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23 Cards in this Set
- Front
- Back
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zygote
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the single cell formed from the union of two gametes, a sperm and an ovum
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gamete
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A reproductive cell; that is, a sperm or ovum that can produce a new individual if it combines with a [blank] from the other sex to make a zygote
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gene
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a small section of a chromosome; the basic unit for the transmission of heredity. Consists of a string of chemicals that provide instructions for the cell to manufacture certain proteins.
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chromosome
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one of the 46 molecules of DNA (in 23 pairs) that virtually each cell of the human body contains and that, together, contain all the genes.
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Human Genome Project
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An international effort to map the complete human genetic code
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23rd pair
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The chromosome pair that, in humans, determines sex
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monozygotic (identical) twins
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Twins who originate from one zygote that splits very early in development.
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dizygotic (fraternal) twins
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Twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time
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genotype
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An organism's entire genetic inheritance, or genetic potential
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phenotype
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the observable characteristics of a person, including appearance, personality, intelligence, and all other traits
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polygenic traits
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Referring to a trait that is influenced by many genes
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X-linked recessive genes
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Referring to a gene carried on the X chromosome. If a male inherits an x-linked recessive trait from his mother, it is always expressed
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Multifactorial
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Referring to a trait that is affected by many factors, both genetic and environmental expression; enhancing, halting, shaping, or altering the expression of genes, resulting in a phenotype that may differ markedly from the genotype
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trisomy-21 (Down syndrome)
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A condition in which a person has 47 chromosomes instead of the usual 46, with 3 rather than 2 chromosomes at the 21st site. Results in unusual facial features, heart abnormalities, and language difficulties
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autosomes
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22 of the 23 chromosomes inherited equally by both males and females
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mitosis
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process of duplication and division in which each new cell contains 23 chromosome pairs = 46 chromosomes; just before cell division, the 46 duplicate and then divide
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Pre-implantation testing
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After in vitro fertilization, one cell is removed from each zygote at the four- or eight-cell stage and analyzed.
Requires surgery, in vitro, etc. Delays implantation and reduces likelihood of successful birth. Used when couples are at high risk of genetic disorders |
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Tests for pregnancy-associated plasma protein (PAPPA) and human chorionic gonadotropin
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Blood tests are done at ~11 weeks to indicate levels of these substances. Test indicates normal pregnancy
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Alpha-fetoprotein (AFP) assay
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Mother is tested for level of this at mid-pregnancy. Indicates neural-tube defects, multiple embryos, Down syndrome.
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Sonogram (ultrasound)
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High-frequency sound waves are used to produce a picture of the fetus as early as 8 weeks. Later in pregnancy can detect less apparent problems, confirm suspicions, and anticipate complications
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Chorionic villi sampling (CVS)
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A sample of the chorion (part of placenta) obtained via sonogram and syringe at 10 weeks and analyzed. Can indicate many chromosomal or genetic abnormalities.
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Amniocentesis
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About 1/2 oz of fluid drawn from placenta at 16 weeks. Cells are cultured and analyzed. Reveals sex of fetus and genetic abnormalities.
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Gamete selection
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ova and sperm are screened to select healthiest, in vitro fertilization
useful only if particular conditions are likely and genetic tests are accurate |
