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Developmetal Genetics Flashcards

1
Q

What is Developmental Genetics ?

A

Developmental Genetics: describes how genes regulate process of transformation and change in development
-Development controls how cells divide and coordinate their activities with each other

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2
Q

Discuss what occurs in Human development

A

Human development:
-we go from a single cell to 37 trillion cells
(single fertilized egg to a developed human )

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3
Q

What are the experimental models of development?

A

To study development we study animals
Experimental models of development:
1. Sea urchins
2. African clawed frogs (big eggs that people experiment with)
3. Chickens (big eggs that people work with)

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4
Q

What is observed in genetic models of development? What are the 4 main genetic models used ?

A

Genetic models of development: Look at mutations that change the developmental process itself
Genetic models
1. Fruit flies (Thomas Hungt Morgan studied flies; leading model of development)
2. Nematodes (worms) another common model
3. Zebrafish (their fish eggs are followed external; study genetics by crossing fish)
4. Mice (have similar biological effects in humans; models for how mammals (like us) work)

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5
Q

What happens to cells in development ?

A

In development, cells divide rapidly and form patterns accurately

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6
Q

What is the outline of Development? What are the major phases?

A

Outline of Development
1. Fertilization
2. Cleavage (cells quickly divide)
-Cell proliferation
-Establishing the body plan
3. Gastrulation (gut moves into the center of animal)
-cell migrations
-Establishing tissues layers
4. Organogenesis (body begins to form recognizable muscles, vertebrate, limbs and other structures)
-The neural tube
-Somites
-Appendages

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7
Q

What occurs in Fertilization ?

A

Fertilization: start of a new life
-Sperm will fertilize a large egg
(egg provides most of the material for new life)

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8
Q

Describe the Acrosomal Reaction that occurs in Sperm during

A

Sperm: The Acrosomal reaction initiates fertilization
1. Egg is surrounded by Zona pellucida.
2. As sperm reaches zone pellucida, it moves through follicle cells that protect the egg, and then initiate the Acrosomal reaction
3. The Sperm has vacuole (with enzymes), when it contacts zone pellucida, the vacuole will dump its enzymes on egg that digests zone pellucida, so sperm can fuse with egg.

Process (bind sperm to zona pellucida, acrosome reaction (vesicle dumps acrosome contents, enzyme) , sperm penetrate through pellucid, fuse with plasma membranes, and sperm nucleus enter egg cytoplasm)

The egg has to respond very quickly to prevent another sperm from coming into egg

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9
Q

What occurs in egg during fertilization ? What kind of reaction occurs.

A

Egg: the Cortical Reaction BLOCKS Polyspermy (multiple sperm from entering egg)
A system where the egg has been set up for years, developing vesicles of its own to allow it to act quickly and prevent polyspermy.
process:
1. The egg has cortical granules with hydrolytic enzymes
2. As soon as sperm make contact and sperm enter cytoplasm they signal for egg with granules to fuse with membrane and dump their contents to the outside
3. their contents cause zona pellucida to change in structure (make HARD boundary) to prevent other sperm from getting through.

For development to work, things are set up in advance
so they can proceed quickly.

two steps: Cortical reaction (exocytosis; dump contents of granule on outside)
2. Block to polyspermy (make impermeable barrier to prevent another sperm from contacting egg)

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10
Q

What must occur in sperm and egg to form nucleus ?

A

The sperm and egg pronucleus (haploid) merge to produce the nucleus
process:
1. Egg pronucleus and sperm pronucleus that has centrosome.
2. They move towards each other .The centrosome duplicate, and nuclei emerge (nuclear envelopes of both egg and sperm)
they then break apart, chromosomes duplicate and a lot of mitosis occurs (lot of mitosis in cleavage phase of developing embryo)
(chromosomes from egg and sperm align on single metaphase spindle and division produces two diploid cells)
-

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11
Q

what is role of the Xenopus fertilization?

A

Xenopus fertilization starts organizing the body plan
When sperm fertilizes egg in African frogs, it causes surface of egg to rotate inside; makes ventral surface (where a lot of yolk is) , and at opposite ends it makes dorsal surface (mirror image )

(hence, some information about body plan is already being worked out as a result of fertilization and early cleavage events)

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12
Q

What occurs during Cleavage? What are the four steps of the cell cycle?

A

Cleavage- initial burst of cell division (happens rapidly)
The typical cell cycle has four steps: M (mitotic) , G1 (pause), S (synthesis) and G2 (pause).
-Cell cycle
M, G1, S, G2 (pause phase)

(normally When cells divide: new cell is formed and has 2 copies of every chromosomes, absorbs nutrients; duplicate DNA and go through mitosis to make two daughter cells)
slow state: where there are pauses before and after DNA synthesis

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13
Q

How many steps are the cell cycle for frog cleavage ?

A

The cell cycle of frog cleavage have only 2 steps: M and S. mitotic phase and synthesis phase back and forth rapidly
This process works in frogs because the proteins that control division/cycles are regulated. The Kinases add phosphate groups to proteins to turn on and phosphatase groups remove phosphate to turn off.

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14
Q

What occurs in Drosophila Cleavage ?

A

Drosophila Cleavage:
-cells are expressing a GFP: tubulin fusion protein that labels the asters
(easily observed due to green flurousecent protein)
-Division occurs rapidly and synchronously
-Courtesty of Rosalind V Silverma- Gavrila
(tubulin helps separates chromosome during mitosis)

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15
Q

How does cleavage occur in Mice?

A

Cleavage in Mice:
-Cleavage produces cells that organize to an inner mass and an outer group that will go on to form the placenta.
reproduction in mice and humans do not involve laying eggs, and eggs form placenta to continue take up new material from mom
placental mammals rely on mother for protection
-slower development compared to other animals.
(form hollowed out ball; outer side of ball form placenta; cells on inside of ball form new mouse or human)

process:
fertilized mouse egg– 2 cells (1 1/2 days) –> morula (8 cells; 2 1/2 days) , compaction—-> 16 cells (3 days) —> section of blastocyst (4 days)

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16
Q

What occurs in Gastrulation?

A

Gastrulation: process of forming the basic body plan (form gut in the middle of body; how we bring in, process and excrete food for energy)

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17
Q

How does gastrulation occur in sea urchins? What are the major layers of cells in human body and which body parts are they found

A

Gastrulation in sea urchins (also same process for humans, mice and other animals )
1. after cleavage, sea urchin forms hollow ball of cells.
2. At one end, some of cells start to migrate into interior)
3. The pinch becomes bigger and bigger forming a tube; when tube hits other wall, it forms hole, and push hole through to form full gut (from mouth to anus)
cells give rise to three layers: endoderm, ectoderm, mesoderm (middle part of body)
In humans;
skin, nervous system- ectoderm
gut- endoderm
muscles, liver- mesoderm

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18
Q

What are the tissue layers in frog embryo ?

A

Tissue layers in frog embryo:
Gut in middle (lined by endoderm)
ectoderm pinches down to from neural crest
**neural crest (in ectoderm) where spinal cord forms
mesoderm- where notochord and somites are
(neural tube also part of ectoderm)

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19
Q

Describe what occurs in human gastrulation

A

Human gastrulation :
a group of cells on one end of inside hollow ball: which form placenta
Humans have flatter disk to where invagination and migration to interior of cell occurs.
it form same basic structures as sea urchin and frog (ectoderm, endoderm and mesoderm)

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20
Q

What is the role of gastrulation? What are the major products formed?

A

Gastrulation forms layer of inner, middle and outer tissues that give basic animal its structure
ectoderm- outer layer of skin, lining of the nose and mouth and nervous system,
endoderm- Digestive tract, respiratory tract, liver, gut, pancreas
mesoderm- muscles, skeletal

(gastrulation: second phase of development, where migration of blastocyst cells inward lead to multiple distinct layers of cell)

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21
Q

What occurs in Organogenesis ?

A

During Organogenesis, cells organize into organs and systems.
-once broad tissues have formed, cells need to adopt more specific identities.
-Groups of cells interact to form organs.
-organs contain many cells of the same type (ex: the heart is made of many muscle cells )
-Organs also contain cells of different types (ex: bone contains bone cells and blood cells)
-Organs interact to make complicated systems

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22
Q

What can cause severe problems in development?

A

*Early defects during development can cause more severe problems *
(if have mistake during early phase of development, may take out half body ; if defect near end of die, might affect less tissues and organs; not as severe)

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23
Q

Which processes are involved in the genetic control of Human development ?

A
  1. Transcription factors
  2. Signal transduction
24
Q

What are transcription factors and what is their role in development?

A

Transcription factors : make proteins who job is to bind DNA and turn genes off (to remain unused until appropriate time) or other transcription factors that turn genes on.
ex: T box genes and brachyury

25
Q

Describe the transcription factors that can be found in mice and what happens if there is a mutation in T gene of mice.

A

Brachyury is a T box transcription factor
-The T gene of mice is also known as brachyury
-A T mutation is dominant for tail defects in mice
-Brachyury mutations are homozygous lethal because it controls very early development

(get rid of 1 copy; tail not grow right; but get rid of 2 copies; development falls apart during gastrulation)

26
Q

How does brachyury affect embryos?

A

LOSS of brachyury disorganizes embryos
-Mutants cause embryo to lose the anterior-posterior axis and mouth
-mouse mutants lose the notochord and have mesoderm defects.
normla embryos- anterior poster axis in mouth (due to gastrulation )
brachyury-inhbiteds embryos- are symmetric; no mouth or anterior posterior axis, no mouse formed. It just becomes a ball of cells.

27
Q

What else does brachyury gene regulate?

A

The bracyhury gene regulates the epithelial-mesenchymal transition.
-Brachyury plays a key role in gastrulation and defining the mesoderm
-it is also expressed along the midline of developing embryos
-When over expressed in adult cells, it can cause an epithelial to mesenchyme transition, leading to Cancer.

28
Q

What are Hox genes? Describe the organization and expression of these genes

A

Hox genes- part of Homeobox genes (family of transcription factors)
-Hox genes- organized into cluster of genes that are next to each other on same chromosome
these hox genes were discovered in fruit flies (8 genes form hox complex)
-**The order that genes are aligned along the chromosome, define order the genes are expressed from head to tail) in developing fruit fly.
The expression pattern is organized in a linear way; important for developing body plan for animal (head, tail middle)

29
Q

What occurs in antennapedia homeotic mutant?

A

The antennapedia homeotic mutant transforms antennae to legs.

(Suggests that these genes tell structures where in body they are, and what they should do)

30
Q

What happened with Ultrabithorax homeotic mutant?

A

The Ultrabithorax homeotic mutant transforms halteres in flies to wings

31
Q

What was discovered about the hox genes? How many hox cluster genes do humans have? flies?

A

The function and organization of the hox genes is conserved (throughout animal evolution)
hox genes- universal code to organize animals from front to back
(Hox genes is organized in humans, same way as flies; genes at one end are expressed in head of developing embryo, genes at other end expressed in toes, limbs)

fruit fly- one chromosome with hox genes
humans- have 4 hox clusters (all expressed )

32
Q

What kind of roles are hox genes?

A

Hox genes are universal code to organize animals from front to back
-Hox genes are also transcription code; each gene make transcription factor. when this transcription factor is active, it tells gene where its active, turn on certain genes involved in making structures for different areas of the body.

33
Q

How do Human hox genes affect patterning in body?

A

Human Hox genes also affect anterior to posterior patterning
-HoxA1 mutations affect the head
-HoxA13 mutations affect digits (fingers)

34
Q

How many sets of hox genes do humans have? Why?

A

Humans have FOUR sets of hox genes because of duplications
(since we have redundant numbers of genes working in each position, if mutation in one gene, minor effect)

(only 3 of them make anterior most gene)

35
Q

What are the effects of mutation in HOXA1 and HOXB1 mutants?

A

HOXA1 and HOXB1 both affect eye function and eye development
(these defects in eye structure, movement)

36
Q

What are the major transcription factors?

A

-T Box transcription factor: helps control a lot of genes in development (including gastrulation)
-Hox gene cluster- set of transcription factors that coordinate which genes turned on in front, middle or outside part of body (to develop properly)
-Pax6 gene

37
Q

What is the role of Pax6 gene?

A

Pax6 gene: transcription factor universally conserved to help control eye development
( it will affect eye development of human, mouse , zebrafish and dropophilia (fruit fly)
all animals have this pax6 gene, if gene is messed up, severe problems
(some humans can become blind)
(Humans turn on pax6 in different part of body, that part will develop eye)

38
Q

What occurs in signal transduction ? What are the three types of Signal pathways

A

signal transduction: process of how cells talk and communicate with each other
Three types of signal pathways:
1. Endocrine Signaling- one cell makes a hormone that flows through blood and go through body and signal many cells (ex; testosterone helps control sexual development)
2. Paracrine Signaling: 2 cells talk to each other. (signal cells send signal to target cell)
3. Autocrine Signaling: some cells send signals to which they receive themselves.

39
Q

What kind of signal controls transcription factors and how does signal transduction occur ?

A

PARACRINE signaling can control transcription factors and what happens in cell
signal transduction carries information to the nucleus.
process;
on outside cell, signal molecule is produced and binds to receptor (1. Reception) This interaction starts the control of other molecules that relay signal into nucleus (2. Transduction) to control transcription factors and form cellular response (3. Response)
-cells talk to each other and dictate how they should develop and what genes they should express

40
Q

What are the Major Signal transduction pathways?

A

Major signal transduction pathways:
1. The WNT pathway
2. The Notch pathway
3. The FGF (fibroblast growth factor) pathway (mutations this pathway causes disorders like Achondroplasia)
4. The EGF/MAPK/ERK pathway (epidermal growth factor pathway involved in many cancers)
5. The hedgehog/Gli pathway (Gli transcription factor involved in regulation number of fingers formed; hedgehog signaling controls gli pathway and how many fingers you have)
6. The TGFB and BMP pathways (bone morphing pathway)

41
Q

What occurs in the WNT Pathway? What happens with active WNT signal vs NO WNT signal ?

A

WNT signals cause the transcription factor B-catenin to activate genes
-Active WNT signal : if signaling molecule binds to receptor, it will bind to complex which causes beta-catenin to be let go. Beta catenin can diffuse into nucleus and interact with transcription factors and control transcription of many target genes

-NO WNT signal: complex Beta-catenin will get phosphorylated and degraded

(hence information from surface of cell can be sent to middle of cell by control destruction of protein or relate of protein to do things in nucleus)

42
Q

What does the WNT signaling pathway promote?

A

BONE GROWTH

43
Q

What occurs in the Notch Pathway?

A

Notch Pathway:
-Notch signal help groups of cells subdivide into different types
group of cells that are in equivalent types of cells express Notch protein. They will start to signal to each other, where they each try to turn off Notch system in other cell. This will result in only one cell staying on (Turing off notch in all other cells) and becomes differentiated cell.

Notch - large protein that sticks through cell membrane and bind on outside to signaling proteins which affects how inside part works, by controlling transcription factor)
(this pathway critical in helping cells become different from their neighbors)

44
Q

Where do B and T cells develop from? What are the role so the B and T cells?

A

B and T cells develop continuously from stem cells
-bone marrow give rise to lymphoid stem cells that divide to form B and T cells
-B cells make antibodies (that fight pathogens)
-T cells differentiate into various kinds of T cells which directly attack invaders
This process is controlled by mutation in Notch gene

45
Q

What is the role of Notch receptor? What occurs if there is a mutation in Notch 1 receptor ?

A
  • The Notch receptor controls T cell development and cancer
    -Notch 1 gene promotes T cell development from precursor cells
    -mutations that activate Notch receptor causing it to be turned on all the time can cause aggressive lymphomas in children cause cancer.
    -These lymphomas are call T-ALL cancers
    T cell development depends on several signaling pathways (Notch, Hedgehog )
46
Q

What occurs in the FGF pathway? How do the FGF signals work?

A

FGF pathway (fibroblast growth factor)
-*FGF signals cause their receptors to dimerize *
The cell membrane have FGF receptors, with kinase domains
if FGF signal comes, it will bind to receptor and come together, become activated and signal to cells to turn on genes
(They can use kinases to phosphorylate; send signal into cells)
*FGF receptor can act through several pathways inside the cell (protein kinase C, RAS) *
multiple different signals interact to specify one of many different possible phase

47
Q

What happens when there is a mutation in FGF ?

A

Mutations can cause FGF receptors to be Active all the time (leads to many problems)
-(ex: mutations that fold receptors together; or other mutations that are inside the cell (that work on their own)

48
Q

What disorder is caused by mutations in FGF receptor FGFR2? What kind of mutation causes this disorder> What are the clinical symptoms and features for this disease?

A

Mutations in the FGF receptor FGFR2 cause Apert syndrome
-Apert syndrome
-bone os the skull fuse prematurely, resulting in abnormal growth
-Developing fingers and toes also fuse
-These changes are caused by DOMINANT mutations in FGFR2 gene
-These dominant mutation same the FGFR2 receptor overactive

49
Q

What are the three disorders that are caused by mutations in FGF receptor FGFR3? Explain how these disorders differ

A

Mutations in the FGF receptor FGFR3 cause three Different disorders:
1. Hypochondroplasia
2. Thanatophoric dysplasia (fatal)
3. Achondroplasia
These disorders differ because….
-humans have at least 5 FGF receptor genes
-Each one can make more than one isoform (type of receptor) by splicing
-Each FGF receptor is expressed in some developing tissues but NOT in others
-The mutations in a specific receptor might cause it to only mildly or severely be overactive

50
Q

What occur sin the EGF/Ras/MAP kinase pathway? What diseases are caused by mutations in this pathway?

A

EGF/Ras/MAP kinase pathway- important for many aspects of development and involve in many cancers
Diseases caused by mutations In Ras pathway:
- Noonan syndrome
-Cardio-facial cutaneous syndrome
-Costello syndorme
-Neurofibramotisis

How Pathway works:
At cell membrane: have receptor that control (by binding ligand) the activity of one of Rat proteins.
The neurofibramatosis is involved in stablizing things. They control kinase, and control transcription factors which control what occurs in nucleus.
Ras protein between receptor and transcription factor (carry signal from outside to inside cell)

51
Q

What causes inactivation of Ras-GTP? How does this occur?

A

Neurofibromin inactivates Ras-GTP.
-In many nerve cells, signals create Ras-GTP, which acts through protein kinases to cause release of the neurotransmitter GABA
(active ras activates other components and change how cell functions; or cause cancer)
-The NF1 gene encodes a protein that inactivates Ras by transforming it to Ras-GDP
(this is used to turn off protein; recycling process)

52
Q

What kind of process if Development?

A

Development is an Ongoing process.
(It is a constant process in humans)
ex; when we are injured, we need coordinated developmental changes to make right cells and fill in damaged tissue)

53
Q

What is Fibrodysplasia ossificans progressive? What are mutations that cause it

A

Fibrodysplasia ossificans progressiva- progressively cause tissues that are damaged, to turn into bone when they are healed.
As life progresses in a child, more muscle becomes bone, making movement harder and harder (eventually kills a person)
slow, progressive painful disorder
-caused by DOMINANT mutations in the ACVR1 gene
-The gene controls which cells express BMP (bone morphogenetic) type I receptor
in affected individuals, the receptor is overactive in the presence of signal activan A

54
Q

What is the key structural mutation that causes Fibrodyspalsisa ossifcians progressive disease?

A

The key mutation (structurally) is CDNA base 617 G–> A
(Amino acid change)
-this causes a protein change of one amino acid, R206H (arginine changes to histidine)

this affects how ACVR1 works with bone morphogenetic protein receptor

55
Q

What is the role of ACVR1 in BMP signaling ?

A

Role of ACVR1 in BMP signaling (Bone morphogenetic protein receptor) ;
i controls pathway of genes in cell that regulate bone and muscle development
(hence development is continuous)

56
Q

What are the four main stages of development?

A

four main stages of development:
Fertilization: produce new embryo
cleavage; make large number of cells (ball of cells)
gastrulation: form basic body plan of gut and inside
Organogeneis; form organs and structures of embryo

57
Q

Which genes play a role in development? How do they work?

A

Many genes provide instructions for how development should occur
-These genes work by controlling:
How cells interact with each other (signal transduction genes)
-How cells turn off some genes and turn on others (transcription factors)

Human Genetics (13 decks)

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