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chapter15ppt2012.pptCopyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
PowerPoint Lectures for Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 15
The Chromosomal Basis of Inheritance
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- Concept 15.1: Where are genes located?
Located on chromosomes?
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Morgan’s Experimental Evidence: Scientific Inquiry
- Thomas Hunt Morgan
- Chromosomes are the location of Mendel’s “heritable factors”
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Morgan’s Choice of Experimental Organism
- Morgan worked with Drosophila
- Breed at a high rate
- New generation every 2 weeks
- 4 pairs of chromosomes
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- Morgan observed:
- Wild type = normal phenotypes common in the fly populations
- Mutant phenotypes = abnormal/non-common
Figure 15.3
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Morgan Experiment
- Mated:
- Female flies with red eyes (wild type)
- Male flies with white eyes (mutant)
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Morgan Experiment
- Mated:
- Female flies with red eyes (wild type)
- Male flies with white eyes (mutant)
- What do you expect in the…
- The F1 generation =
- The F2 generation =
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What chromosomes differ in M vs. F?
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Morgan determined = white-eye mutant allele must be located on the X chromosome
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Morgan determined = white-eye mutant allele must be located on the X chromosome
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Morgan determined = white-eye mutant allele must be located on the X chromosome
P
F1
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Morgan determined = white-eye mutant allele must be located on the X chromosome
P
F1
F2
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Morgan determined = white-eye mutant allele must be located on the X chromosome
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Morgan’s Team
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- Concept 15.2: Sex-linked genes exhibit unique patterns of inheritance
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Inheritance of Sex-Linked Genes
- Sex chromosomes
- have genes unrelated to sex
- Gene located on either sex chromosome
= sex-linked gene
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- Disease caused by recessive alleles on X chromosome
- Color blindness
- Muscular dystrophy
- Hemophilia
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Hemophilia
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- Sex-linked genes
- Follow specific patterns of inheritance
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- Sex-linked genes
- Follow specific patterns of inheritance
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d. What % of offspring will be color blind
g. What % of the males from this mating will be color blind?
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X inactivation in Female Mammals
- Mammalian females
- One of the two X chromosomes in each cell randomly inactivated during development
- Heterozygote for gene on X?
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X inactivation in Female Mammals
- Mammalian females
- One of the two X chromosomes in each cell randomly inactivated during development
- Heterozygote for gene on X?
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X inactivation
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X inactivation
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X inactivation
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- Concept 15.4: Alterations of chromosome Number or Structure genetic disorders
- Number:
- Non-disjunction
- Aneuploidy
- Trisomic, monosomic
- Structure (4):
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Non-disjunction
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- Aneuploidy = Fertilization of gametes in which nondisjunction occurred
5 chromosome organism
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Aneuploidy
- Zygote is trisomic
- 3 copies of a chromosome
- Ex: Down Syndrome
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Aneuploidy
- Zygote is trisomic
- 3 copies of a chromosome
Ex: XYY syndrome
1:1,000 men
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Aneuploidy
- Zygote is trisomic
Ex: Klinefelter's Syndrome (XXY) syndrome
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Aneuploidy
- Zygote is trisomic
Ex: Klinefelter's Syndrome (XXY) syndrome
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Aneuploidy
- Zygote is monosomic
- 1 copy of a chromosome
- Ex: Turner syndrome = monosomy X
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Alterations of Chromosome Structure
- Breakage of a chromosome can lead to four types of changes in chromosome structure
- Deletion
- Duplication
- Inversion
- Translocation
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- Deletion
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- Deletion and Duplication
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- Duplication
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- Inversion
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- Translocation
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Review!
- Ch. 15:
- Morgan’s Experiment: placed gene on chromosome
- Sex-linked inheritance patterns
- X Inactivation in female mammals
- Alterations in chromosome number or structure
