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1

How are the variable regions for heavy and light chains in a mature B cell coded in DNA?

by a single exon-exon 2 but separated from each other within this coding sequence

2

What is exon 1 of the variable region?

antibody's leader sequence

3

What is the function of hte antibody's leader sequence?

directs the antibody into the ER for surface expression or secretion

4

What is the difference between the DNA sequence for the variable-region exon in immature vs mature B cells?

in immature- the exon is encoded by 2 separate DNA segments

5

How are hte separate DNA segments encoding the varibale region joined together?

spliced together during B cell development in the bone marrow

6

Which gene segment do CDR1 and CDR2 come from in the immature B cell

variable/V gene segment --also included beta sheets A-F

7

Which gene segment is CDR3 found in?

partly on V region and rest on J region--as well as beta sheet G

8

What is the exon encoding the complete variable region formed by the joining of the V and J segments in thel ight chain called ?

V-region gene

9

What is this rearranemgent of genes in a maturing B cell known as?

somatic DNA recombination

10

Why does the joining of the V and J segments in the developing B cell also bring hte V gene segment closer to the C segmen/t

J segment is located close to the C region

11

What separates the J gene segment from the C-region in the rearranged V region?

short intron

12

How many gene segments encode the V region in the heavy chain?

3

13

What is the additional gene segment encoding hte V region in the heavy chain?

diversity gene segment

14

Where is the location of the Dh gene segment in relation to the V and J segments of hte heavy chain?

foudn in between the Vh and Jh segments

15

What is hte process of recombination for a heavy chain?

2 stages: 1-D and J segments join; then V joins the DJ segment to complete the V region

16

How are the V regions and C regions joined up?

RNA splicing

17

What creates the great diversity of V regions in immunoglobulin?

there are multiple copies of the V, D and J segments which are combined randomly

18

What is a pseudogene?

gene segments which aren't functional as have accumulated mutations

19

Why are there a large number of pseudogenes in hte V, D and J gene segments?

no single gene segment is essential

20

Which type of light chain has a greater number of unctional genes encoding the V segment?

kappa > lambda

21

What is the name for the immunoglobulin gene segement clusters?

genetic loci

22

Which chromosome is the labda light chain locus?

22

23

Which hcrosome is the kappar light chain locus found on?

2

24

How many constant regions does the kappa light chain have?

1

25

How many constant regions does the lambda chain ahve?

one for each joining region-4/5

26

Which chromosome contains the heavy chain locus?

14

27

Waht is the difference between the organisation of hte J segments in relation to the C regions between light and heavy chain?

in the heavy chain the C regions are all clustered together- each corresponding to a different immunoglobulin isotype

28

How does the expression of other isotypes aside from u and d take place?

thorugh DNA rearragments called class switching (after B cell activation)

29

what guides DNA rearragments?

conserved noncoding DNA sequences- recombination signal sequences

30

Where are the recombination signal sequences found in the chromosomes?

adjacent to the points at which recombination takes palce