49) Dietary factors are now being studied for how they regulate gene activity and how this
contributes to disease. For example, how does a diet high in unsaturated fatty acids help maintain
a healthy blood lipid profile? Within hours of feeding animals with diets rich in polyunsaturated
fatty acids (PUFAs), there is an increase in the activity of genes responsible for making enzymes
that break down fats and a reduction of the activity of genes responsible for making enzymes that
make fats. This has the effect of changing fat metabolism, which leads to a lowering of blood
lipid levels. The control of what type of DNA sequence would PUFAs most likely be affecting?
A) intron sequences
B) exon sequences
C) enhancer sequences
D) micro-RNA sequences
50) What accounts for the fact that cells in different tissues and organisms have different
functions and respond differently to their environments?
A) The cells use the same genes to make different proteins.
B) The cells have different genes.
C) The cells are expressing (using) different genes.
D) The cells use different genetic codes.
E) The cells DNA is different.
51) The human genome codes for 20,000 to 25,000 proteins, but any given cell might produce
only 5,000 different proteins. How is this possible?
A) Every cell contains a different fraction of the genome.
B) All possible proteins are made in all cells, but those that are not needed are degraded.
C) Some cells use introns to produce proteins, and some cells use exons.
D) Genes are regulated so that not all genes are transcribed in all cells.
E) Not every cell has the machinery for transcription and translation.