Monday, November 26 * Lecture: Karyotypes, Chromosomal Mutations and

1. Monday, November 26 * Lecture: Karyotypes, Chromosomal Mutations and Sex-Linked Traits * Homework: Worksheet - Due tomorrow

2. Karyotypes * A karyotype is picture of the homologous chromosomes * Humans have 23 homologous pairs of chromosomes Karyotype Organization * Autosomes - Body chromosomes; pairs 1-22 These are arranged from the longest to shortest * Sex Chromosomes - Determine gender; Pair 23 Females are XX Males are XY

3. Karyotypes *Karyotypes can show:  - an organism's gender  - chromosomal mutations * Karyotypes can't show:  - gene mutations  - dominant and recessive alleles

4. Male or Female?

5. What is Wrong Here? Down Syndrome Trisomy 21 - 3 copies of chromosome #21 Short stature Increased risk of heart problems, immune disorders & cancer Mentally disabled

6. What is Wrong Here? Turner Syndrome Only 1 X chromosome Infertile female - reproductive organs don't develop Short stature Webbed neck

7. What is Wrong Here? Klinefelter Syndrome Extra X chromosome Infertile male Possible mental disablility Some female characteristics

8. Chromosome Mutations Chromosomal Number Mutations * Chromosome number disorders are caused by nondisjunction * This means that chromosomes don't come apart when they are supposed to * This leads to one gamete having one too many chromosomes and one gamete with one less chromosome

9. What is Wrong Here? Look at chromosome The homologous chromosomes are not the same

10. Chromosome Mutations Chromosome Structure Mutations * Chromosome structure mutations occur when the location of a gene on a chromosome is changed Deletion - a gene is deleted Duplication - there are more than one copies of a gene Inversion - the genes are in the wrong order on a 
 chromosome Translocation - the gene is moved to a different 
 chromosome

11. Chromosome Mutations Which is which?

12. Autosomal Disorders * Disorders caused by an allele on an autosomal chromosome Recessive Autosomal Disorders * If the disease is caused by the g allele, what does the genotype need to be in order to be affected by the disorder? * A heterozygous genotype is a "carrier" for the disorder  - This means they are not affected by the disorder even though they "carry" the allele and can pass it on to offspring

13. Autosomal Disorders * Disorders caused by an allele on an autosomal chromosome Recessive Autosomal Disorders * Albinism - the inability to produce melanin, the pigment that gives us color * Cystic Fibrosis - affected individuals produce excess mucus that causes respiratory and digestive problems

14. Autosomal Disorders * Disorders caused by an allele on an autosomal chromosome Dominant Autosomal Disorders * How many copies of an allele would you need to show this type of disorder? * Fatal dominant disorders are rare because people typically die before they can pass them on to offspring

15. Autosomal Disorders * Disorders caused by an allele on an autosomal chromosome Dominant Autosomal Disorders * Huntington Disease - Causes nerve disfunction around     ages 30-40. Most patients pass away within 15 years of the  appearance symptoms * Achondroplasia - a form of dwarfism  - embryos that are homozygous dominant do not survive

16. Sex-Linked Disorders * Disorders caused by an allele on a sex chromosome * The X chromosome is much bigger than the Y chromosome and has many more genes * If a recessive disorder is on the X chromosome, how many copies of the allele would a female need to show symptoms of the disorder? - How many copies would a male need?

17. Sex-Linked Disorders * Males are more likely to have a sex-linked disorder because they only need one copy of the allele to be affected * Carriers of sex-linked disorders are female Examples of Sex-linked Traits * Red Green Colorblindness * Hemophilia - a disorder where blood does not clot properly

18. Sex-Linked Disorders & Punnett Squares * To do a punnett square for a sex-linked trait, you need to show the letter for the trait, attached to the X chromosome  XB - Normal Vision  Xb - Color-blindness  Y - Will not have a trait attached because   the gene isn't on the Y chromosome

19. Sex-Linked Disorders & Punnett Squares  A man with normal vision marries a woman who is  a carrier for colorblindness. Determine the  probability of their children having color-blindness Man's Genotype  Woman's Genotype  Key  XB - Normal vision  Xb - color-blind What are the chances of a female being colorblind? What are the chances of a male being colorblind?