Homozygous normal Heterozygous for BRCA-1 mutation, unaffected Normal cell Cancer cell Heterozygous for BRCA-1 mutation, affected BE A-1- BEA-T BEA-1- BRCA-1 (Inherited mutation) (Occurs in a (Inherited mutation) somatic cell) Heterozygote-cell has one functional copy of BRCA-1 Loss of heterozygosity- cell has zero functional copies of BRCA-1 (a) Pedigree for familial breast cancer (b) Development of cancer at the cellular level FIGURE 25.18 Inheritance pattern of familial breast cancer. (a) A family pedigree that involves a loss-of-function mutation in the BRCA-1 gene. The individuals in this pedigree were tested to determine if they carry a mutation in the BRCA-1 gene. Affected individuals are shown with black symbols. The disorder follows a dominant pattern of inheritance. (Note: Males can occasionally develop breast cancer, although it is much more common in females.) (b) Breast cancer at the cellular level. Normal cells in an affected individual are heterozygous, where as cancer cells in the same individual have lost their heterozygosity. Therefore, at the cellular level, cancer is recessive because both alleles must be inactivated for it to occur.

Homozygous normal Heterozygous for BRCA-1 mutation, unaffected Normal cell Cancer cell Heterozygous for BRCA-1 mutation, affected BE A-1- BEA-T BEA-1- BRCA-1 (Inherited mutation) (Occurs in a (Inherited mutation) somatic cell) Heterozygote-cell has one functional copy of BRCA-1 Loss of heterozygosity- cell has zero functional copies of BRCA-1 (a) Pedigree for familial breast cancer (b) Development of cancer at the cellular level FIGURE 25.18 Inheritance pattern of familial breast cancer. (a) A family pedigree that involves a loss-of-function mutation in the BRCA-1 gene. The individuals in this pedigree were tested to determine if they carry a mutation in the BRCA-1 gene. Affected individuals are shown with black symbols. The disorder follows a dominant pattern of inheritance. (Note: Males can occasionally develop breast cancer, although it is much more common in females.) (b) Breast cancer at the cellular level. Normal cells in an affected individual are heterozygous, where as cancer cells in the same individual have lost their heterozygosity. Therefore, at the cellular level, cancer is recessive because both alleles must be inactivated for it to occur.

Name: Explain why familial breast cancer shows a dominant pattern of inherit
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Description: Explain why familial breast cancer shows a dominant pattern of inheritance in a pedigree even though it is recessive at the cellular level. Homozygous normalHeterozygous for BRCA-1 mutation, unaffectedNormal cellCancer cellHeterozygous for BRCA-1 mut

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter7: Development And Sex Determination

Section: Chapter Questions

Problem 18QP: Equalizing the Expression of X Chromosome Genes in Males and Females Males have only one X...

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