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Mutation
Terms from Mutations unit of 04-350 at NW
| Term | Definition |
|---|---|
| primary structure | the order of amino acids in a polypeptide which influences all higher levels of structure, determined by the order of codons in the mRNA ORF |
| secondary structure | shapes within a polypeptide chain due to hydrogen bonds that occur between the amino groups and carboxyl groups of amino acids in the same chain, may be alpha helix or beta pleated sheets |
| alpha helix | a type of secondary structure within a polypeptide that forms when hydrogen bonding occurs between parts of amino acids in close proximity, a spiral structure |
| beta pleated sheets | a type of secondary structure within a polypeptide that forms when hydrogen bonding occurs between parts of amino acids that are in the same chain but far apart, a planar structure |
| tertiary structure | the overall three dimensional shape of a polypeptide, formed due to chemical interactions between R groups in the polypeptide. interactions may be covalent, hydrogen bonding, ionic, hydrophobic interactions, or van der Wals forces. |
| quaternary structure | when multiple polypeptides fuse together to form a functional protein |
| mutation | a change in the genetic material not caused by mutation that can be inherited, occurs within DNA |
| germinal mutation | a mutation that occurs within a cell responsible for producing gametes (sperm or egg) and is therefore passed on to the products of sexual reproduction (offspring) |
| somatic mutation | a mutation that occurs within a cell that does not go through meiosis and therefore does not produce gametes. passed on to daughter cells when mitosis occurs but is not transmitted to offspring |
| deletion | elimination of nucleotides within a chromosome, may be small scale (1-2 nt) or large scale (100s-1000s) |
| translocation | large scale chromosomal mutation that breaks off a chunk of a chromosome and reattaches it at another location |
| inversion | large scale chromosomal mutation that reverses a segment of a chromosome |
| duplication | large scale chromosomal mutation that provides additional copies of a segment of a chromosome |
| indel | general term used to describe a relatively small insertion or deletion within a DNA molecule |
| frameshift | a potential consequence of an indel if it occurs in the DNA sequence that will code for a portion of the ORF in the mRNA, alters all downstream codons and produces a nonfunctional protein |
| base substitution | replacing one nitrogenous base for another within a DNA strand, also known as a point mutation |
| transition | a type of base substitution that occurs when one purine replaces another purine or one pyrimidine replaces another pyrimidine |
| transversion | a type of base substitution that occurs when a purine replaces a pyrimidine or a pyrimidine replaces a purine |
| missense mutation | potential consequence of a base substitution that occurs in a sequence coding for an ORF if a codon is altered so that it codes for a different amino acid than it had prior to the mutation |
| nonsense mutation | potential consequence of a base substitution that occurs in a sequence coding for an ORF if a codon is altered so that it codes for a stop codon instead of an amino acid. results in premature termination, likely producing a non functional protein |
| silent mutation | a mutation that does not affect the ability of a protein to function, may be due to a mutation outside of the ORF or a mutation in the ORF that alters a codon but it still codes for the same amino acid |
| synonymous mutation | potential consequence of a base substitution that occurs in a sequence coding for an ORF if a codon is altered so that it codes for the same amino acid as it did prior to the mutation due to redundancy in the genetic code. |
| loss of function mutation | mutation that significantly alters the tertiary structure of a polypeptide so that it completely loses its ability to carry out its normal functional abilities, usually a recessive mutation |
| amorphic mutation | another term for a loss of function mutation, implying complete loss of shape (morph) |
| null mutation | another term for a loss of function mutation |
| partial loss of function mutation | a mutation that alters the tertiary structure of a polypeptide so that it retains some functional ability but not as much as prior to the mutation, also known as a leaky mutation, may be due to small changes in shape |
| hypomorphic mutation | another term for a partial loss of function or leaky mutation |
| increase of function mutation | a mutation that alters the tertiary structure of a polypeptide so that it functions better than it did before the mutation |
| hypermorphic mutation | another term for an increase of function mutation |
| gain of function mutation | a mutation that alters the tertiary structure of a polypeptide so that it loses its previous ability but now has a different reaction or ability that it can perform, usually a dominant mutation |
| neomorphic mutation | another term for a gain of function mutation |
| neutral mutation | due to a missense mutation that alters the order of amino acids in the polypeptide but the chemical characteristic of the new amino acid is similar enough that the tertiary structure does not change enough to impact protein function |
| allele | a version of a gene generated as a result of mutations taking place |
| forward mutation | altering a wild type allele so that it is now mutant |
| reverse mutation | altering a mutant allele so that normal function is restored by converting it back to a wild type allele |
| wild type allele | a "normal" version of a gene |
| suppression | a second mutation that corrects or compensates for the effects of the first |
| intragenic suppression | a second mutation within the same gene that corrects for the effects of the first |
| intergenic suppression | a second mutation within a second gene that corrects for the effects of a first mutation in a different gene |
| nonsense suppression | a type of intergenic suppression where a mutation in a tRNA gene creates an anticodon that is able to bind to a codon that normally serves as a stop... therefore correcting for a nonsense mutation |
| homologous chromosomes | chromosomes that are copies of one another but may not be exactly identical for all alleles on those chromosomes |
| homozygous | when homologous chromosomes carry copies of the same allele of a particular gene |
| heterozygous | when homologous chromosomes carry copies of different alleles of a particular gene |
| dominant allele | a version of a gene that codes for a protein that is able to function normally (wild type) or in a new way due to a gain of function mutation |
| recessive allele | a version of a gene that codes for a protein that does not function normally, usually a loss or partial loss of function |
| spontaneous mutation | a mutation due to natural events in the cell with no external cause |
| DNA polymerase | the enzyme responsible for making new strands of DNA during replication prior to each cell division |
| proofreading | the ability of a polymerase to correct errors that it makes, highly effective in DNA polymerase but minimal in RNA polymerase |
| 3' to 5' exonuclease | ability of DNA polymerase to remove nucleotides from the 3' end of the chain if it makes an error during replication, helps to reduce the number of mutations |
| strand slippage | cause of replication error spontaneous mutations, due to improper pairing between two strands of nucleic acid when the same base or same series of bases is repeated, results in indel mutations |
| depurination | spontaneous chemical damage to the DNA molecule when a glycosidic bond is broken between a purine (A or G) and the 1' carbon, results in a hole in the double stranded DNA helix |
| deamination | spontaneous chemical damage to the DNA molecule when an amino group is lost from one of the nitrogenous bases, altering its ability to hydrogen bond with complementary bases |
| transposon | also known as a transposable element, a segment of DNA that is able to remove itself and insert itself within a chromosome at random |
| induced mutations | mutations caused by some substance (mutagen) external to the cell, occurs at a rate higher than spontaneous mutations |
| mutagen | any substance that can cause mutations to occur at higher than the spontaneous rate, include radiation (x rays, uv light) and chemical exposure |
| thymine dimer | covalent bond that forms between adjacent thymines in the same DNA strand, alter the shape and hinder proper base pairing with complementary bases, due to uv light exposure |
| base analogues | artificial substances with chemical structures similar to natural nitrogenous bases but may have altered base pairing rules, a type of chemical mutagen |
| alkylating agents | chemical that will add small hydrocarbon chains (alkyl groups) to nitrogenous bases, altering their base pairing abilities |
| nitrous acid | mutagen that increases the rate of deamination |
| hydroxylamine | mutagen that may alter cytosine so it will pair with adenine |
| ames test | common test used to identify chemicals that have mutagenic effects |
| mismatch repair | DNA repair mechanism used by the cell to identify and correct improper base pairing caused by replication errors |
| adenine methylase | enzyme that adds methyl group to adenine anywhere the sequence GATC is found, resulting in the ability to distinguish old and new strands of DNA for a short period of time |
| hemimethylated | when only one of two strands of DNA has been methylated, state for a short time immediately after replication |
| endonuclease | enzyme able to cut DNA in the middle of the molecule, breaking phosphodiester bonds |
| ligase | enzyme capable of making phosphodiester bonds between adjacent nucleotides |
| photoreactivation | ability of single celled prokaryotes and eukaryotes to use the enzyme photolyase to break the bond between thymine dimers, correcting damage caused by uv light |
| nucleotide excision repair | repair mechanism used to remove thymine dimers by recognizing the abnormal shape created by the dimer and cutting the DNA on either side to remove multiple nucleotides, creating a single stranded segment in the DNA molecule that then must be repaired |
| base excision repair | repair mechanism used to remove chemically damaged bases by removing the damaged base by cutting the glycosidic bond, creates an AP site which is then repaired |
| AP site | apurinic site, when a purine is lost from a double stranded DNA molecule, leaving a gap in the middle of the helix |
| AP endonuclease | enzyme that repairs AP sites generated by base excision or spontaneous depurination |
Created by:
jthorns
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