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Flashcards in Week 8 Random Deck (40):
1

Multifactorial/Polygenic Inheritance

Charactersitics

interaction of genes and environment

recurrence risk varies and is determined empirically

2

Heritabillity

H = 2(cmz- cdz)           

cmz or cdz =concordance mz or dz.

3

Type I diabetes (Juvenile Onset or IDDM)

Autoimmunity disease in which the insulin-producing b-cells of the pancreas are destroyed.

Requires administration of insulin to prevent death (wasting due to inability to utilize glucose, acidosis, and ketosis).

Chronic, lifelong condition.

Although treatable, difficult to manage. blindness, limb amputations, kidney failure

4

Major goals in treatment of type 1 diabetes

1) Use genetic screens/tests to identify at risk individuals.

2) Prevent the destruction of the b-cells by modifying environment (eliminate triggers).

 

5

DPT Diabetes Prevention Trial

Large, multicenter, multiyear study of individuals at high risk of developing type I diabetes (children, twins, and siblings of diabetics).

Examining the influence of specific environmental factors on the risk these individuals will develop diabetes.

IDDM-1 locus: HLA class II DR gene.  95% of Caucasians with type I diabetes have DR3 and/or DR4 alleles, these occur in only 50% of the general population.

IDDM-2 locus:   A VNTR in the 5’ region of the insulin gene itself, accounts for about 10% of the heritability.

HLA DQ alleles confer resistance to diabetes.

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Polygenic/multifactorial disorders:

Recurrence and transmission patterns

Recurrence risk will change from population to population, and from family to family! Due to differences in genetic load.

Although clearly genetic, risk cannot be calculated based on degree of relationship (probability of shared genes).

Recurrence risks are determined from empirical data  (risk based on direct observation of the population data).

 

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Attributes of Polygenic/Multifactorial Inheritance:

1. Recurrence risk decreases rapidly for more distantly related relatives. Risk is less than would be predicted from coefficient of relationship

2. Recurrence risk varies from family to family (genetic load).

3. Recurrence risk increases if more than one family member affected (indicates higher genetic load)

4. The more severe the expression, the higher the risk (indicates higher genetic load)

5. Recurrence risk higher if proband is of the less commonly affected sex

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Relationship between risk and relativeness

If disease is multifactorial, risk decreases more rapidly than predicted from coefficient of relationship.

9

Polygenetic vs. Multifactorial

Polygenic- involves multiple genes.

Multifactorial- environmental trigger as well as genetic causes.

10

Quantitative trait- 

phenotype distributes across a more or less Gaussian (normal) distribution across a population.

11

Threshold of liability

disease does not have a normal distribution, but is the result of a continuous underlying liability. If threshold is exceeded, then disease results

12

Membrane Lipid Composition

Phospholipid

Cholesterol

Glycolipids

13

Lipid Rafts

Lipid rafts has specific proteins. Thus, there are biochemical activities associated with lipid rafts. 

 

Immune mechanisms

Signaling mechanisms
 

14

Five Major Phospholipids

Which one is negative?

What groups are attached?

Which are found in lipid rafts?

Phosphatidyl-ethanolamine (enamine)

Phosphatidyl-serine (serine) (-)

Phosphatidyl-choline (choline)

Sphingomyelin (choline)&OH

Sphingosine OH/NH3/OH

15

Function of Ca2+ in activation of PKC

PKC is a soluble protein in the cytoplasm. After Ca2+ binds to it, PKC moves to the membrane where it binds to phosphatidylserine. 

No phosphatidylserine -> no binding -> no function.

Phosphatidylserine exposed on the cell surface serves as a signal to induce neighboring cells (macrophage) to phagocytose the dead cell and digest it.
 

 

 

16

Types of membrane proteins

Integral

Peripheral

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Structure important in RBC shape

Spectrin

Connected to actin at junctional complex

Holds RBC biconcave

A image thumb
18

Rate of difussion depends on

gradient * temp * surface are * solubilty / distance / sqrt(MM)

19

Osmotic pressure equation

A image thumb
20

Ascites synonym

Endema

21

Charactersitics and examples of faciliated transport

Channels (fast mln/sec)

Carrier (slow 1-100/sec) e.g. sugars

 

22

Energy sources for Active transport

Ion gradient

ATP

Light

A image thumb
23

Na+ driven active transport examples

Glucose/AA symporter

Na+/H+ exchanger

Na+ driven Cl-HCO3- exchange

3x Na+ / 1 Ca2+ exchanger

24

Where is H+-driven active transport found?

The H+ gradient powers coupled transport of many solutes across plasma membrane of bacteria and yeast and intracellular membranes of eukaryotes.

25

26

Pumps that mantain pH

Pump out H+ from the cell (Na+-H+ exchanger)

Bring HCO3- into the cell (Na+-driven Cl- -HCO3- exchanger)

ATP-driven H+ pump

27

ATP driven pumps

Na+-K+ Pump (3/2)

Ca2+ pump

H+-K+ pump

28

Ouabain and pumps

Outbain partially inhibits Na+/K+ pump

This leads to inibition of Na+Ca++ exchanger and the increase Ca++ concentration in cells leading to 

A image thumb
29

Three ways to maintain a very low Ca++ in cell

Na+-driven Ca2+ exchanger

Ca2+ pump

Ca2+ pump in ER membrane
 

30

RMP

Resting Membrane Potential

31

Membrane potential change generation or change

Ions are flowing

32

Charged solutes diffuse due to:

The chemical gradients

Electrical gradients

33

Why tissue differ in RMP?

K+ leaking out

Negative molecules too large

34

Permeability vs. Conductance

High permeability indicates that particle mass moves easily through a membrane.

High conductance indicates that electrical charge moves easily through a membrane.
 

35

Potassium leak channel

K+ can leak out anytime (not protein dependent)

36

Characteristics of action potential

Threshold (all or none)

Refractory period

Conductio

37

Suprathreshold vs. Subthreshold

Supratreshold to cause action potential

38

K+ Na+ channels difference

K+ Open slowly

Na+ Open fast

39

Na+ channel stages

Closed

Open

Inactivated

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