SJU Bio Midterm Review DNA

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

12%

If one strand of a DNA molecule has the sequence of bases 5' ATTGCA 3', the other complementary strand would have the sequence

3' TAACGT 5'

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'

What helps to stabilize mRNA by inhibiting its degradation?

5' cap and poly (A) tail

What is the relationship among DNA, a gene, and a chromosome?

A chromosome contains hundreds of genes, which are made of DNA

In analyzing the number of different bases in a DNA sample, what equation would be consistent with the base-pairing rules?

A+G=C+T

What are the purine nitrogenous bases?

Adenine and guanine

In DNA, the designation 3' and 5' refer to the

Carbon atoms of deoxyribose to which phosphate groups may bond

During translation, chain elongation continues until what happens?

Chain terminator codons occur

The anticodon of a particular tRNA molecule is

Complementary to the corresponding mRNA codon

A biochemist isolates and purifies various molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

DNA ligase

Which enzyme catalyzes the elongation of a DNA strand in the 5' - 3' direction?

DNA polymerase III

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3' end of a growing strand

A new DNA strand elongates only in the 5' to 3' direction because

DNA polymerase can only add nucleotides to the free 3' end

What are polyribosomes?

Groups of ribosomes reading a single mRNA simultaneously

Which enzyme separates DNA during replication?

Helicase

What kind of chemical bond is found between paired bases of the DNA double helix?

Hydrogen

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

Join Okazaki fragments together

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information where?

Sequence of bases

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' to the 3' direction of the other strand

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

The nucleotide sequence of the template strand

What are the components of the class of molecules known as nucleotides?

a nitrogenous base, a phosphate group, and a pentose sugar

The double stranded DNA resembles a twisted ladder in which the backbone or sides are made of

alternating sugars and phsophates

Of the following functions, the major purpose of RNA is to a) make a copy of itself, thus ensuring genetic continuity b) function in the synthesis of a protein c) transmit genetic information to offspring d) act as a pattern or blueprint to form DNA e) form the genes of higher organisms

b

What is the structural feature that allows DNA to replicate?

complementary pairing of the nitrogenous bases

Which of the following is/are true of snRNPs? a) They attach introns to exons in the correct order b) They are made up of DNA and RNA c) They bind to splice sites at each end of the exon d) They join together to form a large structure called the spliceosome e) The act only in the cytosol

d

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes

exision of introns

The strand of DNA that is replicated in Okazaki fragments is called

lagging strand

What covalently connects segments of DNA?

ligase

The 5' end of a DNA nucleotide can be identified by the location of

phosphate group

Where is the attachment site for RNA polymerase?

promoter region

What is an anticodon a part of?

tRNA

Which of the classes of RNA molecules carries amino acids to the ribosome to be added to the growing polypeptide chain?

tRNA

What is responsible for the sequence of amino acids in a protein?

the sequence of codons in mRNA

What is the function of DNA polymerase III?

to add nucleotides to the end of a growing DNA strand

DNA polymerase dominates the process of

transcription