* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Supplemental File S3. Homologous Chromosomes
Essential gene wikipedia , lookup
Public health genomics wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
Comparative genomic hybridization wikipedia , lookup
Non-coding DNA wikipedia , lookup
Copy-number variation wikipedia , lookup
Long non-coding RNA wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Pathogenomics wikipedia , lookup
History of genetic engineering wikipedia , lookup
Gene expression profiling wikipedia , lookup
Genomic library wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Ridge (biology) wikipedia , lookup
Human genome wikipedia , lookup
Microevolution wikipedia , lookup
Designer baby wikipedia , lookup
Minimal genome wikipedia , lookup
Gene expression programming wikipedia , lookup
Segmental Duplication on the Human Y Chromosome wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Genome evolution wikipedia , lookup
Genomic imprinting wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Genome (book) wikipedia , lookup
Y chromosome wikipedia , lookup
X-inactivation wikipedia , lookup
Investigation 1: Homologous chromosomes? Exploring the relationship of human autosomes and sex chromosomes. To view and compare information about human chromosomes, visit the National Center for Biotechnology Information (NCBI) website: http://www.ncbi.nlm.nih.gov/ From the main page, change the drop-down menu selection from "All Databases" to “Genome”. Without filling in anything in the search field, hit the “Search” button. Click “Human Genome” under the heading Custom Resources in the middle of the page. On the left, you will see "Browse your Genome" and a drop-down menu to choose the type of chromosome map shown. Each map represents a physical chromosome and provides information about the chromosome, such as the array of genes on the chromosome. To learn more about the arrangement of genes on chromosomes, let's first look at the genes on the largest chromosome, chromosome 1. View the chromosome by clicking on the appropriate chromosome in the display (it may take a little while to load the map). Scroll down through the page to view the gene map and the “Summary of Maps”, which includes how large the chromosome is in base pairs, how many genes are on the chromosome, and links to other information. Note that you can also zoom in and zoom out on sections of the chromosomes. To view the entire chromosome and answer the questions below, you will need to be fully zoomed out to view the entire chromosome at once. Chromosome 1 is the largest chromosome; that is, chromosome 1 is made up of the most single nucleotide bases (in the double stranded DNA molecule, adenine base pairs with thymine, guanine base pairs with cytosine). One megabase is equal to one million nucleotide bases. Answer the following questions in your laboratory notebook in the “Answers/Conclusions” section: Question 1-1 : How many megabases (M bp) long is chromosome 1? Question 1-2 : How many genes are located on the chromosome (Total genes on chromosome)? Question 1-3: Why do you think there are so many more transcripts that align on the chromosome compared to the number of genes on the chromosome? Question 1-4: What would you expect to find if you were to compare the number of genes present on the maternally and paternally inherited chromosomes for this autosomal chromosome pair in a normal individual? Explain. Now let’s look at the smallest chromosome, chromosome 21. Return to the Genome Browser page, and select chromosome 21 by clicking on it (it may take a little while to load the map). Answer the following questions in your laboratory notebook in the “Answers/Conclusions” section: Question 1-5 : How many megabases (M bp) long is chromosome 21? Question 1-6 : How many genes are located on the chromosome (Total genes on chromosome)? Question 1-7: Would you expect to observe the same genes in the same order on the maternally and paternally inherited chromosomes for this autosomal chromosome pair in a normal individual? Explain. Now, let’s compare the array of genes on the human X and Y chromosomes. Return to “Browse your Genome” as before. View the Y chromosome by clicking on it (it may take a little while to load the map). Scroll down through the page to view the chromosome gene map and the “Summary of Maps.” Answer the following questions in your laboratory notebook in the “Answers/Conclusions” section: Question 1-8 : How many megabases (M bp) is the Y chromosome? Question 1-9 : How many genes are located on the Y chromosome (Total genes on chromosome)? Open a new tab (or a new window) in your internet browser. Navigate to the Genome Browser (http://www.ncbi.nlm.nih.gov/ All Databases Human Genome). View the X chromosome by clicking on the chromosome. Answer the following questions in your laboratory notebook in the “Answers/Conclusions” section: Question 1-10 : How many megabases is the X chromosome? Question 1-11 : How many genes are located on the X chromosome? Question 1-12 : Given the gene maps you have just observed, would you consider the X and Y human chromosomes homologous? The human X and Y chromosomes are hypothesized to have evolved from homologous autosomes into the dimorphic sex chromosomes they are today (11-17). Vertebrates employ different mechanisms of sex determination: not all vertebrates have X and Y chromosomes, many vertebrates do not have sex chromosomes at all (11). The X and Y chromosomes do have some shared homologous elements that remain, although these shared regions are very small compared to the shared regions of homology of autosomal pairs. Recombination can still occur at these shared regions of the X and Y chromosomes, particularly at the ends of the chromosomes where telomeres are located. Additionally, there are several genes located at the ends of the X and Y chromosomes that are homologous and do participate in recombination during meiosis. These regions are known as pseudoautosomal regions (PARs) (18-20). Answer the following question in your laboratory notebook in the “Answers/Conclusions” section: Question 1-13: Given what you know about DNA replication, why do all eukaryotic (linear) chromosomes have telomeres? What purpose do telomeres serve?