1. Warm-Up (11/30)
On the piece of white paper from the back, answer the following question.
Name
Date
Period
Hemophilia is a disease caused by a mutation in the “factor VIII” gene, which is located on the X chromosome. Individuals with at least one copy of the natural allele of the gene, which encodes a functional protein, do not exhibit symptoms of the disease. Draw a monohybrid cross showing the genotype possibilities when a woman who does not have hemophilia mates with a man who does have hemophilia. (Hint: you will have to draw two possible monohybrid crosses for two possible genotypes of the woman). Show the phenotype distributions, including gender, for both possibilities.

2. Critical Thinking Question #1
Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers.
Explain two ways a trait will not follow Mendelian patterns of inheritance from one generation to the next.

3. Many traits do not follow Mendelian genetics
Example #1: traits can be encoded by multiple genes.
“polygenic trait”

4. Many traits do not follow Mendelian genetics
Example #2:
Mitochondria and chloroplasts have DNA, too!

5. Many traits do not follow Mendelian genetics
Mitochondria and chloroplasts have DNA, too!
But their segregation during mitosis is random and uneven, so their genetics are unpredictable. m m M M M m M m m M m M m M m

6. Many traits do not follow Mendelian genetics
Sperm do not give mitochondria to the eggs during fertilization.
Therefore, all mitochondrial genes are inherited through the mother.

7. Critical Thinking Question #2
Discuss this question with your partner and write or represent it. I will call on three people to share their partners’ answers.
Explain how the progeny of a man and a woman carrying two different alleles of a mitochondrial gene would not follow Mendelian patterns of inheritance.

8. Genetic Disorders
Sickle-cell anemia results from the mutation of a single gene, HBB, which encodes a deformed protein.

9. Genetic Disorders
Down’s Syndrome (trisomy 21) results from nondisjunction, where chromosome 21 is not evenly segregated. 1m 1p 1p 1m 2p 2m 2p 3p 3m 3p 2m 4m 3m 4p 4m 4p
2 copies of chr. 4
0 copies of chr. 4
uneven segregation 1m 2p 3p 4m
fertilization 4p
3 copies of chr. 4

10. Genetic Disorders
Down’s Syndrome (trisomy 21) results from nondisjunction, where chromosome 21 is not evenly segregated.
A normal karyotype
Down’s syndrome karyotype

11. Genetic Disorders
Genetic disorders can be determined before birth through amniocentesis.
Second-trimester amniocentesis has a 0.6% risk of miscarriage (mayoclinic.org).
Should amniocentesis be performed in a specific situation? That is for the parents, physician, and ethics boards to decide.

12. Closure
On the piece of white paper from the back, answer the following question:
Name
Date
Period
If you were a physician and expecting parents asked you to perform amniocentesis to determine whether their child has a genetic disorder, what is one question you would ask the parents to determine whether it is ethical to perform the procedure, and why?
Scale 1 – 10