More Human Genetics… Biology

Multiple Alleles

Traits are the result of more than 3 or more types of alleles Example: blood typing There are 3 different alleles for blood type (A, B, & O) A is dominant to O B is dominant to O A and B are codominant

Multiple Alleles

Rh Factor Another gene for proteins on the membrane of blood cells You have them (+) or you don’t (-) (+) is dominant to (-)

Blood Transfusions Type A = A antigens (proteins) Type B = B antigens Type AB = A & B antigens Type O = No antigens Blood can only be transferred to a body of a person who's immune system will "recognize" it. O is the universal donor O blood has no antigens are that are foreign to the body AB is the universal recipient Person with AB blood has both the A and B antigens already in the body Rh factor counts too! (+) can receive (+) or (-) (-) can only receive (-) Ever see ER shows where doctors call for O neg. blood?

Sample Crosses 1. Cross a man with type AB blood with a woman who is heterozygous for type A blood AB x AO Geno: ¼ AA; ¼ AB; ¼ AO; 1/4 BO Pheno: ½ type A; ¼ type B; ¼ type AB

Sample Crosses 2. Cross a man who is heterozygous for type A blood with a woman who is heterozygous for type B blood. AO x BO Geno: ¼ AB; ¼ BO; ¼ AO; ¼ OO Pheno: ¼ type AB; ¼ type B; ¼ type A; ¼ type O

Sex-Linked Traits

Sex-linked Traits A gene that is found only on the X chromosome and not the Y chromosome Examples: Colorblindness Hemophilia Duchenne Muscular Dystrophy Male Pattern Baldness Female Male

Sex-linked Traits More common in men because they only have one X chromosome Females need to have the gene on both X’s to have the trait Females that are heterozygous for the trait are carriers Carriers appear normal but can pass the trait to their offspring

Colorblindness Recessive gene (b) on X chromosome Condition in which certain colors cannot be distinguished Red/Green color blindness is most common (about 99%) Causes problems in distinguishing reds and greens No treatment Life is normal

Hemophilia Recessive gene (h) on the X chromosome Bleeding disorder in which the blood does not clot normally Persons with hemophilia may bleed for a longer time than others after an injury or accident They also may bleed internally, especially in the joints Live life cautiously, receive treatments to help blood clot normally

Duchenne Muscular Dystrophy Recessive gene (d) on the X chromosome Rapidly-worsening muscle weakness that starts in the legs and pelvis, and later affects the whole body No cure Treatment is aimed at control of symptoms to maximize the quality of life Death usually occurs by age 25

Sample Crosses 1. Cross a normal man with a woman who is a carrier for hemophilia X H Y x X H X h Geno: ¼ X H X H ; ¼ X H X h ; ¼ X H Y; ¼ X h Y Pheno: ½ females will be normal; ½ females will be carriers; ½ males will be normal; ½ males will be hemophiliacs

Sample Crosses 2. Cross a colorblind male with a female who is a carrier for colorblindness. X b Y x X B X b Geno: ¼ X B X b ; ¼ X b X b ; ¼ X B Y; ¼ X b Y Pheno: ½ females will be colorblind; ½ females will be carriers; ½ males will be normal; ½ males will be colorblind