MONOHYBRID CROSSES. Among dogs wire hair is a dominant over smooth. If a heterozygous wire haired male is crossed with a homozygous smooth haired female, what would be the genotypes of their puppies? ln rabbits short ears are dominant over long ears. What would the phenotypes be if two heterozygous short eared rabbits were mated? Among guinea pigs black hair is dominant over white. What would be the phenotype of the guinea pigs if a homozygous white male was mated with a homozygous white female?

4. In humans brown eyes are dominant over blue eyes 4. In humans brown eyes are dominant over blue eyes. If a heterozygous brown eyed male marries a heterozygous brown eyed female, what would be the phenotypes of the children? 5. Among tulips yellow color is dominant over blue. If a heterozygous yellow tulip is crossed with a homozygous blue, what would be the phenotypes and genotypes of the tulips? 6. Among squash smooth seeds are dominant over wrinkled seeds. If two heterozygous smooth squash plants are crossed, what would be the phenotypes and genotypes of the seeds?

PATTERNS OF INHERITANCE AND HUMAN GENETICS

SIMPLE RECESSIVE INHERITANCE CYSTIC FIBROSIS:CF Common in white Americans 1:2000 Caused by defective protein in plasma membrane.

CYSTIC FIBROSIS:CF 3. Controlled by physical therapy, diet, drug therapy 4. Life expectancy improving annually 5. Person must have 2 recessive alleles to suffer from CF. 1 allele carrier but shows no symptoms

PHENYLKETOURIA (PKU) Phenylketouria: 1. Caused by the absence of an enzyme that converts the amino acid phenylalanine to tyrosine. 2. Accumulation of phenylalanine leads to mental retardation and CNS damage

PHENYLKETOURIA (PKU) 3. Newborns are given a blood test to check for the absence of the enzyme 4. Milk products are high in phenylalanine 5. Disorder is treatable by controlling diet from birth

OTHER RECESSIVE TRAITS TAY-SACHS ATTACHED EAR LOBES

SIMPLE DOMINANT TRAITS HUNTINGTON’S DISEASE: Lethal disorder, no treatment Certain areas of the brain breakdown Symptoms; neurological and muscular show at the age of 30+ Genetic testing is available before symptoms show

HUNTINGTON’S DISEASE: 5. Ethical issues 6. Every child of an affected person has a 50/50 chance of inheriting the disease 7. Only 1 defective allelle required for person to show disease

OTHER DOMINANT TRAITS Unattached ear lobes Tongue rolling Hapsburg lip Hitchhiker’s thumb Hairy fingers Almond shaped eyes Thick lips Widow’s peak

INCOMPLETE DOMINANCE

INCOMPLETE DOMINANCE Heterozygous phenotype is intermediate between those of the two homozygotes Red flower x white flower Intermediate phenotype is pink F1 F2 R’ R’ R R’ R R R’R R’R RR R’R R R’ R’R R’R R’R R’R’

CODOMINANCE CODOMINANT ALLELES CAUSE THE PHENOTYPE OF BOTH HOMOZYGOTES TO BE PRODUCED IN THE HETEROZYGOTE INDIVIDUALS. BOTH ALLELES ARE EXPRESSED EQUALLY B = black feathers in chickens W = white feathers in chickens BB = black chicken BW = checkered chicken WW = white chicken B W BB BW B BW WW W

CODOMINANT TRAITS SICKLE-CELL ANEMIA: Common among African Americans 1:12 Homozygous people for trait differ by 1 amino acid coding for hemoglobin compared to normal people

SICKLE-CELL ANEMIA: 3. Abnormal hemoglobin is sickle celled 4. Sickle shaped cells block blood vessels reducing the amount of oxygen reaching the tissues 5. Shortened life span

HETEROZYGOUS ADVANTAGE People who are heterozygote for the trait produce both normal and abnormal hemoglobin Show no symptoms of sickle- cell anemia Less likely to suffer from malaria This explains why African’s suffer more from sickle-cell anemia

MULTIPLE PHENOTYPES FROM MULTIPLE ALLELES Traits controlled by more than two alleles have multiple alleles

POLYGENTIC INHERITANCE A trait is controlled by two or more genes. Inheritance of eye color, height, stem length, skin color.

BLOOD GROUPS ABO blood group Single gene (represented as “I”) has 3 different alleles Blood type A genotype IA IA IA i Blood type B genotype IB IB IB i Blood type AB genotype IA IB (codominant) Blood type O genotype ii (recessive) Important in blood transfusions and paternity suits

SEX DETERMINATION Autosomes 22 pairs of homologous chromosomes 23rd pair of chromosomes are sex chromosomes X and Y Female XX chromosomes Male XY chromosomes

Gametes carry either an X or Y chromosome Fertilization results in offspring having either XX or XY chromosomes There is a 50:50 chance of producing a male or female each time an offspring is produced.

SEX-LINKED INHERITANCE Experiments conducted by Morgan Observed males had white eyes more often than females Suggested gene for eye color was carried on the X chromosome and Y chromosome has no corresponding gene for eye color

INHERITANCE OF EYE COLOR IN DROSOPHILA

COLOR BLINDNESS X-linked disorder Inability to differentiate between two colors such as red and green Males are more susceptible because they have to inherit 1 defective X chromosome to suffer from the disorder; females needed to inherit 2 defective chromosomes. Most serious problem is the inability to detect traffic light colors

HEMOPHILIA X-linked disorder Caused by a lack of factor VIII a blood clotting enzyme Inability to clot the blood

Males are more susceptible because they have to inherit 1 defective X chromosome to suffer from the disorder; females needed to inherit 2 defective chromosomes. Treated by blood transfusions and injections of factor VIII. Treatments are expensive and some people have contracted AIDS.

WHO IS RYAN WHITE???

CHANGES IN CHROMOSOME NUMBERS Nondisjunction: paired chromosomes fail to separate properly during meiosis TRISOMY: person has 47 chromosomes total Down’s syndrome: chromosome 21 3 copies inside of 2. Mental retardation etc, higher incidence in women over 40.

Klinfelter’s syndrome: males, extra X or Y chromosome. MONOSOMY: 45 chromosomes Turner’s syndrome: females, missing X chromosome, mental retardation, sterile.

KARYOTYPE Chart of chromosome pairs used to evaluate unusual chromosome numbers in cells. Amniocentesis is the procedure by which the cell are collected for analysis and production of the karyotype.