3C Exam Practice
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Why does age affect the time taken to recover from injuries(stem cells)? (3)
• time will increase with age • due to fewer stem cells with age • fewer stem cells to replace cells in muscle, bone etc tissue
DNA methylation definition
when methyl groups are added to cytosine or adenine bases
Dofference bettwen toti, pluri and multipotent
• 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
Why is DNA methylation involved in development of embryo? (2)
• because genes are switched off and cannot be transcribed - causing the cells to become differentiatied
How do pluripotent stem cells become specialized beta cells?
• chemical stimulus • some genes are switched on • transcription occurs at active genes • mRNA is used to produce proteins • protein modifies cell
Describe epigenetic modification
• changes that affect activation • an example of epigenetic modification is DNa methylation • involved in differentiation
Pluripotent stem cells
Unspeacialized cells that can differentiate to give rise to almost any type of cell in the body, excluding totipotent cells
How epigenetic changes affect the activation of genes in daughter cells (3)
• genes are activated in stem cells • due to DNA methylation • so the same genes will be activated in the daughter cells
Explain why an individual may have a greater adult height than their parents (4)
• 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
Differences between totipotent and pluripotent stem cells
• totipotent cells give rise to any cell - pluripotent cannot give rise to all cells in body
Polygenic inheritance (3)
• more than one gene for a single characteristic • at different loci • giving rise to continuous variation
How does height of adult show that environmental factors interact with genotype (3)
• malnutrition • nutrients such as calcium are required for growth of ( muscle, bone) • health/ disease can affect expression of genotype for height
How a cell gains function? Structure? Differentiates? Become speacialized? develop ibto tissue organ etc (6)
• chemical stimulus • some genes activated • only active genes transcribed • mRNA translated • protein is made • permanently modifies cell
Advantages of using stem cells from patient instead of donor
• genetically identical to patients cells • no risk of rejection • less risk of infection