Cell Bio 11.11.09 -DNA anti parallel double helix 3´and 5´ end between the strands hydrogen bonds major groove and minor groove spherical hindrance makes other parings impossible circular molecule in bacteria chloroplasts mitochondria several viruses problems when denatured or during replication
Cloning: Definition, types and stemm cell research
Table of contents: Definiton of clones 3 types of cloning Stem cell research , Definition of Stem cells, iPS cells
What are clones? -Clones are defined
by having identical genetic material. That means their sequence of
bases in their
Obama about Abortion, Same Sex Marriage and Stem Cell Research In the following pages I will explain president Barack Obama’s thoughts about Abortion, Same Sex Marriage and Stem Cell Research, beginning with abortion. Obama is, other than Governor Mitt Romney, pro-choice. That means he thinks
T cell ion channels and their role for activation
T-Zell Aktivierung und die Rolle von Ionenkanälen
T cell ion channels and their role for T cell activation
1.) T cells
As well as B-cells and natural killer cells (NK), T cells belong to the lymphocytes and present a hallmark of the adaptive immunity in vertebrates.
All T cells originate from a progenitor cell in the bone narrow and undergo maturation in the thymus. During maturation the T lymphocytes are being provided with different membrane-bound receptors and cell surface markers distinguishing distinct T cell subsets with unique functions.
T cell subsets: Depending on the composition of their T cell antigen receptor (TCR) the T cells are subdivided into αβ-T cells and γδ-T cells. Αβ-T cells account for the biggest part of the T cells with around 90-95% and represent about 70% of all peripheral blood mononuclear cells (PBMC).
They circulate continuously from the bloodstream to the lymphatic system and lymphoid organs back to the blood, making contact with antigen presenting cells (APCs). The most important factor for the recognition of different antigens is the T cell receptor (TCR). The α- and β-chains of the heterodimeric TCR are composed of a variable and a constant region, which during maturation are spliced together into a single type of functional αβ-TCR which differs in every T cell.
A further determination of αβ-T cells is made by the expression of different co-receptors on the plasma membrane during thymic maturation.
T cells express either a CD4 co-receptor (CD4+) or a CD8 co-receptor (CD8+) involved in TCR signaling .....[read full text]
They enhance avidity of the TCR to its target and bring the CD3/TCR complex and the co-receptor CD4/CD8 associated with the Scr family kinase Lck in close proximity helping to initiate the signaling cascade (Artyomov et al. 2010). According to the two-signal-hypothesis naïve T cells also require a second, co-stimulatory signal to be fully activated. This signal can be provided by co-stimulatory receptors of which the most commonly described one is CD28. Binding of CD28 to its ligand CD80/CD86 (B7.1/B7.2) expressed on activated APCs leads to downstream signaling critical for T cell activation (.....