BIO 172 EXAM 4 QUESTIONS AND ANSWERS
apoptosis
- some cells are eliminated, normal part of development
- ex. chicken feet could look webbed if defective apoptosis
differentiation
restricts alternative fates
zygote
totipotent, will give rise to all cells
blastocyst
pluripotent, inner cell mass will give rise to all the cells of the embroy
gastrula
multipotent, will give rise to different cell types within a germ layer, but cannot contribute to
other germ layers
adult stem cells
- aka somatic stem cells
- population of stem cells in adult body with limited potential
- multipotent
embryonic stem cells
- can be derived from the inner cell mass of a blastocyst
- can become any type of cell in the body
- pluripotent
why do differentiating cells lose their potential?
hypothesis 1: gene regulation
hypothesis 2: genome reduction
- nuclear transfer experiment: studying tadpoles
- conclusion: differentiated cells contain a complete genome, support hypothesis 1
stages of development
1. fertilization
2. cleavage
3. gastrulation
4. organogenesis
,fertilization
- multiple sperm contact oocyte
- sperm release enzymes to aid movement through outer layers of oocyte
- plasma membrane of sperm and oocyte fuse with each other
- sperm nucleus enters egg cytoplasm
- pronuclei fuse
*is species specific - fertilizin (protein on surface of egg) and bindin (protein on surface of
sperm... only bind to the opposite sperm/egg of its own species (important for fish)
cleavage
- rapid mitotic division without gap phases and without growth
- cytoplasm is divided into smaller and smaller cells
- early cleavage stages, no RNA transcription occurs, transcription from the zygotic genome
begins later in development
- cytoplasmic determinants control initial development
- zygote - morula (clump of cells all pretty much the same)
gastrulation
- dramatic cell movements and rearrangements to generate 3 germ layers
1. ectoderm: gives rise to things on the outside, skin
2. mesoderm: gives rise to things in between inside and outside
3. endoderm: gives rise to things on the inside, internal organs
organogenesis
- organs begin to form
- differentiation: cells begin to produce proteins specific to a particular cell type
- all cells in the body have the same DNA (genes) but express a different set of proteins
animal development needs
1. cell proliferation
2. movement
3. signaling
4. apoptosis
5. differentiation
how do cells acquire info to specify their identity in the embryo?
- mutant fruit fly experiment
- correspondence between adult and larval body parts
bicoid mutant
, - 2 tail mutant (tail at both ends)
- loss of ability to make anterior parts
- bicoid concentrated at posterior part
bicoid
- regulatory transcription factor that activates genes required for building anterior structures
- morphogen: bicoid mRNA and protein in the unfertilized egg forms a gradient, different
concentrations give rise to different things
- high bicoid = head
- low bicoid = thorax
- no bicoid = abdomen
*maternal effect gene
nanos mutant
- lack posterior structure
- concentrated at anterior part
Hox genes
- expressed from zygotic genome, not materal effect genes
- order of genes on the chromosome is the same order on the embryo
- ex: pax6 eyeless function... take eyeless gene and inject it into fruitflies so it carries an extra
piece of DNA activated by antenna enhancer
animal vs plant development
- plant cells do not move during development
- some plant cells are able to de-differentiate (become undifferentiated)
- animals: sperm and egg are produced directly from diploid cells via meiosis
- plants: sperm and egg cells are produced from haploid cells via mitosis
gametogenesis in plants
- gametes: haploid cells (egg/oocytes and sperm)
- formed in reproductive organs of adult organsims, often in the same individual plant
- stamen = males
- carpel = female
double fertilization
- one sperm nucleus fuses with egg, forms zygote
- other sperm nucleus unites with central cell to form tripod cell that gives rise to endosperm
- endosperm: source of nutrients for embryo (and for us: white rice and wheat are the endosperm)
- creates seed: inside there is a diploid embryo surrounded by triploid endosperm
apoptosis
- some cells are eliminated, normal part of development
- ex. chicken feet could look webbed if defective apoptosis
differentiation
restricts alternative fates
zygote
totipotent, will give rise to all cells
blastocyst
pluripotent, inner cell mass will give rise to all the cells of the embroy
gastrula
multipotent, will give rise to different cell types within a germ layer, but cannot contribute to
other germ layers
adult stem cells
- aka somatic stem cells
- population of stem cells in adult body with limited potential
- multipotent
embryonic stem cells
- can be derived from the inner cell mass of a blastocyst
- can become any type of cell in the body
- pluripotent
why do differentiating cells lose their potential?
hypothesis 1: gene regulation
hypothesis 2: genome reduction
- nuclear transfer experiment: studying tadpoles
- conclusion: differentiated cells contain a complete genome, support hypothesis 1
stages of development
1. fertilization
2. cleavage
3. gastrulation
4. organogenesis
,fertilization
- multiple sperm contact oocyte
- sperm release enzymes to aid movement through outer layers of oocyte
- plasma membrane of sperm and oocyte fuse with each other
- sperm nucleus enters egg cytoplasm
- pronuclei fuse
*is species specific - fertilizin (protein on surface of egg) and bindin (protein on surface of
sperm... only bind to the opposite sperm/egg of its own species (important for fish)
cleavage
- rapid mitotic division without gap phases and without growth
- cytoplasm is divided into smaller and smaller cells
- early cleavage stages, no RNA transcription occurs, transcription from the zygotic genome
begins later in development
- cytoplasmic determinants control initial development
- zygote - morula (clump of cells all pretty much the same)
gastrulation
- dramatic cell movements and rearrangements to generate 3 germ layers
1. ectoderm: gives rise to things on the outside, skin
2. mesoderm: gives rise to things in between inside and outside
3. endoderm: gives rise to things on the inside, internal organs
organogenesis
- organs begin to form
- differentiation: cells begin to produce proteins specific to a particular cell type
- all cells in the body have the same DNA (genes) but express a different set of proteins
animal development needs
1. cell proliferation
2. movement
3. signaling
4. apoptosis
5. differentiation
how do cells acquire info to specify their identity in the embryo?
- mutant fruit fly experiment
- correspondence between adult and larval body parts
bicoid mutant
, - 2 tail mutant (tail at both ends)
- loss of ability to make anterior parts
- bicoid concentrated at posterior part
bicoid
- regulatory transcription factor that activates genes required for building anterior structures
- morphogen: bicoid mRNA and protein in the unfertilized egg forms a gradient, different
concentrations give rise to different things
- high bicoid = head
- low bicoid = thorax
- no bicoid = abdomen
*maternal effect gene
nanos mutant
- lack posterior structure
- concentrated at anterior part
Hox genes
- expressed from zygotic genome, not materal effect genes
- order of genes on the chromosome is the same order on the embryo
- ex: pax6 eyeless function... take eyeless gene and inject it into fruitflies so it carries an extra
piece of DNA activated by antenna enhancer
animal vs plant development
- plant cells do not move during development
- some plant cells are able to de-differentiate (become undifferentiated)
- animals: sperm and egg are produced directly from diploid cells via meiosis
- plants: sperm and egg cells are produced from haploid cells via mitosis
gametogenesis in plants
- gametes: haploid cells (egg/oocytes and sperm)
- formed in reproductive organs of adult organsims, often in the same individual plant
- stamen = males
- carpel = female
double fertilization
- one sperm nucleus fuses with egg, forms zygote
- other sperm nucleus unites with central cell to form tripod cell that gives rise to endosperm
- endosperm: source of nutrients for embryo (and for us: white rice and wheat are the endosperm)
- creates seed: inside there is a diploid embryo surrounded by triploid endosperm
