Week 8 Flashcards
1
Q
Which of the following are correct statements about development?
A
Development is gene-directed.
Development is a systematic process.
Development encompasses multiple life stages.
2
Q
A developing animal begins as a fertilized egg, or ________
, that must undergo cell division to produce the new individual.
A
Zygote
3
Q
The acquisition of axial differences in development is called
A
Polarity
4
Q
What is expected to occur during embryogenesis in Drosophila?
A
A larva forms.
5
Q
In Drosophila, the establishment of A/P and D/V polarity is due to how many different genetic pathways?
A
2
6
Q
The process of systematic, gene-directed changes through which an organism forms the successive stages of its life cycle is known as
A
Development.
7
Q
Which of the following is the first subprocess in development?
A
Cell division.
8
Q
Match each Drosophila body region to the number of segments present in that region.
Head
Thorax
Abdomen
A
3 fused head segments, three thoracic segments and 8 abdominal segments.
9
Q
If an embryo has an identifiable anterior-posterior axis, and a dorsal-ventral axis, it can be said to have which of the following?
A
Polarity
10
Q
Which of the following occurs in Drosophila homeotic mutants?
A
Normal structures appear in unexpected places.
11
Q
In Drosophila, the process of going from a fertilized egg to a larva is called
A
embryogenesis
12
Q
Organogenesis occurs either after or during
A
gastrulation
13
Q
The formation of the A/P axis during Drosophila development is due to the proteins ____
and _______.
A
Bicoid
Nanos
14
Q
The anterior-posterior and dorsal-ventral axes in Drosophila specify which of the following?
A
Organ and tissue placement
15
Q
Organogenesis in vertebrates begins with the formation of the ________ and the hollow ____ _______ cord.
A
Notochord
Dorsal nerve cord
16
Q
The determination of structures along the A/P axis in Drosophila embryos is established by the sequential activation of three classes of ________ genes.
A
segmentation
17
Q
Neurulation is the formation of the ____ ____ cord during organogenesis.
A
Dorsal nerve
18
Q
In Drosophila, mutations in ______
genes lead to the formation of normal body parts in inappropriate places.
A
homeotic
19
Q
The process of organ formation in an embryo is called
A
organogenesis.
20
Q
True or false: Neurulation in vertebrate chordates is identical to neurulation in non-vertebrate chordates.
A
False
Reason: Neurulation in vertebrates includes an additional step.
21
Q
Tissue and organ placement are specified by the anterior-posterior and dorsal-ventral _____ in Drosophila.
A
axes
22
Q
Many of the structures found in the vertebrate body develop from neural _____
cells.
A
crest
23
Q
Differentiation of neural crest cells is determined by their ______ pathway and their final _____.
A
migration
location
24
Q
The dorsal nerve cord forms during the process of
A
neurulation
25
A significant change in vertebrate development was the evolution of the ______ chamber from ____ _____ slits.
Gill
Pharyngeal
gill
26
The process of neurulation occurs in all
chordates
27
The appearance of which of the following cell types was a key event in the evolution of vertebrates? These cells migrate and eventually develop into many of the structures found in the vertebrate body.
Neural crest cells
28
Neural crest cells migrate along how many different pathways?
3
29
True or false: The evolution of the gill chamber from the pharyngeal slits in vertebrates marked a significant change from filter feeder to predator.
True.
Reason: The evolution of the gill chamber was a key event in the transition from filter feeding to active predation, which requires a much higher metabolic rate.
30
What is fertilisation and development?
Development is the process in which a single undifferentiated cell will multiply. So you have mitosis producing thousands or millions or trillions of cells. It depends on animal, but its not only about the quantity of cells its also about differentiation. End product will have different cell types, muscles, red blood cells etc.
31
What is Ontogeny?
onto means being, thats a branch of philosophy, studying the nature of being an ‘geny’ from Genesis, from origin. So the origin of beings.
32
What is development?
Development (ontogeny) is the process by which multicellular organisms grow and differentiate tissues and organs.
33
What does development start with?
Starts with a one undifferentiated cell embryo (zygote), ends with a mature adult with multiple differentiated cells.
34
What does development also include?
It also includes regeneration, asexual reproduction, metamorphosis (i.e. insects), and stem cells differentiation
35
Outline the life cycle of an amphibian.
Start with this process in which a female and male get fecundated eggs, the sperm from the male is going to fecundate the female egg. We have a 1st stage that is called a zygote which is a unicellular stage, zygote starts to divide, from this stage of division we will move to the blastula, and then from the blastula until you get a juvenile that will become sexually mature and will close the cycle.
36
What do Fertilization and cleavage initiate?
embryonic development
37
What is Fertilization?
is the formation of a diploid zygote from a haploid egg and sperm
38
Why do we need the molecules in the surface to recognise each other?
allowing the binding of 1 sperm cell to the egg and this will trigger this fusion of the one gamete with the other gamete. This fusion of the two gametes is going to trigger a series of processes that are going to prevent that other sperm cells coming inside the egg.
39
_______ play a crucial role in each step
Molecules
40
Summarise the process of fertilization
- -Sperm penetrate the protective layer around the egg
- -Receptors on the egg surface bind to molecules on the sperm surface
- -Changes at the egg surface prevent polyspermy, the entry of multiple sperm nuclei into the egg
41
What happens in the acrosome reaction (step 1)?
Acrosome contains a vesicle that contains protein hydrolase and other enzymes that are able to digest the protective layer. Acrosome reaction- will be triggered when the sperm and the egg recognise each other, consequence of this recognition is that the sperm is going to release the enzymes that are present in the acrosome. Enzymes are going to digest the protective membrane of the egg.
42
How is the acrosomal reaction triggered by?
The acrosomal reaction is triggered when the sperm meets the egg.
43
What does the acrosome at the tip of the sperm release during step 2?
The acrosome at the tip of the sperm releases hydrolytic enzymes that digest material surrounding the egg
44
What happens during step 3 of fertilization?
- -Cytoskeleton bridge between sperm-egg.
- -when the cell membrane of the egg is available, the sperm will start the acrosomal process, which will build a bridge between its cytoplasm and the cytoplasm from the egg, using the cytoskeleton. So this bridge will communicate the cytoplasm from the cell with the cytoplasm from the egg.
45
What happens during step 4 of fertilization?
- -Membrane fusion sperm-egg.
- -we merge the 2 membranes from the 2 cells and this allows/ facilitates the injection of the DNA present in the sperm inside the egg. Now that we have this fusion the content of the sperm, the genetic content will be inside, will be pushed inside.
46
What happens during step 5 of fertilization?
sperm nucleus enters egg
47
What do we need to prevent once the two cells have merged?
Now that the 2 cells have merged, we need to prevent other sperm cells from entering the egg.
48
What is polyspermy?
would unbalance the amount of genetic material within the embryo.
49
What is the fast block to polyspermy?
----Seconds after the sperm binds to the egg, ion channels open in the egg plasma membrane.
------Sodium ions diffuse (Na+2) and cause the depolarization of the egg membrane.
------The depolarisatin acts as a fast block to polyspermy.
-----as soon as there is a merger of the two cells, all the ion channels that are found surrounding the fusion area will start to open an exchange of sodium ions with the extracellular environment. Will produce a change in the electrical charge of the membrane and now this electrical charge is going to make the cell membrane repulsive, repel any sperm cells that try to bind to them.
50
What is the cortical reaction?
----Fusion of egg and sperm also initiates the cortical reaction
----Seconds after the sperm binds to the egg, vesicles in the egg release their contents (Ca+2 wave) and form a fertilization envelope
-----The fertilization envelope acts as a slow block to polyspermy
51
What does the calcium wave stimulate during the cortical reaction?
calcium wave is going to stimulate the cell membrane of the embryo to produce a fertilization envelope.
52
What is fertilization followed by?
cleavage,
53
What is cleavage?
a period of rapid cell division without growth
We will start of with one big zygote, one single cell that will divide into smaller ones and those smaller cells, with an embryo, is what we call the blastomeres (units of germination).
54
What does cleavage partition?
- --Cleavage partitions embryo into many smaller cells called blastomeres
- -As blastomeres divide they create a cavity in the centre of the embryo and this is called blastocoel
55
What is the blastula?
The blastula is a ball of cells with a fluid-filled cavity called a blastocoel
56
what does the process of cell division (mitosis) involve?
from one cell, division produces many cells
57
What is Gastrulation?
Gastrulation rearranges the cells of a blastula into a layered embryo called a gastrula.
58
What do we start of with in order to produce blastomeres?
We will start of with one big zygote, one single cell that will divide into smaller ones and those smaller cells, with an embryo, is what we call the blastomeres (units of germination).
59
What happens when the blastomeres divide?
As blastomeres divide they create a cavity in the centre of the embryo and this is called blastocoel.
60
When do cells start to produce the first hint of differentiation?
Cells start to produce the first hint of differentiation. Blastula is a perfect sphere and now in gastrulation you have that some of the cells inside the blastula will start to move inwards and we generate this tube inside the embryo. Tube is called the embryonic digestive system or the archenteron.
61
What is the external layer of the embryo called?
External layer of the embryo is called the ectoderm and the endoderm is the digestive system.
62
Where is the first point of entry?
The first point of entry, this invagination is called the blastopore
63
What is the difference between protostomes and the deuterostomes?
is the fate of the blastopore, the blastopore is the first entrance or this first hole that emerges in the embryo as a consequence of gastrulation.
64
What will happen as a result of the gastrulation process?
The primitive streak will thicken and will be the result of the gastrulation process.
65
Why do we have additional membranes during vertebrate gastrulation?
We have additional membranes that will perform different functions. One being a trophoblast.
66
What do you have in addition to the endoderm and ectoderm?
You are going to have a series of membranes, extra embryonic tissues, in addition to the endoderm and ectoderm.
67
What is implantation?
Process of binding the zygote with a womb
68
What are extraembryonic membranes?
because they are outside of the embryo, additional layers to the embryo.
69
What happens once we have the formation of the extraembryonic membranes?
Now that we have this structure, gastrulation is going to be very similar to the one we saw on the chickens. One of the layers in the embryo is going to produce a primitive streak that is going to invaginate and produce a gastrulation.
70
What do we have now the embryo is inside the uterus?
we have that the epiblast and the hypoblast have differentiated and those extra embryonic membranes are forming around. You have the amniotic cavity that is going to be helped by the amnion. The yolk sac with the yolk and the chorion that is going to be mostly the interface between the circulatory system of the mother and the embryo. Structure will start to develop and the epiblast and the hypoblast, we’re going to have the epiblast will invaginate, with the, using the primitive streak, therefore we will end with 3 layers, ecoderm, mesoderm and the endoderm.
71
What is the endoderm in contact with?
Endoderm is in contact with the yolk sac where the food is coming from.
72
What is the Notochord?
is the rudiment, the predecessor of the spinal cord. Looks like a rod that extends along the back, the dorsal side, of the embryo. This notochord will start to secrete some signals. Molecules that will induce other tissues, like the ectoderm to form the neural plate.
73
What is cell differentiation?
the cells become specialised (i.e. differentiation in the gut of neurons, muscular cells, epithelia,…)
74
What are the features of the embryonic layers (or germ layers)?
Germ layer
Ectoderm
Endoderm
75
What is the germ layer?
embryonic tissue (collection of specialized cells)
76
What is the ectoderm?
is the germ layer covering the embryo’s surface (skin).
| epidermis and nervous system, as well as hair, cornea, tooth enamel, etc.
77
What is the endoderm?
```
is the innermost germ layer and lines the developing digestive tube, called the archenteron (gut).
digestive tract (i.e. guts) and organs derived from it (i.e. lungs) as well as secretory organs (liver, pancreas, thyroid, thymus…).
```
78
What is a diploblastic animals?
animals have ectoderm and endoderm, include non-bilaterians
79
What is a triploblastic animals?
Triploblastic animals also have an intervening third layer, the mesoderm; these include all bilaterians.
80
What is the mesoderm?
coelom, notochord in chordates, muscles, bone/cartilage, circulatory, spleen, kidney, reproductive, etc.
81
What is Morphogenesis?
Tissues formation. Differentiated cells form generalised tissues and organs (e.g. embryo gut), the shape and structure of the organism emerges
82
What is symmetry?
Result of applying an imaginary plane that divides an organism into roughly mirror image halves.
83
What is the fate of the blastopore in protstomes?
In protostomes (“mouth first”) the blastopore becomes mouth
84
What is the fate of the blastopore in deuterostomes?
In deuterostomes (“mouth second”) the blastopore becomes the anus.
85
What occurs during the gastrulation in chicks?
----Before gastrulation, the embryo is composed of an upper and lower layer, the epiblast (ectoderm) and hypoblast (endoderm), respectively
---During gastrulation, epiblast cells move toward the midline of the blastoderm and then into the embryo toward the yolk
---The midline thickens and is called the primitive streak.
86
What occurs during the gastrulation in humans?
----Human eggs have very little yolk
---A blastocyst is the human equivalent of the blastula
---The trophoblast is the outer epithelial layer of the blastocyst and does not contribute to the embryo, but instead initiates implantation
87
What happens following implantation?
Following implantation, the trophoblast continues to expand, and a set of extraembryonic membranes is formed.
88
What does gastrulation involve?
Gastrulation involves the inward movement from the epiblast through a primitive streak, similar to the chick embryo.
89
What happens after gastrulation?
After gastrulation, the embryonic germ layers have formed.
90
Outline gastrulation?
1) Blastocyst reaches uterus.
2) Blastocyst implants (7 days after fertilization).
3) Extraembryonic membranes
start to form (10–11 days), and gastrulation begins (13 days).
4)Gastrulation has produced a three-layered
embryo with four extraembryonic membranes:
the amnion, chorion, yolk sac, and allantois.
91
What are the four extraembryonic membranes?
----Chorion: outermost layer, with two sublayers, trophoblast and mesoderm. Forms the placenta. Gas exchange.
----Allantois: “sausage”, full of blood vessels, nutrition, excretion and gas exchange.
----Amnion: full of amniotic fluid, embryo protection.
----Yolk sac: made of hypoblast (endoderm) cells, initial circulation, encloses the yolk (food)
92
What are the Developmental Adaptations of Amniotes (land vertebrates)?
---Land vertebrates (reptiles, birds, and mammals) form the four extraembryonic membranes
---These provide a life-support system for the further development of the embryo
- ---Reproduction outside of aqueous environments required evolution of
- --The shelled egg of birds, other reptiles, and the monotremes
- --The uterus of marsupial and eutherian mammals
93
What adaptions do both mammals and reptiles have?
In both adaptations, embryos are surrounded by fluid in a sac called the amnion.
Mammals and reptiles including birds are called amniotes for this reason.
94
What is the benefit of having an embryo surrounded by fluid?
This allows reproduction on dry land.
95
What happens during Organogenesis?
--Various regions of the germ layers develop into rudimentary organs
--Adoption of particular developmental fates may cause cells to change shape or even migrate to a new location in the body
--Neurulation is the formation of the brain and spinal cord in vertebrates
96
What happens during neurulation?
----Cells from the mesoderm form the notochord, a rod extending along the dorsal side of the embryo
---Molecules secreted (signaling) by the notochord and other tissues cause the ectoderm above to form the neural plate
----This is an example of induction, when cells or tissues cause a developmental change in nearby cells.
----The neural plate soon curves inward, forming the neural tube
----The neural tube will become the central nervous system (brain and spinal cord)
----The notochord will disappear before birth, but contributes to parts of the vertebral disks
97
What is cell migration?
----Neural crest are that cells develop along the neural tube
----Neural cells migrate in the body, eventually forming various parts of the embryo (nerves, parts of teeth, and skull bones)
----Mesoderm lateral to the notochord forms blocks called somites, which will form the vertebrae and the ribs and muscles associated with the vertebral column
98
What is a major force in cell shape changes?
Reorganizing the cytoskeleton is a major force in changing cell shape during development
For example, the contraction of actin filaments at the tip of cells causes them to become wedge shaped
This is a common mechanism for invaginating a cell layer
99
What is the cytoskeleton also responsible for?
The cytoskeleton is also responsible for cell migration
100
What also plays an important role in migration?
Cell adhesion molecules play a key role in migration
101
What does migration also involve?
Migration also involves the extracellular matrix (ECM), a meshwork of secreted glycoproteins and other molecules lying outside the plasma membrane of cells
102
Why is cell death important?
Cell death is also important in development
Apoptosis: programmed cell death
Example: limb development
103
What is Determination?
is a term referring to the process by which a cell or group of cells becomes committed to a particular fate.
104
What is Differentiation?
refers to the resulting specialization in structure and function.
105
What are fate maps?
- --Fate maps are diagrams showing organs and other structures that arise from each region of an embryo
- --Classic studies using frogs indicated that cell lineage in germ layers is traceable to blastula cells
106
Why do we use the nematode in studies?
Studies of the nematode Caenorhabditis elegans used the ablation (destruction) of single cells to determine the structures that normally arise from each cell
The researchers were able to determine the lineage of each of the 959 somatic cells in the worm
107
Using single-cell RNA sequencing to generate
a cell atlas
108
Where will the ligand travel?
Ligand will travel through the extracellular space, and will bind to the receptor in cell number 2. This receptor will start a cascade of activation so this protein will activate a protein in the cytoplasm. This protein will activate one protein in the nucleus membrane. At the end of this pathway/ cascade of activation, you will have transcribed and transcription factor.
109
What are neural crest cells?
There are some cells that are between the neural tube and the ectoderm
110
What are the two processes In morphogenesis or organogenesis?
1st one- is the change in cell shapes and we have seen this with the neural plate and the neural tube. The fact that those tissues and the way they can change their shape is allowing them to produce one new organ. Second process is cell migration- neural crest cells will move from our spinal cord to other parts of the body to contribute to other organs. The mesoderm is going to divide into smaller sections and become compartmentalized in little blocks called somites. Somites- will be the basis of the ribs and muscles in animal cells.
111
What do cell adhesion molecules highlight?
Cell adhesion molecules highlight a pathway of migration for the cells. These molecules will bind to the receptor in the membrane cell of the neural crest and this neural crest will start to follow the trail with movements and move through the parenchyma through the other cells inside the embryo until it reaches their destination.
112
What is single cell sequencing?
extracting the mRNA from cells and measuring it. Can take one cell from the embryo and can sequence all the genes that are being expressed there and you can repeat the same process with other cells but not only in the same developmental stage, not only in the blastula but you can do this later in the grastula and so on. Can use this cluster to group together cells, ell types based on how similar their expression levels are. Can use this to generate a cell Atlas.
113
What is development?
can be defined as the process of systematic, gene-directed changes through which an organism forms the successive stages of its life cycle
114
What is cell division in animals and plants?
A developing plant or animal begins as a fertilized egg, or zygote, that must undergo cell division to produce the new individual. In all cases early development involves extensive cell division, but in many cases it does not include much growth as the egg cell itself is quite large.
115
What are some overlapping processes?
----Cell division (mitosis): from one cell, division produces many cells
----Cell differentiation: the cells become specialised (i.e. differentiation in the gut of neurons, muscular cells, epithelia,…)
----Morphogenesis: Tissues formation. Differentiated cells form generalised tissues and organs (e.g. embryo gut), the shape and structure of the organism emerges
116
How do you make a multicellular organism?
Gene regulation (Transcription factors and signalling pathways)
Cell adhesion
Cell type specialization
Cell cycle
Immunity
117
All the cells have the same
genome
118
Cell differentiation occurs as a result of the
expression of different genes in different cells
119
Cell-specific sets of genes are
“switched on” by proteins called Transcription Factors, the resulting proteins define the type of cell
120
What do muscle cells produce?
Muscle cells (myoblasts) produce muscle-specific proteins (differentiation) that will form mucscles (morphogenesis)
The MyoD protein is a transcription factor that binds to promoters and switches on various target genes
MyoD is one of several “master regulatory genes” that activates the expression of muscle genes
121
What is a gene cascade?
Transcription factors that regulate the expression of other transcription factors, and so on.
122
What is meant by Morphogens?
proteins that establish embryo’s axes and other features using gradients of concentration
123
Outline the Maternal gene: bicoid (determines head)
Protein required for some early steps in pattern formation
It increased understanding of the mother’s role in embryo development
It demonstrated that a gradient of molecules can determine polarity and position in the embryo
124
What are Homeotic genes?
Genes which regulate the development of anatomical structures, usually specifying the position in an axis.
125
What is the Hox code?
combinations of different TFs specify different organs
126
What may homeotic mutants cause?
Mutants in which the position of organs along the anterior-posterior axis is altered (repetitions, change of order, etc.).
Example: ultrabithorax
127
what are hox genes also important for?
Hox genes are also important for limb patterning in development
A mutation in a human Hox gene (HoxD13) is responsible for the condition polysyndactyly seen in the photograph
128
what is the role of death in development?
Cell death is also important in development
Apoptosis: programmed cell death
Example: limb development
129
What do plants also do?
Genes with similar functions are found in plants too.For example, MADS-box genes do similar functions to homeobox (but are not evolutionarily related)SNARE genes (membranes fusion) independently evolve in animals an plants.
130
what are the main differences in plant and animal development?
Animals- Grow by cell division
Cell movement determines shape
Cell death determines shape
Embryonic shape determination
Grow to a fixed size and shape
Plants- Grow by cell expansion
Cell growth determine shape
Cell division plane determines shape
Post-embryonic shape determination
Grow to variable size and shape
131
What is EvoDevo?
Evolutionary developmental biology is the study of the evolution of developmental processes in multicellular organisms.
--Very different organism share very similar developmental genes (e.g. humans and flies)
…but minor differences in gene sequence or regulation can result in striking differences in form
132
Hox genes are shared by
most animal groups
133
What are Homeobox genes involved in?
Homeobox genes are involved in development in distant species
134
Different organisms have evolved
by changes to these key genes that control development
135
Sometimes the genes have evolved
new functions
136
What is an example of homeobox?
Arthropods diversity of body architectures is caused by changes in Hox genes expression
