1. Unit 11 Human Genetics

2. Flashcard Warm-up Pedigree Nature vs. Nurture
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determined based on family/historical documents, interviews, photographs, and medical records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 Male without trait Female WITH trait Male WITH trait
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 Autosomal Trait
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. Gene Disorders vs. chromosomal disorders
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 Autosomal Codominant:
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 pennsylvania dutch 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