Section 1: Basic Patterns of Human Inheritance

2. Complex Inheritance and Human Heredity Section 1: Basic Patterns of Human Inheritance Section2: Complex Patterns of Inheritance Section 3: Chromosomes and Human Heredity

3. Complex Inheritance and Human Heredity Section 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 Section 1 Table 11.2 Recessive Genetic Disorders in Humans

5. Complex Inheritance and Human Heredity Section 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.

6. Complex Inheritance and Human Heredity Section 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

7. Complex Inheritance and Human Heredity Section 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.

8. Complex Inheritance and Human Heredity Section 1 Basic Patterns of Human Inheritance Galactosemia • Recessive genetic disorder characterized by the inability of the body to digest galactose. • Results in: • a lack of energy (lethargy), • a failure to gain weight and grow as expected • yellowing of the skin and whites of the eyes (jaundice), • liver damage, • abnormal bleeding.

9. Complex Inheritance and Human Heredity Section 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.

10. Complex Inheritance and Human Heredity Section 1 Basic Patterns of Human Inheritance

11. Complex Inheritance and Human Heredity Section 1

12. Complex Inheritance and Human Heredity Section 1 Basic Patterns of Human Inheritance Pedigrees • A diagram that traces the inheritance of a particular trait through several generations

13. Complex Inheritance and Human Heredity Section 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.

14. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Incomplete Dominance • The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

15. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Codominance • Both alleles are expressed in the heterozygous condition. • Sickle-cell disease is one example.

16. Complex Inheritance and Human Heredity Section 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

17. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Multiple Alleles • Blood groups in humans • ABO blood groups have three forms of alleles.

18. Complex Inheritance and Human Heredity Section 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.

19. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Epistasis • Variety is the result of one allele hiding the effects of another allele.

20. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Sex Determination • Sex chromosomesdetermine an individual’s gender.

21. Complex Inheritance and Human Heredity Section 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. • In females, one X chromosome is inactivated in each cell. The inactivated X chromosome is visible in stained cells as a Barr body.

22. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Sex-Linked Traits • Genes located on the X chromosome • Red-green color blindness • Hemophilia Sex-Linked Traits

23. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Polygenic Traits • Polygenic traits arise from the interaction of multiple pairs of genes.

24. Complex Inheritance and Human Heredity Section 2 Complex Patterns of Inheritance Environmental Influences • Environmental factors influence an organism’s phenotype • Diet and exercise • Sunlight and water • Temperature

25. Complex Inheritance and Human Heredity Section 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.

26. Complex Inheritance and Human Heredity Section 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.

27. Complex Inheritance and Human Heredity Section 3 Chromosomes and Human Heredity Telomeres • Telomere caps consist of DNA associated with proteins. • Serves a protective function for the structure of the chromosome

28. Complex Inheritance and Human Heredity Section 3 Chromosomes and Human Heredity Nondisjunction • Cell division during which sister chromatids fail to separate properly • Down syndrome, also called trisomy 21