CAS BI 315 Lecture Notes - Lecture 79: Rna Polymerase Iii, Rag1, Transcription Factor Ii E
DNA Rearrangements
- Homologous recombination results in exchange of DNA between chromosomes w/o
altering the arrangement of genes within the genome. Shuffling of DNA
- Important in gene expression
- Evolution.
- Site-specific recombination: DNA rearrangement via homologous recombination
between specific sequences. At localized sites.
- Two major classes of vertebrate immune responses:
-B lymphocytes secrete antibodies (Immunoglobulins) that react with soluble
antigens. Each antibody will recognize different antigens.
-T lymphocytes have cell surface proteins (T cell receptors) that react with
antigens on the surfaces of other cells.
- B-lymph and T-lymph have enormous diversity.
- Unique lymphocyte genes are formed during development by site-specific recombination
between segments of immunoglobulin and T-cell receptor genes
- Structure of immunoglobulin is made of 2 light chains and 2 heavy chains and this
means it has a quaternary structure. Y shape. Variable region is where there is diversity
and where we differentiate the antibodies. REMEMBER: ANTIBODIES ARE PROTEINS
Those proteins come from separate RNAs which come from separate genes.
- LIGHT CHAINS: (Can make 600 LCs)
- One variable region, one joining region and one constant region: C region is the
constant region that doesn’t change when making antibodies.
- Genomic DNA in rearranged DNA of B-lymphs are different because of
site-specific recombination.
- HEAVY CHAINS: (Can make 7200 HCs)
- Two recombination events:
- Joining of J and D segments
- Then, joining of V to DJ segment
- Transcription
- Splicing
- V,D,J,C
- Key Experiment!
- Subsequent deletions and insertions of nucleotides increase the diversity of
immunoglobulins. More mutations is better! You’ll have more types of antigens.
- T cell receptors also consist of two chains (a and b), with variable and constant regions.
They’re bonded via disulfide bridges. Generated by recombination events and that’s why
they have V and C regions. They’re like antibodies but they’re stuck to t-cell membranes
so they travel wherever T-cells go. They’re involved in B-cell and T-cell development.
- V(D)J Recombination (Part 1)
- Has two important proteins: RAG1 and RAG2. Involved in B-cell and T-cell
development. When these cells are developing and responding to antigens,
these proteins will come into play. They’ll cause recombination at recombination
sites (right next to regions like the V or D). RAG2 (mainly) and RAGI will come in
Document Summary
Homologous recombination results in exchange of dna between chromosomes w/o altering the arrangement of genes within the genome. Site-specific recombination : dna rearrangement via homologous recombination between specific sequences. B lymphocytes secrete antibodies (immunoglobulins) that react with soluble antigens. T lymphocytes have cell surface proteins (t cell receptors) that react with antigens on the surfaces of other cells. Unique lymphocyte genes are formed during development by site-specific recombination between segments of immunoglobulin and t-cell receptor genes. Structure of immunoglobulin is made of 2 light chains and 2 heavy chains and this means it has a quaternary structure. Variable region is where there is diversity and where we differentiate the antibodies. Those proteins come from separate rnas which come from separate genes. One variable region, one joining region and one constant region: c region is the constant region that doesn"t change when making antibodies. Genomic dna in rearranged dna of b-lymphs are different because of site-specific recombination.
