Miss Angler's Biology Class: Hemophilia Pedigree Analysis

Introduction

The lecture is focused on interpreting a hemophilia pedigree diagram and answering genetics exam questions.
The allele causing hemophilia is recessive and sex-linked, located on the X chromosome.
Key concepts:
- Hemophilia being a sex-linked trait.
- Recessive allele characteristics.

Initial Steps:
1. Understand whether the cross is sex-linked or autosomal.
2. For sex-linked, males have XY and females have XX chromosomes.
3. Fill in each person's set of alleles for clarity and to minimize mistakes.
Identifying Hemophiliacs:
- Males with hemophilia have one recessive allele on the X chromosome.
- Females require two recessive alleles to exhibit hemophilia.
Analyzing Non-Hemophiliacs:
- Males who are not hemophiliacs must have a dominant allele (capital H) on their X chromosome.
- Females who might be carriers have one dominant and one recessive allele.

Individual Analysis:
- Example of mom (Individual 2) who has two sons with hemophilia, indicating she carries a recessive allele.
Daughter's Inheritance:
- Daughters can inherit X from dad, and based on her children, you can deduce her allelic pattern.

Questions and Answers:
1. Phenotype of Individual 4: Normal female without hemophilia.
2. Genotype of Individual 2: Already calculated from analysis.
3. Explanation of Female Resistance to Hemophilia:
  - Females have two X chromosomes and need recessive alleles on both to express hemophilia, making them less susceptible.
Genetic Cross Representation:
- Elements:
  - P1 and F1 generations.
  - Punnett squares for genotype and phenotype calculations.
- Compulsory Marking:
  - Provide a percentage chance for hemophiliac offspring.
  - Example shown with a 50% chance for having a hemophiliac son.