CHAPTER 2 - BIOLOGICAL BEGINNINGS Flashcards
Chromosomes
Threadlike structures that come in 23 pairs, with one member of each pair coming from each parent. Chromosomes contain the genetic substance DNA.
DNA
complex molecule that contains genetic information
Genes
Units of hereditary information composed of DNA. Help cells to reproduce themselves and manufacture the proteins that maintain life.
Mitosis
Cellular reproduction in which the cell’s nucleus duplicates itself with two new cells being formed, each containing the same DNA as the parent cell, arranged in the same 23 pairs of chromosomes.
Meiosis
A specialized form of cell division that forms eggs and sperm (also known as gametes).
Zygote
A single cell formed through fertilization
Genotype
A person’s genetic heritage; the actual genetic material present in each cell
Phenotype
The way an individual’s genotype is expressed in observed and measurable characteristics.
Sex-Linked Genes
When a mutated gene is carried on the X chromosome, the result is called X-linked inheritance . The implications for males may be very different from those for females. Remember that males have only one X chromosome. Thus, if there is an absent or altered, disease-relevant gene on the X chromosome, males have no “backup” copy to counter the harmful gene and therefore may develop an X-linked disease. However, females have a second X chromosome, which is likely to be unchanged. As a result, they are not likely to have the X-linked disease. Thus, most individuals who have X-linked diseases are males.
Genetic imprinting
occurs when genes have differing effects depending on whether they are inherited from the mother or the father
Chromosomal Abnormalities
Sometimes a gamete is formed in which the male’s sperm and/or the female’s ovum do not have their normal set of 23 chromosomes. The most notable examples involve Down syndrome and abnormalities of the sex chromosomes
fragile X syndrome
A genetic disorder involving an abnormality in the X chromosome, which becomes constricted and often breaks
Ultrasound Sonography
An ultrasound test is often conducted seven
weeks into a pregnancy and at various times later in pregnancy. Ultrasound sonography is a prenatal medical procedure in which high-frequency sound waves are directed into the pregnant woman’s abdomen
Fetal MRI
Currently, ultrasound is still the first choice in fetal screening, but fetal MRI can provide more detailed images than ultrasound. In many instances, ultrasound will indicate a possible abnormality and then fetal MRI will be used to obtain a clearer, more detailed image
Chorionic Villus Sampling
At some point between 9.5 and 12.5 weeks of pregnancy, chorionic villus sampling may be used to detect genetic defects and chromosomal abnormalities
