12.1 Studying Human Inheritance
| Pedigree - chart that shows how a trait, and the genes that control it, are inherited in a family. |
| A shaded circle or square indicates a person who has the trait being studied. |
| Generations in a pedigree are numbered with Roman numerals and individuals with Arabic numerals. |
| Karyotype - photograph that shows an individuals chromosome in homologous pairs. |
| A karyotype can be used to find any chromosomal abnormalities that is visible. |
12.2 Chromosomal Disorders
| Nondisjunction - failure of one or more chromosome pairs to separate during meiosis. |
| People with Down's Syndrome are prone to heart defects. |
| Turner's syndrome - disorder in which a person has only one X chromosome and no other sex chromosome. |
| Defective chromosome structure can result from several defects or mutations. |
| Cri-du-chat syndrome - disorder caused by chromosome structure. |
12.3 Single-Allele Disorders
| A carrier can pass the recessive allele to offspring. |
| The recessive allele that causes Tay-Sachs is found in Ashkenzai Jews. |
| Cystic fibrosis - genetic disorder that results in an excessive secretion of thick mucus from the pancreas, lungs and other organs. |
| Huntington's disease - fatal genetic disorder that involves deterioration of the nervous system, particularly the brain. |
| Sickle cell disease - genetic disorder caused by an abnormal form of hemoglobin. |
| The sickle cell allele is codominant to the normal allele. |
| As a red blood sickles, it loses potassium ions. |
| Disorder related to sex-linked genes are colorblindness and hemophilia. |
12.4 Genetic Testing and Counseling
| Genetic counselors use pedigree analysis or genetic tests to explain disorders in parents, generations, fetus or children. |
| Phenylketonuria (PKU) - genetic disorder that causes inability to use phenylalanine. |
| Amniocentesis - technique used to detect genetic defects by the presence of certain chemicals or abnormal cells in fluid surrounding the fetus. |
| Chrionic villi (CVS) - tiny bits of membrane around the fetus are removed with needle inserted in abdomen. |