1. Pedigrees

2. NGSSS
SC.912.L.16.2 Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic and multiple alleles

3. The four types of inheritance patterns:
Genetic conditions caused by a mutation in a single gene follow predictable patterns of inheritance within families
The four types of inheritance patterns:
Autosomal recessive
Autosomal dominant
X-linked recessive
X-linked dominant

4. PEDIGREE
A pedigree is a tool for studying inheritance in humans (in particular, inherited diseases).
It shows the occurrence and appearance (phenotype) of a particular genetic trait, as it is passed from one generation to the next in a family.

6. How to Read Pedigrees = male = female = parents or
= individual who shows the trait
= heterozygous carrier of autosomal trait or
Figure: FIGURE 12.14
Title:
A family pedigree
Caption:
This pedigree is for a recessive trait, such as albinism. Both of the original parents are carriers. Because the allele for albinism is rare, pairing between carriers is an unlikely event. However, the chance that each of two related people will carry a rare recessive allele (inherited from a common ancestor) is much higher than normal. As a result, pairings between cousins or even closer relations are the cause of a disproportionate number of recessive diseases. In this family, pairings between cousins occurred three times—between III 3 and III 5, III 4 and IV 3, and IV 1 and IV 2.
= offspring 1 2 3
= generation
I, II, III, IV, or V

7. More Symbols
Identical Twins
Non-Identical Twins
Deceased Individuals

8. PATTERNS OF INHERITANCE Autosomal Recessive Trait
Seen when individual has 2 copies of allele (One copy of allele, individual is carrier but does not develop condition)
Males and females affected equally

9. PATTERNS OF INHERITANCE Autosomal Dominant Trait
Condition expressed in individuals with just one copy of allele
Males and females have equal chance of passing on trait to offspring

10. PATTERNS OF INHERITANCE Sex-linked Recessive
Not expressed when one normal allele present
Fully evident in males because they have only one copy of X chromosome
Women rarely affected unless both X chromosomes carry the allele
No father to son transmission, but all daughters will inherit one copy of allele (carrier)

11. PATTERNS OF INHERITANCE Sex-linked Dominant
Located on X chromosome
so no father to son
transmission but all
daughters affected
Expressed when only one copy of allele present
Carriers are not possible

12. Your task… Determine the pattern of inheritance for… Cystic Fibrosis
Achondroplasia
Tay-Sachs Disease
Huntington’s Disease

13. Pattern of Inheritance?
Cystic Fibrosis
Pattern of Inheritance?
autosomal, recessive

14. Achondroplasia Pattern of Inheritance?
autosomal, dominant

15. Tay-Sachs Disease Pattern of Inheritance?
autosomal, recessive

16. Huntington’s Disease Pattern of Inheritance?
autosomal, dominant

17. Hemophilia
Mode of Inheritance?
sex-linked recessive