phase
What happens in G1 phase
Normal functions of the cell: grow, make proteins and ATP, etc
What happens in s phase
DNA is replicated
What happens in G2 phase
Growth and preparation for cell division
What controls the transition form one stage to the next
Cyclins
True or false: Cyclin must bind to CDK to make it an active kinase that can phosphorylate things
True
True or false: the type and amount of cyclin does not change
false, it varies over time
What does activated CDK start
a signal cascade
What is social control
cells in multicellular organisms tell each other when to divide by using growth factors
What triggers signal cascades
growth factors
The loss of quality control of the cell cycle can lead to what
cancer
What is apoptosis
a safe way to remove cells
What is cancer
the result of unregulated growth and division of a cell
Note
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