MCB 250 Final Exam 2025 With
100% Accurate Solutions
In 1985, Helen Blau and coworkers fused human
liver cells to the (much larger) skeletal muscle
cells of mice. Within hours, these hybrid cells
began to stain with antibodies specific for human
muscle proteins. Which of the following do you
think is the most likely explanation of this
observation? – Answer✅️ ☑️Mouse muscle proteins
activated transcription of human genes
One important feature attributed to signal
transduction pathways is that they amplify the
signal as it moves through the cell.
What do you think this means? – Answer✅️ ☑️The
number of molecules representing the signal
increases at successive steps in the pathway.
Why did Spradling and Rubin elect to use two
different
Plasmids in order to introduce P elements into
their
,Transgenic flies? – Answer✅️
☑️If the P element
contains a transposase gene,
After integration it would undergo uncontrolled
Transposition in subsequent generations.
In a different experiment, the researchers simply
deleted
That portion of the cloned oskar cDNA which
normally
Yields the 3’-UTR.
This partially deleted cDNA was then transcribed
into
RNA, and the RNA injected into fertilized fly eggs.
Where
Would you expect this RNA to become localized?
– Answer✅️☑️uniform throughout the embryo
When mutated, all of the genes in this pathway
affect
The differentiation of tissues along the dorsal-
ventral axis
Of the embryo. For all but one of these genes,
loss-offunction
Mutations result in only dorsal tissue being
, Made.
When inactivated by a loss-of-function mutation,
which
Gene would you expect to give only ventral
tissue? – Answer✅️
☑️Cactus
When researchers generate transgenic mice by
DNA
Injection of fertilized eggs, they typically identify
a
Dozen or more transgenic offspring and compare
their
Phenotypes. Why is this important? –
Answer✅️ ☑️Sometimes the transgene inserts into
heterochromatic DNA (e.g. telomere; centromere)
And is not expressed.
Sometimes the transgene inserts after the first
Round of DNA replication, and only affects
Phenotype in a subset of tissues.
Sometimes the transgene causes insertional
Mutagenesis, yielding phenotypes associated
with
A loss of some endogenous gene function.
100% Accurate Solutions
In 1985, Helen Blau and coworkers fused human
liver cells to the (much larger) skeletal muscle
cells of mice. Within hours, these hybrid cells
began to stain with antibodies specific for human
muscle proteins. Which of the following do you
think is the most likely explanation of this
observation? – Answer✅️ ☑️Mouse muscle proteins
activated transcription of human genes
One important feature attributed to signal
transduction pathways is that they amplify the
signal as it moves through the cell.
What do you think this means? – Answer✅️ ☑️The
number of molecules representing the signal
increases at successive steps in the pathway.
Why did Spradling and Rubin elect to use two
different
Plasmids in order to introduce P elements into
their
,Transgenic flies? – Answer✅️
☑️If the P element
contains a transposase gene,
After integration it would undergo uncontrolled
Transposition in subsequent generations.
In a different experiment, the researchers simply
deleted
That portion of the cloned oskar cDNA which
normally
Yields the 3’-UTR.
This partially deleted cDNA was then transcribed
into
RNA, and the RNA injected into fertilized fly eggs.
Where
Would you expect this RNA to become localized?
– Answer✅️☑️uniform throughout the embryo
When mutated, all of the genes in this pathway
affect
The differentiation of tissues along the dorsal-
ventral axis
Of the embryo. For all but one of these genes,
loss-offunction
Mutations result in only dorsal tissue being
, Made.
When inactivated by a loss-of-function mutation,
which
Gene would you expect to give only ventral
tissue? – Answer✅️
☑️Cactus
When researchers generate transgenic mice by
DNA
Injection of fertilized eggs, they typically identify
a
Dozen or more transgenic offspring and compare
their
Phenotypes. Why is this important? –
Answer✅️ ☑️Sometimes the transgene inserts into
heterochromatic DNA (e.g. telomere; centromere)
And is not expressed.
Sometimes the transgene inserts after the first
Round of DNA replication, and only affects
Phenotype in a subset of tissues.
Sometimes the transgene causes insertional
Mutagenesis, yielding phenotypes associated
with
A loss of some endogenous gene function.
