Chromosomes and Disease

Normal Human Chromosomes

Humans have 46 chromosomes. Each of these chromosomes has a specific structure, which can be ascertained by a number of techniques. This node tells the story of why it took so long for scientists to identify the normal human karyotype as well as describe chromosomall nomenclature.

1.1

Human Chromosome Number

Cytologists had been studying chromosome behavior since the late 19th century. Why did it take until 1956 to figure out the correct human chromosome number, thanks to Joe Hin Tjio and Albert Levan?

1.2

Chromosome Mapping: Idiograms

How do scientists find their way around a chromosome? With chromosome maps called idiograms, researchers can pinpoint the locations of genes and locate abnormal gene forms.

1.3

Human cytogenetics: 46 chromosomes, 46 years and counting

Human cytogenetics was born in 1956 with the fundamental, but empowering, discovery that normal human cells contain 46 chromosomes. Since then, this field and our understanding of the link between chromosomal defects and disease have grown in spurts that have been fuelled by advances in cytogenetic technology. As a mature enterprise, cytogenetics now informs human genomics, disease and cancer genetics, chromosome evolution and the relationship of nuclear structure to function.

Unit 2

Techniques for Studying Chromosomes

This node reviews some of the techniques that are used in studying chromosome number and structure. These are critical for diagnosing different birth defects and other disorders.

2.1

Fluorescence In Situ Hybridization (FISH)

Cytogeneticists can now go "FISH-ing" for chromosomal abnormalities, which are deletions and duplications that can cause disease. How exactly does FISH work?

2.2

Cytogenetic Methods and Disease: Flow Cytometry, CGH, and FISH

Some diseases involve regions of chromosomes that have been flipped or damaged. Find out what techniques scientists are using to dissect these chromosomes at the molecular level.

2.3

Karyotyping for Chromosomal Abnormalities

Each chromosome pair viewed in a karyotype appears to have its own distinct "bar code" of bands. What changes do scientists look for in a karyotype when diagnosing diseases and disorders?

2.4

Prenatal Screen Detects Fetal Abnormalities

How can prospective parents ensure that they will have a healthy baby? Prenatal testing can provide parents with information about their child’s genetic identity.

Unit 3

Types of Chromosomal Abnormalities

The content in this node will examine: aneuploidies, duplications, deletions, and other chromosomal abnormalities and their role in human disorders.

3.1

Chromosomal Abnormalities: Aneuploidies

Aneuploidies disturb the delicate balance of gene products in cells by changing the chromosome number. What are the causes and phenotypic consequences of these meiosis mishaps?

3.2

Trisomy 21 Causes Down Syndrome

A century after Down syndrome was first described, scientists discovered that the root cause of this disorder is a condition called trisomy 21. What strides in research have been made since then?

3.3

DNA Deletion and Duplication and the Associated Genetic Disorders

Deletions and duplications of single-base pairs typically arise during homologous recombination and cause diseases. But what happens when a mutation occurs over multiple genes?

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