Chapter 15 - The Chromosomal Basis of Genetics

Chapter 15 - The Chromosomal Basis of Genetics - Chapter 15...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 15 Class Notes – The Chromosomal Basis of Inheritance – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 15 The Chromosomal Basis of Inheritance Locating Genes on Chromosomes: A century ago, the relationship between genes and chromosomes was not obvious. Today, we can show that genes are located on chromosomes. The location of a particular gene can be seen by tagging isolated chromosomes with a fluorescent dye that highlights the gene. Mendelian Inheritance Has Basis in Chromosomes: Several researchers proposed in the early 1900s that genes are located on chromosomes. The behavior of chromosomes during meiosis was said to account for Mendel’s laws of segregation and independent assortment. The Chromosome Theory of Inheritance: Mendelian genes have specific loci on chromosomes. It is the chromosomes that undergo segregation and independent assortment. Morgan’s Experimental Evidence: The first solid evidence associating a specific gene with a specific chromosome came from embryologist Thomas Hunt Morgan. Morgan’s experiments with fruit flies provided convincing evidence that chromosomes are the location of Mendel’s heritable factors. Morgan’s Choice of Fruit Flies: Fruit flies are a convenient organism for genetic studies because they breed at a high rate, a generation can be bred every two weeks, and they only have four pairs of chromosomes. Phenotypes: Morgan noted wild type (normal) phenotypes that were common in the fly populations. Traits alternative to the wild type are mutant phenotypes. Behavior of Gene’s Alleles & Behavior of a Chromosome Pair:
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Chapter 15 Class Notes – The Chromosomal Basis of Inheritance – Page 2 In one experiment, Morgan mated male flies with white eyes with female flies with red eyes (wild type). The F 1 generation all had red eyes. The F 2 generation showed the 3:1 red to white eye ratio, but only males had white eyes. Morgan determined that the white-eyed mutant allele must be located on the X chromosome. Morgan’s finding supported the chromosome theory of inheritance. Linked Genes: Linked genes tend to be inherited together because they are located near each other on the same chromosome. Each chromosome has hundreds or thousands of genes. Genes located on the same chromosome that tend to be inherited together are called linked genes. This violates the law of segregation. How Linkage Affects Inheritance: Morgan did other experiments with fruit flies to see how linkage affects inheritance of two characters. Morgan crossed flies that differed in traits of body color and wing size. From the results, Morgan reasoned that body color and wing size are usually inherited together in specific combinations because the genes are on the same chromosome. However, nonparental phenotypes were also produced.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

Page1 / 7

Chapter 15 - The Chromosomal Basis of Genetics - Chapter 15...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online