1. Macromolecules can move into and out of the cell nucleus throughpassages called _______________.

2. A nucleosome consists of a DNA molecule wound around a group ofeight proteins called _______________.

3. _______________ are pre-existing protein molecules that help regulate thethree-dimensional folding of a newly synthesized protein.

4. Environmental factors that cause mutations are called _______________.

5. Environmental factors that cause cancer are called _______________.

6. A nucleotide triplet on mRNA must bind to a complementary tripleton tRNA called a/an _______________ for translation to occur.

7. Many single genes cause multiple phenotypic effects. This iscalled _______________.

8. An allele is said to be _______________ if it is not phenotypically expressedin the presence of another allele of the same gene.

9. Oncogenes may trigger cancer by stimulating the development ofreceptors for _______________ secreted by other cells.

10. Malignant tumors are characterized by the ability to spread, or_______________.

11. The stage of mitosis at which chromatids are divided between thetwo daughter cells is _______________.

12. Cancer cells often exhibit _______________, in which they revert to a lessspecialized form similar to embryonic cells.

13. A new DNA helix is synthesized in short segments which must beput together end-to-end by an enzyme called _______________.

14. The law of _______________ enables one to predict the nucleotide sequence ofone DNA strand when the sequence of the other is known.

15. Cytosine, uracil, and thymine are single-ringed nitrogenousbases called _______________.

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