Chapter 11

1. Chapter 11

2. 11-1 Basic Patterns in Human Inheritance Objectives • Analyze genetic patterns to determine dominant or recessive inheritance patterns • Summarize examples of dominant and recessive disorders • Construct human pedigrees from genetic information

3. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Recessive Genetic Disorders • A recessive trait is expressed when the individual is homozygous recessive for the trait.

4. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Cystic Fibrosis • Affects the mucus-producing glands, digestive enzymes, and sweat glands • Chloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat. • Without sufficient chloride ions in the cells, a thick mucus is secreted.

5. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Albinism • Caused by altered genes, resulting in the absence of the skin pigment melanin in hair and eyes • White hair • Very pale skin • Pink pupils

6. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Tay-Sachs Disease • Caused by the absence of the enzymes responsible for breaking down fatty acids called gangliosides • Gangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration.

7. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Galactosemia • Recessive genetic disorder characterized by the inability of the body to digest galactose.

8. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Dominant Genetic Disorders • Huntington’s disease affects the nervous system. • Achondroplasia is a genetic condition that causes small body size and limbs that are comparatively short.

9. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance

10. Complex Inheritance and Human Heredity Chapter 11

11. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Pedigrees • A diagram that traces the inheritance of a particular trait through several generations

12. Complex Inheritance and Human Heredity Chapter 11 11.1 Basic Patterns of Human Inheritance Inferring Genotypes • Knowing physical traits can determine what genes an individual is most likely to have. Predicting Disorders • Record keeping helps scientists use pedigree analysis to study inheritance patterns, determine phenotypes, and ascertain genotypes.

13. 11-2 Complex Patterns of Inheritance Objectives • Distinguish between various complex inheritance patterns • Analyze sex-linked and sex-limited inheritance patterns • Explain how the environment can influence the phenotype of an organism

14. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Incomplete Dominance • The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

16. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Codominance • Both alleles are expressed in the heterozygous condition.

17. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Sickle-cell Disease Normal red blood cell • Changes in hemoglobin cause red blood cells to change to a sickle shape. • People who are heterozygous for the trait have both normal and sickle-shaped cells. Sickle cell 7766x

18. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Multiple Alleles • Blood groups in humans • ABO blood groups have three forms of alleles.

20. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Coat Color of Rabbits • Multiple alleles can demonstrate a hierarchy of dominance. • In rabbits, four alleles code for coat color: C, cch, ch,and c.

21. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Coat Color of Rabbits Chinchilla Albino Light gray Dark gray Himalayan

22. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Epistasis • Variety is the result of one allele hiding the effects of another allele. eebb eeB_ E_bb E_B_ Dark pigment present in fur No dark pigment present in fur

23. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Sex Determination • Sex chromosomesdetermine an individual’s gender.

24. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Dosage Compensation • The X chromosome carries a variety of genes that are necessary for the development of both females and males. • The Y chromosome mainly has genes that relate to the development of male characteristics. • Chromosome inactivation • Barr bodies

25. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Sex-Linked Traits • Genes located on the X chromosome • Red-green color blindness • Hemophilia Sex-Linked Traits

26. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Polygenic Traits • Polygenic traits arise from the interaction of multiple pairs of genes.

27. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Environmental Influences • Environmental factors • Diet and exercise • Sunlight and water • Temperature

29. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Twin Studies • Helps scientists separate genetic contributions from environmental contributions • Traits that appear frequently in identical twins are at least partially controlled by heredity. • Traits expressed differently in identical twins are strongly influenced by environment.

31. Complex Inheritance and Human Heredity Chapter 11 11.3 Chromosomes and Human Heredity Karyotype Studies • Karyotype—micrograph in which the pairs of homologous chromosomes are arranged in decreasing size. • Images of chromosomes stained during metaphase • Chromosomes are arranged in decreasing size to produce a micrograph.

32. Complex Inheritance and Human Heredity Chapter 11 11.3 Chromosomes and Human Heredity Telomeres • Telomere caps consist of DNA associated with proteins. • Serves a protective function for the structure of the chromosome

33. Complex Inheritance and Human Heredity Chapter 11 11.3 Chromosomes and Human Heredity Nondisjunction • Cell division during which sister chromatids fail to separate properly • Down syndrome Visualizing Nondisjunction

34. Complex Inheritance and Human Heredity Chapter 11