Recessive Genetic Disorders! A recessive trait is expressed when the individual is homozygous recessive for the trait.

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1 Section 1 Basic Patterns of Human Inheritance Recessive Genetic Disorders! A recessive trait is expressed when the individual is homozygous recessive for the trait.

2 Section 1

3 Section 1 Table 11.2 Recessive Genetic Disorders in Humans

4 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.

5 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

6 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.

7 Section 1 Basic Patterns of Human Inheritance Galactosemia! Recessive genetic disorder characterized by the inability of the body to digest galactose.

8 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.

9 Section 1 Basic Patterns of Human Inheritance

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11 Section 1 Basic Patterns of Human Inheritance Pedigrees! A diagram that traces the inheritance of a particular trait through several generations

12 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.

13 Section 2 Complex Patterns of Inheritance Incomplete Dominance! The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

14 Section 2 Complex Patterns of Inheritance Codominance! Both alleles are expressed in the heterozygous condition.! Sickle-cell disease is one example.

15 Section 2 Complex Patterns of Inheritance Sickle-cell Disease! 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 Normal red blood cell 7766x

16 Section 2 Complex Patterns of Inheritance Multiple Alleles! Blood groups in humans! ABO blood groups have three forms of alleles.

17 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, c ch, c h, and c.

18 Section 2 Complex Patterns of Inheritance Epistasis! Variety is the result of one allele hiding the effects of another allele.

19 Section 2 Complex Patterns of Inheritance Sex Determination! Sex chromosomes determine an individual s gender.

20 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.

21 Section 2 Complex Patterns of Inheritance Sex-Linked Traits! Genes located on the X chromosome! Red-green color blindness! Hemophilia Sex-Linked Traits

22 Section 2 Complex Patterns of Inheritance Polygenic Traits! Polygenic traits arise from the interaction of multiple pairs of genes.

23 Section 2 Complex Patterns of Inheritance Environmental Influences! Environmental factors influence an organism s phenotype! Diet and exercise! Sunlight and water! Temperature

24 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.

25 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.

26 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

27 Section 3 Chromosomes and Human Heredity Nondisjunction! Cell division during which sister chromatids fail to separate properly! Down syndrome, also called trisomy 21

28 Section 3