Term
| Any change in the DNA sequence of an organism is called a __________ whether a phenotypic change is induced or not. |
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Definition
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Term
| Mutations that occur in the absence of an experimentally applied mutagenic treatment are called __________ mutations (even if they are due to naturally occurring known mutants). |
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Definition
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Term
| Mutations created by the experimental application of a mutagen are called __________ mutations. |
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Definition
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Term
| Mutations in __________-__________ cells (eggs / sperm) may be passed on to the next generation; mutations in all other cells of a complex organism (__________ cells) only affect that organism and are not transmitted to progeny. |
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Definition
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Term
__________ mutations are those which cause a detectable phenotypic change under one condition (the __________ condition) but not under another condition (the __________ condition).
A widely used class of conditional mutations are __________ __________ mutations, in which cells are able to grow at one temperature but not another. |
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Definition
1) Conditional
2) Restrictive
3) Permissive
4) Heat / cold sensitive |
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Term
| Most mutations are __________ and often result in a complete loss of function (also called __________ or __________ mutations); they are __________ to the wild type. |
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Definition
1) Deleterious
2) Null
3) Knockout
4) Recessive |
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Term
Gain of function mutants are __________ over the wild type allele.
Expression of a wild type gene in an abnormal tissue location is also called __________ __________. |
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Definition
1) Dominant
2) Ectopic expression |
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Term
| __________ mutations result in a reduction of a function of a gene while __________ result in the increase in a function of a gene. |
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Definition
1) Hypomorphic
2) Hypermorphic |
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Term
| A __________ mutation is one that has a base change that does not change the protein (such as a UUU -> UUC mutation which still results in the amino acid Phe at the specific position in the protein). |
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Definition
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Term
| Change of one amino acid to another is called a __________ mutation. |
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Definition
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Term
| Those missense mutations that change one amino acid to a similar amino acid are called __________ mutations. |
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Definition
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Term
| Replacement of an amino acid codon by a chain termination codon is called a __________ mutation. |
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Definition
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Term
| Replacement of one nucleotide by a different nucleotide is called a __________-__________ mutation. |
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Definition
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Term
Replacement of a purine by a purine or a pyrimidine by a pyrimidine is called a __________ mutation.
Replacement of a purine by a pyrimidine and vice-versa is called a __________ mutaiton. |
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Definition
1) Transition
2) Transversion |
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Term
| Addition / deletion of nucleotides usually cause a change in the reading from of mRNA during protein synthesis; such mutations are called __________ mutations. |
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Definition
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Term
Some human disease are caused by expansion of __________ repeats.
In this case of mental retardation, there is a chromosome break near the end of the long arm of the X-chromosome (the __________ __________-__________). |
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Definition
1) Triplet
2) Fragile X-site |
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Term
| Down's syndrome (or __________) is caused by an extra copy of chromosome __________. |
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Definition
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Term
Triplet repeat expansion occurs due to __________ __________ and __________ __________ __________.
Sometimes there is misalignment of DNA sequences near the growing strand end in the DNA replication fork. This results in the gain of __________.
In some of the triplet expansion disease, the expansion does not occur in just one generation, but expands over several (a phenomenon known as __________). With each passing generation, the symptoms become more severe. |
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Definition
1) Replication slippage
2) Mismatch repair mechanism
3) Triplets
4) Anticipation |
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Term
Some of the cystines in the CGG repeats may be __________. As the triplets increase in number, the number of target sites for __________ methylation also increases. Methylation of __________ in the triplet repeats turns off the expression of the __________ gene (fragile-site mental retardation 1).
This gene codes for a protein that binds to __________ that are capable of intra-strand base pairing in G-rich areas creating a __________-__________.
The binding of the FMR1 protein to the G-quartets in the RNAs regulates the creation of __________ of these mRNAs which play important roles in the brain and nervous system abnormal regulation. |
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Definition
1) Methylated
2) Cytosine
3) Cytosine
4) FMR1
5) mRNAs
6) G-quartet
7) Proteins |
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Term
Many mutations are caused by the disruption of the __________ __________ sequence of a gene by the insertion of a foreign piece of DNA.
Such mutations are often unstable and revert back to the __________ __________ when the foreign insert leaves the gene.
These moveable DNA sequences were first discovered in __________. |
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Definition
1) Protein coding
2) Wild type
3) Corn |
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Term
| The process of a foreign DNA movement from one location to another in the genome is called __________. |
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Definition
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Term
Most __________ are small pieces of DNA that have short inverted repeats at their ends. They also have a gene that codes for the enzyme __________ which recognizes the inverted repeat sequences and cuts the transposon cleanly out from its __________ site.
Insertion into a new site is catalyzed by the same enzyme; it makes a __________ cut somewhere else in the genomic DNA and inserts the __________ in this cut site.
Once the gaps in the DNA flanking the transposon have been filled, short direct repeats of the host DNA are created at the two ends of the inserted transposon. Such a mechanism of transposition is called a __________ __________ __________ mechanism.
Some transposons make a copy of the transposon and insert the copy into a new location (__________ __________ __________ mechanism).
A third class of transposons (called __________) makes an RNA copy of the transposon; the RNA is then __________ transcribed into the DNA and the DNA copy is inserted into a new location.
Retrotransposons usually have several hundred nucleotides long direct repeats called __________ __________ __________ at their two ends. |
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Definition
1) Transposons
2) Transposase
3) Insertion
4) Staggered
5) Transposon
6) Cut and paste
7) Copy and paste
8) Retrotransposons
9) Reverse
10) Long terminal repeats |
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Term
Recombination between two __________ in the same chromosome have different outcomes depending upon how they are oriented.
If they are oriented in the __________ direction, recombination causes the deletion of the intervening chromosomal DNA.
If they are oriented in __________ direction leads to inversion of the chromosomal DNA between two transposons.
Recombination between two transposons located in nonhomologous chromosomes can cause transfer of large chunks of DNA between two nonhomologous chromosomes (a chromosome abnormality called __________ __________). |
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Definition
1) Transposons
2) Same
3) Inverse
4) Reciprocal translocation |
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Term
| __________ mutations are slowly eliminated from the population due to natural selection against them. |
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Definition
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Term
| Analysis of a large number of mutations in a few well studied genes revealed that most sequences have a low rate of mutation; however, there are rate sequences that show a very high rate of mutation - these are __________ __________. |
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Definition
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Term
| What are the two type of mutation hotspots? |
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Definition
1) Repeated sequences
2) 5-methyl Cytosine residues |
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Term
A small fraction of __________ in DNA are methylated at the __________-position of the pyrimidine ring.
Cytosines deaminate spontaneously and convert to __________; this is a mutagenic event since uracil pairs with __________.
To prevent such mutations, cells have a mechanism for the monitoring of DNA for the presence of uracil and then removing them and replacing them with __________.
The uracil is cut out of the __________ backbone by an enzyme leading behind an __________ __________ (apurinin / apyrimidinic site).
A __________ cuts the backbone and the stretch of backbone with the AP site is discarded; the gap is filled by a DNA polymerase and DNA ligase restores the backbone continuity. |
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Definition
1) Cytosines
2) 5
3) Uracil
4) Adenine
5) Cytosine
6) Phosphodiester
7) AP site
8) Nuclease |
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Term
| Any agent that increases mutations is called a __________. |
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Definition
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Term
| What are the two categories of mutagens? |
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Definition
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Term
DNA bases spontaneously are cleaved from the sugar backbone due to hydrolytic attack by __________.
__________ are lost much more readily than __________.
The resulting AP sites are corrected in the same manner as 5-methylated Cytosine residues. |
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Definition
1) Water
2) Purines
3) Pyrimidines |
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Term
An example of a deaminating mutagen is __________ __________. It causes GC -> AT and AT -> GC mutations.
It deaminates G to __________, A to __________, and C to __________. |
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Definition
1) Nitrous acid
2) Xanthine
3) Hypoxanthine
4) Uracil |
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Term
| __________ __________ are compounds closely resembling normal DNA bases in structure such that they can become incorporated into DNA during DNA replication / repair. |
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Definition
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Term
A very well studied base analog is __________-__________-__________ (BU), an analog of thymine.
In bromouracil, the __________ group at the __________-position of the pyrimidine ring is replaced by a bromine atom. When added to a cell as a free base, or deoxynucleotide, the base analog is converted to the triphosphate nucleotide and used by DNA polymerase as a substitute for __________, the normal substrate.
Bromouracil is a __________ mutagen, causing AT -> GC and GC -> AT mutations. |
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Definition
1) 5-bromo-uracil
2) Methyl
3) 5
4) TTP
5) Transition |
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Term
It is thought that BU is mutagenic because it tends to tautomerize to the mutagenic __________ form of the base more often than does thymine.
The normal keto form of BU pairs like __________; however, the tautomeric enol form pairs like __________. This leads to an increase in __________ mutation rates.
The __________ of BU mutagensis occurs because it can go to the mutagenic enol form either as a __________ __________ causing AT -> GC transition or as a __________ __________ pairing with a template G-residue and later reverting to its keto form causing GC -> AT transition. |
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Definition
1) Enol
2) Thymine
3) Cytosine
4) Transition
5) Bidirectionality
6) Template residue
7) Free nucleotide |
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Term
A variety of powerful chemical mutagens add __________ groups (either methyl or ethyl) to DNA bases and change their pairing properties.
__________-__________ __________ pairs like an A, __________-__________ __________ pairs like a C, and so forth.
This primarily causes transition mutations. |
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Definition
1) Alkyl
2) O-ethyl guanine
3) O-methyl thymine |
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Term
| __________ mutagens can cause both AT -> GC and GC -> AT mutations. __________ is an example of a __________ mutation which can only cause GC -AT mutations. |
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Definition
1) Bidirectional
2) Hydroxylamine
3) Unidirectional |
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Term
| An oxidation product of guanine (__________-__________-__________) is known to cause GC -> TA transversion mutations. |
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Definition
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Term
| Some chemicals induce frameshift mutations exclusively; most are flat __________-ring structures resembling a base pair. They insert themselves in between two base pairs (__________) and this causes misalignment of DNA during DNA replication causing gain or loss of one nucleotide. |
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Definition
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Term
| Muller in 1927 discovered that __________-__________ induce mutations and chromosome breaks and rearrangements at a high rate. |
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Definition
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Term
In contrast to X-rays, __________-__________ does not make __________ __________ (non-ionizing radiation).
Here, DNA directly absorbs the energy of UV radiation and the bases become excited and undergo chemical rearrangements.
The commonest damage products are __________ linking of adjacent __________ __________ (such as TT, CC, TC, and CT dimers) |
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Definition
1) UV-light
2) Free radicals
3) Covalent
4) Pyrimidine dimers |
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Term
| High energy radiation like __________-__________ induce formation of reactive ions from water (__________ __________) and these react with DNA causing a large variety of base alterations as well as single and double-strand breaks in DNA. |
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Definition
1) X-rays
2) Free radicals |
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Term
| X-rays and similar radiations are called __________ __________ and extensive studies have shown that the amount of mutations induced is directly proportional to the dose of __________ (no way for mutation to not form if exposed to radiation). |
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Definition
1) Ionizing radiation
2) Radiation |
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Term
| What are the eight types of DNA repair? |
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Definition
1) Post-replication mismatch repair
2) Excision repair of small DNA damages
3) Repair of bulky DNA damage
4) Photoreactivation of pyrimidine dimers
5) Excision repair of bulky damage
6) Recombinational repair
7) Error-prone or SOS repair
8) Reversion of mutations |
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Term
Despite its high accuracy some mistakes are left behind by the __________ apparatus.
The high accuracy of replication is achieved in two steps; what are they? |
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Definition
1) Replication
2) There is a high level of discrimination between the correct and incorrect nucleotide during the polymerization step
3) Proofreading of errors by the 3' -> 5' nuclease activity of replication polymerases makes an additional 100x difference. |
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Term
| What are three of the most important enzymes required for the mismatch repair process in E. coli? |
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Definition
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Term
| All cells contain a variety of enzymes that recognize modified bases and break the bond between the deoxyribose sugar and the damaged base to free the base. This creates an __________ __________ which is repaired as with 5-methyl Cytosine residues. |
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Definition
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Term
| UV light-induced pyrimidine dimers can be converted back to the two original undamaged bases by an enzyme called __________ provided visible light energy is available. |
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Definition
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Term
| Excision repair of bulky damage in E. coli is done by what three proteins? |
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Definition
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Term
| What is the last resort repair mechanism in E. coli? What occurs in this mechanism? |
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Definition
1) SOS repair pathway
2) During SOS repair, a new sloppy DNA polymerase is synthesized copying past the damaged site even though no base pairing is possible due to damaged template nucleotides. |
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Term
| Most spontaneous and induced mutations can be reverted back to the __________ __________, the only exception are __________ mutations. |
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Definition
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Term
| When a wild type revertant is obtained from a mutant, it is done so by what two mechanisms? |
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Definition
1) True reversion
2) Second site suppressor mutations |
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Term
| __________ __________ is the return of the original wild type DNA sequence |
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Definition
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Term
__________-__________ __________ mutations restore the wild type phenotype by creating a second __________ mutation.
The second mutation may be in the same gene as the original mutation ( __________ __________) or in a gene different from the site of the original mutation (__________ __________). |
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Definition
1) Second-site suppressor
2) Compensating
3) Intragenic suppression
4) Intergenic suppression |
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Term
| A very common mechanism of intragenic suppression is seen with __________ mutations. |
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Definition
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Term
Many mutations result in the creation of a __________ __________ __________ in the middle of the protein coding information of a gene.
This can happen in any gene and the result is a __________ protein which is usually very defective and often degraded by proteasome.
The most prevalent cases of intergenic suppressor mutations which are found in __________ genes. |
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Definition
1) Chain termination codon
2) Trunacted
3) tRNAs |
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Term
| The __________ __________ detects cancer causing chemicals. The hormone __________ __________ is an example of a rare cancer causing hormone. |
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Definition
1) Ames test
2) Diethyl-stilbesterol (DES) |
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