Extending Mendelian Genetics Chapter 7 sections 1,2,4 Extending Mendelian Genetics

Section 1 Standard: Discuss observed inheritance patterns cause by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenetic, and multiple alleles.

Section 1: Chromosome and Phenotype Autosomal chromosomes do not play a role in sex determination. You have two alleles for each gene; one from each parent. Most traits are the result of autosomal genes. Curly or straight hair Many genetic disorders are caused by autosomal genes. You can predict how likely someone will be to inherit a disorder by using a Punnett Square. Two copies of each autosomal gene affect phenotype.

Section 1: Chromosome and Phenotype Disorders caused by recessive alleles. Two copies of the recessive allele must be present for a person to have the disorder. Often occur when the parents are heterozygous for the disorder. Cystic fibrosis A carrier is someone who does not show disease symptoms but has one recessive allele. Allows for lethal disorders to still show up in the population’s gene pool

Section 1: Chromosome and Phenotype Disorders caused by dominant alleles. These are far less common than recessive disorders. Huntington’s disease damages the nervous system and symptoms only show up during adulthood. 50% chance of the offspring having the disorder if only one parent carries the trait and 75% chance if both parents carry the trait.

Section 1: Chromosome and Phenotype Males and females can differ in sex-linked traits. Sex-linked genes Genes that are located on sex chromosomes. X and Y chromosomes XX=female, XY=male Females can only pass on X and males can pass on either an X or Y X chromosomes have more influence on phenotype. (has a lot more genes than the Y chromosome).

Section 1: Chromosome and Phenotype Expression of Sex-Linked Genes Pattern of expression is different in sex chromosomes than in autosomes. Males only have one allele due to only having one X, while females have two. Male express all alleles on the X. Female mammals go through a process called X chromosome inactivation. One X is randomly “turned off” Due to this females are a mixture of two types of cells; one showing mom allele, one showing dad allele. Female calico cats.

Section 2: Complex Patterns of Inheritance Standard: Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles.

Section 2: Complex Patterns of Inheritance In incomplete dominance, neither allele is completely dominant not completely recessive. Heterozygous phenotype is intermediate between the two homozygous phenotypes. Homozygous parental phenotypes not seen in F1 Phenotype can depend on interactions of alleles.

Section 2: Complex Patterns of Inheritance Codominant alleles will both be completely expressed. Codominant alleles are neither dominant nor recessive. The ABO blood types result from codominant alleles. Many genes have more than two alleles. Blood type

Section 2: Complex Patterns of Inheritance Many genes may interact to produce one trait. Polygenetic traits are produced by two or more genes. Eye color Skin color

Section 2: Complex Patterns of Inheritance An epistatic gene can interfere with other genes In mice fur color is determined by 5 genes. Albinism is a single gene that can interfere with the expression of other genes

Section 2: Complex Patterns of Inheritance The environment interacts with genotypes. Phenotype is a combination of genotype and environment. The sex of sea turtles depends on both genes and the environment. Height is an example of a phenotype strongly affected by the environment. Poor diet when growing can stunt your growth.

Section 4: Human Genetics and Pedigrees Standard: Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles.

Section 4: Human Genetics and Pedigrees Human genetics follows the patterns seen in other organisms The basic principles of genetics are the same in all sexually reproducing organisms. Inheritance of many human traits is complex. Single-gene traits are important in understanding human genetics.

Section 4: Human Genetics and Pedigrees Females can carry sex-linked genetic disorders. Males (XY) express all of their sex linked genes. Due to them only having one allele for the trait. Expression of the disorder depends on which parent carries the allele and the sex of the child. If the father carries the trait the male offspring will not have the trait. (father can only give Y to male offspring, not the X)

Section 4: Human Genetics and Pedigrees A pedigree is a chart for tracing genes in a family. A pedigree is a chart that can help trace phenotypes to help determine genotypes. Phenotypes are used to infer genotypes on a pedigree. Autosomal genes show different patterns on a pedigree than sex-linked genes.

Section 4: Human Genetics and Pedigrees If the phenotype is more common in males, the gene is likely sex-linked. Colorblindness

Section 4: Human Genetics and Pedigrees Several methods help map human chromosomes. A karyotype is a picture of all chromosomes in a cell X Y

Section 4: Human Genetics and Pedigrees Karyotypes can show changes in chromosomes. Deletion of part of a chromosome or loss of a chromosome. Large changes in chromosomes Extra chromosomes or duplication of a part of a chromosome.