Chapter 5 - Organization And Expression Of Immunoglobulin Genes

Front 1

Germ-line theories

Back 1

theories that explain antibody diversity by postulating that all antibodies are encoded in the host chromosomes

Front 2

Somatic-variation theories

Back 2

theories maintaining that the genome contains a small number of immunoglobulin genes from which a large number of antibody specificities are generated in somatic cells by mutation or recombination

Front 3

J (joining)gene segment

Back 3

the part of a rearranged immunoglobulin or T-cell receptor gene that joins the variable region to the constant region and encodes part of the hypervariable region. There are multiple J gene segments in germ-line DNA, but rearrangement leaves only one in each functional rearranged gene

Front 4

Signal peptide (leader peptide)

Back 4

a small sequence of amino acids, also called the leader sequence, that guides the heavy or light chain through the endoplasmic reticulum and is cleaved from the nascent chains before assembly of the finished immunoglobulin molecule

Front 5

V (variable) gene segment

Back 5

the 5; coding portion of rearranged immunoglobulin and T-cell receptor genes. There are multiple V gene segments in germ-line DNA, but gene rearrangement leaves only one segment in each functional gene

Front 6

D (diversity) gene segment

Back 6

that portion of a rearranged immunoglobulin heavy-chain gene or T-cell receptor gene that is situated between the V and J gene segments and encodes part of the hypervariable region. There are multiple D gene segments in germ-line DNA, but gene rearrangement leaves only one in each functional rearranged gene

Front 7

Pseudogene

Back 7

nucleotide sequence that is a stable component of the genome but is incapable of being expressed. They are thought to have been derived by mutation of ancestoral active genes

Front 8

Recombination signal sequences (RSSs)

Back 8

highly conserved heptamer and nonamer nucleotide sequences that serve as signals for the gene rearrangement process and flank each germline V, D, and J segments

Front 9

One-turn recombination signal sequences

Back 9

immunoglobulin gene-recombination signal sequences separated by an intervening sequence of 12 base pairs

Front 10

Two-turn recombination signal sequences

Back 10

immunoglobulin gene recombination signal sequences separated by an interveneing sequence of 23 base pairs

Front 11

V(D)J recombinase

Back 11

the set of enzymatic activities that collectively bring about the joining of gene segments into a rearranged V(D)J unit

Front 12

Recombination-activating genes (RAG-1 and RAG-2)

Back 12

two closely linked genes, RAG-1 and RAG-2, that encode proteins essential for the rearrangement of immunoglobulin gene segments in the assembly of a functional immunoglobulin gene

Front 13

Terminal deoxynucleotidyl transferase (TdT)

Back 13

an enzyme that adds deoxynucleotide triphophates to the 3' ends of DNA

Front 14

P region nucleotides

Back 14

P-addition is the addition of nucleotides from cleaved hairpin loops formed by the junction of V-D or D-J gene segments during Ig or TCR gene rearrangements

Front 15

N region nucleotides

Back 15

N-addition is the adition of nucleotides by terminal deoxyribonucleotidyl transferase during the process of D-J joining or V-to-DJ joining