1. Complex Patterns of Inheritance
Packet 9
Complex Patterns of Inheritance

2. How do we trace traits through families? (Notes: pg.1-2)
Pedigrees
Biologists use charts called __________________ to study the pattern of phenotypic inheritance in individuals and their family.

3. How do we make a pedigree?
When making a pedigree the following rules must be followed:
____________ = male
___________ = female  II
A _________ in square or circle = individual displays the trait
A ______ of a shaded in square or circle = individual is a carrier (may not display the trait). This is not always known or shown.
square
circle
shaded
half

4. How do we make a pedigree?
The size of the pedigree chart will be determined by the number of individuals in the immediate family and how many generations are used.
When possible, at least 3 generations should be used.

5. What kinds of traits do we use pedigrees to track?
GENETIC DISORDERS are diseases or debilitating conditions that have a genetic basis.

6. What kinds of traits do we use pedigrees to track?
Autosomal Disorder:
Genes for some diseases are found on one of the 44 ____________ (non-sex chromosomes). These genes are said to be autosomal linked.
autosomes
We’ve already learned about some of these:
Edward’s Syndrome
Down’s Syndrome
Patau’s Syndrome

7. What kinds of traits do we use pedigrees to track?
Patterns of Recessive Disorders:
When a disease is caused by a recessive allele, _______ recessive alleles are required for the disease to be present in an individual.
two
Ex: Cystic Fibrosis is an autosomal recessive disorder. In order for a child to suffer Cystic Fibrosis, they must inherit the defective recessive allele from both parents.

8. Recessive Disorders Male with cystic fibrosis
His parents don’t have the disease. What do we know about their genotypes if they have the dominant phenotype but a child with the recessive phenotype?
Male with cystic fibrosis
They must be heterozygotes (carriers)

9. Recessive Disorders What about these two?
They have to be carriers too. They are normal but they have a child with the disorder

10. What kinds of traits do we use pedigrees to track?
Patterns of Dominant Disorders:
When the disease is caused by a dominant allele only ______ dominant allele is required for the disease to be present in the individual.
one
Ex: Huntington’s Disease is caused by an autosomal dominant disorder. Therefore a child that receives a normal (healthy) gene from one parent, but inherits a

11. What are some examples of disorders we use pedigrees to track?
Huntington’s Disease
Gradual Deterioration of brain tissue in middle age; shortened life expectancy.
Autosomal Dominant Disorder- we only need one dominant allele to have the disorder
Shows up in 30’s or 40’s so by the time someone knows that they have it, they have probably already passed it on to their children

12. What are some examples of disorders we use pedigrees to track?
Cystic fibrosis
Mucus clogs lungs, liver, and pancreas; victims don’t survive late into adulthood (life expectancy is about 37 years)
Autosomal Recessive- we need two recessive alleles to have the disorder
Occurs 1 out of every 2,080 births and is most common in Caucasians of European descent.

13. What are some examples of disorders we use pedigrees to track?
Sickle Cell Anemia
Abnormal Red Blood Cells cause impaired blood circulation; organ damage
Autosomal recessive- we need 2 recessive alleles to have the disease
Occurs 1 out of every 500 births and is most common in African Americans.
Having the disorder is dangerous but being a carrier helps prevent malaria so it’s helpful to have 1 sickle cell allele but harmful to have 2

14. What are some examples of disorders we use pedigrees to track?
Tay-Sachs Disease
Normal at birth, but deterioration of central nervous system begins in infancy; death occurs in early childhood
Autosomal recessive
Occurs 1 in 1,600 births (primarily in people with European descent)

15. What are some examples of disorders we use pedigrees to track?
Phenylketonuria (PKU)
Inability of the body to break down the amino acid phenylalanine. Build up of phenylalanine leads to problems w/brain development, seizures.
Phenylalanine is found in artificial sweeteners such as in diet soft drinks

16. Practice! Pg. 2
Complete the following pedigree that shows the inheritance pattern of attached earlobes (ee). In the spaces below each symbol, write as much of the genotype of the individual that can be determined from the information that is provided.
First, we’ll fill in the ones we know for sure: the affected individuals. They have to be homozygous recessive. ee ee ee ee

17. Practice! Pg. 2
Since the rest of the individuals don’t have the disorder, their first allele has to be dominant (E). We can go ahead and fill those in. E E

18. Practice! Pg. 2 e

19. Practice! Pg. 2
1. How can you tell if someone is a carrier of a recessive trait (or heterozygous)?
____________________________________________ 
2. If you know that someone is a carrier, shade in half of the circle or square. 
3. What is the relationship between the top left square and the circle in the bottom-left corner?
___________________________________________
Look at the parents and the offspring to see if a dominant or recessive allele was passed down.
They are grandfather and granddaughter.