Module 6: Cellular Control Flashcards
What are the different types of mutation
Point
Indel
Chromosomal
What are the different types of point mutations
Silent: which replaces letter but makes same amino acid (code is degenerate)
Nonesense: introduces a stop coding, making the protein truncated
Missense: changes the codon to a different amino acid, can be
conservative changes to a similar amino acid, or non conservative changes to a different amino acid
What happens during an insertion or deletion
A codon is inserted or deleted
This causes a frame shift
Causing the amino acid sequence to change
For example insertion, all the letters shift one down, changing all the amino acids after that point
What causes a chromosomal mutation
Caused by mutagen
How does the chromosomal mutation affect meiosis
Deletion: a section breaks off
Duplication: section of chromosome breaks of and joins another one
Inversion: section of chromosome is broken of reversed and placed onto another chromosome
What are the causes of mutation
Physical mutagens: causes break in DNA (ionisation and X-rays)
Chemical mutagens: changes base sequence
Biological agents
-alkylating agents (changes base sequence
-base analogs (incorporated into DNA)
Viruses: inserts itself into genome and changes base sequence
What are the benefits and disadvantages
(sort this flashcard out)
Benefits
-lactose one
Disadvantages
-check textbook
Explain the transcriptional level of control
Histone modification and chromatin remodelling)
DNA is tightly wrapped around histones (heterochromatin)
To make gene more accessible you can add a phosphate group or an acyl group (decreases postiive charge of histones) to turn it itno euchromatin
This allows for RNA polyermase to bind
To make it back hetrochromatin you add a methyl group ( increase hydrophobic nature of histone)
What are the post transcriptional factors
Splicing
RNA editing
What is an intron
non coding DNA
What is an exon
Coding DNA
How does splicing work
A splicosome is used
Causes a loop to form
Introns are spliced out, remaining exons fused together to make mature mRNA from pre mRNA
mRNA leaves the nucleus
How does mRNA editing work
add polyA tail and cap (this stabilises mRNA and prevents mRNA degradation, which now makes mature mRNA)
you can edit mRNA through base deletion and subsituation
What are the types of post-translational control
Protein modification
How do we regulate genes at a translational level (mRNA after it leaves the nucleus and wants to bind to a ribosome)
To decrease translation you can bind of inhibitory proteins on mRNA which prevents it from binding onto the ribsosone
To increase translation you can activate inititaion protein aids binding of mRNA to ribosome
How does protein modification occur in post-translation control?
Add non-proteins (phosphates, lipids)
Can modify amino acids by adding bonds (like disulphide bridges)
Fold or shorten proteins
Or can modify by using cAMP in the example of protein kinase where, when cAMP binds it causes a change in the 3D structure of the enzyme, making it active
What is an operon
a group of genes controlled by the same regulatory mechanism and expressed at the same time
What is a promoter
DNA sequenence that RNA polyermase binds to
What is a repressor
transcription factor that stops transcription
What are structural genes
genes that code for proteins not involved in DNA regulation
What are regulatory genes
code for proteins involved in DNA regulations eg repressor protein
what is the operator
DNA sequence where repressor protein binds to
How does the lac operon work
Glucose present
Lac I codes for repressor protein
person protein binds to operator
so RNA polymerase cannot bind
How does a lac operon work
Lactose present
Lactose binds to the repressor protein
this changes the shape of repressor protein so it can no longer bind to the operon
RNA polymerase cann bind to to promotor so structural genes can be made
How does a lac operon work
Lactose present
Lactose binds to the repressor protein
this changes the shape of repressor protein so it can no longer bind to the operon
RNA polymerase can bind to promotor so structural genes can be made
CRP can bind to cAMP which can make it easier for RNA polymerase to bind
How does the lac operon work when
Glucose and lactose is present
Cell prefers glucose (provides more energy)
Glucose decreases cAMP concentration, so the CRP-CAMP-RNA polymerase complex will dissociate
downregulating transcription
What do the three structural genes (lacY, lacZ, lacA) make in a lac operon
Beta galactosidase
lactose permease, lactose transferacylase
What are homebox genes
regulatory genes (180 base pairs long) -Code for homeodomain (part of protein)
What are the functions of homeobox genes
- Controls body development (poistioning of body parts)
- Highly conserved in plants, animals, fungi
- Regulate mitosis and apoptosis by responding to internal and external stimuli
How do homeobox genes help with development
-homeodomain of the protein can act as a transcription
factors and bind to sites of DNA
- binds to DNA at the start of developmental
- can alter production of proteins involved in the development of the body plan
What are hox genes
Homeobox genes found in animals
39 across mutiple chromosomes
What is apoptosis
Programmed cell death
Give an example of internal stimulas where apotosis may need to occur
- DNA damage
- If damage is detected during the cell cycle then apotosis may be triggered
Give an example of external stimulas where apotosis may need to occur
- lack of nutrients availability could result in apoptosis
- or a pathogen
- stress
How does apoptosis happen
- DNA in the proteins and nucelus in the cytoplasm
- Other cell components e.g mitochondria and cytoskelton are broken down by enzymes.
- As cell contents are broken down it begins to shrink are also broken down
- Blebs develop on cell surface
- Blebs are engulfed by phagocytes and are digested
This is to prevent harmful products being released into the body
What is necrosis
- can happen due to trauma or infection
- unprogrammed cell death
What is epigenetic regulation
noticiable changes in gene functions without changes to the base sequence
changes are caused by the enviorment
