QUIZ

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SNPs

 

Each person has the same set of genes – about 20,000 in all. The differences between people come from slight variations in these 1) ___. For example, a person with red hair doesn’t have the “red hair gene“ while a person with brown hair has the “brown hair gene.“ Instead, all people have genes for hair color, and different versions of these genes dictate whether someone will be a redhead or a brunette. The human 2) ___ contains 50 trillion cells, and almost every one of them contains the complete set of instructions for making an individual human. These instructions are encoded in your DNA, which is a long, ladder-shaped molecule. Each rung on the ladder is made up of a pair of interlocking units, called bases, that are designated by the four letters in the DNA alphabet – A, T, G and C. ‘A’ always pairs with ‘T’, and ‘G’ always pairs with ‘C’.

 

The long molecules of DNA in each cell is organized into pieces called chromosomes. Humans have 23 pairs of 3) ___. Other organisms have different numbers of pairs – for example, chimpanzees have 24 pairs. The number of chromosomes doesn’t determine how complex an organism is – bananas have 11 pairs of chromosomes, while fruit flies have only 4. Chromosomes are further organized into short segments of DNA called genes. Each gene has a list of instructions, written in the DNA alphabet: – A, T, C, and G. Each gene’s instructions tell each cell how to function and what traits to express. For example, curly hair results, because the genes inherited from parents are instructing hair follicle 4) ___ to make curly strands. Cells follow the instructions, written in genes, to make proteins. Proteins do much of the work in the cells and in the body. Some proteins give cells their shape and structure. Others help cells carry out biological processes like digesting food or carrying oxygen in the blood. Using different combinations of the As, Cs, Ts and Gs, DNA creates the different 5) ___.

 

Cells come in a array of types; there are brain cells and blood cells, skin cells and liver cells and bone cells. But every cell contains the same instructions in the form of DNA. Cells know whether to make an eye or a foot because of intricate systems of genetic switches. Master genes turn other genes on and 6) ___, making sure that the right proteins are made at the right time in the right cells. To make new cells, an existing cell divides in two. But first it copies its DNA so the new cells will each have a complete set of genetic instructions. Cells sometimes make mistakes during the copying process – kind of like typos. These typos lead to variations in the 7) ___ sequence at particular locations, called single nucleotide polymorphisms, or SNPs (pronounced “snips“). SNPs are the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide. Millions of SNP’s have been cataloged in the human genome. Some SNPs cause disease, like sickle cell anemia. Other SNPs are normal variations in the genome. SNPs can generate biological variation between people by causing differences in the 8) ___ for proteins that are written in genes. Those differences can in turn influence a variety of traits such as appearance, disease susceptibility or response to drugs. While some SNPs lead to differences in health or physical appearance, most SNPs seem to lead to no observable differences between people at all.

 

DNA is passed from parent to 9) ___. SNPs are inherited versions from parents. An individual will be a match with siblings, grandparents, aunts, uncles, and cousins because of these SNPs. Each person will have far fewer matches with distantly related people. The number of SNPs that match another person can therefore be used to tell how closely related you are. The next generation of SNP annotation webservers can take advantage of the growing amount of data in core bioinformatics resources and use intelligent agents to fetch data from different sources as needed. From a user’s point of view, it is more efficient to submit a set of SNPs and receive results in a single step, which makes meta-servers the most attractive choice. However, if SNP annotation tools deliver heterogeneous data covering sequence, structure, regulation, pathways, etc., they must also provide frameworks for integrating data into a decision algorithm(s), and quantitative confidence measures so users can assess which data are relevant and which are not.

 

An associated freeware computer program called Promethease, developed by the SNPedia team, allows users to compare personal genetics results against the SNPedia database, generating a report with information about a person’s attributes, such as propensity to diseases, based on the presence of specific SNPs within their genome. In May 2008 Cariaso, using Promethease, won an online contest sponsored by 23andMe to determine as much information as possible about an anonymous woman based only on her genome. Cariaso won in all three categories of “accuracy, creativity and cleverness“. In 2009, the anonymous woman (“Lilly Mendel“) was revealed to be 23andMe co-founder Linda Avey, allowing a direct comparison between her actual traits and those predicted by Promethease a year earlier.

 

A single 10) ___ polymorphism (SNP) is a change to a single nucleotide in a DNA sequence. The relative mutation rate for an SNP is extremely low. This makes them ideal for marking the history of the human genetic tree. SNPs are named with a letter code and a number. The letter indicates the lab or research team that discovered the SNP. The number indicates the order in which it was discovered. For example, M173 is the 173rd SNP documented by the Human Population Genetics Laboratory at Stanford University, which uses the letter M.

https://ghr.nlm.nih.gov/primer/genomicresearch/snp; 23andMe.com; Wikipedia

 

ANSWERS: 1) genes; 2) body; 3) chromosomes; 4) cells; 5) proteins; 6) off; 7) DNA; 8) instructions; 9) child; 10) nucleotide

 

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