Exam 3: Lect. 19

What are the different steps in the control of gene expression in eukaryotes? Which occur in the cytoplasm and the nucleus?

shannon's: In eukaryotes, gene expression can be controlled by either controlling the transcription of mRNA or controlling the translation of proteins; the control of transcription occurs in the nucleus, while the control of translation occurs in the cyto

What does the term motif mean?

A motif is a NUCLEOTIDE OR AMINO ACID SEQUENCE pattern that is widespread throughout the molecule; more specifically, in proteins, a structural motif is a motif formed by the three-dimensional arrangement of the amino acids, which are not necessarily adja

How do DNA binding proteins recognize specific sequences? Does this binding disrupt the base pairing that holds complementary strands of DNA together?

BY CONTACTING NUCLEOTIDE BASES IN THE MAJOR GROOVE OF DNA because they display MOLECULAR RECOGNITION ELEMENTS such as hydrogen bond acceptors/donors, methyl, and hydrogen. The binding of the DNA binding proteins to the major groove does NOT interrupt the

Explain why most DNA binding proteins recognize specific sequences by making contact through the major groove rather than the minor groove of DNA?

DNA binding proteins typically bind to the major groove of DNA, because THE MAJOR GROOVE EXPRESSES MORE OF THE MOLECULAR RECOGNITION ELEMENTS (hydrogen bond acceptors/donors, methyl, hydrogen, etc.) than the minor groove; however, it should be noted that

What type of amino acid is usually enriched in the DNA binding domain of proteins? Why?

BASIC PROTEINS BECAUSE THEIR POSITIVE CHARGE ATTRACTS THEM TO THE NEGATIVELY CHARGED SUGAR PHOSPHATE BACKBONE

What is the secondary structure present in all three types of DNA proteins we discussed in class that makes contact with the DNA?

ALPHA HELICES are present in helix-turn-helix, zinc finger, and helix-loop-helix proteins

What are the three advantages of dimerization of DNA binding proteins?

Homodimerization or heterodimerization INCREASES THE SPECIFICITY OF THE PROTEIN, BINDING STRENGTH, AND NUMBER OF DNA SEQUENCES IT CAN RECOGNIZE

Bacterial promoters have operators and promoters. What's the difference between these two types of sequences and what proteins recognize these two sequence elements?

Promoters are sequences in the DNA necessary for RNA polymerase to bind, allowing transcription to take place. operons are sequences in the DNA, typically upstream of the promoter, that binds activators or repressors (types of DNA binding proteins), allow

Lambda repressor functions as a repressor at one promoter and an activator at another promoter in bacteria. Explain how the same protein can have opposite activities at two promoters?

A protein can function as both a repressor and an activator, depending on the location of the binding site relative to the promoter. If the operator is directly adjacent to the promoter, the protein will act as an activator, allowing for expression of the

Describe how the tryptophan repressor regulates gene expression.

The operator for the tryptophan repressor is located inside the promoter sequence�therefore, in order for the tryptophan repressor to bind, it must block the promoter, preventing RNA polymerase from binding, discouraging gene expression; however, if the t

The lac operon and its regulation is a bacterial paradigm for how a series of on/off switches regulate the activity of this operon. Explain how the DNA binding activities of CAP (activator) and Lac repressor are regulated by glucose and lactose respective

Glucose is the preferred energy source for the cell, since the cell gets more energy from one glucose molecule than it does from one lactose molecule. As a result, the Lac operon (in control of the catabolism of lactose) is highly regulated by a repressor