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Human Genetics and the Pedigree Section Objectives • Understand how different mutations occur. • Be able to identify different diseases and disorders. Causes of Mutations • Some mutations seem to just happen, but many mutations are caused by factors in the environment. • Any agent that can cause a change in DNA is called a mutagen. Mutagens include radiation, chemicals, and even high temperatures. Human Traits are Affected By: • 1. Dominant and recessive genes that are inherited • 2. Environmental Factors like diet and exercise Mutations in Reproductive Cells • Gamete: Sex Cells • Zygote: Fertilized egg • Human diploid cell has 46 chromosomes • Human Haploid cell has 23 chromosomes Mutations in reproductive cells • Occurs by changing the sequence in a sperm or an egg cell. • If this cell is involved in fertilization, the offspring has the mutation. • The mutation may produce a new trait or it may result in a protein that does not work correctly. Sometimes, it is nonfunctional, and the embryo may not survive. Mutations in body cells/autosomes • A cell’s DNA is changed, this mutation would not be passed on to offspring. • Damage to a gene may impair the function of the cell. Some mutations of DNA in body cells affect genes that control cell division. This can result in the cells growing and dividing rapidly, producing cancer. Sex linked Traits/Disorders • Carried on either the X or the Y chromosome • Different diseases –Colorblindness: Caused by genes on the X chromosome, causes people not to make pigments in the eye needed for color Sex Linked Traits/Disorders • Colorblindness: Most people with this disorder cannot distinguish between reds and greens • Why does this affect mostly males? • 8% of males less than 1% of females Sex Linked Traits/Disorders • Hemophilia: free bleeders, people that lack a factor for normal blood clotting • 1:10,000 males • 1:100,000,000 females Sex Linked Traits/Disorders • Muscular Dystrophy: progressive wasting of skeletal muscle. A defective gene that codes for a muscle protein dystrophin and is located on the X chromosome Chromosomal and Gene Mutations • A mistake on one or more of the segments in DNA in either the gene or the chromosome • Types: deletion, inversion, translocation and nondisjunction Nondisjunction •In nondisjunction, both chromosomes of a homologous pair move to the same pole of the cell during meiosis I anaphase. •Types: •Down Syndrome (trisomy 21): mental retardation, extra 21 chromosome •Klinefelter Syndrome: extra X chromosome with the Y chromosome (male) •Turner Syndrome: missing X chromosome (female) Nondisjunction • Turner Syndrome: appear female but are sterile (XO) no second sex chromosome present 1:1,000 births • Klinefelter Syndrome: male in appearance but are sterile (XXY) there is a second X chromosome present 1:1,000 births Nondisjunction • Down’s Syndrome: nondisjunction of autosomes (trisomy 21) There is an extra copy of chromosome 21. Results in Mental Retardation mild to severe, short neck, eyes spaced apart, short webbed fingers Tests to Detect Chromosomal Abnormalities • 1. Amniocentesis – remove a small amount of amniotic fluid • 2. Chorionic Villus Biopsy – sample of embryo cells from the choroin (placental tissue) Inherited Traits • Blood Types: A, B, AB, O • RH Factor: + or – ( used to determine the risk of hemophilia) • A has the A antigen on red blood cells and the B antibody in plasma • B has the B antigen on red blood cells and the A antibody in plasma Blood Types Cont: • AB has bot A and B antigens in red blood cells but neither A or B antibodies in plasma • O has neither A or B antigens in red blood cells but has both A and B antibodies in plasma Blood Donation Rules • Negative Blood is given to negative blood type • Positive Blood or negative blood can be given to positive patients • Universal red blood cell Donor is O• Universal plasma donor is AB+ Sickle Cell Anemia • Red blood cells are moon shaped and deprive organs of oxygen •Can result in death •Mostly in African Americans 10% African Americans 40% of African Population Other Genetic Disorders • Huntington Disease: nervous system disorder with loss of muscle control, mental deterioration and death starts from age 30 to 40. •Cystic fibrosis: thickening of mucus lining in lungs. •PKU: can develop into retardation (prevented if caught at birth) Polygenic Traits • Traits controlled by many genes Examples: height, weight, skin color • This is why children of 1 couple skin color height and weight may vary Section Objectives: • Interpret a pedigree. • Identify human genetic disorders caused by inherited recessive alleles. • Analyze the pattern of sex-linked inheritance. Pedigrees illustrate inheritance • A pedigree is a diagram made up of a set of symbols that identify males and females, individuals affected by the trait being studied, and family relationships. • Carriers (have 1 copy of the recessive allele) Male Parents Female Siblings Affected male Affected female Mating Known heterozygotes for recessive allele Death Pedigrees illustrate inheritance Section Objectives: • Discuss new methods in genetic technology. Genetic Engineering • A new form of manipulation that biologists created where they can engineer a set of genetic changes directly into an organisms DNA CLONING The production of organisms with identical genes Human Genome Project • Determines what genes are carried on each chromosome of the human •Helped in diagnosis of many inherited diseases and will lead to many advances in our future