Human Genetics & Pedigrees Ch. 8.18-8.22 PDF

Human Genetics and Pedigrees Ch. 8.18 – 8.22 (cont)  Learning Objectives Today you will learn to: ⚫ Evaluate karyotype charts and make a determination of the gender and genetic health of an individual. Unit Organizer Genetics...

Human Genetics and Pedigrees Ch. 8.18 – 8.22 (cont)  Learning Objectives Today you will learn to: ⚫ Evaluate karyotype charts and make a determination of the gender and genetic health of an individual. Unit Organizer Genetics is about The Inheritance of including Unique according to Traits inheritance which can be to Gregor predicted using determine patterns Mendel Probability & Traits Punnett Squares like in Phenotypes Genotypes Monohybrid crosses Dihybrid crosses  Human Genes and Chromosomes ⚫ How many chromosomes does a typical human have? ⚫ 46 ⚫ Two are sex chromosomes. ⚫ The other 44 are autosomes or non-sex chromosomes.  Karyotype ⚫ A karyotype is an organized display of magnified images of an individual's chromosomes arranged in pairs. ⚫ Chromosomes are photographed in mitosis, enlarged and arranged by size, from largest to smallest. ⚫ Helps scientists quickly identify chromosomal abnormalities that may result in genetic disorders. Figure 8.19-1-3 Packed red Hypotonic Fixative and white solution blood cells Stain White Centrifuge blood Blood culture cells Fluid A blood culture is The cells are mixed with a These swollen cells centrifuged to hypotonic solution to make are separated, separate the blood the white blood cells swell so preserved, placed cells. their chromosomes spread on a slide and out. stained. Figure 8.19-2 Figure 8.19-3 Centromere Sister chromatids Pair of homologous chromosomes Sex chromosomes Karyotype cont’d Down Syndrome  Is it a boy or a girl? ⚫ All egg cells carry a single X chromosome. ⚫ Sperm carry an X or a Y (50/50). ⚫ So….. Women = XX Men = XY Figure 9.20b-0 Male Female 44 44 Parents + + (diploid) XY XX Gametes 22 22 22 + + + (haploid) X Y X Sperm Egg Offspring 44 44 + + (diploid) XX XY Female Male  Chromosomal Disorders ⚫ Meiosis works most of time, but sometimes goes wrong ⚫ Nondisjunction – When chromosomes or chromatids fail to separate normally in meiosis. ⚫ Trisomy- having 3 copies of a chromosome instead of 2 ⚫ Examples: Down Syndrome Figure 8.18-1-1 Meiosis I Nondisjunction Figure 8.18-1-2 Meiosis I Nondisjunction Meiosis II Normal meiosis II Figure 8.18-1-3 Meiosis I Nondisjunction Meiosis II Normal meiosis II Gametes Number of n+1 n+1 n−1 n−1 chromosomes Abnormal gametes  Down Syndrome ⚫ Trisomy of chromosome 21 ⚫ 3 chromosomes ⚫ Affects one in 800 babies ⚫ Produces mild to severe mental learning disabilities ⚫ Increased susceptibility to disease and other birth defects  Other Trisomy Disorders ⚫ Down Patau Edward’s Syndrome Syndrome Syndrome (Trisomy 21) (Trisomy 13) (Trisomy 18)  Sex Chromosome Disorders ⚫ Turner’s Syndrome ⚫ Female ⚫ One X chromosome ⚫ Sterile ⚫ Klinefelter’s Syndrome ⚫ Male ⚫ Multiple X and one Y chromosomes ⚫ Usually sterile ⚫ XYY can also occur ⚫ No know instances of individuals born without X chromosome 18  EVOLUTION CONNECTION: ⚫ The Y chromosome provides clues about human male evolution because ⚫ Y chromosomes are passed intact from father to son and ⚫ mutations in Y chromosomes can reveal data about recent shared ancestry.  EVOLUTION CONNECTION: ⚫ In 2003, geneticists discovered that about 8% of males currently living in central Asia have Y chromosomes of striking genetic similarity. ⚫ Further analysis traced their common genetic heritage to a single man living about 1,000 years ago. ⚫ This helped historians trace Genghis Kahn to nearly 16 million men living today  Section Review 1. Evaluate karyotype charts and make a determination of the gender and genetic health of an individual.