BIOL 1010 Online K ARYOTYPING AND G ENDER T ESTING O BJECTIVES • Define and discuss karyotyping. • Explain homologous chromosomes. • Understand gender identification with X and Y. • Describe gender development. • Explain X linked traits. I NTRODUCTION DNA is packaged inside the eukaryotic cell as chromosomes . Chromosomes are rod-like structures containing both DNA and associated proteins called histones . The number of chromosomes varies with each species but there are 46 chromosomes in human somatic or body cells. These 46 chromosomes can be grouped into pairs called homologous pairs based on centromere location and size of the chromosome. Of the 23 pairs, 22 pairs are autosomes (non-sex chromosomes) and 1 pair represents the sex chromosomes consisting of an X and either another X, if the individual is female, or a Y, if male. Of the autosomes, the largest pair is designated as pair 1 and the smallest is designated as pair 22. During genetic testing, a karyotype of the chromosomes is performed. Homologous chromosomes are arranged as pairs and large chromosomal abnormalities can be detected. Any extra (Trisomy 21/Down’s Syndrome or Klinefelter’s Syndrome) or missing (Turner’s Syndrome) chromosomes indicate an abnormal karyotype. For example, Down’s Syndrome is denoted by the presence of three #21 chromosomes. Therefore, an individual with Down’s syndrome
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