In Down syndrome,
a. as the age of the mother increases, the chance of the defect occurring in the unborn
children increases.
b. the age of the father usually has an equal influence on the defect.
c. most embryos abort before complete term.
d. a person with the defect cannot have a normal child.
e. 80% of trisomic 21 babies are born to women over the age of 40.
A
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) Places of economic activity organized around one or more high-growth industries are known as
A) growth poles. B) north poles. C) economic poles. D) industrial poles. E) government poles.
What pattern of inheritance is occurring if one person in a population has two different alleles of a particular gene and other people in the population have a third allele of this gene?
A) codominance B) pleiotropy C) incomplete dominance D) multiple allelism
Synapsis between chromosomes in some species is promoted by special DNA sequences known as
A) centromeres. B) telomeres. C) pairing sites. D) chiasmata. E) bouquets.
The system of flexing and extending muscles makes movement of appendages easy to understand. But how are some actions possible (sticking out your tongue, beating of your heart) when these structures have no bone structure with opposing flexors and extensors in them?
A. Muscle cells running diagonally or crosswise amidst the longitudinal muscles must contract and force the long relaxed muscle cells to elongate. B. These structures must be empty chambers, and fluids forced into them expand them. C. One set of muscle cells must therefore be able to both contract and expand. D. This cannot be explained at present.