1 Chapter 12 College Prep Biology Patterns of Heredity & Human Genetics

2 Chapter 12 Differing hormone levels among sexes can cause a single genotype to express more than one phenotype Differing hormone levels among sexes can cause a single genotype to express more than one phenotype Co-Dominant Alleles are when phenotypes of both homozygotes are produced in the heterozygous ex. Roan color in cattle Co-Dominant Alleles are when phenotypes of both homozygotes are produced in the heterozygous ex. Roan color in cattle Multiple Alleles occur when there are more than two alleles for a single trait. Multiple Alleles occur when there are more than two alleles for a single trait.

3 A trait for example that is controlled by four alleles is said to have multiple alleles A trait for example that is controlled by four alleles is said to have multiple alleles Eye color in humans/ Blood type are both examples of Multiple Allelic inheritance Eye color in humans/ Blood type are both examples of Multiple Allelic inheritance Incomplete Dominance -a blending of traits; a type of inheritance shown when a red flower is crossed with a white flower and only pink flowers are produced Incomplete Dominance -a blending of traits; a type of inheritance shown when a red flower is crossed with a white flower and only pink flowers are produced Most human genetic disorders are caused by the expression of Recessive Alleles Most human genetic disorders are caused by the expression of Recessive Alleles

4 Humans have 22 pairs of Autosome type chromosomes Humans have 22 pairs of Autosome type chromosomes 23 rd pair that differs in males and females are called sex chromosomes 23 rd pair that differs in males and females are called sex chromosomes Sex Linked traits are those traits carried on the X and Y chromosomes. For the most part it is said that they are carried on the X-chromosome. Sex Linked traits are those traits carried on the X and Y chromosomes. For the most part it is said that they are carried on the X-chromosome. Examples- red/green color blindness and Hemophilia Examples- red/green color blindness and Hemophilia But a few are actually carried on the y chromosome called the maleness chromosome But a few are actually carried on the y chromosome called the maleness chromosome

5 B/c most sex-linked traits are carried on the X-chromosome it is normally NOT possible for a color blind father to pass the sex-linked gene on to his son (as he gives the y chromosome to his son and not the X) B/c most sex-linked traits are carried on the X-chromosome it is normally NOT possible for a color blind father to pass the sex-linked gene on to his son (as he gives the y chromosome to his son and not the X) Red green color blindness in humans is a sex-linked trait that shows POLYGENTIC inheritance. It is caused by a recessive allele carried on the X-chromosome Red green color blindness in humans is a sex-linked trait that shows POLYGENTIC inheritance. It is caused by a recessive allele carried on the X-chromosome Polygenic inheritance: shows the inheritance pattern of a trait that is controlled by two or more genes. Ex. Skin. Color and height Polygenic inheritance: shows the inheritance pattern of a trait that is controlled by two or more genes. Ex. Skin. Color and height

6 PKU – human genetic defect that results in the failure to metabolize the amino acid phenylalanine. It can result in mental retardation PKU – human genetic defect that results in the failure to metabolize the amino acid phenylalanine. It can result in mental retardation Dietary adjustments – used to treat PKU Dietary adjustments – used to treat PKU Cystic Fibrosis – Defective protein in the plasma membrane, resulting in the formation of thick mucus in the lungs and digestive tracts. Cystic Fibrosis – Defective protein in the plasma membrane, resulting in the formation of thick mucus in the lungs and digestive tracts. Tay-Sachs: Recessive disorder opf the central nervous system. Results from the absence of an enzyme that normally breaks down a lipid. Tay-Sachs: Recessive disorder opf the central nervous system. Results from the absence of an enzyme that normally breaks down a lipid.

7 Which one does not belong? Heterozygous, Hybrid, Carrier, Homozygous. Homozygous b/c the other terms involve contrasting alleles for a trait. A homozygous individual possesses two identical alleles for a trait. Heterozygous, Hybrid, Carrier, Homozygous. Homozygous b/c the other terms involve contrasting alleles for a trait. A homozygous individual possesses two identical alleles for a trait. Red blood cells, phenylalanine, oxygen deprivation, hemoglobin. Phenylalanine b/c the other terms all relate to sickle cell anemia. Phenylalanine is the amino acid that cannot be metabolized by individuals with PKU Red blood cells, phenylalanine, oxygen deprivation, hemoglobin. Phenylalanine b/c the other terms all relate to sickle cell anemia. Phenylalanine is the amino acid that cannot be metabolized by individuals with PKU

8 Which one does not belong? Huntingdon’s disease, cystic fibrosis, PKU, tay- Sachs disease. Huntington's disease b/c it is caused by an autosomal dominant allele, whereas the others are the result of autosomal recessive alleles. Huntingdon’s disease, cystic fibrosis, PKU, tay- Sachs disease. Huntington's disease b/c it is caused by an autosomal dominant allele, whereas the others are the result of autosomal recessive alleles. Huntington’s – lethal disorder-results in a breakdown of certain areas of the brain. Huntington’s – lethal disorder-results in a breakdown of certain areas of the brain.

9 Which one does not belong? Genotype, phenotype, heterozygous, homozygous Phenotype b/c the other three terms describe the gene combination of an organism and not the expression of those genes

10 A pedigree is a graphic representation of genetic inheritance A pedigree is a graphic representation of genetic inheritance Insert – handout on pedigree chart Insert – handout on pedigree chart