Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Memmler’s The Human Body in Health and Disease 11 th edition Chapter 25 Heredity and Hereditary Diseases Heredity is what sets the parents of a teenager wondering about each other. Laurence J. Peter

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins One Chromosome – Many Genes

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Methodical Investigation into Heredity How traits are transmitted from parents to offspring 19th century Gregor Mendel Genes (units of heredity)

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genes and Chromosomes Genes are DNA segments Thousands of genes per chromosome Gene carries code for specific trait Cell contains 46 chromosomes (except sex cell) –1 pair sex chromosomes (23 rd chromosome) –22 pairs autosomes Allele—Any form of gene on a specific site on a chromosome Alleles for each trait exist in pairs

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-1: What is a gene and what is a gene made of?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Dominant and Recessive Genes Dominant gene –Always expresses effect –Needed from one parent only Recessive gene –No effect unless paired allele is also recessive –Need one affected gene from each parent Heterozygous alleles Homozygous alleles

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Dominant and Recessive Genes (cont’d) Phenotype – and characteristic that can be observed. –Example: eye color, blood type Karotype – determination of sexual make up Genotype – a person’s genetic makeup –Example: heterozygous dominant

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-2: What is the difference between a dominant and a recessive gene?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: Paired genes for a given trait are called: a. chromosomes b. gametes c. alleles

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: c. alleles

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Distribution of Chromosomes to Offspring Meiosis –Produces gametes with 23 chromosomes –Cells receive chromosomes at random from parents –“Makes little a ‘me’ ” Punnett square XY X X

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-3: What is the process of cell division that forms the gametes?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: True or False?: Genotype is all the characteristics of a person (or an organism) that can be seen or tested for.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: False: Phenotype is all the characteristics of a person (or an organism) that can be seen or tested for.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sex Determination Sex chromosomes not matched in size, appearance Female (X) chromosome larger Male (Y) chromosome smaller Females—two X chromosomes Males—X, Y chromosomes Sperm—X or Y chromosome, therefore sperm determines the sex of the offspring

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sex determination. If an X chromosome from a male unites with an X chromosome from a female, the child is female (XX); if a Y chromosome from a male unites with an X chromosome from a female, the child is male (XY).

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sex-Linked Traits Traits carried on sex chromosomes Most are carried on X (X- linked – represented as x) Appear almost exclusively in males xX xY XX XY XY x X

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Hereditary Traits Determined by single pair of genes –Less common Determined by gene pairs acting together –More common –Multifactorial inheritance

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Clubbed feet and treatment

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Gene Expression Gene effects on phenotype are influenced by many factors Sex – male pattern baldness; color blindness Presence of other genes – XO, XXY Environment – nature aspect of nature vs nuture

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genetic Mutation Genes or chromosomes that do not replicate exactly Changes in genes or chromosomes Chromosomal breakage or loss, gene fragment rearrangement May occur during cell division –Spontaneous –Induced by mutagen

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genetic Diseases Gene disorders All are genetic Some are hereditary –Passed from parent to offspring –Genetic research can identify some causes

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Congenital Versus Hereditary Diseases Congenital Present at birth Possible causes –Maternal infections –Environmental toxins –Maternal alcohol (fetal alcohol syndrome), smoking –Maternal nutrition Hereditary Genetically transmitted or transmissible Not always evident at birth EX diabetes, hypertension, BRACA

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Examples of Fetal Alcohol Syndrome

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-7: Can a disorder be congenital but not hereditary? Explain.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Examples of Genetic Diseases Down syndrome (trisomy 21) © Huntington disease (D) Marfan syndrome © Phenylketonuria (PKU) (M) Sickle cell disease ® Cystic fibrosis ® Tay-Sachs disease ® Progressive muscular atrophies (9 types with all 3 patterns of inheritance) Albinism ® Osteogenesis imperfecta (D) Neurofibromatosis (D) Fragile X syndrome (X) Hemophilia (X) Some cancers

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Inheritance Pattern

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Marfan Syndrome Neurofibromatosis Neurofibromatosis

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-8: What causes phenylketonuria?

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Treatment and Prevention of Genetic Diseases More than 400 genetic diseases identified List is growing as science advances

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genetic Counseling Family history (pedigree) Laboratory studies –Amniocentesis –Chorionic villus sampling (CVS) –Karyotype analysis (determines sex of infant) Counseling prospective parents

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Amniocentesis. A sample of amniotic fluid is removed from the amniotic sac. Cells and fluid are tested for fetal abnormalities. (Reprinted with permission from Cohen BJ. Medical Terminology. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2004.)

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: Which of these is the least invasive method for testing for genetic disease? a. amniocentesis b. chorionic villus sampling c. karyotype analysis

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: c. karyotype analysis

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Progress in Medical Treatment Some diseases respond to early diagnosis and treatment Dietary control –Maple syrup urine disease –Wilson disease (+ drug therapy)- liver cannot rid copper from the body –PKU Drug therapy Hormone therapy –Klinefelter syndrome (+ psychotherapy) Psychotherapy