(6.1.1) Cellular Control Flashcards
(21 cards)
Define Mutation
change in the sequence of bases in DNA
The change in base sequence can be caused by:
- Substitution
- Deletion
- Insertion
What can the insertion or deletion of a nucleotide lead to?
A frameshift mutation
What are the 3 effects of different mutations?
- No effect
- Damaging - phenotype
affected in a negative way - Beneficial - protein synthesised that results in a new and useful characteristics in the phenotype
How is the rate of mutation increased?
Increased by mutagens
What is a mutagen?
A chemical, physical, or biological agent which causes mutations
Example of physical mutations
- ionising radiation such as XRAYS - break one or both DNA strands - some breaks can be repaired but mutations can occur in the process
Example of chemical mutations
deaminating agents - chemically alter bases in DNA such as converting cytosine to uracil in DNA changing the base sequence
Examples of Biological agents
- Alkylating agents - methyl or ethyl groups are attached to bases resulting in the incorrect pairing of bases during replication
- Base analogs - incorporated into DNA in place of the usual during replication, changing the base sequence
-Viruses - viral DNA may insert itself into a genome, changing the base sequence
Explain how it is possible for a mutation to have no effect on the protein produced from that gene?
- some triplets code for the same amino acid bc they are degenerate
- so the amino acid sequence is not altered
- some alternative amino acids will not alter the shape of the protein
-the mutation occurs in intron so is removed
Explain how a mutation could alter the protein so that it no longer performs its correct function in the cell?
- an insertion/deletion will cause a frame shift
- all triplets downstream will be different
- the protein will have a different sequence of amino acids after the mutation
- Therefore the tertiary structure will be different
Mitosis is involved in growth and repair of tissues.
State two other roles of mitosis in multicellular organisms.
- development of body plan
- production of new stem cells
- asexual reproduction
How is transcription controlled in eukaryotes?
- Hormone enters cell and binds to a transcription factor
- The transcription factor is activated
- This binds to the promoter region
- RNA polymerase is then able to bind
Describe how gene expression can be regulated after transcription.
- The primary mRNA can be modified
- Removal of introns produces mature mRNA
- Alternative splicing can produce different versions of mRNA
- Protein has to be activated by cAMP/phosphorylation and the binding of cAMP alters the shape of the protein
How does the structure of galactose allows it to be used as a respiratory substrate
The bonds contain energy so they can be broken by respiratory enzymes
They are also soluble so can move within the cell
The H/OH groups are able to form H bonds with water
Suggest and explain why lactose cannot cross cell membranes
- Lactose is too big
- This means that it is unable to pass between phospholipids
-It may also have a small/no concentration gradient so requires a carrier protein to pass membranes.
In order for lactose to enter the cytoplasm of E. coli a protein is required.
The E. coli living in the digestive system of young mammals are more likely to contain this protein than
E. coli living in the digestive system of old mammals.
Suggest an explanation for this observation.
Young mammals have a diet which is higher in milk. This means that it has a high lactose concentration.
The structural gene for the lactose permease gene / lacY is transcribed and switched on
The protein is lactose permease
Why are fruit flies chosen for research into genes controlling the development of body plan?
- Low cost
-Rapid reproduction rate so more generations in a given time
-Fruit fly genetics is well understood
-Simple genetics/body plan
-Many mutations/structures are observable with light microscope
The development of body plan in eukaryotic organisms is controlled by
……………………………………………… genes. These genes code for proteins that are able to bind
to ……………………………………………… and turn specific genes on and off and are known as
……………………………………………… factors. These proteins contain a sequence of base pairs
that varies little between species within the animal, ……………………………………………… or
fungus ……………………………………………… .
1) homeobox
2) DNA
3) Transcription
4) Plant
5) Kingdoms
Investigations into the activity of genes that control body plan frequently use fruit flies and mice.
There are some public concerns about the ethics of using mice in these investigations.
Suggest two reasons why mice are chosen as a suitable species for investigation
They are more similar to humans
They are low cost
They have rapid reproduction rate
They show effects are generalisable to more than one species
