Post transcriptional control and body plans Flashcards
(22 cards)
What is produced in the initial transcript from transcription?
Precursor mRNA (pre-mRNA)
What happens during RNA processing?
Introns (non-coding regions of DNA) transcribed but then removed from pre-mRNA
exons (coding regions) joined together to form mature mRNA for translation
What happens during pre-mRNA processing?
Addition of 5’ cap = stabilises mRNA delaying degradation and assisting in ribosome binding
Addition of 3’ poly-A tail = stabilises mRNA delaying degradation
Splicing = introns removed and exons joined together providing instructions for protein sequence
How does RNA editing further modify mRNA nucleotides?
Through substitution, addition, or deletion of bases
can alter protein product in manner similar to point mutations so different proteins can be synthesised from single mRNA molecule
How does mRNA degradation affect translation rate?
- mRNA that degrades slowly is more stable and lasts longer
- can increase translation and protein synthesis
How do inhibitory proteins affect translation rate?
- can bind to mRNA preventing it from attaching to ribosomes
- decreases translation and protein synthesis
How do initiation factors affect translation rate?
- activated initiation factors help mRNA bind to ribosomes
- initiates translation and increases protein synthesis
What are protein kinases?
Enzyme type controlling many aspects of cellular activity including protein modification
How do protein kinases control cellular activity?
1) protein kinases add Pi groups to proteins through phosphorylation
2) phosphorylation changes protein’s tertiary structure and function
3) often activates enzymes
4) activity of protein kinases can be regulated by cyclic AMP
What are examples of post-transcriptional modifications?
- addition of carbohydrates, lipids, or Pi groups
- formation of disulfide bridges between amino acids
- shortening of peptide chains
- folding into specific 3D shapes
- modification by cAMP as seen in lac operon
What is a body plan?
Basic structured arrangement of organism’s parts which are determined by genetic and developmental factors
What is a homebox gene?
Group of regulatory genes with a conserved DNA sequence that guides development of body plans
What is a homebox sequence?
Highly conserved DNA sequence found within homeobox genes crucial for the development of an organism’s body plan
What is a hox gene?
Subset of homeobox genes in animals containing homeobox sequences essential for correct positioning of body parts
How does a hox gene control body plan development?
1) homeobox sequences encode homeodomain part of protein that binds to DNA
2) homeodomain operates as transcription factor
3) binds to DNA switching developmental genes on or off
4) modifies transcription of proteins necessary for development of body plans
What can hox genes control?
- number of body layers
- symmetry of body
- anterior-posterior axis ensuring head is at one end and any tail is at other
- segmentation of body into head, thorax, abdomen
- position and development of limbs eyes and other structures
Why are homebox genes highly conserved?
- mutation would have large effects by altering organism’s body plan
- other genes would also be affected by a mutation in homeobox gene
- mutations are likely to be lethal and selected against
Why are fruit flies often used in the study of genes affecting body plans?
- are fewer ethical concerns than other animals
- are low cost
- genetics and development are well understood
- have rapid reproduction rate
- have simple body plan
- mutations can be studied with low-powered microscope
How is body morphology in body plans controlled?
Combination of cell death (apoptosis) and cell division (mitosis) alongside cell specialisation via differentiation
hox genes control rate and location of cell division during growth and tissue formation and control programmed cell death during development
What is the role of developmental genes?
Correct deviations and adapt to environmental conditions by responding to a range of signals usually achieved by regulating cell cycle and apoptosis
What are internal stimuli and how do they affect regulatory genes?
Regulatory genes respond to internal stimuli like stress, drugs, or hormones which can cause DNA damage
when DNA is damaged, regulatory genes trigger the cell cycle to stop and initiate apoptosis preventing DNA damage being replicated into new cells.
What are external stimuli and how do they affect regulatory genes?
Regulatory genes can respond to external stimuli like changes in temperature or light intensity
e.g lack of nutrients may trigger cell division
