Cell biology theme 3 Flashcards
(234 cards)
1
Q
What is the most basic function of the cell cycle ?
A
duplicate DNA
separate into genetically identical cells
2
Q
Besides DNA what else duplicates ?
A
macromolecules
organelles
doubles in size
3
Q
what are the 4 phases of the cell cycle
A
M phase (mitosis and cytokinesis)
G1 phase
S phase these make up interphase
G2 phase
4
Q
What happens in the S phase ?
A
DNA replication
5
Q
What happens in G1 and G2 ?
A
the cell continues to grow and monitors the external and internal environment
6
Q
Why do cells need to monitor the external/internal environment ?
A
ensures the conditions are suitable for reproduction and preparations are complete before the cell commits to S phase and M phase
7
Q
What are the 2 mechanical process that take place in the M phase ?
A
separation of the duplicated chromosomes
division of the cytoplasm
8
Q
Which assemblies carry out the nuclear and cytoplasmic divisions ?
A
nuclear division is carried out by the mitotic spindle
cytoplasmic division is carried out by the contractile ring
9
Q
What is the mitotic spindle made of ?
A
microtubules and motor proteins
it arises from centrosomes
10
Q
What is the contractile ring made of ?
A
Actin and myosin microfilaments
arranged in a ring at the equator
11
Q
What happens during prophase ?
A
chromosomes condense and the mitotic spindle assembles
12
Q
What happens in prometaphase ?
A
nuclear envelope breaks down and spindle attaches to chromosomes
13
Q
What happens in metaphase ?
A
chromosomes align at the equator of the spindle
14
Q
What happens in anaphase ?
A
paired chromatids separate to form daughter chromosomes , migration to opposite poles
15
Q
What happens in telophase ?
A
the nuclear envelope re-assembles and the contractile ring assembles
16
Q
What happens in cytokinesis ?
A
the completed nuclear envelope now surrounds the chromosomes
the contractile ring pinches to create 2 daughter cells and cells enter G1.
17
Q
What are kinetochores ?
A
microtubules from the spindle grab hold of chromosomes at the kinetochore , kinetochores are protein complexes that form at the centromere of each chromosome.
18
Q
How do kinetochores recognise the centromeres ?
A
there is a special DNA sequence at the centromeres , if this is altered the kinetochores fail to assemble and chromosomes dont segregate
19
Q
What are the 3 phases of interphase ?
A
G1
S
G2
20
Q
What happens during interphase ?
A
allows cell to duplicate contents
monitor the external and internal environment befre committing to S phase
21
Q
Why do eukaryotic cells need a cell cycle control system ?
A
this guarantees the events of the cell cycle occur in the correct sequence
22
Q
How is progression through stages of the cell cycle monitored ?
A
regulation at cell cycle checkpoints
receive feedback on processes
23
Q
What are the cell cycle checkpoints ?
A
G1 to S
G2 to M
M to G
24
Q
What is checked at the progression from G1 to S ?
A
the environment is favourable for DNA replication
25
What do cells require to avoid delayed progress through G1 ?
nutrients are signals from the extracellular environment
26
What is checked at the progression from G2 to M phase ?
the DNA is undamaged and fully replicated
27
What is ensured during mitosis ?
chromosomes are fully attached to the spindle
28
What do cells need to receive to grow ?
signals (esp during G1)
29
What is the G0 phase ?
a phase where cells arent dividing/preparing to divide because there is a lack of nutrients and growth factors
30
Which cells are stuck in G0 ?
Neurones and red blood cells - they have reached their mature state and dont need to divide again
31
What are mitogens ?
signals that stimulate cell division - cells only divide when they receive mitogens
32
What are growth factors ?
stimulate cell growth when the cells are not dividing
33
What are survival factors ?
they inhibit apoptosis and therefore promote cell survival
34
disruption in cell signaling pathways can lead to what ?
cancer
35
How is the cell cycle controlled ?
activating and deactivating proteins that initiate DNA replication , mitosis and cytokinesis
36
What controls the activity of these cell cycle initiator proteins
kinases - the activity of kinases follows a cyclic pattern as they are only activated when approproate
37
what do kinases depend on ?
cyclin
38
What does cyclin do ?
forms a complex with kinases - cyclic changes in the amount of cyclin drive the assembly and activation of these complexes - they trigger various cell cycle events
39
different CDK complexes ...
trigger different cell cycle events ?
40
How are mitogens and CDKs linked ?
mitogens promote cell division by stimulating the accumulation of cyclin
41
how are CDKs switched off ?
by destroying cyclin - this happens via an anaphase promoting complex which tags the cyclin with ubiquitin - the CDK is inactivated.
42
What is apoptosis ?
the elimination of unwanted cells by programmed cell death - it is a regulated and normal event
43
How is the number of cells in a community controlled ?
by controlling the rate of cell division
44
What is necrosis ?
accidental cell death - die to disease , injury or failiure to supply adequate blood
45
How does necrosis occur ?
cells swell and undergo lysis
the contents is released into tissues
this triggers the inflammatory response which leads to damage.
it is unprogrammed and unregulated
46
How does apoptosis occur ?
the activation of an inbuilt suicide pathway
cells develop irregular blebs - the cell shrinks and condenses
the cytoskeleton collapses
the nuclear envelope disassembles
47
why is apoptosis described as clean death ?
the alteration in the cell surface atracts phagocytic cells
| they engulf the apoptotic cell before it spills its contents
48
Which molecules are responsible for apoptosis ?
a family of proteases - called caspases
49
`What are the inactive form of caspases called and why are they activated ?
procaspases
| they are activated in response to signals that induce apoptosis
50
How can apoptosis be triggerred by caspases ?
apoptosis is triggered by a protease cascade where initiator caspases cleave and activate downstream caspases - this amplifies and broadcasts the response.
51
Is the caspase cascade reversible or not ?
no- it is irreversible the decision to die is highly regulated
52
How can you activate a caspase ?
remove a peptide from the procaspase
53
What is the function of activated caspases ?
cleave other caspases in a cascade - activate them
cleave nuclear lamins - structural proteins in the nucleus - nuclear fragmentation
Activate DNase which turns DNA into fragments
cleave the cytoskeleton loosing contact with the ECM
54
in an apoptotic cell how will the DNA fragments appear ?
as a ladder as the DNA is now in fragments
55
Why is apoptosis needed in development ?
to remove tissue and to model organs into the correct shape. to allow the formation of complex tissues
56
Why else is apoptosis needed ?
to control cell numbers (eg. removal of autoreactive T cells)
removal of infected cells (eg. cytotoxic T cells can kill virally infected cells)
Removal of stressed or damaged cells (DNA)
57
What signal types can induce apoptosis ?
hormonal signals
cytokines
direct signals from a contracting cell
58
How does the death receptor Fas work ?
a cytokine signal from the TNF family causes a death receptor be expressed
this is activated by binding of a ligand
triggers the death inducing complex- caspase cascade
59
Which signals suppress apoptosis ?
survival factors
mitogens
growth factors
60
How can survival factors control the number of nerve cells ?
survival factors are secreted by target cells
they are picked up by nerve cells
survival factors suppress the suicide program
there is an over production of nerve cells so some cells wont receive the survival factor - apoptosis of these cells occurs
this ensures that the number of nerve cells matches the number of target cells
61
How do mitogens suppress apoptosis ?
they bind to receptors that trigger intracellular pathways that release molecular brakes blocking transition from G1 to S.
62
how do growth factors suppress apoptosis ?
they activate intracellular pathways that lead to an accumulation of certain proteins required for the cell to grow.
63
What are integrins and how do they promote cell survival?
fibronectin , a glycoprotein attaches to collagen (at the membrane of fibroblasts) via integrin which is attached to actin in the cell cortex
this inhibits apoptosis as there is a contact with the ECM
64
which molecules regulate activation of caspases ?
members of the Bcl2 family - some promote caspase activation others inactivate caspases leading to apoptosis being inhibited
65
What determines whether a cell dies or survives ?
the balance of activities of different members of the Bcl2 family
66
How can mitochondrial injury lead to apoptosis ?
damaged mitochondria leak cytochrome C (from between the inner and outer membrane) into the cytosol
Cytochrome C activates caspases - this is the action of BAX and BAD proteins (members of Bcl2)
this leads to a caspase cascade
some Bcl2 members can also inhibit apoptosis
67
damaged DNA leads to what being activated ?
p53- a protein
68
what does activation of p53 do ?
it inhibits CDKs
69
Excessive damage to DNA causes what ?
a large amount of p53 being activated
this overcomes a threshold
overcoming the threshold means apoptosis is activated as Bcl2 members are activated.
70
What are diploid cells ?
they have 2 versions of each chromosome
one from each parent
only the sex chromosomes differ
71
Where does meiosis only occur ?
in the ovaries and the testes
72
What is the process of meiosis ?
DNA replication
duplicated chromosomes attach to the corresponding homolog
2 sets of cell division
diploid cells turn into haploid gametes
73
the assignment of each homolog to a haploid cell is ...
random - each gamete receives a mixture of maternal and paternal chromosomes creating diversity
74
what do the 2 separate cell divisions entail ?
the first division separates the chromosomes at anaphase
| the second division separates the sister chromatids at anaphase
75
What is recombination ?
the exchange of fragments of maternal and paternal homologous chromatids
76
when does recombination occur ?
during prophase of meiosis 1
77
How does recombination lead to genetic variation ?
produces individuals with novel assortments of alleles
| can provide an evolutionary advantage
78
Are chromosomal abnormalities acquired or inherited ?
they are acquired
79
What are most chromosomal abnormalities to do with?
structure and number - they produce abnormal embryos that are not viable
80
What is aneuploidy ?
the loss or gain of one or more chromosomes
81
What is an example of aneuploidy ?
trisomy 21 - where an individual has an additional chromosome 21 - 3 in total leading to Downs Syndrome
82
What is polyploidy ?
the addition of one or more complete haploid complements (46,69,92 etc)
83
What is an example of polyploidy ?
triploidy- where individuals have 3 sets of chromosomes (69) leads to spontaneous miscarriages.
84
What is chromosome non-disjunction ?
the failure of homologous chromosomes/sister chromatids to separate properly during cell division. leads to gametes with an unusual number of chromosomes
85
Why does non-disjunction usually occur ?
inappropriate spindle formation
86
What is translocation ?
a chromosomal abnormality caused by rearrangements of parts between non homologous chromosomes- they are usually identified by karyotype analysis.
87
What is the 9:22 translocation ?
exchange of genetic material between chromosomes 9 and 22 - this results in the formation of the philadelphia chromosome - a chromosome 22 derivative
88
What are structural abnormalities in chromosomes ?
includes chromosome breakage and reunion in a new configuration.
89
What are the p and q regions of the chromosome ?
refers to the parts of the chromosome separated by the centromere - the p is the short region and q is the long region.
90
what is the 15q12 chromosome partial deletion ?
the long (q) arm is deleted on one copy of the chromosome. it increases the risk of birth defects and developmental delay.
91
what is a karyotype ?
the full complement of chromosomes in the cells of an individual
92
how do we create a karyotype ?
the metaphase spread
all cells are given phtochemagglutinin which inhibits the formation of the spindle
cells are stuck in metaphase and are condensed
93
What do we use karyotypes for ?
observing number and shape
| cytogenetics
94
What is chromosome painting ?
stain chromosomes based on DNA sequences usin complementary probes
chromosomes have different banding patterns and size
95
What is NIPD ?
non-invasive prenatal diagnosis
| Analyses the DNA fragments present in maternal plasma for sex determination etc.
96
What are the 2 types of DNA sequences ?
Extragenic
| Genes
97
Genes can be classified as what ?
Unique
Gene families
Gene superfamilies
98
What are unique genes ?
Pseudogenes which appear as genes and are not expressed
99
How can extravehicular sequences be classified ?
Low copy
Moderately repetitive
Highly repetitive
100
What are tandem repeats ?
Satellite
Mini satellite
Micro satellite
101
What is satellite DNA ?
Large arrays of repaying non coding DNA
102
Genes code for what
Mainly proteins
Non coding RNA
Prions (misfolded proteins)
103
What are alleles ?
Alternative forms of a gene found at the same locus on homologous chromosomes
104
Mutations can be on what levels ?
Nucleotide levels
| Or the chromosome level (structure and number)
105
What are germline mutations ?
Occur in germ cells
| Responsible for inherited diseases
106
What are somatic mutations ?
Occur in adult life or development
Affect a limited number of cells
They can accumulate in cells with age leading to cancer
107
What is a loss of function mutation ?
Reduced activity
Loss of gene product
Occurs with null alleles and gene deletion
108
What is a hypomorphic mutation ?
The altered gene product expresses as lower level of activity
109
What is haploinsufficiency ?
A LOF mutation occurs in a heterozygous individual - the remaining functional copy was nit adequate to produce the function needed
110
What is a gain of function mutation ?
The gene product acquires a new function and increased activity
111
What is dominant negative mutation ?
A LOF function mutation occurs die to the interference of the mutant gene product with normal gene product of corresponding allele
112
What usually causes chromosomal abnormalities ?
Chromosome non disjunction
113
What is aneuploidy ?
Loss or gain of one or more chromosomes
114
What is polyploidy ?
The gain of one or more complete sets of chromosomes (46,69)
115
What are de novo mutations
They are nit inherited
| Bc they result in embryonic lethality
116
What causes structural chromosomal abnormalities ?
Chromosome breakage and abnormal reunion
117
What is translocation ?
Transfer between non honologous chromosomes
| Robertsonian and reciprocal
118
What is a reciprocal translocation ?
2 fragments from 2 different chromosomes and swap places
119
What is a robertsonian translocation ?
Occurs in acrocentric chromosomes where chromosomes break ball near the top and long arms fuse to form a chromosome
120
What is inversion ?
Chromosome segments are reversed in position
Pericentric- involving the centromere
Paracentric- involving one chromosome arm
121
What is a nucleotide transition substitution ?
When a purine is exchanged for a purine , or a pyrimidine for a pyrimidine. (purines are C and T) (pyramidines are A and G)
122
What is a silent substitution ?
encodes for the same amino acid and has no effect on the protein
123
What is a missense substitution ?
encodes for a different amino acid so the protein structure is altered.
124
What is a nonsense mutation ?
introduce a stop codon which results in loss of gene expression
125
What is a splice site mutation ?
results in exon skipping or intron retention
126
What does it mean by a missense mutation being conservative or non-conservative ?
depends on the new properties of the new amino acid eg if it changes from acid to basic
127
What can multiples of three deletions lead to ?
in frame deletions
can delete amino acids
affects protein structure and stability
128
What can non multiples of three deletions lead to ?
frame shifts
premature termination
loss of gene expression
129
What causes structural changes in chromosomes ?
chromosome breakage and abnormal reunion
| unequal crossovers in homologous combination
130
What are ring chromosomes ?
a broken chromosome segment forms a ring
131
What is an isochromosome ?
when the arm of the chromosome is lost and the other arm is duplicated
132
What is a balanced change ?
no loss of DNA
| usually harmless
133
`what is an unbalanced change in DNA ?
loss of DNA
| can lead to severe disease and syndromes
134
What is a trinucleotide repeat expansion ?
where the repeat sequence becomes unstable as the gene ex
135
What is the effect of a trinucleotide repeat expansion on the huntington gene ?
it leads to qualitative changes in the gene product which leads to aggregation of the product in the CNS.
136
What can larger gene insertions lead to ?
partial gene duplications ?
137
How can mutations be caused by errors in DNA replication ?
proofreading mistakes of DNA polymerase
| proofreading usually prevents mispairing of bases however there can be mistakes
138
How can chemicals lead to DNA mutations ?
chemicals
products of metabolism
lead to the formation of DNA adducts
139
What is depurination ?
A chemical reaction where ethe base is released - a deletion
140
What is deamination ?
the removal of an amine group from cytosine - it froms uracil- hence a substitution
141
How can physucal damage be caused to DNA ?
ionising radiation causes the double hellux to break
142
What does UV light do ?
leads to the formation of thymine dimers which leads to errors in DNA replication and eventually nucletodie deleetion
143
What does mismatch repair do ?
it corrects mismatched bases introduced in DNA replication- cells defective in this have high mutation rates
144
What is nucleotide excision repair ?
removing the thymine dimers and DNA adducts
145
What is base excision repair ?
removes single abnormal bases
146
What is post replication repair ?
corrects double stranded breaks in homologous combination with a sister DNA molecule - ensures no loss of DNA
147
What is a multigene family ?
genes that have similar functions that have arisen through gene duplication - they can be physically close or dispersed in clusters
148
What are classic gene families ?
genes that show a high degree of sequence similarity
| eg.hox genes
149
What are gene superfamilies ?
genes that have limited sequence similarity but are functionally related
have similar structural domains
150
What are pseudogenes ?
they closely resemble genes
| not functionally expressed
151
How can an accumulation of somatic mutations lead to cancer ?
```
if a tumoure suppressor gene is lost
leads to excess cell prolifferation
activates an oncogene
more TSG are lost
metastasis
```
152
What are the consequences of beta globin mutations in cell anaemia ?
A-T transversion leads to an amino acid substitution
reduced solubility
intracellular precipitates
sickle celled erythrocytes
153
What are point mutations ?
changes that effect a single nucleotide pair
154
How can you determine the relative genetic and environmental influence on variation/disease ?
studying identical and fraternal twins
155
What is a mutation ?
The DNA variant has a frequency of less than 1% in the population
156
What is a polymorphism ?
occurs when the DNA variant has a frequency of more than 1% in the population and has at least 2 alleles
157
What is an SNP ?
a single nucleotide polymorphism
arise from replication errors by DNA polymerase
evenly distributed in genes and extrgenic sequences
158
what is a haplotype block ?
a group of specific alleles that are likely to be inherited together - due to homologous recombination
159
How are highly repetitive DNA sequences formed ?
derived from mobile DNA elements
| transposons and retrotransposons
160
What do transposons do ?
they move DNA pieces from one place to another using a cut and paste mechanism , movement is mediated by an enzyme
161
What do retrotransposons do ?
they work via an RNA intermediate
Reverse transcriptase makes cDNA
this is free to integrate in the genome
the cDNA can be a hybrid of viral and human DNA
162
What does retrotransposition mediate the generation of ?
generation of model exons
regulatory regions
exon shuffling
163
what is the genotype of an organism ?
the genetic constitution of an individual
164
How many autosomes do humans possess ?
44
165
A gene with 2 alleles has how many possible genotypes ?
3
166
What is the phenotype ?
the observed characteristics of an individual
167
What determines the phenotype ?
genotype
| environmental factors
168
What does penetrance mean ?
the proportion of individuals who carry a specific genotype and the associated phenotype
can be complete (100%) or incomplete
169
What is expressivity ?
quantitative or qualitative variations in the phenotype amongst individuals carrying a specific genotype
eg. mild , moderate and severe
170
What are monogenic disorders ?
they effect one gene
| they are rare
171
What is a dominant inheritance pattern ?
the effect of one allele masks the contribution of the other allele
172
What is a recessive inheritance pattern ?
for the phenotype to be expressed the individual mist hold 2 mutant alleles
173
What is an autosomal inheritance pattern ?
the diseased gene is present on an autosome
174
What is X-chromosome linked ?
the disease allele is present on the X chromosome
175
What is co-dominant ?
alleles that are equally dominant and contribute to the phenotype equally
176
What is X-linked dominant ?
the dominant gene is carried on the X chromosome
177
What is pseudoautosomal ?
regions that are homologous on X and Y chromosomes and are inherited as if they were autosomal
178
What are features of autosomal dominant inheritance ?
```
both sexes are equally affected
transmission of the disease from male to male
occurs in every generation
homozygotes usually die in utero
50% diseases risk
```
179
What are the features of autosomal recessive inheritance ?
both sexes are equally affected
does not occur in every generation
affected children likely to have carrier parents
25% disease risk , 50% carriers
180
What are the features of X-linked recessive ?
the diseases only effects males (males only have 1 X)
females are carriers
affected males have unaffected parents , not every male is effected
no male to male transmission
25% disease risk
181
Why do complex diseases not follow mendelian inheritance patterns ?
complex ateiology
many symptoms
high varaiation
182
What are additive effects of loci in polygenic traits ?
there is an equal contribution of the involved loci
183
What are non-additive effects of loci in polygenic traits ?
there is an unequal contribution of the involved loci
184
What does it mean if a disease is multifactorial ?
the diseases are influenced by the interaction of both genetic and environmental factors
185
several genes with additive effects form a what ?
a normal distrubution
186
What can be used to determine the risk of getting a disease in the general population and family relatives ?
a liability threshold model
the threshold for developing a disease combines all the environmental and genetic factors
the normal distribution shifts to the right for family members
187
what are the 3 stages of human development in the embryo ?
cleavage
embryonic period
foetal period
188
What happens during cleavage ?
cell proliferation
| cells respond to teratogens (birth defect inducing systems)
189
What happens in the embryonic period ?
morphogenesis
| 4-10 weeks craniofacial development
190
What happens during the foetal period
embryo develops into a foetus
| cell differentiation
191
What causes organ disorders ?
impairment of early embryonic processes such as cell differentiation and morphogenesis
192
How does impairment occur ?
genetic factors - mutations in developmental genes or chromosomal abnormalities
environmental factors
or a combination
193
What does it mean by if a craniofacial disorder is syndromic ?
the defects occur in combimnation woith other anomalies
this is because the mutant gene has multiple functions during the development of different organisms
eg. EDA1 mutations in hypohidrotic ectodermal dysplasia
194
What does it mean by if a craniofacial disorder is non-syndromic ?
the defects aren't associated with other anomalies
| this is because the defective gene function might not be compensated by other genes
195
What are early defects (craniofacial disorders) ?
they affect developmental processes of tissues
| eg. cleft lip/palate is caused by abnormalities in genes that control facial development
196
What are late defects ?
they affect cell differentiation and are often to do with cell types that form specialised tissue
eg. amelogenesis imperfecta is caused by abnormalities with the ameloblasts that produce ename;l
197
What are the 3 different cell sheets that a zygote produces as it divides ?
mesoderm
ectoderm
endoderm
these are germline derivatives that fold into an organism and each sheet develops into structural components
198
What do genetic regulators do to cells ?
they instruct cells to express certain genes which determine the type of cell
199
What determines the type of genetic regulators a cells produces ?
cell signalling
200
Gene mutations in regulatory proteins in early stages of differentiation lead to ?
major abnormalities
201
Gene mutations in regulatory proteins in later stages of differentiation lead to ?
minor abnormalities
202
What regulates the expression of cell signaling molecules ?
combinations of transcription factors
203
what do signaling molecules do after being secreted ?
they bind to corresponding receptors
204
What happens after the signaling molecule binds to its corresponding receptor ?
the signals are induced and then transduced and integrated from many separate pathways leading to the activation of other transcription factors
eventually cell differentiation occurs
205
How many pharyngeal arches does the embryo have ?
3- first,second and third
206
What does the embryo consist of ?
3 pharyngeal arches
a heart
and somites
207
What are somites ?
compartments that the body is subdivided into that is responsible for the development of certain structures
208
What does each pharyngeal arch do ?
forms specific nerves , arteries , muscles and skeletal elements
209
which pharyngeal arch undergoes processes to form the mandible and the maxilla ?
the 1st arch
210
What do CNCs do ?
they migrate along specific pathways from the early brain forward into the arches
they form the majority of craniofacial features (face jaws and teeth)
the cell is programmed to its destination in the embryo
211
how are CNCs regulated ?
a code of HOX genes
| CNCs express a variety of HOX genes which determine the shape and structure of vertical bodies
212
mutations in which genes lead to craniofacial disorders ?
the head is not controlled by HOX genes but HOMEOBOX genes
| mutations in HOMEOBOX genes lead to craniofacial disorders
213
What are the stages of facial and palatal development ?
formation
growth that is forward
fusion of the correct tissues and the correct time and fucntion
214
What is a cleft lip and palate ?
different types with variable expressivity/severity
can be syndromic (treacher collins) or non syndromic
missing teeth associated (share a similar gene)
non syndromic through to have genetic disposition and tiggered environmentally
215
What are the characteristics of treacher collins syndrome ?
hypoplasia of the mandible and facial cheek bones
incomplete penetrance
AD inheritance
heterozygous mutation for genes in ribosome biogenesis means CNCs die by apoptosis before migrating into the craniofacial region.
not sever - happlosufficient
216
What is the hedgehog signaling molecule ?
important in controlling the facial midline
small amounts - cyclopia
abnornally high- facial duplications
217
What is craniosynostosis n?
premature fusion of the cranial sutures
skull is too small for the brain to grow
pressure - mental abnormalities
sagittal or coronal
218
How does the FGFR2 mutation lead to craniosynostosis ?
a receptor is cpded for
mutation means the receptor is constantly active
syndromic- other genetic influences - limb abnormalities
219
how do tooth related disorders arise ?
mutations in genes that code for genetic regulators that control tooth development
220
What are the stages of tooth development ?
initiation
morphogenesis
differentiation
221
Defects during initiation affect ?
tooth number and identity
222
defects during morphogenesis affect ?
tooth shape
223
defects during differentiation affect ?
structure of hard tissues
| enamel and dentine
224
what is hypodontia ?
less than 6 missing teeth (excluding the third molars)
225
What is oligodontia ?
6 or more missing permanent teeth (excluding the third molars )
226
What is anodontia ?
very rare - no teeth
227
missing teeth is syndromic or non syndromic ?
both
228
What is hyperdontia and how does it arise ?
super-numerary teeth
| duplication of the dental lamina by an over dosage of genes leads to a second row of teeth forming
229
What causes downs syndrome ?
trisomy 21
230
What dental abnormalities are associated with Downs syndrome ?
```
hypodontia
delayed eruption
dental tissue hypoplasia
periodntal tissue
malocclusion
```
231
What is amelogenesis imperfecta ?
AD/X-linked
mutations in the enzyme that regulate the ECM
hypoplasia - reduced enamel matrix formation
hypomineralisation - normal enamel but reduced mineral content
hypomaturation- normal enamel thickness but mottled and softer teeth
232
What is dentinogenesis imperfecta ?
defects in dentine formation (odontoblasts)
blue/grey or brown teeth
bulbous crowns and short rootd
enamel more likely to be chipped as denetine is shock absorber
mutations in DSPP ggenes
233
What is osteoporosis ?
short and fracture prone individuals
delayed tooth eruption and increased dental caries
failure to resorb bone leads to caries
234
What is Ehelra-Danlos Syndrome ?
connective tissue effected
elastic and fragile skin periodontitis
fragile oral mucosa - internal bleeding
small fragile teeth
