6.1.1 - Cellular Control Flashcards
What is a mutation?
a change in the base sequence of DNA
What are the types of mutations?
substitution -silent -mis-sense -non-sense frame shift -insertion -deletion
What is a substitution mutation?
a mutation where one base is replaced by another
-can change the amino acid or it could stay the same
What is a silent mutation?
a mutation where different codons code for the same amino acid (degenerate code)
What is a mis-sense mutation?
a mutation where a different amino acid is coded for
-could cause issues or could do nothing
What is a non-sense mutation?
a mutation where a stop codon is part way through a sequence of bases, resulting in a shortened polypeptide
What is a frame shift mutation?
a mutation where every amino acid after the mutation changes
two types:
- insertion
- deletion
What is an insertion mutation?
a mutation where an additional base is added to the sequence
What is a deletion mutation?
a mutation where there is a missing base in the sequence
What is a point mutation?
a mutation where only 1 base changes
What is an inversion mutation?
a mutation where a sequence of bases is reversed, resulting in one amino acid changing
What effects can mutations have?
- harmful (protein is non functional)
- neutral (mutation has no effect/protein still has same function)
- beneficial (advantageous)
What is a mutagen?
a chemical, physical or biological agent that causes a mutation
eg. UV light, viruses, etc
What are house keeping genes?
genes that control metabolic processes
What are tissue specific genes?
genes which have specific roles in specific tissue proteins
-turn genes on and off
What are the types of gene regulation?
- transcriptional (during transcription)
- post-transcriptional (after transcription)
- translational (during translation)
- post-translational (after translation)
What is epigenetics?
environment affecting gene regulation
What happens in transcriptional gene regulation in eukaryotes?
chromatin remodelling aka histone modification
- histones are modified to increase/decrease how tightly the histones and DNA are packed together
either. .. - ACETYLAT|ON (acetyl group is added) - histones become less positive so DNA loosens + translation occurs
- METHYLATION (methyl group is added) -histones become more positive (more hydrophobic) so bind more closely together, causing DNA to coil more tightly + prevents translation from occuring
What is the structure of a chromatin?
DNA is coiled around histones (proteins)
- heterochromatin -tightly wound DNA
- euchromatin - loosely wound DNA
What does acetylation do to DNA (in histone modification)?
- DNA loosens (coiled less tightly)
- translation occurs
What does methylation do to DNA (in histone modification)?
- DNA coils more tightly
- no translation occurs
What happens in transcriptional gene regulation in prokaryotes?
LAC operon
-glucose or lactose can be used as a respiratory substrate…
GLUCOSE
-regulatory gene produces a repressor protein, which binds to the operator, blocking the promotor
-RNA polymerase can’t bind to promotor so there is no transcription of structural genes (prevents energy waste as structural genes aren’t needed for glucose)
LACTOSE (used when glucose is in short supply)
-lactose binds to repressor protein, which changes its tertiary structure (+ shape), meaning it can’t bind to the operator anymore
-RNA can bind to promotor so transcription of structural genes can occur
-structural genes code for enzymes:
-lac Z codes for β galactose (splits lactose into glucose and galactose)
-lac Y codes for lactose permease (increases e.coli’s permeability to lactose so it can absorb more)
-lac A codes for transacetylase (adds an acetyl group)
What is an operon?
a group of genes under the control of the same regulatory gene
What genes are in the LAC operon?
- regulatory gene (produces repressor protein)
- promotor (where RNA polymerase binds)
- operator (where repressor protein binds)
- structural genes (synthesise enzymes) - lac Z, lac Y and lac A
What happens when prokaryotes (eg. e.coli) use glucose as a respiratory substrate?
- regulatory gene produces a repressor protein
- repressor protein binds to the operator, which blocks the promotor
- RNA polymerase can’t bind to promotor so there is no transcription of structural genes (prevents energy waste as structural genes aren’t needed for glucose -makes glucose easier to metabolise)
What happens when prokaryotes (eg. e.coli) use lactose as a respiratory substrate?
- lactose binds to repressor protein, which changes its tertiary structure (+ shape)
- repressor protein can’t bind to the operator anymore
- RNA can bind to promotor so transcription of structural genes can occur
- structural genes code for enzymes:
- lac Z codes for β galactose (splits lactose into glucose and galactose)
- lac Y codes for lactose permease (increases e.coli’s permeability to lactose so it can absorb more)
- lac A codes for transacetylase (adds an acetyl group)
What does lac Z code for?
β galactose
-splits lactose into glucose and galactose
What does lac Y code for?
lactose permease
-increases e.coli’s permeability to lactose - can absorb more
What does lac A code for?
transacetylase
-adds an acetyl group
What happens in post-transcriptional gene regulation?
RNA is processed (pre-mRNA is modified to form mature-mRNA)
-capping (phosphates are added to one end -stabilises mRNA and delays degradation in cytoplasm and aids binding to ribosomes)
-splicing (introns are removed)
-polydenylation (adenine tail is added)
RNA is edited
-bases are added or deleted and exon order is changed
What are introns?
non-coding sections of DNA
What are extrons?
coding sections of DNA
What happens in translational gene regulation?
degrading of mRNA
-the more resistant the molecule, the longer it will last in the cytoplasm, the more protein synthesis will occur
binding of inhibitors to mRNA
-prevents it binding to ribosomes + synthesising proteins
activation of initiation factors
-aids mRNA binding to ribosomes
What happens in post-translational gene regulation?
proteins that have been synthesised are modified
- non-protein groups are added (eg. phosphates, lipids, carbohydrate chains)
- amino acids are modified alongside the bonds being formed
- proteins are folded or shortened
- cAMP modifies the proteins
What is morphogenesis?
the regulation of the pattern of anatomical development
What are homeotic genes?
genes which regulate morphogenesis by controlling the development of all organisms
What is a homeobox?
a section of DNA 180 bases long
-codes for a protein 60 amino acids long that is highly conserved (very similar) in plants, animals and fungi, which binds to DNA to switch genes on and off
What is a homeobox gene?
a gene containing a homeobox (DNA 180 bases long) which codes for a protein transcription factor (regulates gene transcription)
-highly conserved and similar in plants, animals and fungi
What are hox genes?
group of homeobox genes only present in animals which is responsible for positioning body parts correctly (determines identity of embryonic body regions)
How do Hox genes affect the development of body plans?
- homeobox sequences of Hox genes code for a homeodomain
- homeodomain binds to specific sites near the start of the target developmental gene
- homeodomain acts as a transcription factor
- homeodomain activates/represses the transcription of the developmental gene
- this alters the production of a protein involved in body plan development
What is a transcription factor?
a protein which controls the transcription of a protein
- binds to a specific site on DNA
- coded for by a homeobox gene
What is necrosis?
unprogrammed cell death
What is apoptosis?
programmed cell death
What causes apoptosis?
- hormones
- cytokines
- nitric oxide
- growth factors
- immune system
What happens in apoptosis?
- enzymes break down cell’s cytoskeleton
- cytoplasm becomes more dense and organelles pack together
- plasma membrane breaks up, forming blebs
- chromatin condenses and DNA fragments
- cell fragments are taken up by phagocytosis
What is the importance of mitosis in controlling the development of body forms?
increases number of cells to cause growth
What is the importance of apoptosis in controlling the development of body forms?
removes unwanted cells and tissues to shape different body parts
