Exam 2: additional RAT questions

Question 1

Junctional diversity during gene rearrangement results from the addition of __________________.

Answer 1

P and N nucleotides

Question 2

The _______ contribute to antigen specificity of immunoglobulins, and _______ make up the more conservative flanking regions.

Answer 2

Hypervariable loops; framework regions

Question 3

In contrast with leader peptides and the C regions, the V regions in immunoglobulin heavy-chain genes

Answer 3

Are composed of V, D, and J gene segments that must undergo gene rearrangement to generate a transcribable exon

Question 4

All of the following comprise heavy-chain isotypes of immunoglobulin except _______.

Answer 4

beta

Question 5

Indicate which of the following statements is false.

Answer 5

On the heavy-chain locus, V rearranges to D first, then J joins the combined VD sequence

Question 6

Gene rearrangement by somatic recombination involves recombination signal sequences (RSSs) that flank V, D, and J segments and are recognized by the enzymes involved in cutting and rejoining the gene segments. An RSS is composed of a conserved nonamer sequence and heptamer sequence separated by a spacer region. There are two types of RSS, one with a spacer of 12 bp and one with a spacer of 23 bp. To ensure that segments are brought together in the right order, an RSS with a 12-bp spacer is always brought together with one with a 23-bp spacer. This is called the 12/23 rule. This ensures that in the heavy-chain locus, V rearranges to DJ and not directly to J or another V, and in the light-chain locus, V rearranges to J and not to another V.

Answer 6

True

Question 7

The five classes (isotypes) of immunoglobulins comprise

Answer 7

IgA, IgD, IgE, IgG, IgM

Question 8

Which of the following statements about the production and use of monoclonal antibodies is incorrect?

Answer 8

Production of monoclonal antibodies requires a purified form of antigen

Question 9

The process used to produce either surface or secreted forms of the immunoglobulin heavy chain is called __________________.

Answer 9

Alternative RNA processing

Question 10

Neutralizing antibodies _________________________.

Answer 10

Inhibit interaction of antigen with human cell surfaces

Question 11

Igalpha and Igbeta proteins are highly variable, because they interact directly with antigen. Igalpha and Igbeta perform specific signaling functions, which require particular amino acid sequences and also have evolved a sequence and structure that enable them to interact with all the different immunoglobulin isotypes. Extensive variation in Igalpha and/or Igbeta could therefore compromise their interaction with immunoglobulins and their signal transduction capabilities.

Answer 11

False

Question 12

Which of the following statements regarding immunoglobulins is correct?

Answer 12

Immunoglobulins make up five classes (or isotypes) called IgA, IgD, IgE, IgG and IgM

Question 13

The process of _____ results in change in the constant region of the heavy chain of antibodies, causing a change in the effector function and transport properties of antibodies.

Answer 13

Isotype switching

Question 14

The process of _____ results in the amplification of particular B-cells with specificity for antigen.

Answer 14

Clonal selection

Question 15

Which of the following is mismatched?

Answer 15

Affinity maturation: isotype switching

Question 16

Which of the following statements regarding T-cell receptor recognition of antigen is correct?

Answer 16

Alpha:beta T-cell receptors recognize antigen only as peptide bound to an MHC molecule

Question 17

During T-cell receptor _____-gene rearrangement, two D segments may be used in the final rearranged gene sequence, thereby increasing overall variability of this chain.

Answer 17

Delta

Question 18

The rejoining and repair of DNA during the recombination process leads to additional variation in sequence at the junctions between the rearranged gene segments. This is called junctional diversity and contributes considerably to the final diversity of T cell receptor specificities. Two sources of junctional diversity are introduced: P (palindromic) and N (nontemplated) nucleotides. P nucleotides are generated through endonuclease activity and repair around a hairpin loop at the ends of the gene segments to be joined. N nucleotides are nucleotides added at random at the junctions by terminal deoxynucleotidyl transferase (TdT) activity.

Answer 18

True

Question 19

Gene rearrangement by somatic recombination involves recombination signal sequences (RSSs) that flank V, D, and J segments and are recognized by the enzymes involved in cutting and rejoining the gene segments. An RSS is composed of a conserved nonamer sequence and heptamer sequence separated by a spacer region. There are two types of RSS, one with a spacer of 12 bp and one with a spacer of 23 bp. To ensure that segments are brought together in the right order, an RSS with a 12-bp spacer is always brought together with one with a 23-bp spacer. This is called the 12/23 rule. This ensures that in the beta-chain locus, V rearranges to DJ and not directly to J or another V, and in the alpha-chain locus, V rearranges to J and not to another V.

Answer 19

True

Question 20

The _____ refers to the complete set of HLA alleles that a person possesses on a particular chromosome 6.

Answer 20

Halotype

Question 21

The diversity of MHC class I and II genes is due to ___________________.

Answer 21

The existence of many similar genes encoding MHC molecules in the genome and extensive polymorphism at many of the alleles

Question 22

Of the following HLA-chain loci, which one exhibits the highest degree of polymorphism?

Answer 22

HLA-B

Question 23

MHC molecules have promiscuous binding specificity. This means that __________________.

Answer 23

A particular MHC molecule has the potential to bind to different peptides

Question 24

Which of the following cell types does not express MHC class I?

Answer 24

Erythrocyte

Question 25

The combination of all HLA class I and class II allotypes that an individual expresses is referred to as their ____________.

Answer 25

HLA type

Question 26

All of the following are highly polymorphic except _____________.

Answer 26

HLA-DO beta chain

Question 27

Antigen processing involves the breakdown of protein antigens and the subsequent association of peptide fragments on the surface of antigen-presenting cells with ________________.

Answer 27

MHC class 1 or class 2 molecules

Question 28

Antigen processing involves the breakdown of protein antigens and the subsequent association of peptide fragments on the surface of antigen-presenting cells with ________________.

Answer 28

MHC class I or class II molecules

Question 29

Cross-priming of the immune response occurs when ______________________________.

Answer 29

Viral antigens are presented by MHC class I molecules on the surface of a cell that is not actually infected by that particular virus or peptides of nuclear or cytosolic proteins are presented by MHC class II molecules.

Question 30

Which is the most likely reason that HIV-infected people with heterozygous HLA loci have a delayed progression to AIDS compared with patients who are homozygous at one or more HLA loci?

Answer 30

The greater number of HLA alleles provides a wider variety of HLA molecules for presenting HIV-derived peptides to CD8 T cells even if HIV mutates during the course of infection

Question 31

Which of the following is mismatched?

Answer 31

Interallelic conversion: recombination between two different genes in the same family

Question 32

One type of bare lymphocyte syndrome is caused by a genetic defect in MHC class II transactivator (CIITA), which results in the inability to synthesize MHC class II and display it on the cell surface. The consequence of this would be that ____________________________.

Answer 32

CD 4 T cells cannot function