Bio-Pac 06: Objective 07-10 Flashcards
Objective 7. Describe how the sex of organisms is determined, using a human as an example.
The sex of an organism is determined by two chromosomes. Male = XY and Female =XX. Humans have two sex chromosomes and 44 autosomes in all cells in the body (except gametes). Female gametes (eggs) all contain 22 autosomes and one sex chromosome (the X) and male gametes (sperm) all contain 22 autosomes and one sex chromosome (the X or Y). This means that the male determines the sex of the offspring.
Objective 8. Describe how fraternal twins and identical twins are produced.
Fraternal twins come from two eggs and two sperm. They are completely different people and can be different sexes. Identical twins which are better to study human genetics come from one egg and one sperm. The fertilized egg will then split and form two identical people that are alike physically and mentally, and are the same sex. Identical twins may be attached when born. Both fraternal and identical twins usually happen to older women and it may run in the family.
Objective 9. Explain the inheritance of the following genetic disorders: Huntington’s disease, polydactyly, PKU, and sickle cell anemia.
Huntington’s disease is a lethal disorder caused by a rare autosomal dominant allele. The nervous system will undergo progressive degeneration, uncontrolled movements of the head and limbs, and mental deterioration. There is no effective treatment that exists. Usually a dominant allele with such severe effects would be expected to occur only as a new mutation and not be transmitted to future generations. The allele for polydactyly (having more than five fingers or toes) is dominant to the allele that produces only five digits on each hand and foot. Phenylketonuria (PKU) is a recessive disorder that results from the absence of an enzyme that converts one amino acid, phenylalanine, to a different amino acid, tyrosine. Because phenylalanine can’t be broken down, it and its products accumulate and result in severe damage to the central nervous system. It usually brings mental retardation and mental deterioration. It is common in ancestors of Norway and Sweden. Sickle cell anemia is a blood disorder. It is inherited as an autosomal recessive trait. It is most common in black Americans whose families originated in Africa, and countries surrounding the Mediterranean Sea. Sickled cells contain hemoglobin, the oxygen carrying protein. Since sickled cells have a shorter life span, the person suffers from anemia, a low number of red blood cells. Sickled cells can clod small blood vessels and cause tissues to be deprived of oxygen and nutrients, which causes severe pain. Treatment is blood transfusion and drug therapy.
Objective 10. Explain multiple allele traits using blood types as an example.
Blood types have to do with co-dominance. The blood types are A, AB, B, and O. The blood varies with the protein agglutinogen. (either A or B). People will have one, both, or neither. The genotypes AA and AO results in the phenotype blood type A; the genotypes BB and BO results in the phenotype blood type B; the genotype AB results in the phenotype blood type AB; the genotype OO results in the phenotype blood type O.
