Cellular Control M6

Question 1

Give two reasons why substitution mutation may have a neutral effect on the protein.

Answer 1

1. degenerate code means that the altered triplet base may still code for the same amino acid
2. The altered amino acid may still have a very similar function to the original amino acid

Question 2

describe the difference between structural and regulatory gene

Answer 2

Some genes are structural genes, which code for proteins needed for cell structure or function, such as the lac structural genes in bacteria needed for lactose metabolism, or the structural protein actin in eukaryotic cells. Other genes are regulatory genes, which code for proteins that turn other genes on or off.

Question 3

Desribe the dffernec between pre trsbcriptional and post transcriptional control on gene expression

Answer 3

PRE - This involves switching genes on or off- (gene expression) and so determines whether transcription occurs and whether mRNA is produced.
Transcription factors
POST - This involves editing the mRNA by the removal of introns/non-coding sections and then the splicing of exons together

Question 4

Explain how hox genes affect the development of body plans.

Answer 4

1. homeobox sequences of hox genes code for part of Hox proteins (homeodomain). The domain binds to a specific site near the start of the developmental gene. This acts as a transcription factor. The homeodomain activates or represses transcription of the developmental gene and alters the production of a protein involved in the development of body plan.

Question 5

Explain what is meant by a homeobox gene.

Answer 5

the regulatory gene that controls the development of the body and its body plan

Question 6

Explain how the webbing between digits in humans is removed in a developing embryo.

Answer 6

An internal/external stimulus triggers apoptosis in the cells that make up the webbing ;
This causes enzymes inside the cells to break down the cell components ;
This causes the cells to break up into fragments which are engulfed and hydrolysed by phagocytosis

Question 7

Describe the role of mitosis in the development of the body forms of multicellular organisms.

Answer 7

1. Mitosis produces genetically identical cells so all the cells produced will have the same genotype
2. Mitosis increases the size of an organism. It also produces cells which can then go on to specialise to form different tissues/cells
   3, In many organisms mitosis only occurs in certain areas ie. end of bones- the growing regions

Question 8

Outline the process of apoptosis.

Answer 8

Programmed cell death. Enzymes inside the cell cause the cell to shrink and the cytoskeleton to break up. The DNA breaks into fragments and the proteins in the nucleus are broken down. Nuclear envelope breaks down and organelles like mitochondria. Bulges called blebs to appear on the surface of cells. These blebs are ingested by phagocytes /macrophages