Cell Cycle and Development Flashcards
1
Q
What are the 2 main phases of the cell cycle?
A
1/ Interphase
2/ Mitotic phase
2
Q
What are the sub-phases of Interphase?
A
1) G1 phase
2) S (synthesis of DNA) phase
3) G2 phase
G is Growth of GAP phase
3
Q
What are the sub-phases of Mitotic phase?
A
Mitosis
Cytokenisis
4
Q
What happens in G1? (3)
A
- Cell is metabolically active
- Cell replicates all of its cellular organelles and components EXCEPT DNA AND NUCLEUS
- Replication of centrosomes begun
5
Q
What happens in S? (2)
A
- In nucleus, DNA strands separate at H bonds which held the nucleotides together
- New strand of DNA is synthesized opposite the old strands
6
Q
What happens in G2? (3)
A
- Cell makes sure DNA synthesis has been completed (correctly)
- Prepares fro Mitotic phase (synthesis of proteins and enzymes, gathering of reactants)
- Replication of centrosomes complete
7
Q
Why do you have replication of things (organelles) in the cell?
A
Because the cell has been divided into 2 and you only have half the number of things like organelles in each half of the cytoplasm. Cytoplasm grows in the G1 phase.
8
Q
What are the sub - phases of mitosis (as mitosis is a phase of the MITOTIC PHASE)?
A
Prophase Prometaphase Metaphase Anaphase Telophase
9
Q
What happens in Mitosis? Summary
A
It is a continuous process
1. the nuclear membrane is dismantled,
2. two copies of DNA are separated from each other
3. two nuclei are reformed each containing 1 copy of DNA
4 PHASES IN TOTAL
10
Q
What happens in Prophase? (2)
A
- Chromatin condenses into chromosomes, 2 copies held at centromere
- Mitotic spindles start to form (extension of microtubules from centromere)
11
Q
What happens in Prometaphase? (3)
A
- Nuceloulus disappears and nuclear envelope breaks down
- Spindle fibres attach to sister chrmotid at kinetochores located at centomeres
- Kinetochore microtubles now start moving chromosomes toward middle of cell
12
Q
What happens in metaphase?
A
- Microtubles of mitotic spindle align centromeres at centre of mitotic spindle (metaphase plate)
13
Q
What happens in anaphase?
A
Centromeres split so one copy of each chromosome (chromatid) is sent towards each chromosome dragged by microtubules of mitotic spindle.
14
Q
What happens in telophase?
A
- Chromosomes revert to chromatin
- nuclear envelop reform
- each nucleolus reappears
- mitotic spindle breaks down
15
Q
Why does DNA have to be spread out during the S phase (prior to mitosis)?
A
Machinery needs to get there to replicate DNA and has to be spread as all machinery needs to access genome to provide RNA transcript, contentiously re orientate itself.
16
Q
What are microtubles structures as?
A
Alpha Beta Alpha Beta sub-units stuck together to elongate the cylindrical structure.
17
Q
Which organelles are essential for cell division?
A
Centrioles and centrosomes where spindle will be anchored, specialized proteins will attach to build microtubules
18
Q
What are kinetochores?
A
Series of proteins attach to centromeres and microtubles look for them
19
Q
How does cytokenisis occur
A
Actin and myosin ring causes the plasma membrane to begin pinching in
20
Q
How can you get abnormal non identical daughter cells?
A
Anaphase chromosome are lost or 2 set at wrong pole at the end aniploidy. If you add or miss a chromosomes it will be dysfunctional.
21
Q
In rapid dividing cells, which phase in Interphase is deleted?
A
G1
22
Q
If not replicating cells, which phase are they stuck in and what else is it called?
A
G1 and then its called G0
23
Q
What determines the rate of cell division?
A
Respond to changes in conditions
24
Q
Which cells do not divide And what how many years does it take to be a complete new person?
A
Eye cells and 7 years. `
25
How is the Cell Cycle regulated?
With checkpoints. There are three checkpoints.
26
When is the first checkpoint?
G1 to S checkpoint
1. Cell is fit
2. Enough growth
3. Has replaced the missing organelles
4. the cytosolic synthesized all the material needed
27
When do you exit and not continue the rest of the other checkpoints from the first one?
If in contact to other cells around you or ran out of nutrients, you do not go through G1 to S checkpoint, you exit to G0.
28
When is the second checkpoint?
| And when will the cell stop growth here?
G2 to M
1. DNA is synthesized is taken placed and repaired everything
If not repaired and not sufficient nutrients available
29
The last checkpoint is...
SAC spindle assembly checkpoint
triggered by all kinetochores being attached to microtubules lining up and metaphase plate. If not, it will stopthe cell cycle at this point
30
What is regulating the cell cycle?
MPF (mitosis promoting factor) and many protein complexes
31
What d the MPF protein complexes do to regulate cell cycle?
1. Hold cells in a particular stage
| 2. Stimulate their passage to the next stage
32
In general what does the MPF do>?
induces mtosis in all eukaryotes
33
What are the two sub units of MPF?
1. CDK1 (cyclin dependent kinase)
| 2. Cylclin B1 major player
34
What is the concentration of cyclin during interphase and phase?
Conc increase during interphase, then peaks at M phase and decreases
35
What is MPF?
Regulatory molecule which is mitosis promoting factor
36
What does CDK do?
Cyclin dependent kinase catalyses phosphorylation of other proteins to start mitosis
37
What rae he concentration of CDK lilke in CC?
Doesnt change much during CC
38
What is so different of turning on a MPF ?
MPF is activated by PHOSPHORYLATION of MPF CDK
39
MPF protein kinase is a cyclin dependent kinase (CDK) ture or false?
TRUE
40
When is MPF active?
When bound to cyclin subunit. thus when conc of cyclin is high, more MPF is active and target proteins are phosprylated, causes the initiaition of mitosis
41
Cyclin conc reg MPF conc
True
42
Which phase in interphase do enzymes dephophorylate cyclin to activate MPF for phosphorylation of many diff protein types?
G2
43
What are the 4 effects of activated MPF (unphosphorluayted cyclin subunit)
1. initiate M phase
2. Phosphorylate lamins initiate nucleaur envelope breakdown
3. Phosphorylate icrotubule assocuated proteins
4. Phosphorylate enzymes that degrades cyclin, thus conc of cylin declines
44
How are tumors made?
Non effective CC checkpoints keep growing and form tumor
45
Why do Docs check other tumor places when they find one in liver?
Liver is in contact with many other systematic organs
46
What is cancer?
Complex fam of dis-eases caused buy cells grow in uncontroallable fashion that invade nearby tissues and that spread to othersites in the body
47
Cancer is derived from....
cells in which cell cycle checkpoint have failed
48
Cancer onset involves 2 aspects of DNA change/mutation:
1. Genes that ordinarily promote growth proto oncogense become oncogenes
2. genes that stop pf inhibit growth tumor supressor genes become inactive
49
Which oconegnes type is good and which is bad?
Protooncongene is good
| Ocogene is bad
50
What 3 ways can cancer develop?
1. Mutation within gene (oncogene growth stimulatin protein) an oncongene
2. Multiple copies of the gene excess of stimulating growth proteins
3. Gene moved to new DNA position and under new control excess of stimulating growth proteins
51
RAS signalling describe
Growth factor ligand attaches to (RTK) triosine receptor kinase signals molecule until RAS g protein
52
What is an example of a mutation which can develop into cancer?
Defective or missing transcription factor like p53 cannot activate transcription
53
Human fertilization compared to animals is that....
Highly selective process
Not synchronised insemination and ovulation not many signals. Thus, sperm has developed (some stay in the lower reproductive, sperm stay behind in case there is no egg)
54
What is the path of the sperm cell?
Corona radiata
Zona pellucida
Plasma membrane of secondary oocyte
Cytoplasm of secondary oocyte
55
What is the first polar body?
egg has already undergone first miotic division containing unwanted chromosomes.
Large cell containing all nutrients and proteins for few days of life and can tomake new transcripts on the first few days of life. Invest in one
56
Which layer does the sperm penetrate?
Zona pellucida
57
What happens when a sperm penetrates the zona pellucida?
The egg fuses and engulfs the sperm.
58
What happens in fertilisation?
Acrosome reaction allowing sperm to penetrate zona pellucida then plasma membrane binding (oolemma) and sperm egg fusion
59
Sperm penetration differs in humans as the.....
Sperm tail is not cut off when its is penetrated into the zona pellucida
60
What is cortical granule release?
Block polyspermy, releases enzymes which harden zona pellucida to prevent more sperm from coming in
61
When do eggs undergo cleavage?
AS the fertilised egg is being wafted down the fallopian tubes
62
What are stages/names of pre implantation development of the zygote?
1. cleavage of zygote two cell (made up of two blastomeres polar bodies, and the zona pellucida)
2. Cleavage of zygote 4 cell
3. Morula
4. Blastocyst
63
Blastocyst is made out of 2 things which are:
1. Trophoblast (food and precursor)
| 2. Inner cell mass
64
What is the trophoblast role?
outer layer of the blastocyst will later be part of placenta provides nutrients to developing embryo
65
ICM role?
Insulated from contact with intraterine evironment
| Will form embryo
66
Blastocyst needs much energy to grow, where does the energy come from/
gLYCOLOSIS
67
What is the blastocoele?
Space inside the blastocyst where ICM resides to one side surrounded by the TROPHOLBLAST
68
What happens in day 7?
Blastocyst needs to burrow into the uterine endometrium and becomes enclosed within endometrium by day 10
69
Trophoblast develops into 2 different kinds of extraembroyonnic tissue:
Cytotrophoblast
| Synctiotrophoblast
70
Cytotrophoblast
Protective membrane outside the embryo itself
71
Synctiotrophoblast
Multinucleate layer of cytoplasm very invasive release enzymes make hole for blastocyst to migrate into
72
Two tissue types in embryo development of day 8
Hypoblast primitive endoderm
| Epiblast primitive ectoderm
73
OUtgrowth of hypoblast is...
mesoderm like tissue beginning of yolk sac
74
What is the first stage of the maternal fetal interface?
formation of amniotic cavity, lacunae where mothers blood fill syncotiotophoblast absorb nutrients and give to ICM
Fluid filled amniotic cavity develops as ICM separates from trophoblast
Provides shock absorbance, prevent adhesion and drying out
75
Role of yolk sac?
1. provides blood cells
2. supplies nutrients
3. shock absorber
4. prevent drying out
5. gives rise to GI tract
6. primoridal germ cells
76
What is the role of chorion?
Prtects embryo and fetus from maternal immune system. Also gives rise to the placenta
77
What happens in week 3?
Gasturalation
Three primary germ cells layer established
Organ development begins
78
By week 5 the embryo is where?
Hanging out of the endometrium, in the uterine cavity.
79
What is gasturaltion?
Formation of primitive streak
Inavigation (push cells out strat process of embryo proper)
Endoderm Mesoderm Ectoderm
Where they can feel pain
80
Cloacal membrane is the...
tail end anus rectum
81
Orpharngeal membrane is the ....
head end form mouth connect to oral cavities.
82
What is role of notochordial process?
drives the action release morphagens cells close to morphogens change rapidly the far you are the less change differently DEGRADATION
83
What does notochord give rise to?
Vertical bodies like neural plate spinal cord, give rise to vertebrae discs and rarely a tumor called chrodoma
84
Spina bifida women prevent by eating?
Bread with folate
85
Which end is the primitive streak at?
The tail end
86
Notochord induces what cells?...
induction of ectodermal cells above it (as the notochord is in the mesoderm layer) to form the neural plate
87
Why do humans not reproduce asexually?
We want genetic variation
88
Meiosis makes
half the number of chromosomes of sperms and egg
89
What is meiosis
a type of nuclear division
90
What two cell divisions make up meiosis?
Meiosis I and meiosis II
91
What happens before meiosis?
Each chromosome in the diploid 2n parent cell is replicated
92
What results when replication is complete?
Each chromosome consists of 2 identical sister chromatids attached at centromere
93
What happens in meisois I
homolougous chromosomes of each pair separate and go to different daughter cells.
Although each daughter cell is hapoloid, each chromosome has two identical sister chromatids still attached at the centromere
94
What happens in meiosis II ?
Sister chromatids of each chromosome separate and go to each of two daughter cells
95
What happens at the end of meiosis II?
There are 4 haploid gametes each containing one copy of each chromosome.
96
What are the 5 phases of Meiosis I?
```
Early prophase
Late prophase
Metaphase
Anaphase
Telophase
```
97
What happens in early prophase ?
Homologous chromosome pairs come together in a process called synapsis.
Structure resulting is tetrad, 2 homologs. Non sister chromatids
98
What happens in prophase II?
chromosomes condense, nuclear membrane dissolves, mitotic spindle begins to form
99
What happens in metaphase I?
Tetrads migrate to metaphase plate.
Spindle form and attach to centromeres on chromosomes, homologous pairs of chromosomes align along the middle of the cell (random assortment??)
100
What happens in anaphase I?
Homologs separate and begin moving top opposite sides of cell
Spindle fibres shorten and pull homologous chromosomes apart to opposite poles of the cell (paired chromatids remain attached)
101
What happens in telophase I and cytokinesis?
Chromosomes move to opp sides of cell then cell divides
Chromosomes decondense, nuclear membrane (may) reform, cleavage furrow forms
division into 2 haploid daughter cells. Haploid as only one copy of each chromosome
102
What are the phases of Meiosis II?
Prophase II
Metaphase II
Anaphase II
Telophase II and cytokenisis
103
What is the key difference between meiosis and mitosis?
Homologs pair in meiosis (in prophase of meiosis I) they migrate together to metaphse plate and separate at anaphase result in REDUCTION DIVISION but not in mitosis
Meiosis produces 4 daughter cells with half genetic material while mitosis produce 2 genetically identical daughter cells to the parent cells
104
How many cell divisions in Mitosis and Meiosis?
Mitosis - 1
| Meiosis - 2
105
What is the number of chromosomes in daughter cells compared to the parent cell is mitosis and meiosis?
Mitosis - Same
| Meiosis - Half
106
Synapsis of homologs in mitosis and meiosis?
Mitosis - no
| Meiosis - yes
107
Number of crossing over events in mitosis and meiosis?
Mitosis - none
| Meiosis - one or more per pair of homologous chromosomes
108
Makeup of chromosomes in daughter cells? Mitosis vs Meiosis
Mitosis - identical
| Meiosis - different only one of each chromosome type present, paternal and maternal segments mixed within chromosome
109
Role in life cycle? Mitosis vs Meiosis?
Mitosis - asexual repro in eukaryotes; cell division for growth of multi cellular organisms
Meiosis - precedes production of gametes in sexually reproducing animals
110
what are the three ways of genetic variation?
1. Independent assortment (metphaseI)
2. Crossing over (prophase I)
3. Fertilisation (random union of gametes)
111
What is the role of crossing over?
Genetic recombo produces new combo of alleles on the same chromosome
112
What is the role of independent assortment?
Random segregation of homologous chromosomes in anaphase I generating genetic diversity.
113
What happens in polycystic ovaries?
Eggs stop growing and get arrested in immature state. S
114
What does polycystic ovaries look like in ultrasound?
Ring of follicles around the outside of ovary
115
How does chlamydia affect fallopian tube damage or blockage?
Chlamydia gets into cells and replicates which damages the cell, thus no mechanism to waft through the fallopian tube
116
What can blockage of fallopian tube lead to?
Ectopic pregnancy
117
Early menopause causes? (3)
Turner syndrome ( exhaust eggs in their teens) genetic
Radiation therapy or chemo
Cigarette smoking
118
Male infertility
Low numbers of sperm which don't swim very well
Undescended testicles
Genetic defects
Infections like chlamydia
Overexposure of chemicals
119
Undescended testicles?
Sperm damaged cos it is heated in the body
120
What is a way to help with infertility for conception?
In vitro fertilisation
121
What are the steps of in vitro fertilisation?
1. Super ovulation
2. oocyte ovulation
3. insemination
4. zygote culture
5. embryo transfer
122
How can people tackle the sperm issue of not being able to fertilise the egg?
Intra cytoplasmic sperm injection during the insemination stage (ICSI)
123
What is teratogen?
Agent or chemical that can disturb the development of an embryo or fetus
124
What can teratogens o?
1. Birth defect in child
| 2. Halt the pregnancy outright
125
What are the classes of teratogens?
1. radiation
2. maternal infections (zika virus, rubella)
3. drugs
4. chemicals
126
How do women check prenatal?
Fetal ultrasound
Amniocentesis invasive
Chronic villus sampling invasive
Maternal alpha feto protein testing QUAD AFP plus
127
What is the chorion made out of?
It is formed by extraembryonic mesoderm and the two layers of trophoblast that surround the embryo and other membranes.
128
What emerges from the chorion and what does it do?
The chorionic villi emerge from the chorion, invade the endometrium, and allow the transfer of nutrients from the maternal blood to fetal blood.
129
What is the zona pellucida made out of?
Glycoprotein coat
130
What is cleavage? Why it happens in zygote?
Splitting without growth, it is rapid splitting a number of times.
131
How many times do you undergo cleavage? Do you keep in the zona pellucida?
Until Morula stage (16 cell mass) and yes, still within zona pellucida.
2, 4, 8, 32 cells
132
What happens after the formation of the morula?
Compaction
133
What is compaction?
Cell are in the middle and physically get more compacted, and cells get different.
134
How are the cells different from compaction process?
Trophoblasts and embryoblast
135
What happens when the embryoblast clump even more in the middle?
They are now called inner cell mass (ICM)
136
What is the process called AFTER cleavage?
Blastulation
137
What happens to the zona pelucida in the first step of blastulation?
It starts disintegrating
138
What is the first step of blastulation?
The embroyblast clumps to become ICM
Zona pellucida starts to disintegrate
Morula is now Blastocyst
139
When do you lose zona pellucida?
Second step of blastulation
140
What happens in the second step of blastulation?
Zona pellucida is GONE
Inner cell mass starts to differ:
- There is a cavity within the ICM called AMNIOTIC CAVITY
- Differentiate even more, the bottom of the ICM clump is HYPOBLAST and above it is EPIBLAST
141
What makes up the bilaminar disk?
Epiblast
| Hypoblast
142
What does the primitive streak formation mark?
The next stage of embryonic development, GASTURLATION
143
What is the primitive streak?
The site where the cells in the epiblast layer of bilaminar disc start to migrate
144
Where do the epiblast migrate to?
They heap themselves up at the primitive streak and start burrowing their way down into the bilaminar disk into the hypoblast and everywhere
145
What do the migrating epiblast cells consequent to?
More differentiation, not 2 layers of different cells but now a TRILAMINAR DISK of 3 germ layers
146
What is the order of the new trilaminar disk germ layers? From top to bottom
Ectoderm
Mesoderm
Endoderm
147
What is the step after gasturalation?
Neurolation
148
In the first step of neurulation?
A core called notochord is formed in mesoderm layer (2nd layer) which induces change in the above layer (ectoderm) to make a neural plate
149
What happens in the second step of neuraltion?
The neural plate cells start diving into the mesoderm layer creating a ring/tube structure called a NEURAL TUBE
Neural crest cells are also broken off
150
What are neural crest cells?
As the cells from the neural plate move up and down into the mesoderm layer, cells break off from the ectoderm going into the mesoderm.
151
What is the neural crest function?
Cells which had broken off called neural crest differentiate into their own special tissues
152
What is happening in the first step of implantation?
The zona pelucida is disintegrating and the endometrium is anticipating arrival of blastocyst and creates a crypt (valleys) until the blastocyst touches the valley called APPOSITION
153
Are you inside the endometrium in the first step?
No you are resting, can be be easily dislodged. You want to be stuck in their for nutrient transfer
154
How does adhesion happen into the endometrium?
The trophoblast cells start multiplying and migrate/invade into the uterine endometrium
But the endometrium cells also get larger and surround the blastocyst so you embedded now
155
What happens to the trophoblast when it is doing the process of adhesion?
It is differentiating into different sub types, syncitiotrophoblast (invasive into the crypt, and the ones that did not change is the cytoblast
156
What do the syncitiotrophoblast develop?
As they grow into the endometrium, they develop finger like projections called villi. Cytotrophoblast also line the villi through time
157
What develops in the blood vessels? What are they real close to?
Fetal blood vessels close to the uterine blood vessels in the endometrium but to mixed together because of the cytotrophroblast but so close nutrients can diffuse into and out (waste) fetal blood.
158
Endoderm derive into?
GI tract and Pulmanary, lungs, liver, pancreas,
159
Mesoderm derive into?
Muscles, Skeletal, Genitourinary - some inner layers of skin, muscles, bone, caridac musce, kidneys ,bladder, ovaries and testes
160
Ectoderm derive into?
Skin, Nervous system - Outer layer of skin. skin related items like hair and glands, and NERVOUS SYSTEM.
161
The testes function?
Sperm production
| Testosterone (hormone) production
162
What do we see inside the testes?
Convoluted set of tubes called semineferous tubules
163
Where inside the testes are sperm made?
Seminiferous tubules
164
Where are testosterone made in the testes?
Laid egg cells hang outside of the semninferous tubules
165
Sperm travel from...
Seminiferous tubules,
(drain out to) Rate testis
(drain out to) Epididymis, (to mature),
Get out via ejaculation
166
Movement of sperm from this tubes are?
Peristalsis
167
What is the male germ cell called?
Spermatogonium (2n diploid cell)
168
Male germ cell going through meiosis is called...
primary spermatocyte (2n diploid)
169
What happens in meiosis I?
Secondary haploid spermocytes are made.
DNA replication of Primary spermatocyte
SYNAPSIS AND TETRAD FORMATION
Split into 2 secondary spermatocytes (haploid)
170
What happens in meiosis II?
Sister chromatids separated
| End up with 4 unique daughter cells, spermatids
171
What are mature spermatids?
Sperm
172
Why are spermatids not ready?
They need to mature, lose cytoplasm, add a tail, add a cap
173
Where do spermatids mature to become sperm
In the epididymus
174
How can these sperm be unique??
Crossing over and independent assortment
175
Oogensis occurs?
In the ovaries
176
The starting female germ cell is called?
Oogonium (diploid)
177
When does oogensis occur in a female?
Begins in the fetal stage, in female fetus.
178
When does oogenesis stop?
Stop in prophase I of mitosis I in fetal development
179
First division in meiosis I creates?
A polar body `
| Secondary oocyte
180
What is the size of polar body in relation to secondary oocyte?
Smaller
181
What does the secondary oocyte do now?
Waits to be ovulated every month. If it does, it will travel through the fallopian tube for fertilisation
182
What happens if fertilisation doesn't occur?
Shed in monthly period
183
If fertilised?
Meiosis II will complete,
sister chromatids separate
one of the daughter cells which come out of the cytoplasmic division will be big and the other one will be small polar body (stuck to it but not part of the egg)
The egg will have the cytoplasm and the egg while the polar body gets nothing.
184
When does fertilisation occur?
12-24 hours after ovulation (day 0)
185
When does first cleavage happen?
30 hours (a day and a bit) after fertilisation
186
When does the morula form?
3-4 days after fertilisation
187
When does a blastocyst form?
4.5-5 days after fertilisation
188
When does implantation (apposition) occur?
6-7 days after fertilisation
189
What is happening around 8 days?
Trophoblast differentiates into syncytiotrophoblast and cytotrophoblast.
Embryoblast cells also differentiate into two layers; hypoblast and epiblast
Soon a small cavity forms within epiblast becoming amniotic cavity.
190
What happens as the amniotic cavity enlarges?
Layer of squamous cells line the roof above epiblast to form amnion. The floor is the epiblast. Amnion overlies (lies on) the bilaminar disc
191
What fills the amniotic sac, (amniotic fluid) ?
maternal blood initially then the fetus urine. This acts as a shock absorber, body temp, prevent drying out, and adhesions between skin and other surrounding tissues.
192
How does amniocentesis test work?
Embryonic cells normally go to amniotic fluid. As they examine fetal cells and dissolved substances.
193
How does the exocoelomic membrane form on the 8th day?
Cells at the edge of the hypoblast migrate and cover inner surface of blastocyst wall from columnar to squamous and then a form of thin membrane called exocoelomic membrane.
194
What do the exocoelomic membrane and hypoblast form?
Wall of yolk sac. The bilaminar disc is now between yolk sac and amniontic cavity
195
Fully embedded in endometrium is in what day and what else is happening?
Blastocyst fully embedded in endometrium. Syncytiotrophoblast expands, small spaces called lacunae develop within it.
196
What is happening on the 12th day?
extraembryonic mesoderm forms which are derived from yolk sac and mesenchymal tissue around amnion and yolk sac.
More cavities form in the extraembryonic mesoderm and the larger one called extraembryonic coelom.
197
How does the chorion protect embryo/fetus from mother immune response?
1. secretes proteins that block antibody production in mum
| 2. promote T lymphocyte prod. suppressing immune reponse in uterus
198
By the end of the 2nd week?
bilaminar disc connect to trophoblast by a band of extraembryonic mesoderm called connecting stalk. Connecting stalk is the future umbilical cord.
199
What are 2 neural tube defects? and what is their prevalence?
Spina bifida
Anencephaly
1:1000 live births
200
Week 3 is...
Gastrulation, around 15 days after fertilisation
201
What is primitive node?
small group of epiblastic cells form round structure called primitive node.
202
Which out of the three germ layers are loose?
Mesoderm
the other two are dense
203
16 days...
notochoridal process
204
what is allantois and when it forms?
When cloacal membrane forms ( during 3rd week) wall of yolk sac forms vascularised outpouching called allantois.
205
allantois function
early formation of blood and blood vessels and associated with the development of urinary bladder
206
17th day?
mesoderm adj to neural tube forms paraxial mesoderm.
Paraxial meso and lateral mesoderm form intermediate meso.
207
End of 5th week how many somites pairs made?
42-44 pairs present
208
by the end of 2nd week. what develops?
chorionic villi
209
What forms placenta?
chorionic villi and decidua basalis of endometrium of mother
210
what happening in 4th week?
embryo undergoes
very dramatic changes in shape and size, nearly tripling its size. It
is essentially converted from a flat, two-dimensional trilaminar embryonic
disc to a three-dimensional cylinder, a process called embryonic
folding
211
What is cylinder composed of?
The cylinder consists of endoderm
in the center (gut), ectoderm on the outside (epidermis), and
mesoderm in between.
212
Go through foldings to get a C shape
Folding in the median plane produces a head
fold and a tail fold; folding in the horizontal plane results in the two
lateral folds. Overall, due to the foldings, the embryo curves into a
C-shape
213
what else develops as it undergoes folding?
Five pairs of pharyngeal arches form
| somite and neural tube develop
214
What do the five pairs of pharyngeal pouches consist of?
ectoderm
mesoderm
endoderm (contain blood, cranial nerves, cartilage. and muscular tissue)
215
Incomplete or codominance
Heterozygous have an intermediate phenotype
Think cows, either brown (mix of black and white) or white with brown spots
216
Environmental effects
Degree of allele expression may depend on the environment
217
Epistasis
One gene interferes with the expression of another gene
218
Multiple alleles
When different combo of alleles produce more than two distinct phenotypes, trait is polymorphic
219
Pleiotropism
A gene than influence many traits rather than just one
Marfan syndrome
220
autosomal dom
unusual (largely fetal don't survive)
not common, too sick to reproduce except huntigtons
221
autosomal recessive
normally 2 siblings get it but the previous generations do not (the parents are carriers like cystic fibrosis)
222
Sex linked
Only affected are all male
The transmitters are female. Daughter are carrier because son is affected. TRACE BACK MATERNAL.
223
Why the garden pea?
Many hybrids previously produced (expect segregation of traits)
Large number of true breeding varieties
Small and easy to grow (short generation time)
Secual organs enclosed in flower (self fertilisation and cross fertislisation)
