Hammerlings experiments with Acetabularia- lqc 6a

Question 1

acetabularia is

Answer 1

a single celled algae

Question 2

acetabularia cell contains

Answer 2

cytoplasm and cell organelles

Question 3

experiment 1

Answer 3

Hats cut off each of the two species of Acetabularia. Stems were swapped over.

Question 4

results of experiment 1

Answer 4

Both species developed hats with mixed features – disc shaped but branched

Question 5

explanation of results of experiment 1

Answer 5

A messenger molecule is made in the rhizoid/ nucleus and is transported through the cell cytoplasm to the stem tip, where it initiates hat development. The messenger molecule is different in each species, so different hats develop. In Experiment 1, when the hats were first cut off, some of the original messenger molecules were still present in each of the stalk and so moved up to the stalk tip . The different messenger molecule was also made by the original rhizoid, which also travels up to the stem tip. The two types of messenger molecules mix , causing mixed feature hats to develop (disc shaped and branched ).

Question 6

experiment 2

Answer 6

The mixed feature hats were cut off and the hats allowed to develop again

Question 7

results of experiment 2

Answer 7

Hats developed which were the same as the ones originally present

Question 8

explanation of results of experiment 2

Answer 8

By Experiment 2, there are no messenger molecules left in the stalks, so the only messenger that can affect hat development is the messenger being made by the rhizoid/nucleus . Hats develop which match the rhizoid, so the same as the hats originally present. After some further similar experiments, Hämmerling concluded that it must be the nucleus in the rhizoid which controls hat development. We now know that the nucleus transcribes a gene to produce mRNA and that the messenger molecule is likely to be a protein (made from the mRNA by translation) which controls hat development.

Question 9

hammerings experiments provided evidence for

Answer 9

the role of the nucleus in development