Genetics Exam questions and
answers graded A+
Developmental genetics - ANS✅✅-developmental biologists study what makes totipotent cells
(zygotes, embryos, stem cell) undergo cell determination
cell determination - ANS✅✅how a cell's fate is determined
pattern formation - ANS✅✅development of spatial organization and specialization of cells
egg->embryo-> adult
programmed patterns of gene expression - ANS✅✅determine order and timing of developmental
events
autonomous - ANS✅✅programmed changes in cells themselves
positional information - ANS✅✅cell signaling
mutations - ANS✅✅are key in developmental genetics
yeast - ANS✅✅mating types and gene regulation
c. elegans - ANS✅✅cell signaling
drosophila - ANS✅✅embryonic differentiation
egg->embryo-> adult
arabidopsis - ANS✅✅floral development
transcriptional control of yeast mating types - ANS✅✅haploid mating types alpha and a types
,diploid cells alpha and a
tetrad spore with both types- alpha and a types
yeast- transcriptional control of mating types - ANS✅✅-two mating types a and alpha are
controlled by MAT locus, encodes mating type transcriptional regulators
-mating types are haploid
-a cells expresses a-specific genes (asg)
-alpha cells expresses alpha specific genes (alpha sg)
-both express haploid specific genes (hsg)
mating types determined by cell-specific regulators - ANS✅✅-a specific=a1
-alpha specific= alpha 1 and alpha 2
-Mcm1 in both
-haploid specific= HO endonuclease (mating type conversion)=RME1 repressor for meiosis specific
genes
Mcm1 - ANS✅✅minichromosomal maintenance
in a cells, a1 and Mcm1 are expressed - ANS✅✅-a1 has no regulatory activity by itself
-Mcm1 positively regulates aSG expression
-haploid-specific genes are turned on as default
in alpha cells, alpha 1, alpha 2, and Mcm1 are expressed - ANS✅✅-Mcm1 and alpha1 positively
regulate aSG expression
-Mcm1 and alpha2 turn off aSG expression
-haploid-specific genes are turned on as default
in diploid cells, a1, alpha1, alpha2, and Mcm1 are expressed - ANS✅✅-Mcm1 and alpha2 turn off
aSG expression
-a1 and alpha2 turn off hSG and alpha1
c.elegans development - ANS✅✅-soil nematodes are diploid organisms with two sexes
,-hermaphrodite (xx) and male (xo)
-hermaphrodite produces eggs and sperm and can self replicate
-male produces sperm and fertilizes hermaphrodites
-nematode development is unusual; the pattern of cell division and differentiation is virtually
identical from one individual to the next
-hermaphrodites have 959 somatic cells, and males contain 1031 somatic cells
-animals are transparent and you can track the developmental history of each somatic cell
tracking cell lineages using lineage diagrams - ANS✅✅dies signifies programmed cell death
(apoptosis)
- the lowercase letters a and p denote anterior and posterior daughter cells. For example, cell A.ap is
the posterior daughter of the anterior daughter of cell A.
early cell differentiation in c. elegans is both autonomous and controlled by cell signaling -
ANS✅✅-polar granules= cytoplasmic particles in P cells
-cell signal from P2
-APX-1 signal to GLP-1 receptor
-Mom-2 - signal or receptor?
mutants of key developmental genes often are identified by their unusual properties - ANS✅✅-
dominant and recessive mutations often have opposite effects
-recessive mutations= LOSS OF FUNCTION
-the mRNA is not produced or the protein is inactive
-dominant mutations= GAIN OF FUNCTION
-the gene is over-expressed or expressed at the wrong time
loss/gain of function mutants demonstrated by LIN-12 mutants in c. elegans - ANS✅✅-LIN-12 gene
controls developmental decisions in a number of cells- example=anchor cells (AC)
-in wildtype embryos, Z1.ppp differentiates into AC and Z4.aaa differentiates into VU, or the other
way around
-if either cell is destroyed, the either differentiates into AC
-in Lin-12 mutants, both cells differentiate into either AC (lin-12(0)), a loss of function mutations or
VU (lin-12(d), a gain of function mutation
, LIN-12 gene product is a transmembrane receptor protein - ANS✅✅-amino acid sequence similar
to region found in epidermal growth factor (EGP)
-amino acid sequence similar to LIN-12 (c. elegans) and Netch (drosophila)
-amino acid sequence similar to region found in proteins encoded by cdc10 (s.pombe) and SW16 (s.
cerevisiae)
in worms, LIN-12 and LAG-2 (signaling, ligand) determine which of two cells will be the anchor cell
via cell signaling - ANS✅✅-cell signaling betweeen LAG-2 and LIN-12
the anchor cell controls the formation of the vulva (the opening through which eggs are laid) -
ANS✅✅-anchor cell expressing LAG-2:: GFP
-the purple cells are vulva precursor cells
cell decision- anchor cell or VU cell? - ANS✅✅-the anchor cell is the "default state". The VU has to
be told DONT be an anchor cell
-in wildtype embroys, Z1.ppp differentiates into AC and Z4.aaa differentiates into VU, or the other
way around
-if either cell is destroyed, the other differentiates into AC
each cell sends a signal to prevent the other from becoming the anchor cell - ANS✅✅-LAG2=
transmembrane protein ligand
-LIN12= transmembrane protein receptor
at first, the cells are at an impasse - ANS✅✅-don't you be the anchor cell!
one of the cells will randomly start to express more LAG2 signal than the other - ANS✅✅-don't you
be the anchor cell!
-positive feedback results in more and more expression of the LAG2 signal on the "winning" cell
winning LAG2 expressing cell becomes the anchor cell. The other cell becomes the ventral uterine
cell. - ANS✅✅-don't you be the anchor cell!
-alright, already!
recessive mutants at LIN-12 dont "listen"
answers graded A+
Developmental genetics - ANS✅✅-developmental biologists study what makes totipotent cells
(zygotes, embryos, stem cell) undergo cell determination
cell determination - ANS✅✅how a cell's fate is determined
pattern formation - ANS✅✅development of spatial organization and specialization of cells
egg->embryo-> adult
programmed patterns of gene expression - ANS✅✅determine order and timing of developmental
events
autonomous - ANS✅✅programmed changes in cells themselves
positional information - ANS✅✅cell signaling
mutations - ANS✅✅are key in developmental genetics
yeast - ANS✅✅mating types and gene regulation
c. elegans - ANS✅✅cell signaling
drosophila - ANS✅✅embryonic differentiation
egg->embryo-> adult
arabidopsis - ANS✅✅floral development
transcriptional control of yeast mating types - ANS✅✅haploid mating types alpha and a types
,diploid cells alpha and a
tetrad spore with both types- alpha and a types
yeast- transcriptional control of mating types - ANS✅✅-two mating types a and alpha are
controlled by MAT locus, encodes mating type transcriptional regulators
-mating types are haploid
-a cells expresses a-specific genes (asg)
-alpha cells expresses alpha specific genes (alpha sg)
-both express haploid specific genes (hsg)
mating types determined by cell-specific regulators - ANS✅✅-a specific=a1
-alpha specific= alpha 1 and alpha 2
-Mcm1 in both
-haploid specific= HO endonuclease (mating type conversion)=RME1 repressor for meiosis specific
genes
Mcm1 - ANS✅✅minichromosomal maintenance
in a cells, a1 and Mcm1 are expressed - ANS✅✅-a1 has no regulatory activity by itself
-Mcm1 positively regulates aSG expression
-haploid-specific genes are turned on as default
in alpha cells, alpha 1, alpha 2, and Mcm1 are expressed - ANS✅✅-Mcm1 and alpha1 positively
regulate aSG expression
-Mcm1 and alpha2 turn off aSG expression
-haploid-specific genes are turned on as default
in diploid cells, a1, alpha1, alpha2, and Mcm1 are expressed - ANS✅✅-Mcm1 and alpha2 turn off
aSG expression
-a1 and alpha2 turn off hSG and alpha1
c.elegans development - ANS✅✅-soil nematodes are diploid organisms with two sexes
,-hermaphrodite (xx) and male (xo)
-hermaphrodite produces eggs and sperm and can self replicate
-male produces sperm and fertilizes hermaphrodites
-nematode development is unusual; the pattern of cell division and differentiation is virtually
identical from one individual to the next
-hermaphrodites have 959 somatic cells, and males contain 1031 somatic cells
-animals are transparent and you can track the developmental history of each somatic cell
tracking cell lineages using lineage diagrams - ANS✅✅dies signifies programmed cell death
(apoptosis)
- the lowercase letters a and p denote anterior and posterior daughter cells. For example, cell A.ap is
the posterior daughter of the anterior daughter of cell A.
early cell differentiation in c. elegans is both autonomous and controlled by cell signaling -
ANS✅✅-polar granules= cytoplasmic particles in P cells
-cell signal from P2
-APX-1 signal to GLP-1 receptor
-Mom-2 - signal or receptor?
mutants of key developmental genes often are identified by their unusual properties - ANS✅✅-
dominant and recessive mutations often have opposite effects
-recessive mutations= LOSS OF FUNCTION
-the mRNA is not produced or the protein is inactive
-dominant mutations= GAIN OF FUNCTION
-the gene is over-expressed or expressed at the wrong time
loss/gain of function mutants demonstrated by LIN-12 mutants in c. elegans - ANS✅✅-LIN-12 gene
controls developmental decisions in a number of cells- example=anchor cells (AC)
-in wildtype embryos, Z1.ppp differentiates into AC and Z4.aaa differentiates into VU, or the other
way around
-if either cell is destroyed, the either differentiates into AC
-in Lin-12 mutants, both cells differentiate into either AC (lin-12(0)), a loss of function mutations or
VU (lin-12(d), a gain of function mutation
, LIN-12 gene product is a transmembrane receptor protein - ANS✅✅-amino acid sequence similar
to region found in epidermal growth factor (EGP)
-amino acid sequence similar to LIN-12 (c. elegans) and Netch (drosophila)
-amino acid sequence similar to region found in proteins encoded by cdc10 (s.pombe) and SW16 (s.
cerevisiae)
in worms, LIN-12 and LAG-2 (signaling, ligand) determine which of two cells will be the anchor cell
via cell signaling - ANS✅✅-cell signaling betweeen LAG-2 and LIN-12
the anchor cell controls the formation of the vulva (the opening through which eggs are laid) -
ANS✅✅-anchor cell expressing LAG-2:: GFP
-the purple cells are vulva precursor cells
cell decision- anchor cell or VU cell? - ANS✅✅-the anchor cell is the "default state". The VU has to
be told DONT be an anchor cell
-in wildtype embroys, Z1.ppp differentiates into AC and Z4.aaa differentiates into VU, or the other
way around
-if either cell is destroyed, the other differentiates into AC
each cell sends a signal to prevent the other from becoming the anchor cell - ANS✅✅-LAG2=
transmembrane protein ligand
-LIN12= transmembrane protein receptor
at first, the cells are at an impasse - ANS✅✅-don't you be the anchor cell!
one of the cells will randomly start to express more LAG2 signal than the other - ANS✅✅-don't you
be the anchor cell!
-positive feedback results in more and more expression of the LAG2 signal on the "winning" cell
winning LAG2 expressing cell becomes the anchor cell. The other cell becomes the ventral uterine
cell. - ANS✅✅-don't you be the anchor cell!
-alright, already!
recessive mutants at LIN-12 dont "listen"
