Unit 11 Human Genetics

1. Unit 11 Human Genetics

2. Flashcard Warm-up • Pedigree • A chart of an individual's ancestors used in human genetics to analyze inheritance of certain traits • Nature vs. Nurture • Nature is our DNA (genes) • Nurture is our environment • The debate is over which has a greater influence • We use identical twins to study

3. Problems studying human genetics • 1. Ethically unresponsible to conduct testcrosses on humans. • Testcross: method to determine the genotype for a dominant phenotype, always use homozygous recessive • 2. Humans have long life spans and it requires decades to produce several generations to study. • 3. Small number of offspring (and long gestational periods)

4. Techniques used to study human genetics • Population Sampling: • determine how often a trait appears in a small randomly selected group, then apply to the entire population • ex. How many people can roll their tongue? • Take this number and project for the entire population.

5. Techniques used to study human genetics • Pedigrees: graphical record of the inheritance of a single trait over several generations. • determined based on family/historical documents, interviews, photographs, and medical records

6. Pedigrees • Shapes represent individuals in pedigrees, connecting lines represent relationships Female Without trait Male without trait Female WITH trait Male WITH trait

7. Ticket Out the Door • 1. When red cattle are bred with white cattle they produce roan (red and white spotted). Cross a roan cow with a red cow. Give phenotype percentages of the offspring. • 2. Colorblindness is sex-linked recessive. Cross a colorblind male with a female carrier. What is their chance of having a colorblind son? • 3. Cross a mom with type AB blood with a dad who is type O. List all possible phenotypes.

8. Helpful Hints for figuring out pedigrees • If the pedigree is showing a SEX-LINKED trait: • No male carriers • Trait cannot be passed from father to son • More males will express the trait • If the pedigree is showing an AUTOSOMAL recessive trait • Trait can skip a generation • Trait CAN be passed from father to son

9. Flashcard Warm-up • Aneuploidy • Having too many or too few chromosomes • Caused by mistakes in Meiosis--nondisjunction- homologous pairs do not separate during meiosis • Autosomal Trait • Trait inherited on one of the first 22 pairs of chromosomes……. • NOT sex-linked

10. Flashcard Warm-up Gene Disorders vs. chromosomal disorders • Gene disorders: Diseases inherited as a single gene on a single chromosome • Arise from mutations on within a single gene • Chromosomes disorder: caused by receiving a missing or extra chromosome--- like Down Syndrome • Often caused by NONDISJUNCTION during Meiosis • Called ANEUPLOIDY • Can be detected on a KARYOTYPE: a picture of the chromosomes

11. Pattern of Inheritance for Genetic Disorders • Autosome: the first 22 pairs of chromosomes • Autosomal Dominant: dominant trait found on any of the first 22 chromosomes • Example : Huntington’s disease, found on chromosome 4, causes brain to break down, symptoms appear in your 40’s

12. Genetic Disorders • AutosomalCodominant: • Found on chromosomes 1-22, and both version of trait are equally dominant • Example: Sickle-cell Anemia, leads to misshapen red blood cells, leads to poor circulation and pain, • Heterozygous individuals are resistant to malaria • Primarily in African-Americans

13. Genetic Disorders • Autosomal Recessive: recessive traits found on any of the first 22 chromosomes • Examples: • Cystic fibrosis (increased mucus in lungs and digestive tract) caucasians • Tay-Sach’s disease- break down of central nervous system leading to premature death (die before 2) • Found in jewish and pennsylvaniadutch populations • PKU (phenylketonuria) • Inability to break down the amino acid phenylalanine • Can be controlled by diet • Can build up in brain and lead to decreased mental function

14. Cystic Fibrosis- autosomal recessive

15. Sex Chromosomes: Pair 23; XX- female, XY- Male • Sex-linked disorder: Disorder carried ON the X • Examples: • Hemophilia (sex-linked recessive trait)-blood does not clot normally • colorblindness

16. Chromosomal Disorders • Inherited due to problems with the ENTIRE chromosome • Example: Down’s Syndrome, caused by a mistake in MEIOSIS • Nondisjunction= incorrect distribution of chromosomes; occurs during meiosis

17. Chromosomal Disorders • Anueploidy: an incorrect number of chromosomes in a fertilized zygote • Autosomal Chromosome Aneuploidy: having an extra autosome • Example: Down’s Syndrome is caused by an extra chromosome #21

18. Sex Chromosome Aneuploidy • Examples • Klinefelter’s Syndrome (XXY) --male but develops female secondary sex characteristics -- usually sterile --use testosterone therapy to treat

19. Sex Chromosome Aneuploidy • Turner’s Syndrome (XO) • Female with underdeveloped gonads, infertile

20. Detection of Genetic Disorders • Genetic Counseling: can help parents determine the chances of passing a harmful genetic trait to their child • Sonograms: use of sound waves to produce a picture of a fetus • Used to evaluate baby’s growth and development

21. Detection of Genetic Disorders • Blood tests: • Screen for proteins • Alpha-Feto protein test (AFP) • Levels determine if baby is at risk for Down’s syndrome, Turner’s , or spina bifida

22. Detection of Genetic Disorders • Amniocentesis: • Removes amniotic fluid with fetal cells which can be cultured and produce a karyotype • Karyotype: a picture of the chromosomes • Chorionic Villi Sampling: removes tissue from the placenta for karyotyping, • Can be done earlier in pregnancy and more risky

23. Karyotypes

24. Human Genome Project • Human Genome Project: • develop certain genetic markers to detect presence of certain gene variations on the chromosomes Knowledge of a genome unlocks the secrets of what DNA is making which proteins. This will ultimately help scientist to better understand the inner workings of biology.

25. Prevention/Treatment Genetic diseases cannot be cured but treated: • Pain medication: manage pain • Occupational Therapy: help people who have conditions improve their ability to perform every day tasks • Blood Transfusions: Sickle-cell/ Hemophiliacs may require • Gene Therapy: use vectors (viruses) to replace defective genes with normal ones

26. Environmental Factors • Diet: • can stop the progression of PKU, andlimit the risk for genetic predispositions such as heart disease, alcoholism, and certain cancers. • Environmental Toxins: environmental factors such as UV radiation or tobacco can directly change our genes