7 1 Chromosomes and Phenotype KEY CONCEPT The

7. 1 Chromosomes and Phenotype KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits.

7. 1 Chromosomes and Phenotype Two copies of each autosomal gene affect phenotype. • Mendel studied autosomal gene traits, like hair texture.

7. 1 Chromosomes and Phenotype • Mendel’s rules of inheritance apply to autosomal genetic disorders. – A heterozygote for a recessive disorder is a carrier. – Disorders caused by dominant alleles are uncommon. (dominant)

7. 1 Chromosomes and Phenotype Autosomal Dominant disorders. • Hutchingson-Gilford Syndrome Progeria. • Autosomal Dominant Disorder. • Rare genetic disorder that accelerates aging in children

7. 1 Chromosomes and Phenotype Autosomal Dominant disorders. • Marfan Syndrome. • Autosomal Dominant Disorder. • Affects the connective tissue in the body. • Caused by a protein in the connective tissue.

7. 1 Chromosomes and Phenotype Autosomal Recessive disorders. • Blood disorder of deformed blood cells, • As a result children affected cannot maintain Hemoglobin in the normal range. • Prevalent in Mediterranean people.

7. 1 Chromosomes and Phenotype Autosomal Recessive disorders. • Ehlers Danlos Syndrome • A defect in their connective tissue. • Caused by a reduced amount of collagen. • Typically affects the joints, skin and blood vessels.

7. 1 Chromosomes and Phenotype Males and females can differ in sex-linked traits. • Genes on sex chromosomes are called sex-linked genes. – Y chromosome genes in mammals are responsible for male characteristics. – X chromosome genes in mammals affect many traits.

7. 1 Chromosomes and Phenotype • X-linked recessive trait. • Hemophilia. • A blood disorder in which certain blood clotting factors are not produced. • Results in excessive bleeding that can damage organs and tissue.

7. 1 Chromosomes and Phenotype • X-linked dominant traits • Color Blindness. • Expressed in both males and females who have an X-chromosome.

7. 1 Chromosomes and Phenotype • X-linked recessives traits • Duchenne Muscular Dystrophy • A condition that causes muscle degeneration.

7. 1 Chromosomes and Phenotype Y Linked disorders • Y Chromosome infertility is a condition that affects the production of sperm. • This makes it difficult or impossible for affected men to father children. • This disorder will be passed on to sons.

7. 1 Chromosomes and Phenotype • Y-Linked disorder. • Swyer Syndrome • A condition in which people with one X and one Y chromosome (normally present in males) have a female appearance. • The gonads (testes/ovaries) are non functional.

7. 1 Chromosomes and Phenotype • X-linked recessives traits • Fragile X Syndrome • Results in learning, behavioral and intellectual disabilities.

7. 1 Chromosomes and Phenotype Klinefelter Syndrome

7. 1 Chromosomes and Phenotype • 47 XYY Syndrome • males with this condition may be taller than average, but typically causes no unusual physical features. • Most males have normal sexual development and are able to father children. • Some symptoms may include learning problems and delayed emotional maturity. Twin Brothers: The taller has 47 XYY

7. 1 Chromosomes and Phenotype

7. 1 Chromosomes and Phenotype • Male mammals have an XY genotype. – All of a male’s sexlinked genes are expressed. – Males have no second copies of sex-linked genes.

7. 1 Chromosomes and Phenotype • Female mammals have an XX genotype. – Expression of sex-linked genes is similar to autosomal genes in females. – X chromosome inactivation randomly “turns off” one X chromosome.