3C Exam Practice

Question 1

Why does age affect the time taken to recover from injuries(stem cells)? (3)

Answer 1

• time will increase with age
• due to fewer stem cells with age
• fewer stem cells to replace cells in muscle, bone etc tissue

Question 2

DNA methylation definition

Answer 2

when methyl groups are added to cytosine or adenine bases

Question 3

Dofference bettwen toti, pluri and multipotent

Answer 3

• zygotes are totipotent because they give rise to all cell types
• blastocysts are pluripotent because they give rise to the cells in the embryo/ most cell types
• cells im the developing embryo are multipotent as they become only some cells

Question 4

Why is DNA methylation involved in development of embryo? (2)

Answer 4

• because genes are switched off and cannot be transcribed

- causing the cells to become differentiatied

Question 5

How do pluripotent stem cells become specialized beta cells?

Answer 5

• chemical stimulus
• some genes are switched on
• transcription occurs at active genes
• mRNA is used to produce proteins
• protein modifies cell

Question 6

Describe epigenetic modification

Answer 6

• changes that affect activation
• an example of epigenetic modification is DNa methylation
• involved in differentiation

Question 7

Pluripotent stem cells

Answer 7

Unspeacialized cells that can differentiate to give rise to almost any type of cell in the body, excluding totipotent cells

Question 8

How epigenetic changes affect the activation of genes in daughter cells (3)

Answer 8

• genes are activated in stem cells
• due to DNA methylation
• so the same genes will be activated in the daughter cells

Question 9

Explain why an individual may have a greater adult height than their parents (4)

Answer 9

• height is affected by environment
• height is an example of polygenic inheritance
• so offspring can inherit a mixture of alleles from both parents
• example of environmental factor: more calcium in diet

Question 10

Differences between totipotent and pluripotent stem cells

Answer 10

• totipotent cells give rise to any cell

- pluripotent cannot give rise to all cells in body

Question 11

Polygenic inheritance (3)

Answer 11

• more than one gene for a single characteristic
• at different loci
• giving rise to continuous variation

Question 12

How does height of adult show that environmental factors interact with genotype (3)

Answer 12

• malnutrition
• nutrients such as calcium are required for growth of ( muscle, bone)
• health/ disease can affect expression of genotype for height

Question 13

How a cell gains function? Structure? Differentiates? Become speacialized? develop ibto tissue organ etc (6)

Answer 13

• chemical stimulus
• some genes activated
• only active genes transcribed
• mRNA translated
• protein is made
• permanently modifies cell

Question 14

Advantages of using stem cells from patient instead of donor

Answer 14

• genetically identical to patients cells
• no risk of rejection
• less risk of infection