Quiz: Regulation of Gene Expression & Mutations 

Learning Objectives

1. Describe the types of interactions that regulate gene expression.

2. Explain how the location of regulatory sequences relates to their function.

3. Explain how the binding of transcription factors to promoter regions affects gene expression and/or the phenotype of the organism

4. Explain the connection between the regulation of gene expression and phenotypic differences in cells and organisms.

5. Describe the various types of mutation.

6. Explain how changes in genotype may result in changes in phenotype

7. Explain how alterations in DNA sequences contribute to variation that can be subject to natural selection

Essential Concepts

Understanding(s):

GENE EXPRESSION REGULATION

1.     Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription.

2.     Epigenetic changes can affect gene expression through reversible modifications of DNA or histones.

3.     The phenotype of a cell or organism is determined by the combination of genes that are expressed and the levels at which they are expressed—

4.     Observable cell differentiation results from the expression of genes for tissue specific proteins.

5.     Induction of transcription factors during development results in sequential gene expression

6.      Both prokaryotes and eukaryotes have groups of genes that are coordinately regulated—

a.      In prokaryotes, groups of genes called operons are transcribed in a single mRNA molecule.

b.     The lac operon is an example of an inducible system.

c.      In eukaryotes, groups of genes may be influenced by the same transcription factors to coordinately regulate expression.

7.     Promoters are DNA sequences upstream of the transcription start site where RNA polymerase and transcription factors bind to initiate transcription.

8.     Negative regulatory molecules inhibit gene expression by binding to DNA and blocking transcription.

9.     Gene regulation results in differential gene expression and influences cell products and function.

10.  Certain small RNA molecules have roles in regulating gene expression.

MUTATIONS 

1.   Changes in genotype can result in changes in phenotype

1.     The function and amount of gene products determine the phenotype of organisms.

a.      The normal function of the genes and gene products collectively comprises the normal function of organisms.

b.     Disruptions in genes and gene products cause new phenotypes.

2.     Alterations in a DNA sequence can lead to changes in the type or amount of the protein produced and the consequent phenotype. DNA mutations can be positive, negative, or neutral based on the effect or the lack of effect they have on the resulting nucleic acid or protein and the phenotypes that are conferred by the protein.

3.     Errors in DNA replication or DNA repair mechanisms, and external factors, including radiation and reactive chemicals, can cause random mutations in the DNA—

a.      Whether a mutation is detrimental, beneficial, or neutral depends on the environmental context.

b.     Mutations are the primary source of genetic variation.

4.     Errors in mitosis or meiosis can result in changes in phenotype—

a.      Changes in chromosome number often result in new phenotypes, including sterility caused by triploidy, and increased vigor of other polyploids.

b.     Changes in chromosome number often result in human disorders with developmental limitations, including Down syndrome/ Trisomy 21 and Turner syndrome. Topic was covered in mitosis (unit 4) and meiosis (unit 5)

5.     Changes in genotype may affect phenotypes that are subject to natural selection. Genetic changes that enhance survival and reproduction can be selected for by environmental conditions—

a.      The horizontal acquisitions of genetic information primarily in prokaryotes via transformation (uptake of naked DNA), transduction (viral transmission of genetic information), conjugation (cell-to-cell transfer of DNA), and transposition (movement of DNA segments within and between DNA molecules) increase variation.

b.     Related viruses can combine/recombine genetic information if they infect the same host cell.

c.      Reproduction processes that increase genetic variation are evolutionarily conserved and are shared by various organisms.