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MTM Flashcards

1
Q

What is the name for an egg and what are the layers surrounding it?

A

Oocyte
Surrounded by zona pellucida
Coruna radiata is cell layer surrounding this

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2
Q

What is a 16 cell zygote called?

A

Morula

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3
Q

What does a morula divide into?

A

A blastocyst (collection of 32 or more cells)

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4
Q

What happens at approximately day 7 after fertilisation?

A

The blastocyst sheds the zona pellicida and implants in the uterine wall.

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5
Q

What are the two cell types in a blastocyst?

A

Embryoblast (inner cell mass)

Trophoblast (outer cell mass)

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6
Q

After implantation into the endometrial wall what does the trophoblast differentiate into?

A

Cytotrophoblast (outside of the endometrium)

Syncytiotrophoblast (invading into the endometrium)

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7
Q

What happens when the blastocyte becomes fully implanted in the endometrial wall?

A

The cytotrophoblast becomes entirely surrounded by the syncytiotrophoblast

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8
Q

How does the bi-laminar disc form?

A 
The embryoblast (inner cell mass) divides into the epiblast (amniotic cavity) and the hypoblast (yolk sac)
where these two meet is the bilaminar disc
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9
Q

What are the first landmark features to form on the bilaminar disc?

A

The primitive node and the primitive streak

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10
Q

How does the trilaminar disc form from the bilaminar disc?

A

The ectoderm or epiblast layer migrates towards the primitive streak invaginating downwards and folding back on itself to form the mesoderm layer beneath. (day 16)

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11
Q

What does the ectoderm eventually form?

A

The skin and nervous system

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12
Q

What does the mesoderm eventually form?

A

Muscular skeletal, cardiovascular and urogenital

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13
Q

What does the endoderm eventually form?

A

GI tract, lungs, pancreas and some of the liver

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14
Q

What are the only two spots where the mesoderm does not seperate the ectoderm and endoderm?

A

buccopharyngeal (future mouth) and cloacal membranes (forms anus)

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15
Q

What is the extraembryonic mesoderm and how does it form?

A

mesoderm layer surrounding the inside of the cytotrophoblast layer

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16
Q

What is the intraembryonic mesoderm?

A

mesoderm layer surrounding the trilaminar disc

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17
Q

How does the neural tube form?

A

The ectoderm layer invaginates towards the notochord of the mesoderm
The two edges of the ectoderm fuse to leave a neural tube and a neural crest
Similar to how an oxbow lake forms

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18
Q

What are the three types of mesoderm that make up the intraembryonic mesoderm?

A

Lateral plate mesoderm: surrounds the ecto and endoderms
Intermediate mesoderm: lateral on either side of neural tube
Paraxial mesoderm: medial on either side of the neural tube, eventually forms vertebrae

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19
Q

How does the embro fold to form a recognisable cross section?

A

Ectoderm folds into a circle around other parts with its two layers of mesoderm, this creates the skin and amniotic cavity
Endoderm remains as a circle to form the respiratory and digestive systems
The tube of endoderm that formed the neural tube forms the CNS
Mesoderm forms urogenital and cardiovascular systems

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20
Q

What is the name for overproduction of aldosterone and what does it cause?

A

Conn’s syndrome

Causes high blood pressure and low renin levels

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21
Q

What is the main function of the cell cycle?

A

To regulate cell division in order to control growth

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22
Q

What are the types of chromosomal anomaly?

A

Numerical:
-Aneuploidy : Monosomy, trisomy (3 copies of a particular chromosome)
-Polyploidy: Triploidy (3 copies of every chromosome)
Structural:
-Translocations (reciprocal or robertsonian (centric fusion))
-Deletions
-Duplications
-Inversions
Different cell lines
-Mosaicism

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23
Q

What are the three forms of downs syndrome?

A

Trisomy 21
translocation
mosaicism

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24
Q

What happens during meiosis?

A

During interphase the chromosomes replicate in order to form two chromatids joined at the centromere for each chromosome
Before meiosis I the homologous pairs line up next to each other and crossing over (recombination) occurs
During meiosis I the homologous pairs are seperated resulting in two haploid daughter cells with chromosomes made of two chromatids joined at the centromere
During meiosis II the chromosomes are seperated at the centromere resulting in in more haploid daughter cells from the individual chromatids

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25
Q

What happens during mitosis?

A

During interphase the chromosomes replicate forming two chromatids joined at the cetromere
During mitosis these chromatids are seperated resulting in two identical daughter cells

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26
Q

What is recombination (crossing over)

A

When homologous pairs of chromosomes line up for separation in Meiosis I crossing over of chromatids occurs
This causes them to break off and exchange bits of the chromatids
This, along with the independent segregation in meiosis I, leads to variation

27
Q

What is the difference between recombination and a reciprocal translocation?

A

Recombination occurs between homologous chromosomes that are paired whereas reciprocal translocations occur between unpaired non-homologous chromosomes (chromosomes 4 and 20)

28
Q

What is a robertsonian translocation?

A

Breaking of chromosomes at or near the centromere causing fusion of the long arms and loss of the short arms
Only occurs in acrocentric chromosomes (have p and q arm)
This includes chromosomes 13,14,15,21,22

29
Q

Down’s syndrome can occasionally happen through robertsonian translocation, how does this happen?

A

Translocation between the chromosomes 14 and 21
A q arm of the 21 swaps with the p arm of chromosome 14
This results in both chromosome 21 and another q arm of 21 being present after Meiosis due to chromosome 14 carrying a chromosome 21 p arm aswell
This means that these two chromosome 21s will combine with the other parents chromosome 21 to form trisomy 21

30
Q

What is a reciprocal translocation and how does it occur?

A

Breakage of parts of two non-homologous chromosomes that result in the exchange of fragments
This can occur in meiosis when non-homologous pairs line up side by side

31
Q

What are the possible outcomes of a reciprocal translocation?

A

Balanced carrier- there is a direct exchange between the two chromosomes causing the same amount of genetic information to still be present
Partial trisomy + partial monosomy- when the exchange is not balanced e.g. one homologous pair is still complete whereas another has part of that homologous pair translocated onto it
This results in a partial trisomy because of the intact homologous pair+the little bit then a partial monosomy due to the other homologous pair-the little bit that is missing

32
Q

What do unbalanced translocations tend to cause?

A

miscarriage, still birth, infertility, intellectual impairment

33
Q

How do chromosome deletions/duplications occur?

A

Due to unequal crossing over at meiosis

34
Q

What is a chromosomal inversion?

A

When there are two breaks in the same chromosome causing that part to invert and reattach

35
Q

What is mosaicism?

A

two populations of cells with different genetic constituents

36
Q

What are the two types of mosaicism and how do they arise?

A

Somatic mosaicism- the result of non-disjunction in cell division
Gonadal mosaicism-the result of a chromosomal anomoly e.g. translocation occurring in meiosis hence it only affects gonadal cells

37
Q

Give an example of an autosomal dominant condition?

A

ostosclerosis (leads to deafness)

38
Q

What is penetrance?

A

Refers to patients with a genetic condition showing clinical signs

39
Q

What is anticipation in terms of genetics?

A

disease occurs more frequently and with increasing severity as it passes from generation to generation
e.g. huntington’s- progressive cell death in the brain

40
Q

What is a common cause of autosomal dominant disorders?

A

Gonadal mosaicism causing mutations

41
Q

What is cystic fibrosis?

A

Mutation of the CFTR (cystic fibrosis transmembrane conductance regulator) protein
This affects chlorine membrane transport
This causes many problems such as frequent lung infections due to thick mucus and poor absorption from the gut

42
Q

Give two examples of diseases with heterozygous advantage?

A

Sickle cell anaemia- resistance to malaria

Cystic fibrosis- resistance to typhoid

43
Q

What are the methods for prenatal diagnosis of genetic diseases?

A 
Source of foetal tissue can include:
-Chorionic villus samples
-Amniocentesis
-Study foetal cells in maternal blood
Direct mutation analysis is the best
Amplify (using PCR) surrounding the mutation
Look for matching bases
44
Q

What is a barr body?

A

An inactive X chromosome present in female somatic cells

Also a Barr body in Klinefelters syndrome

45
Q

What is DMD due to?

A

X linked recessive disorder due to deletions or point mutations in the gene that codes for the dystrophin protein

46
Q

What are the 3 phases of x inactivation?

A
  • initiation- occurs from the X inactivation centre
  • spreading- compacting and inactivating X chromosome occurs by a gene called Xist
  • maintenance- remains as a barr body and divides with other chromosomes
47
Q

How does the pedigree of x-linked dominant appear?

A

Similar to autosomal dominant but excess of affected females

48
Q

Give some examples of multifactorial conditions?

A

Diabetes mellitus
hypertension
coronary artery disease
spina bifida

49
Q

What are the regions of the primitive brain?

A

1st vesicle forms the forebrain which swells to form the two cerebral hemispheres
A further division also forms the diencephalon from which the eyes protrude
2nd vesicle forms the aqueduct of sylvius which allows fluid to drain from the forebrain
Causes hydrocephalus if blocked
3rd vesicle is the hindbrain
This forms the cerebellum and the medulla oblongata

50
Q

How do you diagnose neural tube defects prenataly?

A

increase levels of a-fetoprotein as leaks from neural tube

51
Q

What are pre-paraxial somites?

A

condensation of the mesoderm on either side of the midline
differentiate into two cell types
form vertebrae and muscle blocks (forms dermatomes)

52
Q

What does the lateral plate of the mesoderm develop into?

A

outer lateral plate: forms the muscular body wall

inner lateral plate: forms around gut tube to allow peristalsis

53
Q

What do mesonephrons in an embryo form?

A

The kidneys

54
Q

What are the different types of spina bifida?

A

occulta- bony projections don’t close however skin and meninges still present so no major problems
Meningocele (cystica): When arch hasn’t formed properly, meninges may herniate out, forms blister full of fluid on surface. Damage allows for infection
Myelocoele (compound): Bony canal remains open, the neural tube is lifted out and fails to close. That area of the body doesn’t develop properly as there are no spinal nerves etc… More frequent in the lumbar region

55
Q

What is digeorge syndrome and what are its distinguishing features?

A 
CATCH22
Deletion from chromosome 22
Cardiac problems
Abnormal facies
Thymus
Cleft palate
Hypocalcaemia
56
Q

In which direction is DNA read and synthesised?

A

5’ to 3’

57
Q

What are the types of RNA polymerase?

A

RNA pol I: RNA ribosomes, gene translation
RNA pol II: mRNA formation
RNA pol III: tRNA formation

58
Q

How does the placenta form?

A

The extraembryonic mesoderm layers converge up to the connecting stalk
They send projections into the primary villi (formed by the cytrophoblast penetrating the syncytium)
These form secondary villi
They provide large surface area for the exchange of metabolites
A thin membrane separates the embryo’s blood from the mother’s blood (This surrounds the villi)

59
Q

What are the functions of the placenta?

A
  1. Takes over steroid production from corpus luteum after 8 weeks of pregnancy
  2. Exchange of various molecules (CO2, O2 etc.)
  3. Immunological function (allows transfer of passive immunity from mother to child
  4. Production of protein hormones (e.g. human chorionic godadoctropin)
60
Q

What is embryonic induction?

A

Signals from the notochord to the neural plate as to where the spinal cord should be laid down

61
Q

What does the intermediate mesoderm form?

A

The urogenital system

62
Q

What does the lateral mesoderm form?

A

muscular front body wall

63
Q

What do inner leaflets of mesoderm form?

A

Muscular walls around the gut tube for peristalsis

charlies medicine (9 decks)

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