Deletion, point mutation, and insertion. Deletion is when a base pair is completely omitted from the sequence. A point mutation is when a wrong nucloetide is placed in the sequence in place of the correct one. Insertion is when a nucleotide is added to the sequence between or after correct ones.
2007-01-29 20:02:17
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answer #1
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answered by DavidK93 7
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1-Substitution
It is a mutation that exchanges one base for another(switching an A to a G).
2-Insertion.
Are mutations where extra base pairs are inserted into a new place in DNA.
3-Deletion.
Where a section of DNA is lost or deleted.
4-Frameshift.
2007-01-30 04:15:05
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answer #2
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answered by Anonymous
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In biology, mutations are changes to the base pair sequence of genetic material (either DNA or RNA). Mutations can be caused by copying errors in the genetic material during cell division and by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately under cellular control during processes such as meiosis or hypermutation. In multicellular organisms, mutations can be subdivided into germline mutations, which can be passed on to descendants, and somatic mutations. The somatic mutations cannot be transmitted to descendants in animals. Plants sometimes can transmit somatic mutations to their descendants asexually or sexually (in case when flower buds develop in somatically mutated part of plant).
Mutations create variation in the gene pool, and the less favorable (or deleterious) mutations are removed from the gene pool by natural selection, while more favorable (beneficial or advantageous) ones tend to accumulate, resulting in evolutionary change. Neutral mutations are defined as mutations whose effects do not influence the fitness of either the species or the individuals who make up the species. These can accumulate over time due to genetic drift. The overwhelming majority of mutations have no significant effect, since DNA repair is able to mend most changes before they become permanent mutations, and many
TYPES OF MUTATION
Small-scale mutations affecting one or a few nucleotides, including:
Point mutations, often caused by chemicals or malfunction of DNA replication, exchange a single nucleotide for another. Most common is the transition that exchanges a purine for a purine (A â G) or a pyrimidine for a pyrimidine, (C â T). A transition can be caused by nitrous acid, base mispairing, or mutagenic base analogs such as 5-bromo-2-deoxyuridine (BrdU). Less common is a transversion, which exchanges a purine for a pyrimidine or a pyrimidine for a purine (C/T â A/G). A point mutation can be reversed by another point mutation, in which the nucleotide is changed back to its original state (true reversion) or by second-site reversion (a complementary mutation elsewhere that results in regained gene functionality). These changes are classified as transitions or transversions. An example of a transversion is adenine (A) being converted into a cytosine (C). There are also many other examples that can be found. Point mutations that occur within the protein coding region of a gene may be classified into three kinds, depending upon what the erroneous codon codes for:
Silent mutations: which code for the same amino acid.
Missense mutations: which code for a different amino acid.
Nonsense mutations: which code for a stop and can truncate the protein.
Insertions add one or more extra nucleotides into the DNA. They are usually caused by transposable elements, or errors during replication of repeating elements (e.g. AT repeats). Insertions in the coding region of a gene may alter splicing of the mRNA (splice site mutation), or cause a shift in the reading frame (frameshift), both of which can significantly alter the gene product. Insertions can be reverted by excision of the transposable element.
Deletions remove one or more nucleotides from the DNA. Like insertions, these mutations can alter the reading frame of the gene. They are irreversible.
Large-scale mutations in chromosomal structure, including:
Amplifications (or gene duplications) leading to multiple copies of chromosomal regions, increasing the dosage of the genes located within them.
Deletions of large chromosomal regions, leading to loss of the genes within those regions.
Mutations whose effect is to juxtapose previously separate pieces of DNA, potentially bringing together separate genes to form functionally distinct fusion genes (e.g. bcr-abl). These include:
Chromosomal translocations: interchange of genetic parts from nonhomologous chromosomes.
Interstitial deletions: an intra-chromosomal deletion that removes a segment of DNA from a single chromosome, thereby apposing previously distant genes. For example, cells isolated from a human astrocytoma, a type of brain tumor, were found to have a chromosomal deletion removing sequences between the "fused in glioblastoma" (fig) gene and the receptor tyrosine kinase "ros", producing a fusion protein (FIG-ROS). The abnormal FIG-ROS fusion protein has constitutively active kinase activity that causes oncogenic transformation (a transformation from normal cells to cancer cells).
Chromosomal inversions: reversing the orientation of a chromosomal segment.
Loss of heterozygosity: loss of one allele, either by a deletion or recombination event, in an organism that previously had two different alleles.
2007-01-30 04:51:11
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answer #3
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answered by divagal 2
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Point, deletion, insertion.
2007-01-30 03:59:33
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answer #4
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answered by Pseudo Obscure 6
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