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Karyotype Activity

Part 1: Normal Human Karyotype

Below are human karyotypes, an image of a human cell’s chromosomes. The image on the left is a picture of an actual cell’s chromosomes under a microscope. To generate the image on the right, the chromosomes from the image on the left were arranged into homologous pairs and then ordered in decreasing size. Typically the sex chromosomes are placed after chromosome pair 22.

  1. During which stage in the cell cycle was the first image taken?
  1. How many pairs of chromosomes are in the human genome? How many total chromosomes?
  1. Is this karyotype from a male or female? Explain.
  1. How might a karyotype be useful to a geneticist?

Part 2: Homologous Chromosomes

  1. What is the same about a pair of homologous chromosomes? What can be different?
  1. What do you think is meant a gene location?
  1. Complete the diagram below by filling in the blanks for the missing gene labels (alleles)

Part 3: Gene Mapping

The entire human genome has been sequenced and mapped. This means that we now know the order of bases in all roughly 20,000 genes in humans, what chromosomes each gene is found on, and the location of each gene on the chromosome. The image below and to the left shows the locations of only a handful of genes in the human genome. Genes are often given abbreviations for their names. For example, the HRAS1 gene on chromosome one codes for a protein called transforming protein p21, which helps regulate cell division. To appreciate how many genes are actually on each chromosome, examine the image below and to the right, which is a map of the genes on just chromosome 6.

  1. When a gene map is made, only one of the two homologous chromosomes from every pair is shown. Explain why. (Hint: does a gene map show types of genes or specific alleles?)
  1. Will a gene map be the same for every human on earth? Explain.
  1. A person produces both functional and non-functional transforming protein p21. Explain how this could be possible given that both chromosome ones will have the HRAS1 gene in the same location.

Part 4: Abnormal Karyotype

  1. Read the article “Reading the Future” on pages 210 and 211 of your textbook then ask your instructor for an “abnormal” karyotype as well as “Information on Chromosome Disorders.
  1. Read through all of the disorders, then compare your karyotype to the descriptions to determine which chromosomal abnormality is depicted in your karyotype
  1. Prepare a short presentation (about 2 min) to be given to the class along with a visual that addresses the following:
  2. The chromosomal abnormality and the name of the syndrome
  3. Interesting symptoms as well as the frequency of the disorder and life expectancy if relevant