-
The fate of cells in the embryo is determined by:
cytoplasmic determinants
-
What generates lots of small undifferentiated cells?
cleavage
-
A ____________ gives rise to cells of many different types, each with a different structure and corresponding function
single-celled zygote
-
What does a program of differential gene expression lead to?
the different cell types in a multicellular organism
-
During embryonic development, a fertilized egg gives rise to:
many different cell types
-
Cell types are organized successively into:
tissues, organs, organ systems, and the whole organism
-
What orchestrates the developmental programs for animals?
gene expression
-
The transformation from zygote to adult results from:
cell division, cell differentiation, and morphogenesis
-
What is cell differentiation?
the process by which cells become specialized in structure and function
-
The physical processes that give an organism its shape constitute
morphogenesis
-
Differential gene expression results from
genes being regulated differently in each cell type
-
What are cytoplasmic determinants?
maternal substances in the egg that influence early development
-
Explain what leads to different gene expression:
as the zygote divides by mitosis, cells contain different cytoplasmic determinants
-
What is induction?
- a process in which signal molecules from embryonic cells cause transcriptional changes to nearby target cells
- in other words, switch on genes in nearby cells
-
What is determination and when does it occur?
- determination proceeds differentiation and it commits a cell to its final fate.
- after determination, the cell fully becomes a specialized cell
-
What do myoblasts produce and form?
muscle-specific proteins and form skeletal muscle cells
-
What is one example of a "master regulatory genes" that produce proteins that commit the cell to becoming skeletal muscle?
MyoD
-
What is MyoD protein?
a transcription factor that binds to enhancers of various target genes
-
What is pattern formation?
the development of a spatial organization of tissues and organs
-
In animals, pattern formation usually begins with the establishment of the:
major axis
-
What do maternal genes encode for?
for cytoplasmic determinants that initially establish the axis of the body of drosophila
-
What maximum recombination frequency would be observed if the two genes are on separate chromosomes?
50%
-
What recombination frequency would be observed if two genes are on the same chromosome and they are so close together that a crossing over event is impossible?
0%
-
Are all genes genomically imprinted?
No, only a small subset of genes are genomically imprinted. It is estimated that only approximately 1% of genes may be imprinted.
-
What is responsible for most cases of Beckwith-Wiedemann syndrome?
genomic imprinting
-
What is a bicoid?
a morphogen determining head structures
-
An embryo whose mother has no functional bicoid gene lacks:
the front half of its body and has duplicate posterior structures at both ends
-
The bicoid research is important for three reasons:
- it identified a specific protein required for some early steps in pattern formation
- it increased understanding of the mother's role in embryo development
- it demonstrated a key developmental principle that a gradient of molecules can determine polarity and position in the embryo
-
What are the four stages of embryonic development?
- fertilization
- cleavage
- gastrulation
- organogenesis
-
Define fertilization:
combination of sperm and egg nuclei and egg activation; haploid to diploid
-
Define cleavage:
rapid cell divisions without substantial; growth in size to generate a multicellular embryo
-
Define gastrulation:
mass cell movements to generate three germ layers
-
Define Organogenesis:
localized changes in tissue and cell shape
-
What are blastomeres?
cleavage partitions the cytoplasm of one large cell into many smaller cells
-
What is the blastula?
a ball of cells with a fluid-filled cavity called a blastocoel
-
In frogs and many other animals, what is a key factor influencing the pattern of cleavage?
the distribution of yolk
-
The ____ pole has more yolk; the _____ pole has less yolk
vegetal, animal
-
What does the difference in yolk distribution result in?
animal and vegetal hemispheres that differ in appearance
-
When do animal embryos complete cleavage?
when the ratio of material in the nucleus relative to the cytoplasm is sufficiently large
-
Morphogenesis in animals involves specific changes in:
cell shape, position, and survival
-
What is morphogenesis? What does it involve?
- the process by which cells occupy their appropriate locations
- gastrulation and organogenesis
-
What is gastrulation?
the movement of cells from the blastula surface to the interior of the embryo
-
What is organogenesis?
the formation of organs
-
Where is the ectoderm and what does it make?
- outer layer of embryo
- sweat glands, hair follicles, nervous and sensory systems, pituitary gland, adrenal medulla, jaws, teeth, and germ cells
-
Where is the mesoderm and what does it make?
- middle layer of embryo
- skeletal and muscular systems, circulatory and lymphatic systems, excretory and reproductive systems (except germ cells), dermis of skin, and adrenal cortex
-
Where is the endoderm and what does it make?
- inner later of embryo
- epithelial lining of digestive tract and associated organs (liver and pancreas), epithelial lining of respiratory, excretory, and reproductive tracts and ducts, thymus, thyroid, and parathyroid glands
-
During _______, various regions of the germ layers develop into rudimentary organs
organogenesis
-
Early in vertebrae organogenesis, the ______ forms from mesoderm, and the _________ forms from ectoderm
notochord, ectoderm
-
The neural plate soon curves inward, forming the _________
neural tube
-
The neural tube will become:
the central nervous system (brain and spine)
-
____________ develop along the neural tube of vertebrates and form various parts of the embryo (nerves, parts of teeth, skull bones, and so on)
neural crest cells
|
|