Autosomal Pedigrees

Autosomal Pedigrees

Catalyst:Incest increases the likelihood of having a child with birth defects.

Why do you think this is true?

Write in complete sentences!

Don’t talk during the Catalyst!

Big Qs

Why do some children inherit genetic diseases, but other family members do not?

What does it means for a disease to “skip” a generation?

What are Huntington’s, Cystic Fibrosis, or Tay Sachs?

By the end of today, SWBAT… Determine if an autosomal disorder is dominant or recessive

Analyze autosomal pedigrees to determine the inheritance of disorders

Objectives

Agenda

Catalyst Pedigrees? Pedigreat! Practice Exit Question

Autosomal vs. Sex-Linked

Humans have 23 pairs of chromosomes Autosomes: chromosomes #1-#22 Sex chromosomes: chromosome #23 (X or

Y)

Pedigrees show how traits are inherited across many generations.

Pedigrees

Key Point #1: Symbols show the relationships in a pedigree

Parents

Children

Male

Male

Female

Female

Unaffected: normal (no disorder)

Affected: has disorder

Pedigree Symbols

W MAN

What do the symbols mean?

Dominant and Recessive Disorders Key Point #2: Autosomal

disorders are either dominant or recessive

Dominant disorder Person has disease if there is AT LEAST ONE dominant alleleDD = has disorderDd = has disorderdd = no disorder

Dominant and Recessive Disorders Key Point #2: Autosomal

disorders are either dominant or recessive

Recessive disorder Person has disease if there are TWO

recessive allelesDD = no disorderDd = carrierdd = has disorder

Dominant Disorders

Key Point #3: There are two tricks to figuring out if a disease is dominant or recessive.

If both parents show the disorder but a child does not, the disorder is dominant.

DD = has disorder Dd = has disorder dd = no disorder

Recessive Disorders

If both parents do not show the disorder, but a child does, then it is recessive.

DD = no disorder Dd = carrier dd = has disorder

Example 2 – Ms. S does S, s

Example 3 – Help me out! H, h

Huntington’s Disease

1. How many children did individuals I-1 and I-2 have?2. How are III-2 and II-4 related? How are I-2 and III-5

related?3. Which members of the family above are afflicted with

Huntington’s Disease?4. How many girls did II-1 and II-2 have? How many have

Huntington’s Disease?5. There are no carriers for Huntington’s Disease – you

either have it or you don’t. With this in mind, is Huntington’s disease caused by a dominant or recessive trait? Explain how you determined your answer.

Cystic Fibrosis…and some incest

1. How are individuals III-1 and III-2 related?

2. Is the trait for Cystic Fibrosis dominant or recessive? How do you know?

3. Name 2 individuals that have Cystic Fibrosis. Explain how you determined your answer.

4. Name 2 individuals that were carriers of Cystic Fibrosis. Explain how you determined your answer.

Guided Practice

Try the worksheet.

Skip numbers 4 – 6. (The paragraph’s information is wrong. It is a pedigree for a recessive trait.)

Exit Question

Draw this pedigree, and label the genotype of each individual. (Use B and b)

Write in complete sentences!

Don’t talk during the Exit Question!