General Flashcards
Define genetic sex
Determined by presence/absence of a Y chromosome
Primary sex characteristics
Development of the gonad
Sperm/egg development
Usually dependent on genotype (genetic sex)
Secondary sex characteristics
Sex-specific structures of the urogenital system
External genitalia
Dependent on hormone signalling/signals from the environment
What are pseudo-autosomal regions?
Regions on the X and Y chromosome responsible for pairing during meiosis
Gene responsible for sex determination on Y chromosome
SRY gene
How can have an XX male?
SRY gene is on the X chromosome
How can have an XY female?
Absence of SRY gene on Y chromosome OR
Has a mutation which makes the person immune to testosterone.
What does the SRY gene do?
Usually located on short arm of Y chromosome
Is responsible for sex determination
Encodes testis determining factor (TDF)
TDF
Testis determining factor
From SRY gene
Karyotype XO
Turner Syndrome
Phenotype: female
Fertility: no
Karyotype: XXY
Kleinfelter Syndrome
Phenotype: male
Fertility: no
Karyotype: XYY
XYY syndrome
Phenotype: male
Fertility: yes
Karyotype: XXX
XXX syndrome
Phenotype: female
Fertility: reduced
Karyotype: XXXY
Triple X Y syndrome
Phenotype: male
Fertility: no
Karyotype: XXXX
Tetra X syndrome
Phenotype: female
Fertility: ?
Karyotype: XXXXY
Tetra X Y syndrome
Phenotype: male
Fertility: no
Main adhesion factors
Cadherins
Integrins
IgCAMs
Selectins
Cadherins mediate…
Attachment cell-to-cell
Integrins mediate…
Attachment cell-to-matrix
During development, cadherins…
Mediate cell sorting
Role of HSP90
Chaperone, refolding proteins
Works downstream to HSP70
Refolds kinases, receptors and cytoskeletal proteins; has role in cell cycle and chromosome maintenance
Define phagocytosis
Cell consumes large molecules and whole cells
Define pinocytosis
Cell consumes fluids and small molecules
6 points at which proteins expression is controlled
- Transcriptional control
- RNA processing control
- RNA transport and localising
- Translational control
- mRNA degradation control
- Protein activity control
What is the transcriptional control of protein expression?
Whether and how much a gene is transcribed affects the protein expression
What is the RNA processing control of protein expression?
Different splicing and completing the mRNA affects protein expression
How does control of RNA transport and localising (Step 3) affect protein expression?
The final location of the mRNA is part of determining the final outcome & hence the protein expression
How does translational control affect protein expression?
Whether the mRNA is translated into protein affects protein expression
Explain how mRNA degradation control affects protein expression
If the mRNA is degraded more before it is translated, there is less protein expressed.
If it is degraded less, there is more protein expressed.
Outline the mechanism by which phosphorylation (by CAK) allows the activation of cyclin-Cdk
Phosphorylation alters conformation of protein loop, allowing ATPase activity to drive kinase reaction.
Alpha actin found in…
Muscle cells
Beta and gamma actin found in…
Non-muscle cells
The 4 types of cell adhesion molecule
Cadherins
Integrins
Selectins
IgCAMs
Common feature of IgCAMs
Ig-domain, a beta-sheet stabilised by di-sulfide bonding
What are selectins?
Cell adhesion molecule in the bloodstream.
3 types of selectin
E - epithelia
L - leukocytes (most)
P - platelets (secretory granules of)
Weak adhesion and rolling mediated by…
Selectins
What are integrins?
Cell adhesion molecules
Responsible for cell-matrix adhesion
What are cadherins?
Cell adhesion molecules
Responsible for cell-cell adhesion
What is the most common cell adhesion molecule in vertebrates?
N-CAM
Which type of cell junctions are actin filaments anchored to?
Adherens junctions (cell-cell) Actin-linked cell-matrix adhesions
What type of cell junctions are intermediate filaments anchored to?
Desmosomes (cell-cell)
Hemidesmosomes (cell-matrix)
What are the cadherins in desmosomes?
Desmocollin
Desmoglein
What are the intracellular anchoring proteins associated with desmosomes?
Plakophilin
Plakoglobin
Desmoplakin
Homophilic binding
CAMs only bind to their own kind (cadherins to cadherins, etc.)
Heterophilic binding
CAMs binding to molecules outside their class
The plant equivalent of a gap junction
Plasmodesmata
What are the classical cadherins?
N - CNS
E - embryonic, epithelia
P - placenta and epidermis
VE - endothelia
Why are cadherins Ca++ dependent?
Ca++ binds between the subunits, making them rigid by preventing them from flexing.
Without Ca++, the molecule is limp and can’t bind.
What are the intracellular anchoring proteins associated with cadherin junctions?
alpha, beta and gamma catenins
