1. Chapter 14 Human Genetics

2. 14.1 Human Chromosomes Genome = the full set of genetic information that an organism carries in its DNA Karyotype = the complete diploid set of chromosomes grouped together ▫Arranged in order of decreasing size

3. Fig. 12-3a, p. 187

4. Fig. 12-3b, p. 187

5. Human Karyotype Cells are photographed in mitosis when chromosomes are condensed and easy to see 46 chromosomes (23 pair) ▫2 sex chromosomes (determine male or female)  XX = Female  XY = Male  1200 genes are found on the X chromosome  140 genes are found on the Y chromosome ▫44 autosomes (the other 44 chromosomes)

6. Human genetic disorders Changes in a gene’s DNA sequence can change proteins Changes in the proteins can directly affect a phenotype

7. Chromosomal Disorders Caused by an error in meiosis ▫Nondisjunction = chromosomes don’t separate correctly ▫Results in gametes with too few or too many chromosomes

8. Chromosomal Disorders Down’s syndrome ▫3 copies (trisomy) of chromosome pair 21 (47 total)  Mental retardation and birth defects Turner’s syndrome ▫One X chromosome (45 total) –  sterile female whose sex organs don’t develop at puberty Klinefelter’s syndrome ▫XXY (47 total)  Sterile male

9. Down Syndrome Trisomy 21

10. Turner Syndrome 1/ 2,000 live female births Short stature, loss of ovarian function, lack or incomplete development at puberty Heart defect, infertility, webbed neck

11. Klinefelter’s Syndrome 1/500-1/1000 males less testosterone than normal (less facial hair, infertility) Tall

12. Disorders caused by individual genes - recessive ▫cystic fibrosis  Most cases of CF are caused by deletion of 3 bases in the gene (CFTR) that allows chloride ions to pass through membranes  Causes digestive problems and produce thick, heavy mucus that clogs their lungs and breathing passages  Carried by 1/25 people with European ancestry

13. Disorders caused by individual genes - recessive To have the disorder you need 2 copies of the gene ▫Sickle cell disease  Defect in hemoglobin (oxygen carrying molecule in red blood cells) causes red blood cells to “sickle”  Carried by 1/12 African Americans  Carriers are healthy but are highly resistant to malaria.

14. Disorders caused by individual genes - dominant Individuals with the disorder only need 1 allele to have the disorder ▫Huntington’s Disease  Caused by a repeat of the sequence CAG  Mental retardation and uncontrollable movements that usually don’t appear until middle age ▫Achondroplasia  A form of dwarfism ▫Polydactyly  6 fingers or toes

15. Disorders caused by individual genes – sex-linked Genes in sex-linked disorders are found on the X or Y chromosome (most are on X) ▫Color blindness (X chromosome)  Humans have 3 genes for color vision – all on the X  Red-green colorblindness = 1/12 males & 1/200 females  Males have 1 X chromosomes – females have 2 (the allele for colorblindness can be masked in females)

16. X-Chromosome inactivation In females, most genes in one of the X chromosomes are switched off forming a region in the nucleus known as a bar body ▫In calico cats, a gene that controls the color of coat spots is on the X chromosome ▫In different parts of the body, different X chromosomes are switched off – making it a mixture of orange and black

17. Disorders caused by individual genes – codominant and multiple alleles ABO Blood Types ▫A (I A ) and B (I B ) are codominant ▫O (i) is recessive

18. The Human Genome By using tools that cut, separate, and replicate DNA base by base, scientists can read the sequences in DNA from any cell.