Cellular Control Flashcards
1
Q
What is the difference between euchromatin and heterochromatin?
A
- Euchromatin - loosely packed DNA that allows transcription to occur (caused by histone acetylation - reduces positivity of histones)
- Heterochromatin - tightly packed DNA that prevents transcription from occuring (methylation increases hydrophobicity of histones causing DNA to coil more tightly)
2
Q
How is transcription initiated?
A
By transcription factors binding to specific DNA sequences
3
Q
What are the structural genes in lac operon?
A
- lacZ - codes for B-galactosidase (catalyses the hydrolysis of lactose into glucose and galactose)
- lacY - codes for lactose permease
- lacA - codes for transectylase
4
Q
What does RNA polymerase bind to in the lac operon?
A
The promoter region
5
Q
What is the role of cAMP in the lac operon?
A
- Upregulates the transcription of the structural genes
- It does so by binding to the cAMP receptor protein (CRP)
6
Q
What modifications are made to pre-mRNA after transcription?
A
- Addition of a 5’ cap - this helps stabilise mRNA and delay degredation, and also helps mRNA bind to ribosomes
- Addition of 3’ tail - helps stabilise mRNA and delay degredation
- Splicing - the removal of introns (non-coding) and joining of exons (coding) in pre-mRNA
7
Q
How does RNA editing alter mRNA?
A
- Changes the nucleotide sequence through base addition, deletion or substitution
- Allows many different proteins to be synthesised from one mRNA molecules
8
Q
What is the role of protein kinases in protein modification?
A
- Add phosphate groups to proteins, phosphorylating them
- This changes a proteins tertiary structure and therefore their function
- Protein kinases are often activated by second messenger cAMP
9
Q
What modifications may post translational control include?
A
- All involve modifications to proteins
- Addition of non protein groups like carbs, lipids or phosphates
- Modification by cAMP
- Folding, or shortening of proteins
10
Q
What are some ways in which homeobox genes control development of an organism’s body?
A
- Control number of body layers
- Control symmetry of body
- Control positioning and development of limbs
- Control position and development of eyes and other important structures
11
Q
How do Hox genes regulate mitosis and apoptosis?
A
- Hox genes control the rate and location of cell division during growth and tissue formation
- They also control programmed cell death during development
12
Q
What factors may influence the expression of regulatory genes?
A
- Regulatory genes are able to respond to internal stimuli such as stress, drugs or hormones
- And can also respond to external stimuli like changes in temperature or light intensity
