sert Design Layout References Mailings Review View Calibri i. What does it mean
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sert Design Layout References Mailings Review View Calibri i. What does it mean to sequence DNA? i. What is the initial laboratory experiment that served as the basis of sequencing technology Who developed it? There are several generations of sequences? What is the latest version and how does it basically work? ili. Discuss how has the understanding of the classical Central Dogma roles of DNA and RNA been modified or refined as a result of the "new genetics" of the 21 Century? (e.g. Discuss the roles of microRNAs, RNAi, histones, epigenetics, etc.) b) c) Define exon and intron. How can 20,000 human genes provide the instructions for making hundreds of thousands of different proteins? d) What does SNP stand fork How are SNPs named? (10 pts) Select two of the single gene traits (not a disease) that are commonly used to illustrate human genetic variation in introductory genetics exercises, e.g, left handedness, tongue rolling, Hitchhikers thumb, pattern baldness, freckles, widow's peak, cheek dimples, eye color. Look up your selections using OMIM to determine their genetics/inheritance pattern. Report your findings. Does anything about the 4. genetics of the traits surprise you? 5. (20 pts) Comparative Genomics. Answer the questions about these organisms: Homo sapiens; Pan troglodytes, chimpanzee; Mus musculus, mouse; Canis lupus familigrs, dog: Escherichia coli (0157:H7 pathogenic Use NCBI as your main source. https://www.ncbi.nim.nih govizenome/ Browse by Qreganism a) What are the number of chromosomes and nucleotide bases pairs in each. b) What percentage of the human genome is shared with the other three organisms cl) How many genes are there on each chromosome? d) How many base pairs and genes are there on the mitochondria for each of the organisms? (25 pts) Using OMIM prepare a report on the listed disorders. The format is listed below. (Note: Not all disorders will have information for all the topics listed below. Think about why this would be the case.) 6. a) b) Name of the disease/condition Nomenclature o Phenotype MIM number o Gene/Locus MIM number o Gene symbol What is the normal function of the gene? o Brief description of the disorder/condition o For Familal Breast Cancer, MIM1144B0, what do you note about the entry for the diseuse? c) Choose BRCA2 and RADS4L genes to answer the questions A di Chromosome location and Genomic coordinates (You may include a picture) e) Genetics/ Inheritance pattern 1) Each disease is has a characteristic genetic basis. Discuss the basis each by descrihing the gene structure that accounts for the disorder 6Explanation / Answer
[I] DNA is made up of sugar , phosphates and nitrogen bases [ together these make a molecule called Nucleotide ]. The two strands of DNA are formed by pairing of bases , which are held together by weak hydrogen bonds.
The nitrogenous bases are grouped as Purines and Pyrimidines.
In a DNA molecule,
Purines include Adenine and Guanine.
Pyrimidines include Thyamine and Cytosine [ in RNAs, thyamine is replaced by another base called Uracil]
Adenine always pairs with Thyamine and Guanine always pairs with Cytosine
These pairs are arranged in a DNA molecule in any order. The ordering of these base pairs results in so much variation in the phenotype and genotype of all living organisms in the world. In fact , no two individuals can have the exact same arrangement of base pairs in their DNA !
The process of determining the exact and precise order of Nucleotides in a DNA molecule is called DNA sequencing.
[II] DNA was first isolated by Friedrich Miescher in 1869 but remained unexplored for many decades.
In 1944 , a group of biologists , Oswald Avery, Colin MacLeod and Maclyn McCarty , demonstrated that DNA had the capability to transform the functions of a cell.
Then , in 1953, James Watson and Francis Crick put forward their double helix model of DNA based on crystallized X-ray structures being studied by Rosalind Franklin .They gave us the structure and components of a double helix DNA molecule.
However, the foundation for sequencing was first laid by the work of Frederick Sangers.He ,along with his colleagues, developed the 'chain termination method' for DNA sequencing. Selective " chain terminating dideoxynucleotides " [ ddNTPs] were incorporated by DNA polymerase during in vitro DNA replication. This is called the " first generation DNA sequencing method " and laid the foundation for further methods to be developed. Following the work of Sangers, Crick began to develop a theory which stated that arrangement of nucleotides on the DNA molecule determined the sequence of amino acids in proteins which in turn helps to determine the function of that protein.
The first method for determining DNA sequencing was executed by Ray Wu at Cornell University in 1970. It involved a location specific primer extention strategy .
The first free living organism to have its genome completely sequenced was the bacterium Haemophilus influenzae.
[III] The latest technique of DNA sequencing is based on capillary electrophoresis. The genomic strand is frafmented and the bases in each fragment are identified by emitted signals when the frfragments are ligated against a template strand. It uses array based sequencing which combines the technique developed in Sanger sequencing to process millions of reactions simultaneously. Thus, it is cost effective and less time consuming.
b] The Central Dogma describes the flow of genetic information from the DNA to the mRNA, which carries this information to the ribosomes . The ribosomes can 'read' this information and use it to string amino acids together to form a particular protein.
As more and more research work was done, there were certain findings which challenged the central dogma theory. The discovery of RNAi , which is a natural genetic mechanism in eukaryotes that takes place following transcription. RNAi inhibits gene expression by ' silencing ' certain mRNA and prevent their expression.
Epigenetics, which studies the changes in organisms which are not caused by any alteration to the genetic code but due to modification of gene expression . This states that environmental factors which affect a parent might result in changes in the way genes are expressed in the offspring. This, too, chalanges the Central Dogma theory. So here there might be changes in gene expression without any change in the DNA sequence of the organism.
MicroRNAs are also known to regulate gene expression at the post transcriptional level.
Hence , the 'new genetics of the 21st century ' provides quite a few challanges to the Central Dogma theory of the roles of DNA and RNA in gene expression.
c] Exons are the gene coding regions on eukaryotic DNA while Introns are the non-coding regions. On a DNA strand, the exons are interrupted by introns . During transcription, the entire gene is copied into a pre-mRNA , including exons and introns. During the process of DNA splicing, introns are removed and exons are joined to form a continuous coding sequence.
The mystery and beauty of life lies in the fact that only four base pairs and their sequence on the DNA strand can result in so much variety of life by sequencing of thousands of types of proteins.
d] SNP stands for Single Nucleotide Polymorphism.
It is a variation in a single nucleotide that occurs at a specific position in the genome.
SNPs might be responsible for an individuals susceptibility to a particular disease or even for occurance of certain diseases like sickle cell anemia , cystic fibrosis etc.
Nming of SNPs is still not very well established . Several variations occur for a single SNP and there is no general agreement .
One method is to write SNP with a prefix, period and 'greater than' sign for showing the wildtype or altered nucleotide or amino acid . eg. c.76A>T.
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