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140 Cards in this Set
- Front
- Back
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DNA = polymer
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know
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nucleotide = ___ unit of DNA
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basic
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nucleotide has 3 parts...
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deoxyribose sugar
phosphate group nitrogenous base |
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4 types of nitrogen bases...
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cytosine
guanine adenine thymine |
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cytosine and thymine are...
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single-ringed pyrimidines
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guanine and adenine are...
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double-ringed purines
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nucleotides are connected through phosphate bonds
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know
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DNA is read...
5-->3 or 3--->5 |
5--->3
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DNA forms a double stranded helix
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know
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nitrogen base on the inside...sugar facing outside
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know
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A pairs with...
G pairs with... |
a-->t
g-->c |
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a-t form ___ hydrogen bonds
g-c form ___ hydrogen bonds |
a-t form 2 hydrogen bonds
g-c form 3 hydrogen bonds |
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what factor determines strength of strands?
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number of G-C there are since a triple bond is stronger and closer than a A-T double bond
also more G-C, requires higher temperature to denature |
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antiparallel arrangement of strands...
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5-----3
3-----5 complements of one another... ex) ATGCTAG TACGATC |
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5' end has OH or phosphate group bound to 5' carbon of terminal sugar
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while the 3' end has an OH on number 3 sugar
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DNA undergoes semi-conservative replication...
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each strand contains 1 original parent strand and a complementary copy...
--------------------1 --------------------2 replication... ------------------1 ------------------1' and -------------------2 -------------------2' the 1'/2' are complements while the 1/2 are original parent strands |
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how can you tell the parent from the daughter strands?
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methylation
-aged DNA strands will have methyl groups while newly synthesized daughter strands will not |
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origin of replication is the site on the strand where the helix...
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unwinds
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1 origin of replication and 2 replication forks...
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ex)
/------|-------\ \------|-------/ the slashes = replication forks... the line = origin of replication |
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helicase is a protein enzyme that...
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unwinds the DNA helix
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single strand binding proteins will bind to the individual strands to...
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keep them separated
-stabilize the strands |
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as helicase unwinds the helix at one point..it is supercoiling it at the other points not unwound....to compensate this action, DNA gyrase relieves the overwound DNA and introduces negative supercoils
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know
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supercoil = similar to phone cord that wraps around itself...relieves tension
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know
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DNA polymerase is the enzyme responsible for....
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adding complementary nucleotides to the strand(parent)
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DNA polymerase requires...
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an RNA primer
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Primase is the enzyme that...
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generates the RNA primer
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synthesis covered on pg 346
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know
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leading strand is the continously read strand
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know
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lagging strand is broken into okazaki fragments and is not continously read
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know
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fragmented strands are put together by DNA ligase
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know
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RNA is similar to DNA but there are exceptions..
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1. RNA = single stranded
DNA = double stranded 2. RNA has Uracil DNA has Thymine 3. RNA has ribose sugar DNA has deoxyribose 4. DNA is only found in nucleus RNA is found in the cytoplasm and nucleus |
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RNA is found in...
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nucleus
cytoplasm |
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RNA participates in both transcription and translation
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know
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mRNA = messenger RNA
-created during transcription/translation |
created during transcription
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mRNA carries info from nucleus to the cytoplasm
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know
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in eukaryotes, mRNA is monocistronic = each mRNA molecule translates into 1 product
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know
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prokaryotes/bacteria are polycistronic = each mRNA molecule translates to more than 1 product...
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different proteins can be formed by starting translation at different positions on the mRNA
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tRNA is found in the cytoplasm and carries amino acid sequence complementary to RNA
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tRNA is involved in translation from mRNA to protein
-makes polypeptide chain |
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there are 20 AA
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know
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rRNA
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synthesized in the nucleolus
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hnRNA = heterogeneous nuclear RNA
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larger, precursor to mRNA and includes riboproteins in structure
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DNA --> RNA =
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transcription
-occurs in the nucleus |
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DNA --> RNA requires RNA polymerase
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U substituted for T
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DNA regions called promoters signal RNA polymerase where to start transcription
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know
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termination sequences built into DNA to stop transcription
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know
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newly formed RNA = hnRNA
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know
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before hnRNA can leave the nucleus, must be prepped to move into cytoplasm through a few processes
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know
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the hnRNA must
1. have a 5'guanosyl cap at beginning 2. 3' poly-adenine tail 3. removal of introns |
know
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eukaryotic genes contain
1. exons = coding genes 2. introns = noncoding genes |
know..
removal of introns |
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hnRNA --> mRNA = splicing
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know
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hnRNA ==> mRNA occurs in the nucleus
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know
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each codon represents 1 AA...
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1 AA is represented by multiple codons
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proteins are made of AA, not nitrogenous bases...
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reason for transcription and translation...
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translation occurs in cytoplasm and requires...
1. tRNA 2. mRNA 3. ribosomes 4. AA 5. energy |
ribosomes are site of translation
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anticodon is what the tRNA carries and it is complementary to the codon of the mRNA
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know
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each tRNA has a tRNA synthetase enzyme
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binds amino acid to tRNA using GTP
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tRNA + AA = aminocyl-tRNA complex
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know
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ribosomes have 2 subunits
-composed of rRNA and ribosomal proteins |
large subunit
small subunit |
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ribosomes have 3 binding sites
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1 is for mRNA
2 is for tRNA |
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tRNA binding sites =
A site P site |
A site = holds aminoacyl-tRNA complex
P site = binds tRNA attached to growing polypeptide chain |
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polypeptide synthesis
3 stages.. |
initiation
elongation termination |
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initiation
mRNA and small ribosome bind using initiation factors -starts at codon AUG |
=start codon
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methionine tRNA base pairs with start codon...recruits large ribosome subunit
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tRNA is in P site
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elongation
tRNA binds to A site, peptide in P site shifts to A site polypeptide, kicks off the P site empty tRNA and the A site tRNA shifts over to the P site...repeat |
peptidyl transferase uses energy stored in aminoacyl-tRNA complex when loaded to catalyze formation of peptide bond
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termination
needs termination codon -UGA -UAA -UAG |
recruits a release factor to the A site, releases ribosomal subunits etc
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polyribosome = many ribosomes that translate at same time
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know
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after translation is complete, the polypeptide is subjected to folding into a 2ndary structure
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polypeptide can have sugars added to it or be cleaved
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some additional modifications to the polypeptide include
-methylation -phosphorylation -carboxylation |
know
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mutation types
-base pair mutations -base pair insertions -base pair deletions |
know
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base pair mutations are known as...
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point mutations
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insertions and deletions are known as...
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frameshift mutations
-since they shift the reading frame by inserting/deleting base pairs |
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base pair mutations are known as...
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point mutations
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point mutations
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occurs on a single nucleotide
-it may or may not have an effect in overall expression/mutation |
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point mutations can form in noncoding and coding regions of strand...
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have the potential of not causing any harm even in the coding region
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no effect from a mutation is known as...
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silent mutation
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which nucleotide of a codon is more important? less important?
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the more important is the first two nucleotides of the codon
-the less important nucleotide is the last one |
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a point mutation at the first/second position in the codon is...
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missense mutation
-one AA is substituted for another |
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silent mutations are result of degeneracy of the genetic code
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know
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nonsense mutation is one that produces a premature termination of the polypeptide chain by changing one of the codons to a stop codon
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know
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thalassemia = ex) of previous mutation where RBC are produced with ineffective Hb content
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know
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sickle cell anemia is an example of a missense mutation where the 3nd nucleotide is substituted
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lack of biconcave RBC shape
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frameshift mutations
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mess up the reading frames = codons = 3 back-to-back nucleotides
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frameshift mutations include insertion/deletion
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changes AA sequence or premature truncation of protein
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cystic fibrosis is an example of a frameshift mutation
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defective chloride ion channels
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mutations can arise from
1. DNA polymerases mistakes 2. ionization radiation from UV 3. self-damaging DNA |
elements called transposons can remove and insert themselves into the genome
-can disrupt reading frame in the process |
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mutations that are inheritable occur within the sex chromosome
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know
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mutations in the somatic cells will not be inherited
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know
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UV light is capable of breaking chemical bonds between pyrimidine bases
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most commonly occurs at CC (next to one another) aka pyrimidine dimer
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viruses can only infect cells that have receptors that recognize the viruses protein coat called the capsid
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know
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viruses can fuse and completely insert (HIV) or can insert genetic material and leave capsids outside(bacteriophage)
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know
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DNA-containing viruses have easy access to nucleus
-use DNA/RNA polymerases of cell |
some DNA viruses can carry out replication in the cytoplasm
-although must bring own DNA/RNA polymerases |
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RNA-containing viruses process occurs in the cytoplasm
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viruses can equip RNA replicase
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RNA replicase is an enzyme used to replicate RNA from an RNA template
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know
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some RNA viruses are retroviruses
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create a DNA copy from RNA using reverse transcriptase enzyme
-host cell will replicate this DNA strand as though it were its own... |
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translation of viral RNA --> proteins requires
-ribosome -AA -enzymes(host) -tRNA |
know
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virions = viral particles
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A complete virus particle with its DNA or RNA core and protein coat as it exists outside the cell
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viral progeny can be released in two ways..
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1. host cell may lyse as a result of filling with viral particles
2. viral invasion may also cause apoptosis= cell death |
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cell lysis and release of viral particles has a disadvantage...
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virus can no longer use the cell to replicate itself
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virions can fuse to the plasma membrane and be excreted aka extrusion
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similar to budding
-but advantage is it allows cell to live and allow viral replication |
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productive cycle involves extrusion
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know
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bacteriophages are viruses that specifically attack bacteria
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know
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bacteriophages insert DNA and keep all other structures outside the cell
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know
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virus can enter two stages depending on growth conditions and specific phage...
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1. lytic
2. lysogenic -only for bacteriophages though |
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lytic cycle
-virus makes maximal use of cells machinery with little regard to damaging the cell |
know
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during lytic cycle, cell will swell with virions inside and the cell lyses and release virions
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know
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bacteria in the lytic cell are called virulent
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know
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lysogenic cycle
-no lysing of the bacteria |
integrates itself into host genome as a provirus
-as bacteria preproduces, so will the virus |
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lysogenic cycle; if stil dormant or attached as provirus, radiation, light or chemicals can trigger the provirus to release itself from the strand and enter the lytic cycle
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know
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bacteria are prokaryotes
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single-celled organisms with circular DNA genome and no organelles
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many bacteria contain plasmids
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extrachromosomal DNA
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episomes = type of plasmid
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capable of integration into the genome
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transcription occurs in ...
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the nucleus
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translation occurs in...
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cytoplasm
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bacteria, having no membrane bound organelles, transcription and translation are not separate processes
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can occur simultaneously
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bacteria can produce polycistronic mRNA to which multiple proteins are coded in the same mRNA molecule
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know
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since bacteria genome is circular, it contains far less information and therefore...
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require less origins of replication
-usually only have 1! |
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bacteria utilize binary fission as replication process
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asexual reproduction
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bacteria have 3 approaches to increase genetic diversity since asex. reprod. produces identical daughter cells
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1. transformation
2. conjugation 3. trandsuction |
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transformation
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results from the integration of foreign chromosomal plasmids into host genome
-becomes distinctively different from the parent cells |
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conjugation
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2 bacterial cells form a bridge(cytoplasmic) and transfer genetic material between them
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transfer of cytomplasmic bridge and conjugation is ONE way
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from the male(+) to receiving female(-)
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bridge is made from appendages called sex pilli
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these are found within the male(+)
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to form the pili(bridge material), bacteria must contain plasmids known as sex factors
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know
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F+ = has sex factors
F- = does not have sex factors |
process of conversion from without to with
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sex factor is a plasmid, but through processes of transformation, it can become integrated into host genome
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know
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usually during transaction processes with bridges, the bridge will collapse half-way though and not send/receive the entire genetic material package...
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cells that have experienced this are called Hfr...or high frequency of recombination
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transduction
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accidental process
-bacteriophage inserts DNA -host dna broken up -virions form inside with host dna and phage dna -break out and attack other bacteria -dna inserted and becomes integrated into the host DNA |
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in prokaryotes, ability to transcribe a gene is based on RNA polymerases access to the genome
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know
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operons are a series of genes that control transcription
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know
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operons are made up of..
1. structural genes 2. operator gene 3. promoter gene |
know
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structure gene codes for protein of interest
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know
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operator site
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nontranscribable region of DNA that is capable of binding a repressor protein
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promoter site is similar in function to seen in eukaryotes
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provides a place for RNA polymerase to bind
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repressor
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a protein that can bind to the operator sequence and acts as a roadblock
-stops/stalls RNA polymerase |
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inducible and repressible systems
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inducible- require presence of compound known as inducer to cause transcription of structural gene
repressible do not have inducer to promote transcription |
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inducer blocks the repressor so it can not bind
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without inducer, the repressor would bind and prevent transcription
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lac operon = codes for enzymes that allow bacterium to digest lactose in place of glucose
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basteria use this option only when lactose is high concentration and glucose is in low concentration
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repressible systems
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allow constant production of a protein product
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repressor remains inactive until binds to a co-repressor
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allows repressor to bind to operator region and prevent transcription
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repressor systems act like negative feedback
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product can act as the corepressor
ex) trp operon -tryptophan |
