Karyotype And Pedigrees What is a Karyotype Chromosome

Karyotype And Pedigrees

What is a Karyotype • Chromosome preparation of an individual – They are organized as • Homologous chromosomes are paired by identical centromere position, identical staining pattern and size • Arranged by size • The sex chromosomes are at the end

Human Karyotype

Karyotype Preparation • Cultured cells are arrested at metaphase by adding colchicine • This is when chromosomes are most condensed and easiest to identify

Karyotype Preparation • Arrested cells are broken open • Metaphase chromosomes are fixed and stained • Chromosomes are photographed through microscope • Photograph of chromosomes is cut up and arranged to form Karyotype diagram

Human Karyotype

Uses of Karyotyping • Ascertain sex • Identify chromosomal abnormalities Ex. Down’s syndrome, • Identify abnormal chromosomes Ex. Breakages and nonreciprocal crossing over

Pedigree • Chart that shows genetic connections among individuals • Uses Standardized symbols • Able to use knowledge of probability and Mendelian patterns used to suggest basis of a trait • Conclusions most accurate when drawn from large number of pedigrees

Fig. 11 -7 a, p. 172

Pedigree problem 1. Is this trait dominant or recessive? 2. Is this trait sex linked or autosomal? 3. What does the half shaded symbols mean? 4. What is the genotype of individual A A

Pedigree for Polydactyly Fig. 11 -7 b, p. 172

Why Pedigree Studies? • To understand human inheritance patterns • To understand how traits are inherited without using test crosses • To be able to predict inheritance pattern for prospective parents

Pedigree of Huntington’s Disease Fig. 11 -8, p. 173

Pedigree of European Royal Family and Hemophilia Fig. 11 -13 a, p. 175