Practice theme test C. elegans made by Lisa® ;)
Questions 13
pt.
Question 1
A) Explain how the immunostaining technique works in C. elegans when the following antibodies are
used: (2 pt.)
Primary antibodies: Anti-GFP (rabbit) and Anti-PSD95 (mouse)
Secondary antibodies: Goat anti-rabbit Alexa 488 and Goat Anti-Mouse Alexa 594
B) Why are L4’s used in the immunostaining procedure and not earlier stages or adults? Give for both
a reason (2 pt.)
C) What is observed in the immunostaining that could have an impact on the counted nr. of SC in the
RNAi? (2 pt.)
D) Give 1 reason why you could expect multi-nuclei in the AW673 strain. (1 pt.)
Question 2
A) The vulva of the C. elegans worm is formed by intrinsic / extrinsic polarity, choose one and explain
short and abstract how this type of polarity is regulated. (2 pt.)
B) Explain the 3 different signalling ‘pathways’ that regulate the fate of the 6 vulva cells (VPC’s). (3
pt.)
C) What is a special feature of the anchor cell (AC) that is also observed in metastatic tumour cells? (1
pt.)
, Answers!
Question 1
A) Explain how the immunostaining technique works in C. elegans when the following antibodies are
used: (3 pt.)
Primary antibodies: Anti-GFP (rabbit) and Anti-PSD95 (mouse)
Secondary antibodies: Goat anti-rabbit Alexa 488 and Goat Anti-Mouse Alexa 594
The primary antibody Anti-GFP bind to the GFP in the nucleus of the seam cells in the C. elegans and
the Anti-PSD95 binds to the apical junctions in the cell membrane. (1 pt.)
The Goat anti-rabbit Alexa 488 binds to the primary antibody Anti-GFP. The Goat anti-mouse Alexa
594 binds to the Anti-PSD95. (1 pt.)
The secondary antibodies have the fluorescent markers bound to it that can be observed under the
fluorescent microscope. Alexa 488 is observed as green, and Alexa 594 is observed as red.
B) Why are L4’s used in the immunostaining procedure and not earlier stages or adults? Give for both
a reason (2 pt.)
Not all the seam cell divisions are done in the earlier stages of the C. elegans worm. (1 pt.)
The adults seam cells already had the terminal differentiation of the seam cells, while that is not
wanted in the immunostaining OR the GFP is not visible in seam cells that are not dividing anymore,
and the seam cells are not dividing in adults after the terminal differentiation. (1 pt.)
C) What is observed in the immunostaining that could have an impact on the counted nr. of SC in the
RNAi? (2 pt.)
The seam cells are either single- or multi nuclei. (1 pt.)
In the RNAi are only the nucleus of the seam cell counted and observed as if each nucleus was 1
seam cell. But if the seam cells appear to be multi-nucleu in the immunostaining, then the counted
seam cell number in the RNAi was not correct. (1 pt.)
D) Give 1 reason why you could expect multi-nuclei in the AW673 strain. (1 pt.)
The AW673 strain has hyperplasia of the seam cells. Hyperplasia phenotype corresponds to a cancer
phenotype in humans. In cancer cells is multi-nucleate very common. (1 pt.)
Question 2
A) The vulva of the C. elegans worm is formed by intrinsic / extrinsic polarity, choose one and explain
short and abstract how this type of polarity is regulated. (2 pt.)
Extrinsic polarity (1 pt.)
Extrinsic polarity: the differentiation of the cells are regulated by a ‘niche’. Niches are local tissue
micro-environments that maintain and regulate stem cells. Cells that are close to the niche, remain
their stemness, while the cells further away from the niche are differentiated. Answer should be
something like this (1 pt.)
Questions 13
pt.
Question 1
A) Explain how the immunostaining technique works in C. elegans when the following antibodies are
used: (2 pt.)
Primary antibodies: Anti-GFP (rabbit) and Anti-PSD95 (mouse)
Secondary antibodies: Goat anti-rabbit Alexa 488 and Goat Anti-Mouse Alexa 594
B) Why are L4’s used in the immunostaining procedure and not earlier stages or adults? Give for both
a reason (2 pt.)
C) What is observed in the immunostaining that could have an impact on the counted nr. of SC in the
RNAi? (2 pt.)
D) Give 1 reason why you could expect multi-nuclei in the AW673 strain. (1 pt.)
Question 2
A) The vulva of the C. elegans worm is formed by intrinsic / extrinsic polarity, choose one and explain
short and abstract how this type of polarity is regulated. (2 pt.)
B) Explain the 3 different signalling ‘pathways’ that regulate the fate of the 6 vulva cells (VPC’s). (3
pt.)
C) What is a special feature of the anchor cell (AC) that is also observed in metastatic tumour cells? (1
pt.)
, Answers!
Question 1
A) Explain how the immunostaining technique works in C. elegans when the following antibodies are
used: (3 pt.)
Primary antibodies: Anti-GFP (rabbit) and Anti-PSD95 (mouse)
Secondary antibodies: Goat anti-rabbit Alexa 488 and Goat Anti-Mouse Alexa 594
The primary antibody Anti-GFP bind to the GFP in the nucleus of the seam cells in the C. elegans and
the Anti-PSD95 binds to the apical junctions in the cell membrane. (1 pt.)
The Goat anti-rabbit Alexa 488 binds to the primary antibody Anti-GFP. The Goat anti-mouse Alexa
594 binds to the Anti-PSD95. (1 pt.)
The secondary antibodies have the fluorescent markers bound to it that can be observed under the
fluorescent microscope. Alexa 488 is observed as green, and Alexa 594 is observed as red.
B) Why are L4’s used in the immunostaining procedure and not earlier stages or adults? Give for both
a reason (2 pt.)
Not all the seam cell divisions are done in the earlier stages of the C. elegans worm. (1 pt.)
The adults seam cells already had the terminal differentiation of the seam cells, while that is not
wanted in the immunostaining OR the GFP is not visible in seam cells that are not dividing anymore,
and the seam cells are not dividing in adults after the terminal differentiation. (1 pt.)
C) What is observed in the immunostaining that could have an impact on the counted nr. of SC in the
RNAi? (2 pt.)
The seam cells are either single- or multi nuclei. (1 pt.)
In the RNAi are only the nucleus of the seam cell counted and observed as if each nucleus was 1
seam cell. But if the seam cells appear to be multi-nucleu in the immunostaining, then the counted
seam cell number in the RNAi was not correct. (1 pt.)
D) Give 1 reason why you could expect multi-nuclei in the AW673 strain. (1 pt.)
The AW673 strain has hyperplasia of the seam cells. Hyperplasia phenotype corresponds to a cancer
phenotype in humans. In cancer cells is multi-nucleate very common. (1 pt.)
Question 2
A) The vulva of the C. elegans worm is formed by intrinsic / extrinsic polarity, choose one and explain
short and abstract how this type of polarity is regulated. (2 pt.)
Extrinsic polarity (1 pt.)
Extrinsic polarity: the differentiation of the cells are regulated by a ‘niche’. Niches are local tissue
micro-environments that maintain and regulate stem cells. Cells that are close to the niche, remain
their stemness, while the cells further away from the niche are differentiated. Answer should be
something like this (1 pt.)
