HUMAN HEREDITY&GENETIC ENGINEERING CHAPTERS 14 & 15
CHAPTER 14 HUMAN HEREDITY
KARYOTYPE • A picture of chromosomes arranged in ordered pairs • See diagram in note packet
CHROMOSOME NUMBER • Each body cell (somatic/2N) contains 46 chromosomes • Each sex cell (gamete/1N) contains 23 chromosomes *CHROMOSOME TYPES • Sex chromosomes • Autosomes
SEX CHROMOSOMES • 2 chromosomes; determine an individual’s sex/gender • Males XY or 46XY • Females XX or 46XX * May carry other info
AUTOSOMES • The remaining 44 chromosomes * Chromosomes not required for gender determination
PHENOTYPE AFFECTED BY • Genotype • Polygenic – controlled by many genes; ex. Height & weight • Environmental factors • Affects genetic potential • Ex. Nutrition, exercise
TRANSMISSION OFHUMAN TRAITS • Inheritance follows Mendelian patterns • Simple dominance – presence or absence of one dominant allele controls the trait • Codominant – two dominant alleles to be expressed together
Sex-linked – genes that are located on the X or Y chromosomes • Multiple Alleles – many genes have more than two alleles (Ex. ABO Blood Groups) What is your blood type?
* BLOOD GROUPS • Based on proteins on surface of RBCs; proteins determined by genes • 2 major proteins: A & B • Others: Rh factors • Blood groups: A, B, AB & O
ABO BLOOD GROUP GENES • Alleles: IA, IB, and i * IA & IB are codominant if together * IA & IB are dominant over i * ii = O
DO BLOOD TYPE CROSSES Type A x Type B Type O x Type AB IAIA x IBIB ii x IAIB One more next slide!
DO BLOOD TYPE CROSSES Type A x Type B IA i x IB i
Safe Transfusions Phenotype (Blood Type) Genotype To From
* TRANSFUSIONS • Blood type critical when transfusions required; Must match type • If mismatch, transfusion reaction occurs • Causes shock; Leads to death if not treated immediately
Agglutination Transfusion rxns & RBCs Hemolysis
Rh BLOOD GROUPS • Rh blood group (Rh factor) – determined by a single gene with two alleles (+/-) * Original ID in Rhesus monkey * Most Americans are Rh+
Rh positive (Rh+) - at least 1 + allele; Rh+/Rh- or Rh+/Rh+ • Rh negative (Rh-) – Has 2 Rh- alleles; Rh-/Rh-
Can cause problems during birth is mom is Rh- and fetus is Rh+ • Erythroblastosis - Mom’s antibodies attack fetal blood; will cause clumping * Can cause death of fetus or newborn but not usually with first birth of this type
X-CHROMOSOME INACTIVATION • Women have 2 X chromosomes; genes are switched off on one X chromosome; only 1 functions
TRANSMISSION OF HUMAN TRAITS • Pedigree - a chart that shows how a trait is transmitted through generations of a family; demonstrates inheritance patterns
* MORE ON PEDIGREE • A “family tree” • A graphical representation of genetic inheritance • Used by geneticists to map genetic traits
PEDIGREE SYMBOLS IN NOTES • A = female, carrier • B = male, normal • C = marriage • D = parents & children • E = female, carrier • F = male, affected (has trait) • G = male, normal
* PEDIGREE LINES • Identical twins • Upside down Y • Twins, not identical • Upside down V • 1 row = 1 generation
Human Genetic Disorders (14.2)
*SINGLE ALLELE TRAITS IN HUMANS • Dominant & recessive diseases • >200 human traits due to dominant allele (need 1 allele only) • >250 human traits due to recessive allele (need 2 recessive alleles)
RECESSIVEGENETIC DISORERS • Recessive, single allele trait disorders - carried by recessive allele, shown only when normal trait is absent * Normal is dominant; No cures, skips generations
ALBANISM • Lack of skin pigment (aa) • A = normal • a = no pigment • Effect: aa = no pigment Aa = carrier
CYSTIC FIBROSIS (CF) • Affects lungs and pancreas • Effect: Mucous build-up, more lung infections, “failure to thrive” b/c digestive enzymes affected • C = normal, c = CF • CC = normal, Cc = carrier • cc = has CF
Faulty chloride channel Lung & pancreas affected Percussion treatment
PKU • Lack enzyme to breakdown phenylalanine in milk, (+ NutraSweet); • Effect: harmful by-products build-up; mental retardation Anna with her children Madeleine (centre), who has PKU, and Isobel. Madeleine's PKU is managed successfully by diet and she excels at her school work.
GALACTOSEMIA • Lacks galactase; Galactose (sugar) not broken down • Effect: harmful by-products build-up; liver damage & mental retardation Children with galactosemia are missing the enzyme to convert galactose to glucose for energy in the body. If galactosemia is left untreated, galactose will accumulate in the blood and body tissues and will cause damage. A newborn with untreated galactosemia may develop vomiting and diarrhea and fail to gain weight. The build-up of galactose can eventually lead to jaundice, an enlarged liver, cataracts, mental retardation, and possible death.
TAY-SACHS DISEASE • Lethal !; fat builds-up in brain • Effect: Harmful by-product build-up; Death by 5-6 yrs old Krystie Anna Karl-Steiger has Tay-Sachs disease because both parents -- one of them an egg donor -- carry a genetic mutation. Neither of them were aware of it because of lax screening requirements before the pregnancy was performed. Tay-Sachs is fatal. In the beginning, the couple said, Aetna agreed to pay for an experimental and costly therapy pioneered at Duke University. It requires expensive and long-term care by nurses and therapists. The therapy was successful so far as it went: Benjy’s symptoms eased and he was out of immediate danger. But, months later, the couple said, Aetna refused to pay for further nursing and therapy services, contending that they were not medically necessary.
DOMINANT ALLELE DISORDERS • Carried by dominant allele, always shown * Trait expressed if person is homozygous or heterozygous for a dominant allele,TT or Tt
ACHONDROPLASIA • Type of dwarfism, slow conversion of cartilage to bone When both parents have achondroplasia, in every pregnancy, there is 1 chance in 4 or 25% chance that their child will inherit the faulty FGFR3 gene copy from both parents. The impact of having no working FGFR3 protein produced, means that these children usually do not survive 1 chance in 2 (2 chances in 4) or 50% chance that the child will inherit one faulty FGFR3 gene copy and one working copy and have achondroplasia just like the parents 1 chance in 4 or 25% chance that their child will inherit the working FGFR3 gene copy from both parents and have normal growth
HUNTINGTON’S DISEASE • Progressive degeneration of nervous system • Lethal! No cure! • Persists b/c onset after age 30; many already have children • End = muscle spasms, mental illness & death
Woody Guthrie, a popular American folk singer, was diagnosed with the illness in the 1950's and died in 1967 after 17 years of hospitalization. He had been misdiagnosed, considered an alcoholic, and shuttled in and out of mental institutions and hospitals for years before being properly diagnosed. The discovery of the HD gene in 1993 resulted in a direct genetic test to make or confirm a diagnosis of HD in an individual who is exhibiting HD-like symptoms. Using a blood sample, the genetic test analyzes DNA for the HD mutation by counting the number of repeats in the HD gene region. Individuals who do not have HD usually have 28 or fewer CAG repeats. Individuals with HD usually have 40 or more repeats. Testing helps people decide about having children. Would you want to know????
HYPERCHOLESTEROLEMIA • Extremely high cholesterol & LDL levels • Causes early blockages in arteries Lipid infusion into tendons.
CODOMINANT DISORDERS • Both alleles contribute to phenotype • Sickle Cell Anemia Trait (SDT) & Sickle Cell Anemia Disease (SCT) * Sickle cell anemia - due to abnormal hemoglobin (oxygen carrying protein in RBCs)
SDT • Disease where hemoglobin sticks together in chains; causes “sickle” or C-shaped RBCs; less flexible • Normal (AA) – normal RBCs w/normal hemoglobin • Sickle cell trait (AS) – carrier heterozygous; resistant to Malaria; genetic advantage where Malaria is endemic
SCA • Sickle cell anemia (SS) – sufferer; homozygous; RBCs sickle • Symptoms • Pain & swelling in hands & feet • Clogs blood vessels, organ damage, pain • 1/500 African Americans • Treatment – Turn on fetal hemoglobin
POLYGENIC TRAIT • Trait controlled by many genes • Can have many possible genotypes and phenotypes • Ex. Skin color, height • Most affected by environmental factors • Internal environment – hormone • External environment – nutrition, temperature