for each of these conditions, mutant allele is dominant powerpoints/chapter… · for each of these...

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson LearningFor each of these conditions, mutant allele is dominant over wild type allele

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Marfan Syndrome Is an AutosomalDominant Trait

• Affects skeletal system,eyes, and cardiovascularsystem

• Characteristics – tall, thinarms and legs with long,thin fingers and toes

• Weakened aorta mayenlarge and rupture

Fig. 4.13

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Marfan Syndrome May Affect the Aorta

Gene is located on chromosome 15 = fibrillinFig. 4.14

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Consanguineous mating

Huntington’sRare dominant trait

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Pedigree - Woody Guthrie

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Huntington’s disease-affected brains

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Nancy Wexler

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

The number of CAG repeats in huntingtin gene (htt)is directly correlated with probability of disease

polyQ (glutamine)

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

http://www.birf.info/art/people/media-stories/nd5.gif

Pathology of Huntington’s disease

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson LearningFigure 4.16

Pedigree 1 Pedigree 2

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Examples of Patterns of Inheritance

• Autosomal Recessive

• Autosomal Dominant

• X-Linked Dominant

• X-Linked Recessive

• Y-Linked Inheritance

• Mitochondrial Inheritance

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Transmission of X and Y Chromosomes

Fig. 4.16

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

X and Y Chromosomes

• Females carry two copies of the Xchromosome and may be homozygous orheterozygous for a given trait

• Males carry only one X chromosome andare hemizygous for all genes on the Xchromosome

• A male receives his Y chromosome fromhis father and his X from his mother

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

X-linked Dominant Traits

• Affected males produce all affecteddaughters but no affected sons

• (Criss-cross inheritance)

• Heterozygous females will have unaffectedand affected offspring; sons anddaughters will be equally affected

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

HypophosphatemiaIs an X-linked Dominant Trait

Fig. 4.17

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

X-Linked Recessive

• Hemizygous males and homozygousfemales are affected

• Males are more likely to be affected• Affected males receive the allele from

their mothers• Daughters must receive the allele from

both parents

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Pedigree for X-Linked Recessive Trait

Fig. 4.18

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Colorblindness

• Most common form of color blindness isred-green blindness

• 8% male population of US• Red blindness – unable to see red as a

distinct color• Green blindness – cannot see green or

other colors in the middle of the visualspectrum

• Rare form is an autosomal dominant traiton chromosome 7- blue blindness

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Ishihara plate test for colorblindness

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Defects in the ConesCause Color Blindness

Fig. 4. 21

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

http://home.comcast.net/~john.kimball1/BiologyPages/R/Red-greenGenes.gif

Red-green opsin genes

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Muscular Dystrophy

•Progressive weakness and loss of muscletissue

•Autosomal and X-linked forms

•Most common form is an X-linkedrecessive Duchenne musculardystrophy

•1/3500 males in U.S.

•Disease progresses rapidly

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Duchenne Muscular Dystrophy

• Gene located near end of Xchromosome

• Encodes for dystrophin

• Stabilizes cell membraneduring the stress of musclecontraction

• Several mutations withvariation in phenotype

• Characteristic movementsFig 4.22

Chapter 4 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

Hemophilia and History