IMMS Flashcards
2 haploid gametes fuse forming…
Diploid Zygote
3 phases of interphase
G1- Cells get bigger in prep for division
S- Each chromosome is copied (still 46 chromosomes but each chromosome contains 2 sister chromatids joined at centromere)
G2- Cell does more growing in prep for mitosis
Anaphase (Mitosis)
- Starts when a microtubule from each
centrosome has attached to the
kinetochore of each chromosome - Centrosomes pull on spindle fibre pulling
sister chromatids to opposite poles of cell
Anaphase I
Tetrads split up by spindle fibres (1 chromosome to each pole of cell)
Cytokinesis
Throughout mitosis, cell pinches tighter and tighter until it separates into 2 daughter cells post telophase
G0 phase
Only some cell like neurons which carry on growing but don’t divide have a G0 phase
The difference in the interphase process that occurs between MI and MII
During S phase, chromosomes aren’t replicated
Meiosis produces…
4 genetically different haploid daughter cells
Metaphase (Mitosis)
Prometaphase - Nuclear membrane and nucleolus disintegrate
Actual Metaphase - Chromosomes align along metaphase plate (midline of cell)
Spindle fibres connect to kinetochore of centromere
Metaphase I
Tetrads go to metaphase plate
Non-disjunction
Failure of chromosome pairs to separate during Meiosis I or sister chromatids to separate during Meiosis II (Trisomy 21)
What % of meiosis is prophase I?
90%
What occurs in Prophase I
46 chromosomes of 2 chromatids condense and nuclear membrane disintegrates
Each chromosome finds its homologue (forming a tetrad)
Crossing over occurs between homologues at chiasmata
Prophase (Mitosis)
Chromatin fibres condense (untangle into individual chromosomes)
2 centrosomes at opposite poles of cell each have 2 centrioles (protein structures at right angles to each other)
Each centriole sends spindle fibres made of microtubule protein connecting centriole to centromere
Telophase (Mitosis)
New nuclear envelope forms around centrosome and chromosomes
What does Telophase I and Cytokinesis I produce?
2 haploid daughter cells (containing bivalent chromosomes)
Genotype
Genetic constitution of an orgnaism
Phenotype
Appearance of an individual resulting from interaction of environment and genotype
Allele
1 of several alternate forms of a gene at a specific locus
Haplo-insufficiency
1 gene is inactivated or deleted and the remaining functional copy isn’t sufficient to produce needed gene product for normal function
Polymorphism
Frequent hereditary variations at a locus
Define Genomics
Study of entirety of DNA, the genome, together with technologies that allow sequencing, interpretation and analysis
Pathogenic Variant
Alteration in genetic sequence increasing an individual’s susceptibility to a certain disorder
Name for an alteration in genetic sequence which isn’t disease causing
Benign Variant
Name for an alteration in genetic sequence whose association with disease risk is unknown
Variant of unknown significance
What is penetrance?
Proportion of individual’s with a particular genotype who express the associated phenotype (develop the condition)
When would you carry out a predictive test for a genetic disease?
Testing an unaffected individual for a pathogenic variant known to be present in a family
Name for an individual who has only 1 member of a chromosome pair/segment rather than the usual 2
Hemizygous (males only have 1 X chromosome)
What is the ACMG criteria?
Formal scoring system to decide if a gene variant is pathogenic
Name for something you’re born with
Congenital
A Karyotype shows…
Complete set of an individuals chromosomes in metaphase (so they’re clear to see) from largest to smallest
Centromeres divide chromosomes into…
Long arm (q)
Short arm (p)
Bands are then numbered from centromere outwards to give an idea of where an abnormality is
How would an individual with Down’s Syndrome be written?
47, XX, +21
How would a polyploidy individual be written?
69, XXY
How would an individual with one X chromosome be written?
45, X
What type of mutation is this?
t(1;2)(q24;p12)
Translocation (swap between sections of chromosome 1 and 2)
What type of mutation is this?
inv(7)(q11q21)
Inversion (chromosome folds over at q21 sticking back in at q11)
What type of mutation is this?
dup(11)(p14p15)
Duplication (p14-p15 of chromosome 11 duplicated)
What type of mutation is this?
del(22)(q11q12)
Deletion (p11-p12 of chromosome 22 deleted)
Reciprocal Translocation
Bit of one chromosome snaps off and attaches to another
Acrocentric Chromosome
Non-central centromere (located near end of chromosome)
Robertsonian Translocation
Occurs between Robertsonian/acrocentric chromosomes (one arm present) and one arm attaches to another chromosome (resulting in 1 less chromosome)
What is genomic imprinting?
Term for 1 copy of a gene in an individual being expressed (mother or father) and the other is suppressed
What is FISH testing?
Fluorescence in situ Hybridisation (Tests for several deletions) - DNA probes labelled with fluorophores which bind to regions of DNA you’re interested in
If target DNA region is missing - No/half signal
If target region is duplicated - signal is duplicated (trisomy on a microscope slide)
Multifactorial Inheritance
Diseases due to a combination of genetic and environmental factors
For diseases with high genetic loading, will MZ or DZ twins have a greater concordance rate?
MZ but DZ still have a higher rate than rest of population
Define hereditability
Proportion of aetiology that can be ascribed to genetic factors as opposed to environmental factors (out of 1 / a %)
Microarrays:
What does it test for?
How does it work?
Test for deletions/duplications across the whole genome
-DNA added to test card, if DNA
doesn’t bind, signal shines
through (deletion)
-Binds twice as much reducing signal for duplications
Explain liability threshold model
Liability combines genetic and environmental factors
Normal distribution curve
Curve shifts right with genetic factors meaning less environmental exposure required to result in more severe disease
Name for a germline substitution of a single nucleotide
Short Nucleotide Polymorphism (SNP)
What is SNPs role in GWAS?
Tagged to sections of the chromosome that could be causing phenotype (compares healthy vs patient pools looking for SNPs notably more common in patients)
Mendel’s 3 Laws
- Dominance (in heterozygotes,
1 allele shows) - Segregation (alleles separate
randomly during meiosis) - Independent Assortment (traits transmitted to offspring independent of one another)
Name for receiving 2 copies of a chromosome from 1 parent and 0 from the other
Uniparental disomy
2 types of mitochondrial inheritance
- Homoplasmy - Cell whose
copies of mitochondrial DNA
are identical (normal or
mutated) - Heteroplasmy - Multiple copies
of mtDNA in each cell with
mutations affecting only a
proportion of molecules in the
cell
Pedigree drawing:
What does a triangle mean?
Miscarriage
Pedigree drawing:
What does a diamond mean?
Unknown gender
Pedigree drawing:
What does a double line between parents mean?
Related parents
Pedigree drawing:
What do diagonal lines mean?
If horizontal line across the diagonals is present…
Twins
Twins are MZ (identical)
What is Allelic Heterogeneity?
Different mutations within the same gene result in the same clinical condition
What is Locus Heterogeneity?
Variants in different genes give rise to same clinical condition
What is a compound heterozygous?
Presence of 2 different mutated alleles at a particular gene locus
In what instance(s) does autosomal recessive manifest?
In homozygous and compound heterozygous state
What is consanguinity?
Reproductive union between 2 blood relatives
What is autozygosity?
Homozygosity by descent (inheritance of same altered allele through 2 branches of the same family) (cousins)
In what instance does autosomal dominant inheritance manifest?
Only in heterozygous state
What is expressivity?
Refers to the range of phenotypes expressed by a specific genotype
What is a De novo mutation?
Mutation in genome that wasn’t present/transmitted by parents (mutation occurs spontaneously during DNA replication)
What is anticipation in genetics?
Where genetic disorders affect successive generations earlier or more severely due to expansion of unstable triplet repeat sequences (the trinucleotide repeats get larger like in myotrophic dystrophy)
What is somatic mosaicism?
Genetic fault present only in some body tissues (1 cell line normal, other cell line has mutated allele)
What is gonadal mosaicism? (causes our offspring problems)
Genetic fault in gonadal tissue
What is a late-onset condition?
Condition not manifested at birth (adult-onset)
What are sex-limited genes?
Present in both sexes of sexually reproducing species but are expressed in only one sex and have no penetrance, or are simply ‘turned off’ in the other
What is the only pattern of inheritance with male-to-male transmission?
ADI
What is Lyonization?
The normal phenomenon in which one of the two X chromosomes in female cells is inactivated during embryonic development (can be skewed but typically 50/50) which explains why some individuals in a family get a disease and some don’t
With X-linked inheritance, an affected male can have affected daughters but not affected sons. Why?
No male-to-male transmission in X-linked inheritance
What is a VUS?
In genetic testing, a variant of uncertain significance
What is a splice-site variant?
Alteration occurring at boundary between exon and intron resulting in loss of exons or inclusion of introns (affects accurate removal of introns)
What is nonsense-mediated decay?
Surveillance pathway which reduces errors in gene expression by eliminating mRNA transcripts containing premature stop codons (caused by a nonsense mutation)
What is a missense variant?
Single base pair change (changing type of amino acid in protein)
What is a synonymous variant?
Codon substitution that doesn’t change the encoded amino acid
At what point is a mutation considered benign/polymorphism?
When it’s present in +5% of the healthy population
What are secondary findings in genetic testing?
Incidental findings (finding a non-target DNA mutation)
Explain Sangar Sequencing
Using PCR to amplify regions of interest followed by sequencing PCR products
Useful for single gene testing (very accurate but slow and expensive)
Uses a single start primer and only a single DNA fragment is sequenced (easier to read)
Explain NGS
Quick, lower cost
Can sequence human genome in 1 day using parallel analysis. Harder to interpret, less accurate than Sangar
Must sift through “noise” of NGS due to rare missense variants found in healthy people to find the mutation responsible for disease
What % of total DNA do the following sequence?
-Whole Genome
Sequencing
-Whole Exome
Sequencing
-Targeted Sequencing
95%
1.5%
0.005-0.01%
What are targeted panels?
Selecting specific genes to sequence producing less “noise” and fewer VUS
What is eugenics?
Racial improvement and planned breeding to perfect human beings (but 2 people with high intelligence likely have child of average intelligence due to deviation to the mean)
What is genetic counselling?
Advising patients at risk of a disease its consequences, probability of it developing / you passing it on and ways it can be prevented/ameliorated (non-directive as in your choice)
What is an NIPT?
Why is it done?
Non-invasive pre-natal test - sample of maternal blood and take DNA from embryo that’s leaked across placenta (helps identify a trisomy)
Invasive tests can cause the foetus harm (increases likelihood of miscarriage)
Example of a disease caused by an expansion of a trinucleotide repeat
Huntington’s Disease (CAG repeated more)
What is PGD?
Preimplantation genetic diagnosis - Sperm + egg to make embryo, 8 cell stage embryo biopsied, genetic material extracted and tested for genetic condition. Only embryos without genetic change placed into woman’s womb
When might a child be considered to have 3 parents?
When they’ve had mitochondrial replacement therapy using donor mtDNA
Side chain (R) of an amino acid determines…
Polarity (hydrophilicity) / Non-polarity (hydrophobicity)
How many amino acids are there?
20
What effect does increased pH have on an amino acid?
Dissociation of H+ from carboxyl and dissociation of H+ from NH3+ changing charge of amino acid
Nucleotides bond to form a nucleotide polymer by…
Phosphodiester bonds
Water is liquid over the range…
Max density of water achieved at what temperature?
0-100 degrees celsius
4 degrees celsius
What is an aldose?
A monosaccharide with an aldehyde group
What is a ketose?
A monosaccharide with a ketone group
Proteoglycans
Long, unbranched polysaccharides radiating from a core protein
Nucleotide with no phosphate group attached is called…
With 1 attached is called…
With 2 attached is called…
With 3 attached is called…
Nucleoside (not nucleotide)
Nucleoside monophosphate (NMP) (nucleotide)
Nucleoside diphosphate (NDP) (nucleotide)
Nucleoside triphosphate (NTP) (nucleotide)
What type of glycosidic bond is found in nucleotides?
N-glycosidic bonds between a nucleotide base and pentose sugar (N-C)
What type of bond binds 2 monosaccharides?
O-glycosidic bond
How many monosaccharides in an oligosaccharide?
3-12
4 sugar derivatives
Aminosugars (NH2 group present)
Alcohol-sugars
Phosphorylated sugars
Sulphated sugars
How do melting points change in fatty acids?
Relative degree of unsaturation (less saturated = lower melting point)
5 forces holding proteins together
Van der Waals forces (IDDI)
Hydrogen Bonds (H + O/N binded to H)
Hydrophobic Forces
Ionic Bonds (weakened in aq solution by shielding water molecules and other ions present)
Disulphide Bonds (covalent bonding between side chains)
Formation of a-helix protein
H-bonds between each carbonyl group and the H attached to the N which is 4 aa along the chain
How do we determine protein structure?
X-ray diffraction of protein crystals (Keratin produces X shape due to presence of helices)
Define metabolism
The sum of the chemical reactions that take place within each cell of a living organism
Ligand- vs voltage-gated protein channels
Voltage-gated allow passage of 1 type of ion ligand-gated allow passage of 2+ types of ion
Difference between uniport, symport and antiport membrane carrier proteins
Uniport - Single substance
Symport - 2 substances in same direction
Antiport - 2 substances in the opposite direction
Driving forces moving substances across a membrane
Chemical
Electrical
Electrochemical (net direction equal to the sum of electrical and chemical forces)
GLUT4 carrier protein
Expressed in skeletal muscle and adipose tissue
Glucose uptake (facilitated diffusion)
Expression upregulated by insulin
Common active transport example
Na+/K+-ATPase
Pumps 3 Na+ out and 2 K+ in using hydrolysis of ATP -> ADP + Pi
How does the Na+/K+-ATPase pump allow secondary active transport of glucose?
Creates a concentration gradient of Na to enter the cell allowing co-transport of glucose with Na
Why is glucose intake much more important for a foetus?
Low arterial PO2 in uterus and placenta (prevents activation of gluconeogenic enzymes)
Receptor-mediated endocytosis
Metabolites/proteins/hormones bind to receptors on cell surface triggering invagination of membrane producing a vesicle inside the cell
Exocytosis: Constitutive vs Regulated Secretion
Constitutive (always going on, eg antibody secretion)
Regulated (synaptic transfer)
Where and under what conditions does glycolysis take place?
Cytosol under anaerobic conditions (with or without O2)
3 precursors produced in glycolysis
G-6-P (used to produce nucleotides)
Pyruvate (substrate for fatty acid synthesis)
Glycerol-3-P (backbone of triglycerides)
Glycolysis summary equation
Glucose + 2NAD+ + 2Pi + 2ADP -> 2Pyruvate + 2NADH + 2H+ + 2ATP + 2H2O
Phosphofructokinase (PFK1) allosteric regulation
Converts F-6-P into F-1,6-BP)
Inhibited by: ATP, citrate
Activated by: AMP (when ATP is used up, ADP accumulates and is converted to AMP) (2ADP -> ATP + AMP catalysed by adenylate kinase). Also activated by F-2,6-BP
Fate of pyruvate in anaerobic conditions (reversible reaction)
Pyruvate -> Lactate
Catalysed by lactate dehydrogenase (and NADH and H+ to regen NAD+ for glycolysis)
Fate of pyruvate in aerobic conditions (irreversible reaction)
Enters mitochondria and converted to Acetyl CoA and CO2 by pyruvate dehydrogenase (process inactivated by high concs of Acetyl CoA and NADH)
Where does Kreb’s cycle occur? Under what conditions?
Mitochondrial matrix
Aerobic conditions
Kreb’s cycle overall reaction
Acteyl-CoA + 3NAD+ + FAD + GDP + Pi + 2H2O -> 2CO2 + 3NADH + FADH2 + GTP + 3H+ + CoA
Mnemonic for remembering kreb’s cycle intermediates
Citrate
Is - Isocitrate
Kreb’s - a-ketoglutarate
Starting - Succinyl-CoA
Substrate - Succinate
For -Fumarate
Making - Malate
Oxaloacetate
Net energy gain of Kreb’s cycle per glucose molecule (2 pyruvate per glucose)
6 NADH
2 FADH2
2 GTP
Summarise Oxidative Phosphorylation
NADH and FADH2 oxidised giving off H+ and e
Electrons transferred to electron acceptor and passed along chain of electron carriers releasing free energy which fuels them to pump electrons into the intermembrane space
Creates electrochemical gradient so protons flow through ATP synthase providing energy to produce ATP
Final electron acceptor in oxidative phosphorylation
Oxygen
0.5O2 + 2H+ + 2e- -> H2O
Fatty acid structure
Carboxylic head with aliphatic tail (saturated or unsaturated)
Derivatives of triglycerides and phospholipids
Bile salts role
Emulsify lipids forming mixed micelles so fats are soluble in the gut
Intestinal lipase can then break down triglycerides into free fatty acids
What transports triglycerides around the body?
Triglycerides incorporated with cholesterol and apoproteins into chylomicrons which transport triglycerides around the body
Role of lipoprotein lipase?
Recognises the apoprotein present in a chylomicron triggering lipoprotein lipase to break down triglycerides again into free fatty acids to absorb them into tissues
Fatty acid activation (occurs in cytoplasm of cells)
Fatty acid -> Acyl Adenylate (requires a molecule of ATP)
Acyl Adenylate -> Acyl-CoA (acyl-CoA synthetase required
Acyl-CoA is then transported through mitochondrial membrane for fatty acid oxidation
How does Acyl-CoA get from the cytoplasm through the mitochondrial membrane?
Acyl-CoA <12 carbons (can diffuse straight through membrane)
Acyl-CoA >14 carbons (taken through mitochondrial membrane using the carnitine shuttle) (active process)
Start and end point of fatty acid oxidation
Starts with Acyl-CoA
Ends with an Acetyl-CoA (which enter TCA) and an Acyl-CoA with 2 less carbons (each thiolysis stage chops off 2 carbons)
4 stages of fatty acid oxidation
Oxidation
Hydration
Oxidation
Thiolysis
How is Acetyl-CoA used?
Most is used in TCA cycle
Small amount converted to ketones (when large amounts of acetyl-CoA are produced exceeding TCA cycle capacity) (ketones produced in liver)
Ketogenesis example pathway
2 Acetyl-CoA -> Acetoacetyl-CoA -> HMG-CoA -> Acetoacetate -> Acetone (spontaneously) or B-Hydroxybutyrate (requires enzymes)
How are ketone bodies utilised by extrahepatic tissues?
Conversion of beta-hydroybutyrate and acetoacetate to acetoacetyl-CoA using enzyme succinyl-CoA transferase
Where in the body is succinyl-CoA transferase not found?
Only hepatic tissues (as that’s where ketones are made)
Factors affecting rate of ketogenesis
ATP demand high = acetyl-CoA oxidised by TCA cycle
Greater release of free fatty acids from adipose tissue (from low carbohydrate levels)
High glycerol-3-phosphate conc in liver = greater triglyceride production (less free fatty acids)
Insulin downregulates ketone production (suggests high glucose levels), glucagon upregulates
Phospholipid structure
2 fatty acid tails attached to glycerol attached to a phosphate group attached to either
Serine (phosphatidyl-serine)
Choline (phosphatidyl-choline)
Inositol (phosphatidyl-inositol)
Membrane is permeable to…
Water, gases, small uncharged polar molecules (urea)
Membrane is impermeable to…
Ions, Charged polar molecules, Large uncharged polar molecules
Desmosomes
Join the intermediate filaments in 1 cell to another (make sure contents of a hollow organ either enter cells or stay in the lumen)
Gap Junctions
Allow passage of small water soluble ions and molecules
Hemi-desmosomes
Anchor intermediate filaments in a cell to the basal lamina
Tight junctions
Seals neighbouring cells together to prevent leakage
Nuclear Steroid Receptors
Sit inactive in cytosol
Specific hormone (e.g-oestrogen) binds to receptor resulting in structures change to the NSR so it can enter the nucleus
Then binds to certain sequence of DNA to modulate gene expression
Membrane-bound Steroid Receptors speed of action
Quicker than NSRs in altering gene expression
Growth factor receptors
Stimulate cell growth when a growth hormone binds to them
G-Protein Coupled Receptors made up of…
The receptor (primary specificity))
3 G-proteins (alpha, beta, gamma) (peripheral so can move around freely and provide further specificity)
Adenylyl Cyclase (converts ATP -> cAMP which is a second messenger)
Phosphodiesterase (enzyme converting cAMP -> AMP once cAMP function has been carried out)
Different G alpha subunit’s determine secondary messenger in GPCRs
Can promote (turn on) cAMP pathway
Can turn off cAMP pathway when alpha i (inhibitory) is activated
Gaq makes a different secondary messenger (IP3 and DAG)
pH effect on Ca2+ conc in serum
Acidosis - Less Ca2+ bound to plasma proteins (H+ ions buffered by albumin)
Alkalosis - More Ca2+ bound to plasma proteins (fewer H+ ions on protein)
These 2 change the ratio of Ca2+:Ca in blood (this can effect membrane permeability to Na+ in excitable tissues)
Heat exhaustion temp
Heat stroke temp
37<x<40 (can still sweat)
x>40 (no longer sweat)
How do steroids pass over membrane?
Hydrophobic and fat soluble
How do enzymes increase RoR?
Stabilise intermediates
2 DNA functions
Transcription / Protein Synthesis
Genetic material (for heredity)
How to determine protein structure?
Crystallise protein
Pass a slice through x-ray diffraction which will reflect off electrons giving you an idea of the structure
What connects the phosphate group of 1 nucleotide to the pentose sugar of another?
A phosphodiester (covalent) bond
How many H bonds between:
C and G?
A and T?
3
2
How do proteins alter DNA gene expression?
Slide in major and minor grooves of the helix
DNA wraps around histone protein forming a…
Which as a chain wrap up to form a…
Nucleosome
Solenoid
Condensed form of chromatin called…
More open form called?
Heterochromatin (darker bands when photographed)
Euchromatin (lighter bands)
Proto-oncogene vs oncogene
Proto-oncogene controls normal cell growth (if mutated can become an oncogene resulting in uncontrolled cell growth)
DNA Polymerase path of action
How fast does it act?
Prints 5’ -> 3’
700-1000 bp per second
DNA Polymerase error proofing function
Editing Function
Deletes incorrect insertion of base and will excise and repeat
PCR
-Design 2 primers which will anneal to DNA at right place (1 on each strand)
-Heat up mixture to 96degreesC so DNA separates
-Cool it and primer anneals to sequence
-Add polymerase + nucleotides to extend from each primer to make a copy of the DNA sequence (Then repeat process)
How has the issue of enzymes dying in PCR been overcome?
Use thermostable enzymes
DNA Repair
Proteins detect changes/mismatches in DNA causing enzymes to excise the damaged section of DNA
p53 gene
Tumour Suppressor Gene
Detects DNA damage and stops cell replication
If cell isn’t repaired, p53 commands it to apoptose
The genetic code is…(3)
Degenerate but unambiguous (each codon codes only 1 aa)
Almost universal
Non-overlapping
Transcription factors
Protein factors which control if a gene is turned on
TATA-Binding-Protein (TBP)
Recognises the common TATA base sequence in DNA and binds in the minor groove bending the strand 80degrees (imposed strain lowers required energy for separation)
4 pathways of dietary components
-Biosynthetic Pathways (forming proteins etc.)
-Fuel storage
-Fuel oxidative pathways (respiration)
-Detoxification and waste disposal pathways
Cofactors
Often vitamins which help enzymes catalyse reactions
Breakdown of lactate in the liver
Lactate -> Pyruvate -> Glucose (Gluconeogenesis example)
How much protein do you need a day?
0.8g/kg/day
Stores of:
Fat
Carbohydrates
Proteins
Adipose Tissue (as triglycerides) (only 15% water as fat is hydrophobic)
As glycogen in liver and muscle cells
Muscles (cells 80% water as proteins are hydrophilic)
How much energy released per gram?
Carbohydrate
Protein
Alcohol
Lipid
4kcal/g
4kcal/g
7kcal/g
9kcal/g
Basal Metabolic Rate (BMR)
Energy needed to stay alive at rest (non-exercise body functions like respiration, contraction of heart muscle)
Factors decreasing BMR
Older age
Female gender
Dieting/starvation
Hypothyroidism
Decreased muscle mass
Factors increasing BMR
Higher BMI
Hyperthyroidism
Fever
Define Malnutrition
Deficiency, excess or imbalance of energy, protein or other nutrients, causing measurable adverse effects
Vitamin C
Fruit and Veg
Collagen synthesis
Improves iron absorption
Antioxidant
Vitamin B12
Eggs, meat, milk
Protein and DNA synthesis
Energy production
Folate (Folic acid)
Produce and maintain DNA
Helps make RBCs and prevent anaemia
Vitamin D
Increases amount of Ca and P your body absorbs
Deposits Ca and P in bones and teeth (makes them stronger)
Oocyte is…
Sperm is…
Female Germ Cell
Male Germ Cell
Zygote is…
Cell resulting from union of sperm and oocyte at fertilisation
Blastomeres are…
Early embryonic cells
Morula
Solid mass of 12-32 blastomeres
Blastocyst
Stage where morula has entered uterine cavity and blastocystic cavity develops from within
Gastrula
Stage after trilaminar embryonic disc formation
Neurula
Stage after where neural tube opens
Embryo
Developing human during embryonic stage (to end of 8th week)
Fetus
Period from week 9 to birth
Autocrine vs Paracrine vs Endocrine secretion
Autocrine - Cells talking to themselves
Paracrine - Cells talking to neighbouring cells (signal diffuses across gap between cells)
Endocrine - Cells talking to other cells elsewhere in the body
Steroid hormones
All made from cholesterol
Different enzymes modify cholesterol to make different hormones
Can’t dissolve in water (so binds to protein in blood), can in lipids
Water composition of body
Total body water is 60% of body weight (42L)
Intracellular is 40% of body weight (28L)
Extracellular is 20% of body weight (14L) (11 interstitial, 3 plasma)
Predominant cation in ECF and ICF
ECF - Sodium
ICF - Potassium
Plasma Osmolality
Conc of solution expressed as mmol/kg (normal is 275-295mmol/kg)
3 responses to increased ECF osmolality from dehydration
1) Movement of water from ICF to ECF
2) Stimulation of thirst centre in hypothalamus making you want to drink
3) ADH release from posterior pituitary resulting in renal water retention
Body response to change in ECF volume (Renin-angiotensin-aldosterone system)
1) Decrease in renal perfusion acts on the juxtaglomerular apparatus and causes release of renin form the kidney
2) Renin then acts on angiotensinogen (released from liver) converting it to angiotensin I
3) Angiotensin I converted to angiotensin II by ACE (released from pulmonary and renal endothelium)
4a) Adrenal gland detects angiotensin II and secretes aldosterone which acts on distal kidney tubules to increase water retention (reabsorbing Na+ and Cl- whilst excreting K+)
4b) Angiotensin II also stimulates ADH release from pituitary glands
4c) Angiotensin II also causes arterial vasoconstriction
5) These all increase perfusion of juxtaglomerular apparatus switching the system off
Oncotic pressure
Pressure caused by difference in protein concentration between plasma and interstitial fluid
Water moves interstitial fluid -> plasma
Normal sodium concentration in blood
135-145mmol/L
When does implantation occur?
Day 21 of menstrual cycle
7 days after fertilisation
Upon implantation, how does the zygote gain fuel for growth?
Endometrial cells provide metabolic fuel for growth
Maternal recognition of embryo
By secretion of IL-2 prevents rejection
What attaches embryo to endometrium?
Integrins
What is the decidual reaction?
Differentiation of endometrial stromal cells adjacent to the blastocyst
Differentiation in pregnancy
Splitting of the trophoblast into 2 cell layers (synctiotrophoblast and cytotrophoblast)
Invasion in implantation
Synctiotrophoblast erodes blood vessels by using enzymes to digest basal lamina
