Question 1

Which of the following techniques describes either the rate of a molecule's migration or its final position in a gel?

Accepted Answer

Electrophoretic mobility describes the rate of migration of a molecule in a gel, and can also be used to determine its final position.

Question 2

Given what you know of the inheritance pattern of SCD,what can be said of individual II-5?

Accepted Answer

Individual II-5 must have inherited one mutant allele (βˢ) from his affected mother (I-2) and one normal allele (βᴬ) from his unaffected father (I-1). Therefore, he is a carrier. When he has children with II-4, who is also a carrier (heterozygous), they will each have a 50% chance of inheriting the mutant allele from both parents (βˢβˢ), a 25% chance of inheriting a normal allele from both parents (βᴬβᴬ), and a 25% chance of being a carrier like their parents (βᴬβˢ).

Question 3

Sickle cell is a codominant disease,meaning that heterozygotes exhibit an intermediate blood cell phenotype (a mixture of normal and sickle cells)due to the blend of hemoglobin tetramers in each red blood cell.Which of the following tetramer structures would you expect to find in a carrier of SCD?

Accepted Answer

E

Question 4

Molecular charge is an important characteristic influencing protein migration on a gel.What accounts for the variation in the molecular charge of proteins?

Accepted Answer

The variation in the molecular charge of proteins is primarily determined by the amino acid composition of the protein. The different amino acids have varying side chains that can either carry a positive charge, negative charge, or have no charge. These charges can interact with the surrounding environment, affecting the overall charge of the protein. This ultimately influences protein migration on a gel.

Question 5

The mutation that causes SCD causes what kind of change in the structure of hemoglobin?

Accepted Answer

The mutation that causes SCD involves a single amino acid substitution in the beta-globin chain of hemoglobin. Specifically, a valine replaces a glutamic acid residue, causing a change in the structure of the tetrameric hemoglobin molecule.

Question 6

The βˢ and βᴬ alleles can be distinguished on the basis of

Accepted Answer

The βˢ and βᴬ alleles have a single nucleotide substitution, leading to a change in the amino acid sequence of the hemoglobin beta chain. This change affects protein structure and mobility during electrophoresis, resulting in different electrophoretic mobilities of the protein products. Additionally, this single nucleotide substitution alters the length of the DNA restriction fragments, which can also be used to distinguish between the two alleles. Therefore, option E is the best choice as it includes both variations in DNA restriction fragments and different electrophoretic mobilities due to a single amino acid substitution.

Question 7

From a standpoint of natural selection,we see that the heterozygous advantage for βᴬβˢ individuals is balanced by the disadvantage to those with SCD or the wild-type alleles (and no malaria protection).The action of these conflicting trends produces an overall increase in the mutant allele until it reaches a state where the gain and loss of βˢ alleles is equal.What is the term for this stable condition that allows mutant alleles to remain in a particular population?

Accepted Answer

The answer of From a standpoint of natural selection,we see...

Question 8

The same DNA probe used to measure mRNA levels by northern blotting can also be used on a Southern blot with a restriction digest of genomic DNA.What new information can be gained from Southern blotting (that wasn't already obtained by the northern blot analysis)?

Accepted Answer

Southern blotting with a restriction digest of genomic DNA can provide information about the size of the DNA fragments and the presence of a unique restriction fragment pattern indicating a mutation in a known restriction site. This information cannot be obtained from northern blotting, which only measures mRNA levels. The presence of a unique restriction fragment pattern can be used for genetic analysis and diagnosis of genetic diseases. Therefore, option E is the best choice. Options A, B, C, and D are not correct because they do not reflect the specific advantages of Southern blotting.

Question 9

Pauling used gel electrophoresis to confirm that homozygous individuals produce a single form of β-globin protein that differs depending on the homozygous genotype as well as that heterozygotes produce proteins of both types in approximately equal concentration.What characteristic(s)of the bands proved this?

Accepted Answer

The positions of the protein bands show the size and charge of the β-globin protein, which can differentiate between the different homozygous genotypes. The densitometry peaks of each band show the concentration of the protein, indicating that heterozygous individuals produce both types in approximately equal concentration. Therefore, both the positions and the densitometry peaks of each band provide evidence to confirm the production of single or multiple forms of β-globin protein by different genotypes.

Question 10

Given what you know of the inheritance pattern of SCD,is the following pedigree representative of a typical SCD pedigree?

Accepted Answer

The answer of Given what you know of the inheritance...

Question 11

What term is used to describe the situation when the loss of an allele because of selection against one of its phenotypes is balanced by natural selection in favor of the allele for another phenotype?

Accepted Answer

The term used to describe this situation is balanced polymorphism, where natural selection maintains multiple alleles or phenotypes in stable frequencies. This is because selection against one allele is balanced by selection in favor of another, resulting in both alleles persisting in the population.

Question 12

How is gel electrophoresis used to demonstrate the molecular basis of SCD?

Accepted Answer

The answer of How is gel electrophoresis used to demonstrate...

Question 13

You are interested in designing a molecular probe to detect the region of βˢ SNP,which includes a DdeI (CTNAG)restriction site.Which of the following molecular probe sequences would anneal to the correct position?

Accepted Answer

The sequence "ACTCCTGAGGAGAAG" contains the complementary sequence to the DdeI restriction site (CTNAG), allowing it to anneal to the correct position for detecting the βˢ SNP region.

Question 14

Thalassemia is a recessive blood disease caused by reduced synthesis of one of the globin genes.While SCD is a mutation in the structure of hemoglobin,thalassemias can also be caused by mutations in the regulatory elements,causing too little globin to be produced and resulting in anemia.You've designed a DNA probe that you want to use to screen a family for a rare mutation in the β-globin gene that causes thalassemia.First you will use the probe for northern blotting.What information will the northern blot tell you?

Accepted Answer

Northern blotting will tell you the amount of the β-globin gene transcript is within normal range, and the size of the mRNA gene product.

Question 15

At a biological level,βᴬβˢ heterozygotes suffer fewer cases of malaria than βᴬβᴬ homozygotes,and when they do get malaria,their disease is less severe.What is the biological explanation for the heterozygous advantage?

Accepted Answer

The βᴬβˢ heterozygotes have a shortened average life span of their red blood cells, which interrupts the developmental cycle of Plasmodium larvae by preventing many of the immature parasites from reaching maturity. This means that even if they are infected with malaria, they tend to have a milder form of the disease compared to the βᴬβᴬ homozygotes.

Question 16

How is the DNA visualized on a Southern blot?

Accepted Answer

DNA on a Southern blot can be visualized using either radioactively labeled probes or chemically labeled probes. Ethidium bromide is not used to visualize DNA on a Southern blot, as it is typically used for visualizing DNA on agarose gels. Therefore, option D is incorrect. Option B is also correct, but option E is the best choice as it includes both options.

Question 17

You set up an EcoRI restriction digest for a sample of genomic DNA from an individual with a hemoglobin mutation.To your surprise,you notice a different pattern of bands in the affected individualyou have identified a new SNP! What can you conclude from the pattern of bands from the gel below?

Accepted Answer

The answer of You set up an EcoRI restriction digest...

Question 18

Hemoglobin,the protein responsible for binding and transporting oxygen,forms a tetramer.What is the protein composition of the most common form of hemoglobin,hemoglobin A (HbA)?

Accepted Answer

Hemoglobin A (HbA) is composed of two alpha (α) and two beta (β) subunits, making it a tetramer with the composition α₂β₂.

Question 19

Ingram examined hemoglobin structural variation by breaking down the hemoglobin protein into many fragments by chemical treatment and subjecting the fragments to electrophoresis to separate them in a gel;and then in a second dimension,perpendicular to the first,he separated them by chromatography.This two-step approach is commonly referred to as

Accepted Answer

The two-step approach of breaking down the hemoglobin protein into fragments using chemical treatment, separating them through electrophoresis and chromatography is commonly referred to as peptide fingerprint analysis, as it helps to identify and analyze the specific fragments or peptides of the protein.

Question 20

Which of the following techniques quantifies the amount of protein present in a gel lane by measuring how much light is blocked from passing through the gel by the presence of a band of protein?

Accepted Answer

Densitometry is a technique used to quantitate the amount of protein present in a gel lane by measuring how much light is blocked from passing through the gel by the presence of a band of protein. Hybridization is a technique used to detect the presence of specific nucleic acid sequences. Electrophoretic mobility is a technique used to separate DNA, RNA, or protein molecules based on their size and charge. Restriction fragment analysis is a technique used to analyze DNA fragments obtained by digestion with restriction enzymes. Peptide fingerprint analysis is a technique used to identify proteins based on the unique pattern of peptides produced by digestion with a protease.

Quiz 10: The Integration of Genetic Approaches: Understanding Sickle Cell Disease