Module 6.1 - Cellular Control Flashcards
How can different proteins be made despite all cells having the same DNA? (4)
- Not all genes in a cell are expressed/ transcribed
- Cells show different gene expression
- They determine the cell structure and control cell processes for more gene expressions
- Therefore different proteins can be formed
What are the levels where gene expression can be controlled? (3)
- Transcriptional
- Post-transcriptional
- Post-translational level
What is gene expression also known as? (1)
- Protein synthesis
Gene expression at the transcriptional level? (2)
- Controlled by altering the rate of transcription of gene
- Controlled by transcription factor
Activators? (1)
- Factors that increase the rate of transcription
Repressors? (1)
- Factors that decrease the rate of transcription
Shape of the transcription factor? (2)
-Determines whether it can bind to DNA or not
- Can sometimes be altered by the binding of some molecules
How does the environment control the synthesis of some proteins? (2)
- Amount of certain molecules in an environment or a cell can control the synthesis
- By affecting transcription factor binding
Transcription factor binding in eukaryotes? (1)
- Transcription factors bind to specific DNA sites near the start of their target genes
Transcription factor binding in prokaryotes? (1)
- Control of gene expression involves binding to operons
Operon? (3)
- A section of DNA that contains a cluster of structural genes
- Genes are transcribed together
- They control elements and act as a regulatory gene
Structural genes? (2)
- Code for useful proteins like enzymes
- Control elements promoter and operator
Promotor? (1)
- A DNA sequence located before the structural genes that RNA polymerase binds to
Operator? (1)
- A DNA sequence that transcription factors bind to
Regulatory genes? (1)
- Codes for an activator or repressor
Where is the enzyme needed to respite lactose found? (2)
- Lac operon
- Lac operon has three structural genes
Three structural genes of lac operon? (2)
- lacz, lacy and lacA
- Produce proteins that help the bacteria digest lactose
Lac operon when Lactose is not present? (4)
- Regulatory gene (lacl) produces the lac repressor
- Repressor is a transcription factor
- It binds to the operator site
- Blocks transcription because RNA polymerase can’t bind to the promoter
Lac operon when Lactose is present? (4)
- Lactose binds to the repressor
- Changes repressor’s shape
- No longer bind to the operator site
- RNA polymerase can begin transcription of structural genes
Introns? (1)
- Eukaryotic DNA sections that don’t code for amino acids
Exons? (1)
- Eukaryotic DNA section that code for amino acids
Introns and exons during transcription? (2)
- Are copied into mRNA
- Forms primary mRNA transcripts (pre-mRNA)
Pre-mRNA? (1)
- mRNA strands containing introns and exons
How are introns removed from pre-mRNA strands? (5)
- Splicing
- Introns are removed
- Exons are joined
- Forming mRNA
- Takes place in nucleus
What happens to the mature mRNA after post-transcriptional level? (1)
- Leaves nucleus for translation
Proteins at the post-translational level? (2)
- Some proteins aren’t functional after synthesis
- They need to be activated to work
Protein activation controlled by? (2)
- Hormones or sugars bind to cell membranes
- This triggered cAMP production
cAMP at the post-translational level? (2)
- cAMP activates proteins inside cells by altering 3D structure of an enzyme
- Makes enzyme more or less active
How does CAMP activate protein kinase A (PKA)? (4)
- PKA is an enzyme made of four subunits
- CAMP binds & causes a change in the enzyme’s 3D structure
- Releases the active subunits
- PKA is now active
Body plan? (1)
- General structure of an organism that are arranged in a particular way
What controls the development of a body plan? (2)
- Proteins
- Help set up the basic body plan so that everything is in the right place
What genes code for the proteins that control body plan development? (1)
- Hox genes
Hox genes? (3)
- Similar Hox genes found in animals, plants and fungi
- Body plan development in controlled similarly interspecies
- Have regions called homeobox sequence
Homeobox genes? (2)
- Highly conserved
- Sequence have changed very little during the evolution of different organisms
How do Hox genes control development? (3)
- Homeobox sequences code for a part of the protein called the homeodomain
- Homeodomain binds to specific sites on DNA
- This enables the protein to work as a transcription factor
Where do proteins bind to work as a transcription factor? (2)
- DNA at the start of developmental genes
- Activates or represses transcription
Apoptosis’ role in the development of body plans? (2)
- Programmed cell death
- Refines body parts
Steps in the breaking down of the cell after apoptosis? (3)
- Enzymes inside the cell break down important cell components
- Cell begins to shrink and breaks up into fragments
- Cell fragments are engulfed by phagocytes and digested
Mitosis and differentiation role in the development of body plans? (1)
- Create the bulk of the body parts
How is the correct body plan developed? (1)
- During development, genes that control apoptosis and genes that control mitosis are switched on and off in appropriate cells
How do the genes that regulate apoptosis and the cell cycle respond to stimuli? (3)
- Internal stimulus - DNA damage: if detected during the cell cycle, genes that cause the cycle to pause or trigger apoptosis are expressed
- External stimulus - lack of nutrients available: genres that prevent mitosis are expressed
- External stimulus: pathogen attack: gene that trigger apoptosis are expressed
Types of mutations? (3)
- Substitution
- Deletion
- Insertion
Substitution mutations? (2)
- One or more bases are swapped for another
- e.g. ATGCCT becomes ATTCCT
Deletion mutations? (2)
- One or more bases are removed
- eg. ATGCCT becomes ATCT
Insertion mutations? (2)
- One or more bases are added
- e.g. ATGCCT becomes ATCACCT
What are the effects of mutations in proteins? (3)
- Order of DNA bases = order of amino acids
- Mutation alters primary structure = altered protein codes = alters final 3D shape of protein
- Protein may not work properly
What are the three effects of a mutation? (3)
- Neutral
- Beneficial
- Harmful
Neutral effects - degenerate code? (3)
- The genetic code is degenerate
- E.g. TAT and TAC code for tyrosine
- If TAT is changed to TAC, it won’t affect the amino acid
Neutral effects - substitution mutations? (4)
- The mutation produces a triplet that codes for a different amino acid
- But the amino acid is chemically similar to the original
- So there will be little change in functions of the amino acid
- E.g, (AGG) and (AAG) are coded for by similar triplets - substitution mutation can swap the amino acids
Neutral effects - Silent? (3)
- The mutated triplet codes for an amino acid not involved with the protein’s function
- They are silent
- E.g. triplet is located far from enzyme’s active site - so protein can work normally
Beneficial effects? (2)
- Advantageous effect on an organism
- E.g. antibiotic resistance for bacteria
Harmful effects? (2)
- Disadvantageous effect on an organism
- Cystic fibrosis
Cystic fibrosis? (3)
- Caused by deletion mutations of three bases in the gene that codes for the CFTR protein
- The mutated CFTR protein folds incorrectly and then breaks down
- This leads to excess mucus production which affects the lungs
CFTR? (1)
- Cystic fibrosis transmembrane conductance regulator
How can a harmful effect cause the loss of production of a protein? (3)
- Mutation occurs at the start of a gene
- RNA polymerase can’t bind to it and begin transcription
- The protein coded for by the gene won’t be made
