Download Learning about the Human Genome Explore the 23andMe Browse

 Learning about the Human Genome Explore the 23andMe Browse Raw Data feature at https://www.23andme.com/you/explorer/ 1. Can you see any logic to the way chromosomes are numbered and organized by scientists? Take a quick look at all 22 autosomes. How are they arranged? 2. Which of the 22 autosomes is the shortest, and how long (number of base pairs) is it? 3. What are the four chromosomes with the greatest number of genes? What are the four chromosomes with the greatest number of base pairs? 4. Are you surprised by the four chromosomes with the greatest number of genes when compared to the four chromosomes with the greatest number of base pairs? Which ones? Why? 5. Which is bigger, the X or Y chromosome? What’s the difference in size? What’s the difference in gene number? 6. One of the most significant events in biology in the last decade is the completion of sequencing and decoding of the human genome. As a result of this work, scientists have a better understanding of how many genes are in our genome. Take a look at the chromosome data (https://www.23andme.com/you/explorer/), and calcuate the total number of base pairs and genes in our genome. Does this sound like a little or a lot? Compare this to the genome size of Polychaos dubium (amoeba), C. elegans (round worm), and Mus musculus (house mouse). Learning About the Human Genome: Activity Objective: In this activity, the students are introduced to the human genome and what can be observed about it by looking at chromosome data analyzed by 23andMe. They will discover that: 1. Chromosomes are numbered and organized by scientists from largest to smallest (with one exception ­ chromosomes 21 and 22 are out of order). 2. The number of genes on a chromosome doesn’t always correspond to the length of the chromosome (this is counterintuitive and perhaps surprising to the student). 3. The X chromosome is much larger and contains much more genetic information than the Y chromosome. 4. There is no correlation between the total of number of genes, the genome size and evolutionary status of species. References: 1. Browse Raw Data 23andMe. https://www.23andme.com/you/explorer/ Advanced view of all the uninterpreted SNP data for research and educational use only. 2. Chromosome Map National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/books/NBK22266/ Karyogram of human male and brief description of each chromosome including its size, number of genes, and association with diseases. 3. Comparative Genomics The Nature Educationhttp://www.nature.com/scitable/knowledge/library/comparative­genomics­1323
9404 Comparison of the genome sequences of different species — human, mouse, and a wide variety of other organisms from bacteria to chimpanzees. 4. Human Genome Collection The Journal Nature. http://www.nature.com/nature/supplements/collections/humangenome/chromosomes/ Selected papers on each chromosome based on the human genome project. Student Questions: 1. Can you see any logic to the way chromosomes are numbered and organized by scientists? Take a quick look at all 22 autosomes. How are they arranged? Note that the length of each chromosome is shown visually and numerically. The numerical length is represented by the number of nucleotide base pairs in the chromosome. For example, “249M Bases” next to chromosome 1 means that there are 249,000,000 base pairs in chromosome 1. “102M Bases” next to chromosome 15 means that there are 102,000,000 base pairs in chromosome 15. Answer: From longest to shortest. Chromosome 1 is the longest. The chromosomes get shorter as you move towards chromosome 22. 2. Which of the 22 autosomes is the shortest, and how long is it? Answer: Chromosome 21 is the shortest; it has 48 million base pairs (chromosome 22 has 51 million base pairs and is therefore not the shortest chromosome). This may surprise the students after noticing the trend that chromosomes appear to be arranged from longest to shortest. 3. What are the four chromosomes with the greatest number of genes? What are the four chromosomes with the greatest number of base pairs? Answer: Chromosome 1: 3,492 genes Chromosome 2: 2,349 genes Chromosome 11: 2,160 genes Chromosome 19: 2,063 genes 4. Are you surprised by the four chromosomes with the greatest number of genes when compared to the four chromosomes with the greatest number of base pairs? Which ones? Why? Answer: The number of base pairs in a chromosome does not necessarily correlate with the number of genes it has, i.e. a shorter chromosome does not always have fewer genes. Chromosome 19 is a good example of this. Genes vary greatly in their number of base pairs; some are shorter, some are longer, and a gene's importance in a cell usually has nothing to do with its length, but rather with its specific sequence of base pairs. 5. Which is bigger, the X or Y chromosome? What’s the difference in size? What’s the difference in gene number? Answer: X chromosome is bigger. X chromosome is 155M bases, while Y chromosome is 59M bases. The X chromosome has 1,639 genes, while the Y chromosome only has 397 genes, so the X chromosome has 4.3x as many genes! 6. One of the most significant events in biology in the last decade is the completion of sequencing and decoding of the human genome. As a result of this work, scientists have a better understanding of how many genes are in our genome. Take a look at the chromosome data (https://www.23andme.com/you/explorer/), and calcuate the total number of base pairs and genes in our genome. Does this sound like a little or a lot? Compare this to the genome size of Polychaos dubium (amoeba), C. elegans (round worm), and Mus musculus (house mouse). Answer: According to the chromosome data on 23andMe’s site, there are over 30,000 genes in the human genome. This is more than the commonly reported number of approximately 23,000 genes. This could lead to an interesting discussion about the likelihood of this number changing as the sequence becomes more refined and the genome annotation is improved. Although it’s easy to assume that more complex organisms have larger genomes and more genes, the relationship between the genome size, number of genes, and evolutionary status is not clear. Homo sapiens (human) = 2.9 billion base pairs, 30K genes Polychaos dubium (amoeba) = 670 billion base pairs, number of genes unknown C. elegans (round worm) = 97M base pairs, 19K genes Mus musculus (house mouse) = 2.9 billion base pairs, 25K genes