The figure below depicts the mechanism of iron homeostasis in mammalian cells, in which ferritin is produced to sequester excess iron in high iron conditions, and transferrin receptor is produced to import iron in low iron concentrations. (a) Ferritin mRNA 5 IRE Inactive IRE-BP 5 Active IRE-BP ? High iron Coding region An H₂N COOH Translated ferritin (b) TfR mRNA High iron 5' Coding region Inactive IRE-BP Active IRE-BP Low iron Low iron Coding region A No translation 5' Coding region initiation IRES A ????? a) A mutation in a mammalian cell line in tissue culture was found that constitutively expresses Ferritin. Suggest a possible mutation that could account for this. Degraded mono- nucleotides A Little degradation -Mutation in ires binding protein where it does not bind to iron suggests that cell lysate has high transferrin and low ferritin. I b) Upon further examination of the cell line, it was found that there was normal expression of the Transferrin Receptor. Would the mutation you suggested in part a) be consistent with this finding? Explain why. If the mutation you suggested in part a) is inconsistent, then what alternate mutation in part a) would be consistent with this finding? c) This mutant was found to be barely viable in medium containing a low concentration of iron. Suggest a reason why. Would the mutant be viable in medium with no added iron for a day? Explain. d) A second site partial revertant is found that causes the Transferrin Receptor to now also be constitutively expressed, in addition to the constitutive expression of Ferritin. What kind of second site mutation could account for this phenotype. Explain.
The figure below depicts the mechanism of iron homeostasis in mammalian cells, in which ferritin is produced to sequester excess iron in high iron conditions, and transferrin receptor is produced to import iron in low iron concentrations. (a) Ferritin mRNA 5 IRE Inactive IRE-BP 5 Active IRE-BP ? High iron Coding region An H₂N COOH Translated ferritin (b) TfR mRNA High iron 5' Coding region Inactive IRE-BP Active IRE-BP Low iron Low iron Coding region A No translation 5' Coding region initiation IRES A ????? a) A mutation in a mammalian cell line in tissue culture was found that constitutively expresses Ferritin. Suggest a possible mutation that could account for this. Degraded mono- nucleotides A Little degradation -Mutation in ires binding protein where it does not bind to iron suggests that cell lysate has high transferrin and low ferritin. I b) Upon further examination of the cell line, it was found that there was normal expression of the Transferrin Receptor. Would the mutation you suggested in part a) be consistent with this finding? Explain why. If the mutation you suggested in part a) is inconsistent, then what alternate mutation in part a) would be consistent with this finding? c) This mutant was found to be barely viable in medium containing a low concentration of iron. Suggest a reason why. Would the mutant be viable in medium with no added iron for a day? Explain. d) A second site partial revertant is found that causes the Transferrin Receptor to now also be constitutively expressed, in addition to the constitutive expression of Ferritin. What kind of second site mutation could account for this phenotype. Explain.
Human Anatomy & Physiology (11th Edition)
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Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
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Transcribed Image Text:The figure below depicts the mechanism of iron homeostasis in mammalian cells, in which ferritin is
produced to sequester excess iron in high iron conditions, and transferrin receptor is produced to
import iron in low iron concentrations.
(a) Ferritin mRNA
5%
IRE
i
5%
Inactive IRE-BP
Active IRE-BP
High iron
Coding region - An
85
H₂N
COOH
Translated
ferritin
Low iron
Coding region A No translation
initiation
(b) TfR mRNA
High iron
5'- Coding region
Inactive IRE-BP
Active IRE-BP
Low iron
5'- Coding region
IRES
An
N
a) A mutation in a mammalian cell line in tissue culture was found that constitutively expresses
Ferritin. Suggest a possible mutation that could account for this.
Degraded
mono-
nucleotides
degradation
-Mutation in ires binding protein where it does not bind to iron suggests that cell lysate has high transferrin
and low ferritin.
I
b) Upon further examination of the cell line, it was found that there was normal expression of the
Transferrin Receptor. Would the mutation you suggested in part a) be consistent with this finding?
Explain why. If the mutation you suggested in part a) is inconsistent, then what alternate mutation in
part a) would be consistent with this finding?
c) This mutant was found to be barely viable in medium containing a low concentration of iron.
Suggest a reason why. Would the mutant be viable in medium with no added iron for a day? Explain.
d) A second site partial revertant is found that causes the Transferrin Receptor to now also be
constitutively expressed, in addition to the constitutive expression of Ferritin. What kind of second
site mutation could account for this phenotype. Explain.
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