Mastering bio week 4

If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence

5'TGCAAT3'

If a double- stranded DNA sample were composed of 10 percent thymine, what would be the percentage of guanine?

40

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?

5'-ATGC-3' with 5'-GCAT-3'

What is the structural feature that allows DNA to replicate?

complementary pairing of the nitrogenous bases

The mRNA is smaller than the length of DNA that codes for it because__.

post-transcriptional modification removes the introns

In eukaryotic cells, transcription cannot begin until __.

several transcription factors have bound to the promoter

If a DNA double helix contains 28% T nucleotides, then what is the percentage of A nucleotides?

28%

If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand?

3'-TAAACG-5'

Put the following events of bacterial transcription in chronological order. 1. Sigma binds to the promoter region. 2.The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands. 3. Sigma binds to RNA polymerase. 4. Sigma is released. 5. Transcription begins.

3, 1, 2, 5, 4

The direction of synthesis of an RNA transcript is ___.

5' —> 3' Nucleotides are added to the 3' end of RNA.

If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?

75

Assume the promoter sequence in Figure 17.2b is rotated 180Ëš. How will this rotation affect what is considered upstream and downstream DNA? Also, which strand will now be template and which will be nontemplate ?

Both upstream and downstream DNA and the template and nontemplate strands will be reversed if the promoter sequence is rotated 180Ëš

How is a mutation in a bacterial cell that deletes three base pairs 10 base pairs upstream from the +1 site likely to affect transcription and why?

Initiation will be inhibited because sigma cannot bind to the promoter.

RNA and proteins combine in cells to form structures called ribosomes. Ribosomes contain the active site for peptide bond formation. Based on their chemical structures, do you think protein or RNA molecules actually form the active site within the ribosome?

It could be either, because both molecules have catalytic properties.

which statement concerning a double -stranded DNA molecule is correct?

Only purine-pyrimidine base pairs are allowed.

Which one of the following statements about RNA processing is true?

Ribozymes may function in RNA splicing.

Which of the following statements about the 5' end of a polynucleotide strand of RNA is correct ?

The 5' end has a phosphate group attached to the number 5 carbon of ribose.

Which sections in mature RNA do not code for amino acids?

The 5'cap and the poly(A) tail at the 3' end are part of mature RNA and do not code for amino acids.

DNA double helices are soluble in water but insoluble in alcohol. How do these physical properties reflect the chemical structure of the DNA molecule?

The charged phosphate groups and sugars of DNA are hydrophilic.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly- A tail. Which of the following would you expect her to find?

The molecule is digested by enzymes because it is not protected at the 5' end.

Why is it that RNA can catalyze reactions but DNA cannot?

The sugar of RNA is much more reactive than the sugar of DNA.

How are the structures of RNA and DNA similar?

Their sugar-phosphate backbones are formed by phosphodiester linkages.

In addition to splicing, additional modifications at the 5' and 3' end are required to generate a mature mRNA. What is the significance of these modifications?

These modifications allow the mRNA to be recognized by the protein synthesis machinery and protect it from degradation.

Franklin and Wilkins analyzed DNA by bombarding DNA crystals with X-rays. Their analysis yielded two numbers that sparked interest, 3.4nm and 0.34 nvm. What is the significance of these numbers ?

These numbers demonstrate there are 10 rungs, or steps, on the DNA "ladder" for every turn of the helix.

You want to engineer a eukaryotic gene into bacterial colony and have it expressed. What must be included in addition to the coding exons of the gene?

a bacterial promoter sequence

During RNA processing a(n) ___ is added to the 3' end of the RNA.

a long string of adenine nucleotides.

What is responsible for termination of transcription in eukaryotic protein-coding genes?

a polyadenylation, or poly(A), signal

A ribozyme is _____.

an RNA with catalytic activity

Both DNA and RNA ___.

are information-containing molecules

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). These two regions of the promoter _____.

bind the sigma subunit that is associated with RNA polymerase

Translation occurs in the _____.

cytoplasm

Which of the following best describes DNA's secondary structure?

double antiparallel helical strands

In eukaryotic cells DNA has the appearance of a ___.

double helix

The RNA segments joined to one another by spliceosomes are ___.

exons

One of the primary functions of RNA molecules is to

function in the synthesis of proteins

In a DNA double helix , what kind of chemical bonds form between the complementary nitrogenous bases?

hydrogen bonds

The two strands of a DNA double helix are held together by ___ that form between pairs of nitrogenous bases.

hydrogen bonds

During RNA processing a(n) _____ is added to the 5' end of the RNA.

modified guanine nucleotide

As a result of splicing, most protein-coding genes can encode ______ protein.

more than one

In a nucleic acid polymer, the bonds that help to hold regions of double- strandedness together occur between what parts of the nucleotide monomers?

nitrogenous bases

DNA is composed of building blocks called _____.

nucleotides

A nucleotide is composed of a(n) _____.

phosphate group, a nitrogen-containing base, and a five-carbon sugar

An RNA molecule that can catalyze chemical reactions is called a ___

ribozyme

Spliceosomes are composed of __.

small RNAs and proteins

Which molecule or reaction supplies the energy for polymerization of nucleotides in the process of transcription?

the phosphate bonds in the nucleotide triphosphates that serve as substrates

In eukaryotic, the size of the primary transcript is generally ___ the gene in the template DNA strand.

the same length as

In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.

thymine and cytosine