Chromosome morphology a functional chromosome has

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: • 1959: Most people with the disorder have three copies of chromosome 21 (a condition called trisomy). • In rare cases, people with the disorder are trisomic for smaller parts of chromosome 21. • Compared these smaller fragments to establish the Down Syndrome Critical Region, or DSCR. Introduction: Trisomy 21 results in Down Syndrome • The DSCR is 5 million base pairs long and contains 33 genes. • Down Syndrome likely results from the overexpression of many genes that interact in complex ways. Chromosome Morphology • A functional chromosome has: – Centromere, where spindle fibers attach – Two telomeres at the ends, that stabilize the chromosome Chromosome Morphology • Four basic types of chromosomes: 1. Metacentric – The centromere is in the middle – Two arms of approximately equal length Chromosome Morphology 2. Submetacentric – Centromere is closer to one end – Long (in humans called q) and short arms (in humans called p) – Long arm and a knob, or satellite Chromosome Morphology 1. Acrocentric – Centromere is very close to one end – Long arm and a knob, or satellite 2. Telocentric – Centromere is essentially at one end Karyotype • Complete set of chromosomes possessed by an organism is called its karyotype. • Presented as a picture of metaphase chromosomes lined up in descending order of their size. Karyotype • Staining techniques can distinguish between chromosomes of similar sizes • e.g. Giemsa dye, which stains areas that are A-T rich (called “G bands”) For Wednesday: We’ll discuss aneuploidy and begin to discuss the most common cause of aneuploidy Read Chapter 7: Recombination, linkage, and gene mapping...
View Full Document

This document was uploaded on 02/25/2014.

Ask a homework question - tutors are online