BOW 2 Semester 2 (Blog of the Week)

Sense mutation- this is sometimes seen with a single substitution mutation when the change in the DNA base sequence results in a new codon that is still coding for the same amino acid. (All amino acids are coded for by more than one codon.)

 Reference: http://www.mun.ca/biology/scarr/2250_Mutagenesis.html

Nonsense Mutations- the term "nonsense mutation is used because the stop codon has "no sense" for an amino acid. Nonsense mutations cause the protein to be cut off early and therefore incomplete, which usually renders it non-functional. Cystic fibrosis is a disease caused by a nonsense mutation.

Reference: http://www.drugs.com/cg/cystic-fibrosis.html

Deletion mutation- a type of gene mutation wherein the deletion (as well as addition) of a number of nucleotides cuases a shift in the reading frame of the codons in the mRNA, which may eventually lead to the alteration in the amino acid sequence at protein translation.

Reference: http://www.intelihealth.com/IH/ihtIH/WSIHW000/32193/32195/353894.html?d=dmtGenetics_BasicContent

Insertion Mutation- a type of mutation resulting from the addition of extra nucleotides in a DNA sequence or chromosome.

Reference: http://en.wikipedia.org/wiki/Insertion_(genetics)

Frameshift mutation- a type of gene mutation wherein the addition or deletion of a number of nucleotides causes a shift in the reading frame of the codons in the mRNA, which may lead to a change in the amino acid sequence in protein translation.

Reference:   http://ghr.nlm.nih.gov/handbook/illustrations/frameshift

 Point mutation - the simplest kind of genetic mutation, which can cause dramatic effects to arise from such a small substitution in the genome.

Reference: http://mahnaz-moleculargenetic.blogspot.com/2011/01/point-mutation.html

Translocation mutation- this happens when on of two homologous chromosomes breaks and binds to the other. Usually this sort of mutation is very dangerous.

Reference:  http://my.ilstu.edu/~ddwilso2/nur437/Genetics.htm

Extra Credit Blog Semester 2

What topics really confused you?
There was not any topics that I was really confused on last semester because Mrs.Malonek is a very good biology teacher..
What topics do you feel very clear on?
The topics I feel very clear on is chapter 7 about cell structure and chapter 8 about photosynthesis.
What lab/ activity was your favorite? Why?
The favorite lab last semester was the kimchi lab because that was the first time I had ever made kimchi in my life.
What lab/activity was your least favorite? Why?
There was not any lab last semester that was my least favorite because all the labs I did last semester were very fun.
If you could change something about the class to make it better, for instance the type of homework (not the amount) what would it be and why?
If I could change something about the class to make it better it would be doing more labs this semester because I believe that doing more labs in class will help enhance our knowledge about biology.

Transcription

Transcription is the synthesis of mRNA from a DNA template. It is like DNA replication in that a DNA strand is used to synthesize a strand of mRNA. RNA polymerase recognizes a specific base sequence in the DNA called a promoter and binds to it. RNA polymerase unwinds the DNA. RNA polymerase assembles bases that are similar to the DNA strand being copied. The mRNA produced is called the mRNA transcript. The remaining portions of DNA that are translated into protein are called exons. After the intron-derived regions are removed from mRNA, the remaining fragments are spliced to form a mature mRNA transcipt.

Translation

During translation, the cell uses information fro messenger RNA to produce proteins. Like an assembly line worker who attaches one part of another, the ribosome forms a peptide bond between the first and second amino acids. The ribosome then moves to the third codon, where a tRNA molecule brings it the amino acid specified by the third colon.

Gene Sequence 8

The dystrophin gene is the largest gene found in nature, measuring 2.4 Mb. The gene was identified through a positional cloning approach, targeted at the isolation of the gene responsible for Duchenne (DMD) and Becker (BMD) Muscular Dystrophies. DMD is a recessive, fatal, X-linked disorder occurring at a frequency of about 1 in 3,500 new-born males. BMD is a milder allelic form. In general, DMD patients carry mutations which cause premature translation termination (nonsense or frame shift mutations), while in BMD patients dystrophin is reduced either in molecular weight (derived from in-frame deletions) or in expression level. The dystrophin gene is highly complex, containing at least eight independent, tissue-specific promoters and two polyA-addition sites. Furthermore, dystrophin RNA is differentially spliced, producing a range of different transcripts, encoding a large set of protein isoforms. Dystrophin (as encoded by the Dp427 transcripts) is a large, rod-like cytoskeletal protein which is found at the inner surface of muscle fibers.

Gene Sequence 5

This gene encodes a member of the fibrillin family. The encoded protein is a large, extracellular matrix glycoprotein that serve as a structural component of 10-12 nm calcium-binding microfibrils. These microfibrils provide force bearing structural support in elastic and nonelastic connective tissue throughout the body. Mutations in this gene are associated with Marfan syndrome, isolated ectopia lentis, autosomal dominant Weill-Marchesani syndrome, MASS syndrome, and Shprintzen-Goldberg craniosynostosis syndrome.

Gene Sequence 3

Alzheimer's disease (AD) patients with an inherited form of the disease carry mutations in the presenilin proteins (PSEN1 or PSEN2) or the amyloid precursor protein (APP). These disease-linked mutations result in increased production of the longer form of amyloid-beta (main component of amyloid deposits found in AD brains). Presenilins are postulated to regulate APP processing through their effects on gamma-secretase, an enzyme that cleaves APP. Also, it is thought that the presenilins are involved in the cleavage of the Notch receptor such that, they either directly regulate gamma-secretase activity, or themselves act are protease enzymes.

Gene Sequence 6

The protein encoded by this gene is a negative regulator of the cell cycle and was the first tumor suppressor gene found. The encoded protein also stabilizes constitutive heterochromatin to maintain the overall chromatin structure. The active, hypophosphorylated form of the protein binds transcription factor E2F1. Defects in this gene are a cause of childhood cancer retinoblastoma (RB), bladder cancer, and osteogenic sarcoma.

Gene Sequence 2

This gene encodes a protein that is one of the two components of elastic fibers. The encoded protein is rich in hydrophobic amino acids such as glycine and proline, which form mobile hydrophobic regions bounded by crosslinks between lysine residues. Deletions and mutations in this gene are associated with supravalvular aortic stenosis (SVAS) and autosomal dominant cutis laxa. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]

Gene Sequence 1

Huntingtin is a disease gene linked to Huntington's disease, a neurodegenerative disorder characterized by loss of striatal neurons. This is thought to be caused by an expanded, unstable trinucleotide repeat in the huntingtin gene, which translates as a polyglutamine repeat in the protein product. A fairly broad range in the number of trinucleotide repeats has been identified in normal controls, and repeat numbers in excess of 40 have been described as pathological. The huntingtin locus is large, spanning 180 kb and consisting of 67 exons. The huntingtin gene is widely expressed and is required for normal development. It is expressed as 2 alternatively polyadenylated forms displaying different relative abundance in various fetal and adult tissues. The larger transcript is approximately 13.7 kb and is expressed predominantly in adult and fetal brain whereas the smaller transcript of approximately 10.3 kb is more widely expressed. The genetic defect leading to Huntington's disease may not necessarily eliminate transcription, but may confer a new property on the mRNA or alter the function of the protein. One candidate is the huntingtin-associated protein-1, highly expressed in brain, which has increased affinity for huntingtin protein with expanded polyglutamine repeats. This gene contains an upstream open reading frame in the 5' UTR that inhibits expression of the huntingtin gene product through translational repression. [provided by RefSeq, Jul 2008]

Bow 1 Semester 2 (Blog of The Week)

Protein Synthesis
During protein synthesis, the transcription and translation of specific parts of DNA form proteins. The polypeptide chain grows until the ribosome reaches a stop codon on the mRNA molecule. When the ribosome reaches a stop codon, it releases the newly formed polypeptide and the mRNA molecule.