Regulation of transcription and translation

Question 1

What are transcription factors?

Answer 1

• switches on the gene involved in transcription
• they have a site that binds to a specific base sequence of the DNA in the nucleus
• this causes this region of DNA to begin the process of transcription
• mRNA is produced and the information it carries is then translated into a polypeptide
• when a gene is switched off, the site on the transcriptional factor that binds to DNA is not active
• as the site on the transcriptional factor binding to DNA is inactive it cannot cause transcription and polypeptide synthesis

Question 2

What is the process of hormones affecting DNA Binding site?

Answer 2

• oestrogen is a lipid-soluble molecule and therefore diffuses easily through the phospholipids proportion of cell-surface membranes
• once inside the cytoplasm of a cell, oestrogen binds with a site on a receptor molecule of the transcriptional factor
• the shape of this site and the shape of the oestrogen molecule complement one another
• by binding with the site, the oestrogen changes the shape of the DNA binding site on the transcriptional factor, which can now bind to DNA it is activated
• the combination of the transcriptional factor with DNA stimulates transcription of the gene that makes up the proportion if DNA

Question 3

What is globulin in haemoglobin?

Answer 3

• a haemoglobin molecule is made up of four polypeptide chains each known as a globulin
• in adult humans two of the polypeptides in a haemoglobin molecule are alpha-globulin and two are beta-globulin
• in other words, 50% is beta
• in a human foetus, however, the haemoglobin is different with much of the beta-globulin being replaced by a third type, gamma-globulin
• foetal haemoglobin has a greater affinity for oxygen than adult haemoglobin has a greater affinity for oxygen than adult haemoglobin
• the changes in the production of the three types of globulin during early human development