47 Flashcards
(76 cards)
1
Q
What is present in a human embryo 5 weeks after conception?
A
Eyes, brain, limb buds, heart, and spinal cord.
2
Q
What is fertilization?
A
The formation of a diploid zygote from a haploid egg and sperm
3
Q
Which week of developement are all body features present in a human embryo?
A
Week eight.
4
Q
What are the different stages of embryonic development?
A
- Fertilization
- Cleavage
- Gastrulation
- Organogenesis
5
Q
Molecules and events at the egg surface play a crucial role in each step of fertilization. What are they?
A
Sperm penetrates 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.
6
Q
What triggers the acrosomal reaction?
A
The sperm meeting the egg.
7
Q
What does the acrosome at the tip of the sperm do?
A
Releases hydrolytic enzymes that digest material surrounding the egg.
8
Q
What sets up a fast block to polyspermy?
A
Gamete contact and/or fusion depolarizing the egg cell membrane
9
Q
What is the cortical reaction?
A
Seconds after the sperm binds to the egg, vesicles just beneath the egg plasma membrane release their contents and form a fertilization envelope that acts as a slow block to polyspermy.
10
Q
What initiates the cortical reaction?
A
Fusion of egg and sperm.
11
Q
The cortical reaction requires a high concentration of which ions in the egg in sea urchins?
A
Ca^2+.
12
Q
What does a Ca^2+ spread across the egg correlate with?
A
Appearance of the fertilization envelope.
13
Q
The rise in Ca^2+ in the cytosol increases the rates of [1] and [2] by the egg cell. With these rapid changes in metabolism, the egg is said to be [3]. The [4] and [5] needed for activation are present in the cell. (in sea urchins)
A
- Cellular respiration
- Protein synthesis
- Activated
- Proteins
- mRNAs
14
Q
Is mammalian fertilization internal or external?
A
Internal.
15
Q
What does a sperm need to go through before reaching the extracellular matrix of the egg? (mammals)
A
A sperm must travel through a layer of follicle cells surrounding the egg before it reaches the zona pellucida, or extracellular matrix of the egg.
16
Q
Sperm binding triggers a [1]. In mammals, the first cell division occurs [2] after sperm binding.
A
- Cortical reaction
- 12-36 hours
17
Q
Summary of sea urchin fertilization. (3 steps)
A
- Chemotaxis: sea urchin eggs release species-specific chemical attractants, such as resact, which guide sperm to the egg.
- Acrosomal Reaction: upon contact with the egg jelly, the sperm undergoes the acrosomal reaction, releasing enzymes that help it penetrate the jelly layer
- Bindin: the sperm then uses a protein called bindin to attach to receptors on the egg’s vitelline layer, ensuring species-specific binding.
18
Q
Summary of fertilization in humans. (4 stages)
A
- Capacitation: Human sperm undergo capacitation in the female reproductive tract, which prepares them for fertilization by enhancing their motility and ability to undergo the acrosome reaction.
- Zona Pellucida Binding: human eggs are surrounded by the zona pellucida, a glycoprotein layer. Sperm bind to specific glycoproteins, like ZP3, on the zona pellucida, triggering the acrosome reaction.
- Acrosome reaction: The acrosome reaction releases enzymes that allow the sperm to penetrate the zona pellucida
- Fusion: Once through the zona pellucida, the sperm binds to and fuses with the egg’s plasma membrane, leading to fertilization.
19
Q
Humans do not have an [1]. Both humans and sea urchins have a [2].
A
- Electrical fast block mechanism
- Cortical gradual reaction
20
Q
Sea urchin’s sperm contributions to the next generation. (four)
A
- Genetic Material: provides half of genetic material required for zygote formation
- Centrosome: essential for organizing the microtubules during cell division
- Activation Signals: entry of the sperm into the egg triggers a series of biochemical reactions that activate the egg and initiate embryonic development
- Mitochondrial DNA: Contributes a small amount that typically is degraded and not passed on to the offsrping
21
Q
Human Sperm contribution to the next generation (5).
A
- Chromosomes with epigenetic marks, such as DNA methylation and histone modifications, which can influence gene expression and development in the embryo
- The sperm contributes the centrosome, which is essential for organizing the microtubules during cell division.
- Egg activation
- Completion of meiosis II
- Sperm also contribute various RNAs and proteins that play roles in early embryonic development and gene regulation.
22
Q
What is cleavage? How does cleavage form blastomeres?
A
A period of rapid cell division without growth. It partitions the cytoplasm of one large cell into many smaller cells called blastomeres.
23
Q
What is the blastula?
A
A ball of cells with a fluid-filled cavity called blastocoel
24
Q
What are the four steps of holoblastic cleavage?
A
- Fertilized egg
- Four-cell stage
- Early blastula
- Later blastula
25
What is the cleavage pattern in Frogs?
Cleavage is asymmetric due to the distribution of yolk (stored nutrients). The vegetal pole has more yolk, and the animal pole has less yolk. The yolk greatly affects the pattern of cleavage.
26
The first two cleavage furrows in the frog form four equally sized [1]. The third cleavage is [2] due to the yolk in the [3].
1. blastomeres
2. asymmetric
3. vegetal hemisphere
27
What is holoblastic cleavage and in which species does it occur?
Complete division of the egg occurs in species whose eggs have little or moderate amounts of yolk, such as sea urchins and humans.
28
What is meroblastic cleavage and in which species does it occur?
Incomplete division of the egg occurs in species with yolk-rich eggs, such as reptiles and birds.
29
In Drosophila and other insects, multiple rounds of [1] occur without [2]
1. mitosis
2. cytokinesis
30
What is morphogenesis?
The process by which cells occupy their appropriate locations. It involves both gastrulation and organogenesis.
31
What is gastrulation and what does it do?
The movement of cells from the blastula surface to the interior of the embryo. Gastrulation rearranges the cells of a blastula into a 3-layered embryo called a gastrula
32
What is organogenesis?
The formation of organs
33
What are the 3 layers produced by gastrulation?
Germ layers: each contribute to specific structures in the adult animal
1. Ectoderm - forms the outer layer
2. Endoderm - lines the digestive tract
3. Mesoderm - partly fills the space between the endoderm and ectoderm
34
Explain gastrulation in frogs, including what the different cell groups form.
Gastrulation begins when a group of cells on the dorsal side of the blastula begins to invaginate. Cells continue to move from the embryo surface into the embryo by involution. These cells become the endoderm and mesoderm. Cells on the embryonic surface will form the ectoderm. The newly formed cavity is called the archenteron and opens through the blastopore, which will become the anus.
35
Name 7 structures made from the ectoderm.
1. Epidermis of skin and its derivatives (including sweat glands and hair follicles)
2. Nervous system
3. Sensory system
4. Pituitary gland
5. Adrenal medulla
6. Jaws
7. Teeth
36
Name 8 structures made from the mesoderm.
1. Skeletal system
2. Muscular system
3. Circulatory system
4. Lymphatic system
5. Excretory system
6. Reproductive system (minus germ cells)
7. Dermis of skin
8. Adrenal cortex
37
Name 7 structures made from the endoderm.
1. Epithelial lining of digestive tract and associated organs
2. Epithelial lining of respiratory tract/duct
3. Epithelial lining of excretory tract/duct
4. Epithelial lining of reproductive tract/duct
5. Thymus gland
6. Thyroid gland
7. Parathyroid gland
38
Prior to gastrulation in chicks, the embryo is composed of an upper and lower layer. What are they called?
Upper = epiblast
Lower = hypoblast
39
What happens during gastrulation in chicks to the epiblast cells? Hypoblast cells?
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. The hypoblast cells contribute to the sac that surrounds the yolk and a connection between the yolk and the embryo, but do not contribute the embryo itself.
40
Human eggs have [1] yolk.
1. Very little
41
What is the human equivalent of the blastula?
A blastocyst.
42
What is the inner cell mass in human gastrulation?
A cluster of cells at one end of the blastocyst
43
What is a trophoblast in human gastrulation?
The outer epithelial layer of the blastocyst. It does not contribute to the embryo, but instead initiates implantation
44
What happens following implantation in human gastrulation?
The trophoblast continues to expand, and a set of extraembryonic membranes is formed. These enclose specialized structures outside of the embryo.
45
What does human gastrulation involve that is similar to the chick embryo?
The inward movement of the epiblast through a primitive streak.
46
What is formed after human gastrulation?
The embryonic germ layers with four extraembryonic membranes; the amnion, chorion, yolk sac, and allantois
47
7 components of 10 day old human embryos (see slide 61 for picture)
1. Expanding region of trophoblast
2. Amniotic cavity
3. Epiblast
4. Hypoblast
5. Yolk sac (from hypoblast)
6. Extraembryonic mesoderm cells (from epiblast)
7. Chorion (from trophoblast)
48
What are the four extraembryonic membranes and what do they provide?
The chorion, allantois, amnion, and yolk sac provide a life-support system for the further development of the embryo.
49
Reproduction outside of aqueous environments requires the development of the [1] of birds, reptiles, and the [2] and the [3] of [4] and [5] mammals
1. Shelled egg
2. Monotremes
3. Uterus
4. Marsupial
5. Eutherian
50
Embryos are surrounded by fluid in a sac. What is it called? What does it allow for?
Amnion. This allows for reproduction on dry land. Mammals reptiles and birds are called amniotes for this reason.
51
What does the chorion function in?
Gas exchange.
52
What does the amnion enclose?
The amniotic fluid.
53
What does the yolk sac enlcose?
The yolk.
54
What does the allantois dispose of / contribute to?
It disposes of waste products and contributes to gas exchange.
55
What happens during organogenesis?
various regions of the germ layers develop into rudimentary organs
56
What is neurulation and how does it begin? What is this an example of?
Neurulation is the formation of the brain and spinal cord in vertebrates. Neurulation begins as cells from the dorsal mesoderm form the notochord, a rod extending along the dorsal side of the embryo. Signaling molecules secreted 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
57
What forms the neural tube and what will it become?
The neural plate curves inward, forming the neural tube. The neural tube will become the central nervous system (brain and spinal cord).
58
What happens to the notochord?
It disappears before birth, but contributes to parts of the disks between vertebrae
59
What are 7 structures in a neural plate formation in a frog? (see slide 70 for picture)
1. Neural plate
2. Neural fold
3. Notochord
4. Ectoderm
5. Mesoderm
6. Endoderm
7. Archenteron
60
What are 5 structures in neural tube formation in frogs?
1. Neural fold
2. Neural plate
3. Neural crest cells
4. Outer layer of ectoderm
5. Neural tube
61
Explain cell migration in organogenesis. (frogs)
Neural crest cells develop along the neural tube of vertebrates and 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.
62
What happens to parts of the somites?
They dissociate to form mesenchyme cells, which form the vertebrae, ribs, and muscles associated with the vertebral column.
63
What are 6 structures of somites in frogs? (see slide 77 for picture)
1. Neural tube
2. Notochord
3. Coelom
4. Neural crest cells
5. Somite
6. Archenteron (digestive cavity)
64
Talk about organogenesis in chicks and insects vs frogs.
Early organogenesis in the chick is similar to that in the frog. By the time the embryo is 3 days old, rudiments of the major organs are readily apparent. Pattern and appearance of organogenesis in invertebrates are different from that in vertebrates. However, the mechanisms of organogenesis, such as neurulation, are similar.
65
What are 6 terms associated with late organogenesis? (see slide 82)
1. Eye
2. Forebrain
3. Heart
4. Blood vessels
5. Somites
6. Neural tube
65
What are 11 terms associated with early organogenesis? (see slide 81)
1. Neural tube
2. Notochord
3. Archenteron
4. Lateral fold
5. Extraembryonic membranes
6. Yolk
7. Yolk stalk
8. Yolk sac
9. 3 germ layers (endo-ecto-meso)
10. Coelom
11. Somite
66
What can the movements of parts of a cell bring about or enable in animals? What is essential to these events?
Movements of parts of a cell can bring about cell shape changes or can enable a cell to migrate to a new location. The microtubules and microfilaments of the cytoskeleton are essential to these events.
67
What is a major force in changing cell shape during development? Give an example.
Reorganizing the cytoskeleton. For example, the contraction of actin filaments at the apical end of cells causes them to become wedge shaped. This is a common mechanism for invaginating a cell layer.
68
68
State the order of structures in which the neural tube is formed (6)
1. Ectoderm
2. Cuboidal ectodermal cells
3. Neural plate
4. Microtubules
5. Actin filaments
6. Neural tube
69
What is the name for programmed cell death?
Apoptosis.
70
Explain apoptosis during development. Give an example.
At various times during development, individual cells, sets of cells, or whole tissues stop developing, die, and are engulfed by neighboring cells. For example, many more neurons are produced in developing embryos than will be needed. Extra neurons are eliminated by apoptosis.
71
Concept 47.3: Cytoplasmic determinants and inductive signals contribute to [1]
1. Cell fate specification
72
What is determination?
A term referring to the process by which a cell or group of cells becomes committed to a particular fate
73
What is differentiaition?
Refers to the resulting specialization in structure and function
74
Cells in a multicellular organism share the same [1]. Differences in cell types are the result of the [2] of different sets of [3]
1. genome
2. expression
3. genes
