8c Pedigree Analysis

Question 1

What is a pedigree?

Answer 1

Definition: A pedigree is a diagram that represents the familial relationships and the inheritance of specific traits across generations. It is commonly used in genetics to track the occurrence of inherited traits or genetic disorders.

Question 2

What are the symbols used in a pedigree and what do they represent?

Answer 2

Square: Male
Circle: Female
Shaded: Individual expresses the trait
Unshaded: Individual does not express the trait
Half-shaded: Carrier of a recessive trait
Horizontal Line: Mating between two individuals
Vertical Line: Descendants
Roman Numerals: Represent generations
Numbers: Identify individuals within a generation

Question 3

What are the different patterns of inheritance (or modes)?

Answer 3

Autosomal Dominant: Trait appears in every generation; both males and females are affected equally.
Autosomal Recessive: Trait can skip generations; both males and females are affected equally.
X-linked Dominant: More females are affected; affected males pass the trait to all daughters but no sons.
X-linked Recessive: More males are affected; females are often carriers.
Mitochondrial: Only passed from mother to all offspring, both male and female.

Question 4

Do you know how to determine the inheritance patterns (or modes)?

Answer 4

Determination: Analyze the pedigree for patterns such as:
Presence in each generation (dominant vs. recessive)
Gender distribution (autosomal vs. sex-linked)
Transmission from affected males to daughters only (X-linked dominant)
Transmission from affected mothers to all offspring (mitochondrial)

Question 5

Can you assign genotypes for individuals in a pedigree?

Answer 5

Assigning Genotypes:
Autosomal Dominant: Affected individuals may be heterozygous (Aa) or homozygous dominant (AA); unaffected individuals are homozygous recessive (aa).
Autosomal Recessive: Affected individuals are homozygous recessive (aa); unaffected individuals may be homozygous dominant (AA) or heterozygous carriers (Aa).
X-linked Traits: Consider the gender and pattern of inheritance to determine whether individuals are carriers or affected.

Question 6

Can you assign phenotypes for individuals in a pedigree?

Answer 6

Assigning Phenotypes: Based on genotypes, assign phenotypes by identifying whether the individual expresses the trait or not. Consider the presence of carriers for recessive traits and partial expression in cases like codominance or incomplete dominance.

Question 7

Would you be able to conduct a test cross from a pedigree?

Answer 7

Test Cross: In a pedigree, a test cross can be inferred by observing the offspring’s phenotypes to determine an unknown parent’s genotype, especially if the trait is recessive and the parent’s phenotype is dominant.

Question 8

Can you assign each individual a generational Roman numeral and a number?

Answer 8

Roman Numerals (I, II, III, etc.): Used to indicate generations, starting with the oldest generation at the top.
Numbers: Used to identify individuals within a generation from left to right.

Question 9

Can you discuss the relationships between individuals in a pedigree?

Answer 9

Use terms like siblings, parents, offspring, cousins, etc.
Identify relationships such as parents (horizontal line connecting a male and female), siblings (vertical line branching from parents), and offspring (vertical line connecting parents to children).
Recognize consanguineous relationships (mating between relatives) if indicated.