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

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

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

Section 1 Complex Inheritance and Human Heredity 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.

Section 1 Complex Inheritance and Human Heredity 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

Section 1 Complex Inheritance and Human Heredity 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.

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

Dominant Genetic Disorders Section 1 Complex Inheritance and Human Heredity 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.

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

Section 1 Complex Inheritance and Human Heredity

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

Section 1 Complex Inheritance and Human Heredity 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.

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

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

Section 2 Complex Inheritance and Human Heredity 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

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

Multiple alleles can demonstrate a hierarchy of dominance. Section 2 Complex Inheritance and Human Heredity 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. Option 2 (continued on the next slide)

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

Sex chromosomes determine an individual’s gender. Section 2 Complex Inheritance and Human Heredity Complex Patterns of Inheritance Sex Determination Sex chromosomes determine an individual’s gender.

Section 2 Complex Inheritance and Human Heredity 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.

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

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

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

Section 2 Complex Inheritance and Human Heredity 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.

Images of chromosomes stained during metaphase Section 3 Complex Inheritance and Human Heredity 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.

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

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