11, ERAMESHIFT MUTATION 2: Here is your original DNA sequence from this lab and
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11, ERAMESHIFT MUTATION 2: Here is your original DNA sequence from this lab and the amino acid sequence that was translated from it; C T G A G C T A c T G A G ci T G A G c T G c A G A G c c G A G cl T c ci T G T Gi T A A A c TTG MET THR ARG LEU ASP AL SER ALA ARG GLY HIS ILE STOP a. Now let's simulate a frameshift mutation by deleting the 10 base. Now transcribe this new DNA strand into mRNA. and then also translate it into its amino acid seguence. C T G A G c T A cX G A G ci T G A G c Tel G c A G A G c c G A G c T c ci T G T G T A A A c TT G b. Did this change in the DNA sequence cause any significant change lo the protein produced? Explain. c. Which do you think would cause a more profound biological impact: (1) a deletion/insertion near the beginning of a gene, or (2) a deletion/insertion towards the end of a gene? Explain. 10 of 11 Developed by Kim B. Foglia. www.ExploreBiology.com O2008Explanation / Answer
In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) (sign: ) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is lost during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome. The smallest single base deletion mutations are believed to occur by a single base flipping in the template DNA, followed by template DNA strand slippage, within the DNA polymerase active site. Deletions can be caused by errors in chromosomal crossover during meiosis, which causes several serious genetic diseases. Deletions that do not occur in multiples of three bases can cause a frameshift by changing the 3-nucleotide protein reading frame of the genetic sequence. The examples given below of types and effects of deletions are representative of eukaryotic organisms, particularly humans, but are not relevant to prokaryotic organisms such as bacteria.
Causes include the following:
For synapsis to occur between a chromosome with a large intercalary deficiency and a normal complete homolog, the unpaired region of the normal homolog must loop out of the linear structure into a deletion or compensation loop.
Types of deletion include the following:
Microdeletion is usually found in children with physical abnormalities. A large amount of deletion would result in immediate abortion (miscarriage).
Small deletions are less likely to be fatal; large deletions are usually fatal — there are always variations based on which genes are lost. Some medium-sized deletions lead to recognizable human disorders, e.g. Williams syndrome.
Deletion of a number of pairs that is not evenly divisible by three will lead to a frameshift mutation, causing all of the codons occurring after the deletion to be read incorrectly during translation, producing a severely altered and potentially nonfunctional protein. In contrast, a deletion that is evenly divisible by three is called an in-frame deletion.
Deletions are responsible for an array of genetic disorders, including some cases of male infertility and two thirds of cases of Duchenne muscular dystrophy. Deletion of part of the short arm of chromosome 5 results in Cri du chat syndrome. Deletions in the SMN-encoding gene cause spinal muscular atrophy, the most common genetic cause of infant death.
A frameshift mutation (also called a framing error or a reading frame shift) is a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame (the grouping of the codons), resulting in a completely different translation from the original. The earlier in the sequence the deletion or insertion occurs, the more altered the protein. A frameshift mutation is not the same as a single-nucleotide polymorphism in which a nucleotide is replaced, rather than inserted or deleted. A frameshift mutation will in general cause the reading of the codons after the mutation to code for different amino acids. The frameshift mutation will also alter the first stop codon ("UAA", "UGA" or "UAG") encountered in the sequence. The polypeptide being created could be abnormally short or abnormally long, and will most likely not be functional.
Frameshift mutations are apparent in severe genetic diseases such as Tay–Sachs disease; they increase susceptibility to certain cancers and classes of familial hypercholesterolaemia; in 1997, a frameshift mutation was linked to resistance to infection by the HIV retrovirus. Frameshift mutations have been proposed as a source of biological novelty, as with the alleged creation of nylonase, however, this interpretation is controversial. A study by Negoro found that a frameshift mutation was unlikely to have been the cause and that rather a two amino acid substitution in the active site of an ancestral esterase resulted in nylonase.
b ans. The frame shift mutation that has occured in the codon and resulted in the deletion leads to the production of the protein that doesnt have a stop codon and is non functional.
c ans. The insertion/deletion at the end of the gene causes a more profound effect on the protein that is produced as this is the location where the termination should occur and morever if the protein is produced without the stop codon then it is mostly non functional and it leads to various diseases such as cancer.
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