Semi-conservative replication
Correct theory
-proposed by Watson and Crick
-the double helix is split, and a new strand of DNA is built on each of the original parent strands
Helicase
unzips DNA, also causing it to unwind
Enzyme responsible for relieving tension in the unwinding DNA by untwisting it.
Gyrase
Adds DNA nucleotides during replication.
DNA polymerase III
Stabilizes the unzipped strands to prevent reannealing.
Single Strand Binding Proteins
Name of fragments that are formed on lagging strand.
Okazaki
The direction in which new DNA is built.
Your Answer: 5'-3'
Adds RNA nucleotides.
Primase
Replaces RNA nucleotides with DNA.
DNA polymerase I
Breaks bonds between nitrogenous bases, unzipping DNA.
Helicase
A lesser known enzyme, thought to be responsible mainly for proofreading new DNA.
DNA polymerase II
Which of the following is found in the nucleolus?
rRNA
Which of the following is not found in the cytoplasm?
DNA
Which of the following best represents the mRNA that would result from the following template strand? AATTAACCGGCGAATT
UUAAUUGGCCGCUUAA
Which enzyme is responsible for transcription?
RNA polymerase
A section of mRNA 6 codons long would code for how many amino acids?
6
Which statement is correct regarding the flow of information in the cell?
DNA - mRNA - ribosome - tRNA - protein
What is the function of the poly(A) tail that is added to mRNA?
To prevent degradation of the mRNA
The degeneracy of the genetic code means:
If a mutation occurs, it is more likely to be silent
Which of the following statements is correct?
the promoter region must be easy to unzip
How is mRNA prepared for it's entry into the cytoplasm?
A methyl guanosine cap is added
What is the function of a spliceosome?
remove introns
What is responsible for delivering amino acids to the ribosome?
tRNA
What is responsible for transferring genetic information from the nucleus into the cytoplasm?
mRNA
What is responsible for building protein by making peptide bonds?
ribosome
What is complementary to the mRNA codon?
anticodon
What is the end product of transcription?
mRNA
What is the end product of translation?
polypeptide
Gyrase (topoisomerase)
relieves tension in the DNA that builds up as a result of the unzipping
Single strand binding proteins (SSB's)
proteins that stabilize the unzipped single strands
Replication fork
the opening where DNA is unzipped. There are several i eukaryotic DNA, resulting in replication bubbles
Primase
Adds RNA primers to the single DNA strands to initiate polymerization
DNA polymerase III
Adds DNA nucleotides in the 5' to 3' direction (moves from 3' to 5' direction on the parent strand)
The lagging strand is built in what direction
5 to 3 direction
The leading strand
The faster strand that is made continuously in the direction that the DNA is unzipping
DNA ligase
glues the Okazaki fragments together
DNA polymerase I
Replaces RNA primers with DNA nucleotides.
DNA polymerase II
Involved in proofreading the newly formed strands
The genetic code is DEGENERATE
this means that more than one triplet or codon codes for the same amino acid or stop command...why is this important? (allows small errors to go unnoticed)
Codons
3 nitrogenous bases on DNA or mRNA = a codon. A codon codes for an amino acid.
Start Codon
AUG (methionine, or met)
The codon that signals the start of a polypeptide chain and initiates translation
Stop codon
UAA, UAG, UGA
A codon that signals the end of a polypeptide chain and causes the ribosomes to stop translation
What do the ribosomes do?
Produce polypeptides
rRNA
Ribosomal RNA; normally located in the nucleolus of the cell, where ribosomes are formed
Ribosomes are made of rRNA and proteins
tRNA
transfer RNA; each tRNA carries a particular amino acid - this is dictated by its anticodon (which is complementary to the codon found on the mRNA)
mRNA
molecular expression of the DNA ge
Direction genetic code is read in
5 - 3 direction on mRNA
Small Scale mutations
Small scale mutations include mutations of an individual base pair called point mutations, and of small groups of base pairs. There are several different types of point mutatoins including: substitution, insertion or deletion, and inversion.
Large Scale Mutation
Large-scale mutations can involve multiple nucleotides, entire genes, or whole regions of chromosomes. Translocation? and Inversion occur.
Translocation
Occurs when entire genes or sequences are moved to a different chromosome. This can change the regulation of the gene or even the protein that results.
Inversion
Occurs when a section of the DNA is flipped. This results in a mutation only if the inversion occurs in a section that codes for protein.
Silent mutation
a change in a non-coding part of DNA or the third base of a codon that is redundant in its coding for an amino acid. Silent mutations have no effect on the amino acid made by translation.
Misence Mutation
a change in a codon so that a different amino acid is produced. This can either be small scale (one or two amino acids) or large (entire protein changes).
Nonsense mutation
a change in a codon so that the codon acts as a punctuation, stopping a transcription prematurely.
How do mutations occur
Some are spontaneous, arising in the duplication actions of DNA. There are also that occur because of the presence of particular chemicals or radiation, mutagenic agents. Their presence induces mutations at a far higher rate than found normally.
Transcription
Copying information from DNA into mRNA
Initiation stage
RNA polymerase binds to the DNA at a promoter region (a region that is 'upstream', or a bit before, the actual gene). It is often a string of A's and T's - since they each only have 2 hydrogen bonds, it takes less energy for RNA polymerase to break them a
Elongation stage
The mRNA is built on only one of the strands - the template strand is the one that the mRNA is built on, and the coding strand is the one that is not used. Note: the coding strand is identical to the resulting RNA, except that the DNA contains T's and the
Termination stage
Terminator sequence tells RNA polymerase to stop transcription. The mRNA detaches itself, and can leave the nucleus.
What are biological molecules responsible for?
- the storage and transmission of inherited information
- providing structure for cells and organisms
- carrying out functions necessary for life
Translation
Utilization of mRNA as a blueprint to make polypeptide(s)
Substitution mutation
? a substitution occurs when one base is replaced with another - this can result in silent, missense, nonsense mutations
Insertion or deletion mutation
? an insertion or deletion occurs when a base is inserted or deleted - this results in a frameshift, which in turn will result in multiple missense, or nonsense mutations. (insertion of 3 bp does not cause frameshift)
DNA mutations
Changes in DNA base sequence
Bio technology
the use of a living organism to develop useful products (alcohol, insulin).
Recombinant DNA
fragment of DNA composed of sequences from at least 2 different sources. .
Restriction Endonucleases:
enzymes that cleave double-stranded DNA into fragments at a particular point called a "recognition site". (only come from bacteria!)
EcoR1
lways cleaves DNA at:
� This type of cleavage results in "sticky ends" (a series of unpaired bases).
Suma1
Sma1 - always cleaves DNA at:
� Other enzymes such as Sma1 produce "blunt ends" which are fully paired.
Lac Operon
The lac operon is a cluster of three genes that code for the proteins involved in the metabolism of lactose. The lac operon consist of a promoter (the site where DNA transcription begins), an operator (the sequence of bases that contron transcription), an
methylase
� Bacterial cells produce the enzyme methylase that will add methyl groups (CH3) to their DNA to prevent the naturally occurring restriction enzymes from cleaving their own DNA.
� Molecular biologists can also use DNA methylase to protect a DNA fragment f
Prokaryotic cell
Prokaryotes can be divided into two domains, Archaea and Bacteria.
-translation (synthesis of proteins) starts while transcription of the mRNA is occurring (ie. Prokaryote ribosomes don't even wait for transcription to be done before they start using the
Eukaryotic cell
These are plant and animal cells
- takes hours or days for protein synthesis to take place
- -mRNA must be transported from nucleus to cytoplasm before proteins can be synthesized
Nucleic acids
Nucleic acids are polymers that are made up of nucleotide monomers. Examples of nucleic acids include deoxyribonucleic acids (DNA) and ribonucleic acid (RNA).
Polymer Structure
� backbone of double helix is sugar / phosphate (backbone of ladder)
� 2 strands attached through H bonding on base pairs (rungs of ladder)
� Ladder is twisted into what is referred to as a double helix
Denaturation of DNA
Heat can break H bonds between N bases, unzipping DNA. If the damage is not too great, the DNA can "rezip" itself once it is cooled.
Nucleotide structure
nucleotide contains ribose sugar (or deoxyribose, seen in DNA), phosphate group, and one of 4 possible nitrogenous bases.