Cellular Control

Question 1

What is the inducer on the lac operon

Answer 1

Lactose

Question 2

Describe the role of CAMP in activating proteins

Answer 2

cAMP activates PKA which then activates other proteins by phosphorylating them. The other proteins are usually enzymes, so a metabolic reaction or pathway is activated. This could involve the making of molecules other than proteins. Phosphate groups could also activate CREB protein that then enters the cell nucleus and acts as a transcription factor, regulating transcription of a particular gene

Question 3

Why is a piece of mRNA shorter than the gene from which it is transcribed

Answer 3

The whole gene introns and exons are first transcribed to give a length of primary RNA that also has both introns and exons. The introns are then removed and the exons are joined up, so the final mRNA is shorter as it does not contain introns

Question 4

Homeobox sequence

Answer 4

part of a homeobox/homeotic gene, 180 bp long (- introns) that codes for a 60 amino acid sequence in a protein that is a transcription factor

Question 5

Homeodomain

Answer 5

homeodomain – the 20 amino acid sequence, encoded by the homeobox sequence.
It is part of the transcription factor protein that plays a part in gene regulation during development of embryo to adult form; this sequence can fold into a particular shape

Question 6

Difference in homeobox genes and Hox genes

Answer 6

Hox genes are a subset/type of homeobox genes; found only in animals whereas homeobox sequences/genes are in plants, animals and fungi. They are expressed early in embryonic development and the genes in the clusters are expressed in sequence – corresponding to development of the various organs along anterior-posterior axis of animals. Hox genes encode transcription factors that activate other genes that promote mitotic cell division, apoptosis, cell migration and help to regulate the cell cycle

Question 7

Why are pregnant mothers not advised to eat liver

Answer 7

It contains high amounts of retinol that the body can change to retinoic acid. If there is too much retinoic acid in the blood going to the fetus, it could interfere with the Hox genes controlling body plan development and cause abnormalities.

Question 8

Why should the rate of apoptosis in an adult equal the rate of mitosis

Answer 8

Adults are not growing. If the two processes do not balance, then either a tumour or cell loss and degeneration will occur.