1. Human Heredity Sections 14-1 and 14-2 Objectives: 7.2 Interpreting inheritance patterns shown in graphs and charts 8.5 Relating genetic disorders and disease to patterns of genetic inheritance Examples: hemophilia, sickle cell anemia, Down's syndrome, Tay-Sachs disease, cystic fibrosis, color blindness, phenylketonuria (PKU)

2. Human Chromosomes How many chromosomes do we have? Answer: 46 How many of those are sex chromosomes? Answer: 2 What are the possible combinations of sex chromosomes? Answer: XX or XY What are the other chromosomes called? Answer: autosomes

3. Karyotype: Def: a picture of chromosomes, taken in mitosis metaphase, and paired up. Why would the picture be taken at this point? Source: http://www.dnalc.org/view/16243- Gallery-8-Human-female-karyotype.html

4. Pedigree Charts Source: http://www.citr uscollege.edu/ lc/archive/biol ogy/Pages/Ch apter10- Rabitoy.aspx http://www.citr uscollege.edu/ lc/archive/biol ogy/Pages/Ch apter10- Rabitoy.aspx

5. Pedigree Charts Activities 1.Class Activity: Figure 14-3, p.342 2.Individual Assignment: Problem Solving, p.343. Add the following questions: a.Identify the genotype of each individual. b.Is albinism a dominant or recessive trait? c.What is the probability of the second-generation couple having another albino child?

6. Sex-Linked Genes The X chromosome is much larger than the Y chromosome, carrying many more genes. (See Figure 14-12, p.350) More than 100 sex-linked genetic disorders have been mapped to the X chromosome.

7. Sex-Linked Genes Since males have only one X chromosome, if an allele for a disorder is present on that chromosome, the trait will be expressed. Common sex-linked disorders: 1.Colorblindness a.Color vision is controlled by three genes on the X chromosome. b.1 in 10 males in the U.S. have some form of colorblindness. 2.Hemophilia – 2 genes on the X chromosome help control blood clotting (1/10,0000) 3.Duchenne Muscular Dystr ophy – (1/3000)

8. X-Chromosome Inactivation Females have two X chromosomes. One of those chromosomes is switched off, becoming a Barr body --- a dense (but inactive) region in the nucleus. Males cannot switch off their X chromosome. Source: http://www.123rf.com/photo_2 531003_spotted-cat-with-no- tail-stands-attentive-and- alert.html http://www.123rf.com/photo_2 531003_spotted-cat-with-no- tail-stands-attentive-and- alert.html

9. Chromosomal Disorders Nondisjunction of homologous chromosomes during _____________, would give gametes abnormal numbers of chromosomes. When these gametes become diploid again, the number of chromosomes is abnormal. Some of these zygotes cannot survive; others produce offspring with genetic disorders.

10. Chromosomal Nondisjunction Source: http://drugline.org/img/term/meiotic-nondisjunction- 9351_3.JPGhttp://drugline.org/img/term/meiotic-nondisjunction- 9351_3.JPG

11. Some Nondisjunction Disorders 1.Down syndrome a.Autosomal nondisjunction b.3 copies of chromosome 21 (“trisomy 21”) Source: http://www.buzzle.co m/articles/teaching- children-with-down- syndrome.html http://www.buzzle.co m/articles/teaching- children-with-down- syndrome.html

12. Some Nondisjunction Disorders 2.Sex chromosome disorders: a.Turner’s syndrome – females with only one X chromosome 1)Fertile 2)Sex organs do not develop at puberty b.Klinefelter’s syndrome – males with too many X chromosomes 1)Interferes with meiosis, usually not permitting reproduction 2)No known cases of babies born without an X chromosome, so it must contain genes important for survival.

13. Some Nondisjunction Disorders 2.Sex chromosome disorders: c.Y chromosome contains a sex- determining region necessary to produce male sexual development 1)Can develop even in the presence of multiple X chromosomes 2)Will not develop if this region of the Y chromosome is absent.

14. DISORDER DETECTIVES ACTIVITY http://www.youtube.com/watch?v=th6Njr-qkq0