Question 1

Which type of variation would be most detectable by gel electrophoresis if the differences in the DNA were between two recognition sites for a restriction enzyme?

Accepted Answer

Short Tandem Repeats (STRs) are the most detectable by gel electrophoresis if the differences in the DNA were between two recognition sites for a restriction enzyme. STRs are stretches of DNA that contain repeating patterns of two to six nucleotides, and the number of repeats can differ between individuals. This variation can be visualized on a gel as differences in the size of the fragments produced by the restriction enzyme digestion. SNPs (A), PCRs (B), HMRs (C), and transitions (E) are not directly related to the differences in recognition sites for restriction enzymes and are not typically detected by gel electrophoresis in the same way as STRs.

Question 2

Suppose restriction enzyme A makes two cuts in a linear DNA fragment and restriction enzyme B makes one cut in that same DNA.The cuts are not in the same place, and no two of the cut fragments is exactly the same size.The digested samples are run in an electrophoresis gel.How many bands should the gel pick up if only enzyme A is used in the restriction digest?

Accepted Answer

If enzyme A makes two cuts and enzyme B makes one cut, then using only enzyme A will result in 3 fragments (assuming no fragments are too small to be detected on the gel). Each of the two cuts from enzyme A will create a separate fragment, and the third fragment will be the remaining piece of DNA between the two cuts. Therefore, the gel should pick up three bands if only enzyme A is used in the restriction digest.

Question 3

Refer to the figure.  The restriction enzyme EcoR1 recognizes the palindromic sequence of GAATTC.You know the sequence of a protein but not the DNA sequence.You would like to have an idea about where in the gene there could be EcoR1 active sites.Which two consecutive amino acids could have nucleotide codons that would generate an EcoR1 active site in the DNA sequence?

Accepted Answer

The answer of Refer to the figure.  The restriction...

Question 4

Which statement regarding short tandem repeats (STRs) is false?

Accepted Answer

Short tandem repeats (STRs) are usually not the result of a single nucleotide base mutation, but rather due to variation in the number of repeats of a short DNA sequence. This variation is inherited and allows for individual identification in applications such as forensic DNA testing. The other statements are true.

Question 5

In a gel electrophoresis experiment, researchers notice that one DNA band on the gel appears much darker than the others.The DNA fragment forming the band is most likely _______ than the others.

Accepted Answer

The most likely reason for a DNA band appearing much darker than others on gel electrophoresis is that it is more abundant than the others. This could be due to differences in the starting amount of DNA used, the efficiency of the PCR amplification or sample preparation processes, or other factors.

Question 6

The "P" in SNP stands for

Accepted Answer

SNP stands for single nucleotide polymorphism, which refers to a variation in a single nucleotide (the building blocks of DNA) within a person's DNA sequence. This variation can occur in different forms within a population, hence the term polymorphism.

Question 7

Which DNA sequence forms a palindromic sequence?

Accepted Answer

A palindromic sequence in DNA is one where the sequence reads the same forwards and backwards on complementary strands. "ACGT" is palindromic because its complement "TGCA" reads the same in reverse.

Question 8

Which statement is not one of the reasons that STRs can be used for DNA fingerprinting?

Accepted Answer

All the statements (A, B, C, D) provided are indeed reasons why STRs are effective for DNA fingerprinting. STRs have high variability and can be amplified and analyzed using PCR and gel electrophoresis, making them suitable for identifying individuals.

Question 9

Which mutation would result in a SNP?

Accepted Answer

A SNP (single nucleotide polymorphism) is a change in a single nucleotide base pair in DNA. A transition is a type of point mutation that involves the substitution of a purine nucleotide (A or G) for another purine or a pyrimidine nucleotide (C or T) for another pyrimidine. Therefore, a transition mutation can result in a SNP.

Question 10

A restriction enzyme cuts a 25,700 bp segment of DNA into three fragments: fragment A is 5,800 bp; fragment B is 6,600 bp; and fragment C is _______ bp.Fragment _______ will move the farthest in an electrophoresis gel.

Accepted Answer

The answer of A restriction enzyme cuts a 25,700 bp...

Question 11

Multifactorial (complex) diseases

Accepted Answer

Multifactorial diseases involve the interaction of many genes with environmental factors, making them complex in nature. They are more common than single-gene diseases and can affect a significant percentage of the population. The answer choice of E, sickle-cell disease, is incorrect as it is a single-gene disorder. The answer choices of A, C, and D are also incorrect as they are not accurate statements about multifactorial diseases.

Question 12

Bacteria add _______ to their DNA to protect it from their own restriction enzymes.

Accepted Answer

Bacteria add methyl groups to specific nucleotide sequences in their DNA called recognition sites to protect them from cleavage by their own restriction enzymes. This process is known as DNA methylation and is used by bacteria to differentiate between their own DNA and foreign DNA.

Question 13

Because DNA has a _______ charge, it moves to the _______ end of the field in gel electrophoresis.The _______ DNA molecules migrate the most quickly.

Accepted Answer

DNA has a negative charge, so it moves towards the positive end of the field in gel electrophoresis. Smaller DNA molecules migrate more quickly than larger ones.

Question 14

Suppose restriction enzyme A makes two cuts in a linear DNA fragment and restriction enzyme B makes one cut in that same DNA.The cuts are not in the same place, and no two of the cut fragments is exactly the same size.The digested samples are run in an electrophoresis gel.How many bands should the gel pick up if both enzymes A and B are used in the restriction digest?

Accepted Answer

Each cut by enzyme A will produce two fragments, and the cut by enzyme B will produce one fragment. Therefore, the total number of bands will be 2 x 2 + 1 = 5. As no two fragments are the same size, there will be five distinct bands on the gel.

Question 15

In a DNA electrophoresis procedure, a geneticist will most likely use a longer-than-usual gel matrix and allow the procedure to proceed for a longer length of time than usual when

Accepted Answer

If the DNA fragments are fairly similar in size, they may be difficult to distinguish on a shorter gel matrix or if the procedure is not allowed to proceed for a sufficient length of time. Using a longer gel and longer procedure time allows for better resolution and separation of the fragments.

Question 16

Which DNA sequence would most likely be recognized by a restriction enzyme? (Note: Only the coding strand is shown.)

Accepted Answer

Restriction enzymes typically recognize and cut at specific sequences called restriction sites. The restriction site for the common restriction enzyme EcoRI is GAATTC. The sequence TAGCTA contains the EcoRI restriction site in the reverse complement strand (CTAGAT), indicating it is the most likely DNA sequence to be recognized by the EcoRI restriction enzyme.

Question 17

Which enzyme is used by bacteria as a defense against bacteriophage?

Accepted Answer

Restriction enzymes (or restriction endonucleases) are used by bacteria as a defense mechanism against bacteriophages. These enzymes recognize specific DNA sequences and cleave the DNA, thereby preventing the virus from replicating within the host cell. This is known as the restriction modification system. Reverse transcriptase, phosphofructokinase, DNA polymerase, and DNA ligase do not play a significant role in bacterial defense against bacteriophage.

Question 18

In a gel electrophoresis experiment, researchers notice that one band has migrated much farther on the gel than the others.They conclude that it is _______ than the others.

Accepted Answer

In gel electrophoresis, smaller (or shorter) DNA fragments move faster and farther through the gel compared to larger (or longer) fragments because the gel matrix poses less resistance to the movement of smaller molecules.

Question 19

Which technique usually requires pedigree information?

Accepted Answer

DNA linkage analysis is a technique that examines how genes are inherited together in a family. Pedigree information is necessary for this analysis because it allows for the identification of individuals who carry the gene(s) of interest and their relationships to each other. DNA fingerprinting, sequencing, gel electrophoresis and genetic screening may not require or benefit from pedigree information.

Question 20

The research area of molecular genetics is bolstered by DNA sequencing for all of the following reasons except

Accepted Answer

The statement "it is now routinely used in medical diagnosis" is incorrect. While DNA sequencing is becoming more common in medical diagnosis, it is not yet routine. The other choices are all accurate reasons why DNA sequencing is bolstering the research area of molecular genetics.

Quiz 15: Gene Mutation and Molecular Medicine