How is the control of gene expression different between methylation of histone proteins and direct methylation of DNA?
What will be an ideal response?
Methylation of histone proteins changes accessibility of genes. It tightens the chromatin so that promoters are not accessible to activate transcription. Direct methylation of DNA also suppresses gene expression, but in a way that is often more permanent than histone modification. Once a particular nucleotide has become methylated in a cell's DNA, it will usually stay methylated in all of the cell's
descendants.
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The direct result of natural selection is a new species
Indicate whether the statement is true or false.
The accompanying figure shows that the rate of alarm calls made by black-tailed prairie dogs is dependent on a perceived threat by a predator. This behavior most closely approximates that predicted by ________
A) mutual benefit B) selfishness C) altruism D) spite
A mass extinction is defined as
a. the permanent loss of major groups of organisms. b. the loss of 20% of a population. c. the rapid growth of species diversity in a particular area. d. the temporary loss of major groups of organisms. e. all of these.
A cell may meet the demand for large quantities of a specific protein by:
a. blocking transcription of the gene that encodes the protein. b. decreasing the half-life of the mRNA that specifies the protein. c. adding methyl groups to the gene that encodes the protein. d. gene amplification e. inhibition of DNA synthesis