Chapter 15 and 16 MasteringBio
Translation
(genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm
Diploid cell with 2n=6 Nondisjunction of all three chromosome pairs in meiosis I (asume all chromosomes go to the same pole). Number of chromosomes in gametes?
0 or 6 (0n), (0n), (2n), (2n)
Diploid cell with 2n=6 Nondisjunction of all three chromosomes in one daughter cell in meiosis II (assume all chromosomes go to the same pole). Number of chromosomes in gametes?
0, 3, or 6 (0n), (n), (n), (2n)
Diploid cell with 2n=6 Nondisjunction of one chromosome pair in meiosis I. Number of chromosomes in gametes?
2 or 4 (n-1), (n-1), (n+1), (n+1)
Diploid cell with 2n=6 Nondisjunction of one chromosome in one daughter cell in meiosis II. Number of chromosomes in gametes?
2, 3, or 4 (n-1), (n), (n), (n+1)
If a sample of DNA is composed of 30% thymine, what percent of guanine should be in the sample?
20%
Proofreading requires
3' to 5' exonuclease activity
Proteins are made up of 20 different amino acids. How many fewer amino acids would have to be used in order to have the genetic code be made up of two-letter words?
4 x 4 = 16 amino acids
QUANTITATIVE Assuming that each replication fork moves at a rate of 500 base pairs per second, how long would it take to replicate the E. coli chromosome (with 4.6 million base pairs) from a single origin of replication?
4600 seconds 4.6 million / 500 / 2 (because 2 strands being simultaneously replicated)
The sequence of a polypeptide is determined by the order of codons that specify the amino acids in the polypeptide. How many different sequences of codons can specify the polypeptide sequence methionine-histidine-alanine-leucine?
48 (The sequence of a polypeptide is determined by the order of codons that specify the amino acids in the polypeptide. The polypeptide sequence methionine-histidine-alanine-leucine can be specified by 48 sequences of codons. To calculate this, you need to multiply the total number of codon sets that can code for each of the amino acids in the sequence. Therefore, 1 x 2 x 4 x 6 = 48 (see figure).)
The following DNA sequence occurs at the start of a DNA strand. Which of the sequences below would be most likely to bind to this sequence to initiate DNA replication in a cell? 3′ AATTGCAGATTCA 5′
5′ UUAACGUCUAA 3′ Primers used during cellular DNA synthesis are short RNA strands, not DNA strands. The RNA primer has uracil (U) instead of thymine (T) and will proceed in the 5′ to 3′ direction.
Why is the genetic code unambiguous?
A given codon never codes for more than one amino acid
How do cells correct a damaged base in double-stranded DNA?
A section of the DNA containing the mismatched base is removed and replaced.
Conservative DNA replication would result in
After one generation, both of the daughter DNA strands would pair in a double helix.
DNA polymerase forms what kind of bond between a phosphate group and a hydroxyl group?
Covalent
The RNA on the lagging strand is excised by
DNA Polymerase I
What additional proteins, other than those required for the synthesis of the leading strand, would be required for the synthesis of the lagging strand?
DNA Polymerase I and DNA ligase
During DNA replication, mismatched bases are inserted approximately once in every 100,000 bases. The exonuclease activity of which enzyme repairs these mismatches?
DNA Polymerase III
Which enzyme will remove an RNA primer?
DNA polymerase I
In proofreading
DNA polymerase III corrects the mismatched bases
Why are the results of studies of DNA replication in E. coli applicable to the same process in humans?
E. coli is similar to humans because it replicates its entire genome (entire complement of DNA) before every cell division.
True or false? A codon is a group of three bases that can specify more than one amino acid.
False. A codon is a group of three bases that can specify only one amino acid. An amino acid can, however, be coded for by more than one codon.
In the Meselson-Stahl experiment, cells were grown for one generation in a growth medium containing a relatively heavy nitrogen isotope, then transferred to a new medium containing a lighter nitrogen isotope. After one round of DNA replication, what was true of the DNA in the cells?
Half of the DNA strands contained only the light nitrogen isotope.
A researcher did an assay on a solution and found the following enzymes: primase, DNA polymerase III, and sliding clamps. What part of DNA replication is this solution of enzymes capable of doing?
Leading strand synthesis
What's an example of the genetic code being redundant?
Most amino acids are specified by more than one codon.
Primase is an example of an RNA polymerase. How is primase different than DNA polymerase?
Primase does not require a primer
What is the role of primase in the replication of DNA?
Primase synthesis the RNA primer
What's an exception to the central dogma of molecular biology, with regard to viruses?
Single-stranded RNA from a virus is used as a template for producing DNA that inserts into the host genome.
How many different amino acids would be found in a polypeptide made from translation of an RNA containing only cytosines (C) and adenines (A) in random order?
Six The six resultant codons would be the following: AAA (lysine), AAC (asparagine), ACC, ACA (both threonine), CCC, CCA (both proline), CAC (histidine), and CAA (glutamine).
Why does telomerase have to have a built-in template for DNA synthesis?
Telomerase is involved in adding DNA to the end of the lagging strand. ... At the ends of linear chromosomes (telomeres), telomerase uses its built-in RNA template to extend the parent DNA template near the end of the lagging strand, providing room for an RNA primer so that lagging strand synthesis can be completed to the end of the chromosome.
Is donor age or telomere length more important in determining how many cell divisions a cell will undergo?
Telomere length is more important in determining the number of cell divisions because all cells with longer telomeres divided more times than cells with shorter telomeres, regardless of donor age.
How does DNA polymerase add dNTP monomers to the growing chain?
The 3′ carbon of the DNA chain forms a covalent linkage with the phosphate group on the 5′ end of the dNTP.
When replicating the lagging strand, DNA polymerases cannot replicate ...
The 3′ end of a lagging strand
Why is it possible for a point mutation to have no effect on an individual's fitness?
The encoded protein may be unchanged due to the redundancy of the genetic code.
If a cell could not produce DNA ligase, which of the following would occur?
The gaps between Okazaki fragments would not be closed
If DNA polymerase fails to correct an error
a mutation occurs
The function of mRNA is to
carry information from DNA out of the nucleus to the site of protein synthesis
DNA ligase
catalyzes the formation of a phosphodiester bond between adjacent Okazaki fragments in the 3' to 5' direction
Polyploidy
condition in which an organism has extra sets of chromosomes
DNA polymerase moves along the lagging strand in what direction
discontinuously in the 3' to 5' direction
DNA polymerase moves along the lagging strand...
discontinuously in the 3′ to 5′ direction (as in the old strand, 3' to 5') DNA polymerases can add deoxyribonucleotides only to the 3′ end of a growing DNA chain.
Because the dNTPs have three closely spaced phosphate groups, dNTPs...
have high potential energy! ...high enough to make the formation of phosphodiester bonds in a growing DNA strand exergonic as two of the phosphates are cleaved off. The triphosphate group of the dNTP binds to the 3′ hydroxyl group of a growing chain.
RNAs with a poly A tail (a long series of A nucleotide bases) produce which amino acid in that section of protein?
lysine
Which type of mutation causes a premature termination of protein synthesis?
nonsense change in nucleotide that results in early stop codon
In a human karyotype, chromosome 15 has four chromosomes visible. This is an example of
polyploidy Humans have two copies of each chromosome normally. The addition of more than this is referred to as polyploidy.
Knock-out mutation
refers to the loss of a protein's function but not necessarily to its complete absence.
Which enzyme allows RNA to be coded into DNA?
reverse transcriptase
intron
sequence of DNA that is not involved in coding for a protein
During replication, the lagging strand is made up of
short DNA/RNA fragments
The lagging strand is made up of what during replication?
short DNA/RNA fragments
The secondary structure of a double-stranded DNA helix molecule can best be described as a ...
sugar-phosphate backbone with the bases of the complementary base pairs adenine-thymine and guanine-cytosine projecting toward the inside of the backbone
Which enzyme catalyzes the synthesis of DNA from its own RNA template?
telomerase ... Telomerase adds DNA onto the end of a chromosome to prevent it from getting shorter. DNA polymerase polymerizes deoxyribonucleotides into DNA.
When replicating the lagging strand, DNA polymerases cannot replicate
the 3' end of a lagging strand
Before mRNA can be translated into an amino acid sequence...
the mRNA must first be synthesized from DNA through transcription. Base pairing in mRNA synthesis follows slightly different rules than in DNA synthesis: uracil (U) replaces thymine (T) in pairing with adenine (A). The codons specified by the mRNA are then translated into a string of amino acids.
What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage?
the regularity of DNA's overall structure
The function of RNA polymerase is to
transcribe DNA to RNA
What is the most common number of codons that specifies a single amino acid?
two Of the 20 amino acids, nine are coded by two codons.
How many amino acids are represented in the genetic code by just one codon?
two The start codon, methionine, is only represented by AUG, and tryptophan is only represented by UGG. The code is redundant. All amino acids except methionine and tryptophan are coded for by more than one codon. This is sometimes referred to as degeneracy of the code.