Exam 5: DNA and Chromosomes

The core histones are small, basic proteins that have a globular domain at the C-terminus and a long, extended conformation at the N-terminus.Which of the following is NOT true of the N-terminal "tail" of these histones?

What type of macromolecule helps package DNA in eukaryotic chromosomes?

A.Explain the reason why the cell requires a mechanism for identifying specific sequences of DNA. B.On average, how often would the nucleotide sequence CGATTG be expected to occur in a DNA strand 4000 bases long? Show your work and explain your answer. C.Molecular processes depend upon sequence-specific interactions of proteins with DNA.Recognition sequences can be 4, 5, 6, 7, or even 8 base pairs in length for a single protein.What might be the advantages of a short recognition sequence? What might be the advantage of a longer recognition sequence?

When double-stranded DNA is heated, the two strands separate into single strands in a process called melting or denaturation.The temperature at which half of the duplex DNA molecules are intact and half have melted is defined as the T_m. A.Do you think T_m is a constant, or can it depend on other small molecules in the solution? Do you think high salt concentrations increase, decrease, or have no effect on T_m? B.Under standard conditions, the expected melting temperature in degrees Celsius can be calculated from the equation T_m = 59.9 + [0.41 × %(G + C)] − (675/length of duplex).Does the T_m increase or decrease if there are more G + C (and thus fewer A + T) base pairs? Does the T_m increase or decrease as the length of DNA increases? Why? C.Calculate the predicted T_m for a stretch of double helix that is 100 nucleotides long and contains 50% G + C content.

Hershey and Chase used radiolabeled macromolecules to identify the material that contains heritable information.What radioactive material was used to track DNA during this experiment?

The complete set of information in an organism's DNA is called its

Using terms from the list below, fill in the blanks in the following brief description of the experiment with Streptococcus pneumoniae that identified which biological molecule carries heritable genetic information.Some terms may be used more than once. carbohydrate lipid R-strain DNA nonpathogenic RNA identify pathogenic S-strain label purify transform Cell-free extracts from S-strain cells of S.pneumoniae were fractionated to __________ DNA, RNA, protein, and other cell components.Each fraction was then mixed with __________ cells of S.pneumoniae.Its ability to change these into cells with __________ properties resembling the __________ cells was tested by injecting the mixture into mice.Only the fraction containing __________ was able to __________ the __________ cells to __________ (or __________) cells that could kill mice.

How do changes in histone modifications lead to changes in chromatin structure?

Early studies of chromosome structure relied on isolating chromatin from cells followed by nuclease treatment in vitro, followed by analysis of the products of this treatment.Demonstrate your understanding of this process by answering the questions below: A.How can nucleosome core particles be isolated from chromatin? B.What molecular components were identified after this treatment was complete? C.What portion of the nucleosome was destroyed/removed during this treatment and what function does it normally serve?