©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
CMMB403 Final Exam Questions and
Answers 100% Solved
72 hours (8 cells) (BEFORE BLASTOCYST STAGE) - ✔✔what is the
human MZT
Mid-blastula transition/maternal-zygotic transition - ✔✔when the
transcription of zygotic genes begins and maternal mRNAs are degraded,
the cell cycle lengthens, gap stages are added (before is only M and S) and
the synchronicity of cell division is lost. - embryo runs on maternal
resources (mRNAs and proteins in the egg @ time of fertilization) until this.
is when maternal effect genes are turned off.
gap genes - ✔✔organize cells into groups of segments along anterior-
posterior axis - are activated OR repressed by MEG products expressed
from the zygotic genome (after MZT) and have broad expression domains -
divide embryo into regions about 2 segments wide - when lose function
causes large gaps in embryo where multiple segments lost, missing several
segments in a row - they have 1 or 2 broad stripes of expression and define
,©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
boundaries in the early embryo - are ZYGOTICALLY expressed - ex:
Kruppel
maternal effect genes - ✔✔A gene that, when mutant in the mother, results
in a mutant phenotype in the offspring, regardless of the genotype -
mRNAs deposited in oocyte set up early polarity translated at fertilization -
dads genes do not matter for this - create the anterior/posterior axis
(cytoplasmic polarity) through bicoid and nanos that form morphogen
gradients possible due to syncytium and are incorporated into cells during
cellularization
pair-rule genes - ✔✔organize cells into individual segments/ divide the
embryo into segment-sized units along the anterior/posterior axis - are
activated OR repressed by products of gap genes - helps to define the
spatial domains of the homeotic genes - expressed at ONSET of
cellularization - have 7 stripes of expression - miss portions of every other
segments and may delete boundaries or reduce segment numbers - when
mutated have half as many segments and result in only 7 stripes instead of
14 and - ex: fushi tarazu and even skipped
homeotic genes - ✔✔Genes that determine basic features of where a body
part is - define the identities of each of the segments - their expression
,©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
domain is correlated with where they are on the chromosome - are all TFs
that regulate segment specific genes - have vertebrate homologs!
segment polarity genes - ✔✔activated by pair rule gene products after
cellularization, give each individual segment its polarity - have 14 stripes of
expression - when mutated polarity disrupted in each segment (segment
number doesn't change will get 14) - encode for members of shh and wnt
pathways
maternal effect - ✔✔which gene is transcribed BEFORE and upon
fertilization
gap - ✔✔which genes are transcribed after fertilization but before
cellularization and the MZT
pair rule - ✔✔what genes are expressed at the onset of cellularization/just
before - with the MZT
segment polarity - ✔✔what genes are expressed after cellularization and
the MZT
1 or 2 - ✔✔how many stripes of expression do gap genes have (broad)
7 - ✔✔how many stripes of expression do pair rule genes have
14 - ✔✔how many stripes of expression do segment-polarity genes have
, ©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
Parasegments - ✔✔transient subdivisions that occur in the Drosophila
embryo prior to the formation of segments - are off register by one half from
those of the segments, is made up of the cells in the posterior compartment
of one segment and the anterior compartment of the next segment. the
expression patterns of early segmentation genes are at THESE boundaries
- is the "fundamental unit of embryonic expression"
kruppel - ✔✔gap gene expressed in parasegments 4-6, is repressed by
hunchback, if mutated will be missing several segments in a row (4-6ish)
fushi tarazu (ftz) - ✔✔pair rule gene in drosophila that is expressed in even
# parasegments, if mutated results in no boundaries btw parasegments and
reduced (by half) segment number from 14 to 7
even-skipped (eve) - ✔✔pair rule gene in drosophila that is expressed in
ODD # parasegments, if mutated results in no parasegment boundaries
and reduced segment number from 14 to 7
engrailed (en) - ✔✔segment polarity gene expressed in cells w high [ ] of
either even skipped or fushi tarazu proteins, is a hedgehog pathway
regulator that marks the anterior compartment of each parasegment (which
is also the posterior part of each segment) - this reinforces parasegment
CMMB403 Final Exam Questions and
Answers 100% Solved
72 hours (8 cells) (BEFORE BLASTOCYST STAGE) - ✔✔what is the
human MZT
Mid-blastula transition/maternal-zygotic transition - ✔✔when the
transcription of zygotic genes begins and maternal mRNAs are degraded,
the cell cycle lengthens, gap stages are added (before is only M and S) and
the synchronicity of cell division is lost. - embryo runs on maternal
resources (mRNAs and proteins in the egg @ time of fertilization) until this.
is when maternal effect genes are turned off.
gap genes - ✔✔organize cells into groups of segments along anterior-
posterior axis - are activated OR repressed by MEG products expressed
from the zygotic genome (after MZT) and have broad expression domains -
divide embryo into regions about 2 segments wide - when lose function
causes large gaps in embryo where multiple segments lost, missing several
segments in a row - they have 1 or 2 broad stripes of expression and define
,©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
boundaries in the early embryo - are ZYGOTICALLY expressed - ex:
Kruppel
maternal effect genes - ✔✔A gene that, when mutant in the mother, results
in a mutant phenotype in the offspring, regardless of the genotype -
mRNAs deposited in oocyte set up early polarity translated at fertilization -
dads genes do not matter for this - create the anterior/posterior axis
(cytoplasmic polarity) through bicoid and nanos that form morphogen
gradients possible due to syncytium and are incorporated into cells during
cellularization
pair-rule genes - ✔✔organize cells into individual segments/ divide the
embryo into segment-sized units along the anterior/posterior axis - are
activated OR repressed by products of gap genes - helps to define the
spatial domains of the homeotic genes - expressed at ONSET of
cellularization - have 7 stripes of expression - miss portions of every other
segments and may delete boundaries or reduce segment numbers - when
mutated have half as many segments and result in only 7 stripes instead of
14 and - ex: fushi tarazu and even skipped
homeotic genes - ✔✔Genes that determine basic features of where a body
part is - define the identities of each of the segments - their expression
,©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
domain is correlated with where they are on the chromosome - are all TFs
that regulate segment specific genes - have vertebrate homologs!
segment polarity genes - ✔✔activated by pair rule gene products after
cellularization, give each individual segment its polarity - have 14 stripes of
expression - when mutated polarity disrupted in each segment (segment
number doesn't change will get 14) - encode for members of shh and wnt
pathways
maternal effect - ✔✔which gene is transcribed BEFORE and upon
fertilization
gap - ✔✔which genes are transcribed after fertilization but before
cellularization and the MZT
pair rule - ✔✔what genes are expressed at the onset of cellularization/just
before - with the MZT
segment polarity - ✔✔what genes are expressed after cellularization and
the MZT
1 or 2 - ✔✔how many stripes of expression do gap genes have (broad)
7 - ✔✔how many stripes of expression do pair rule genes have
14 - ✔✔how many stripes of expression do segment-polarity genes have
, ©JOSHCLAY 2024/2025. YEAR PUBLISHED 2024.
Parasegments - ✔✔transient subdivisions that occur in the Drosophila
embryo prior to the formation of segments - are off register by one half from
those of the segments, is made up of the cells in the posterior compartment
of one segment and the anterior compartment of the next segment. the
expression patterns of early segmentation genes are at THESE boundaries
- is the "fundamental unit of embryonic expression"
kruppel - ✔✔gap gene expressed in parasegments 4-6, is repressed by
hunchback, if mutated will be missing several segments in a row (4-6ish)
fushi tarazu (ftz) - ✔✔pair rule gene in drosophila that is expressed in even
# parasegments, if mutated results in no boundaries btw parasegments and
reduced (by half) segment number from 14 to 7
even-skipped (eve) - ✔✔pair rule gene in drosophila that is expressed in
ODD # parasegments, if mutated results in no parasegment boundaries
and reduced segment number from 14 to 7
engrailed (en) - ✔✔segment polarity gene expressed in cells w high [ ] of
either even skipped or fushi tarazu proteins, is a hedgehog pathway
regulator that marks the anterior compartment of each parasegment (which
is also the posterior part of each segment) - this reinforces parasegment
