6.1 Cellular Control Flashcards
What is a Mutation?
An random alteration to the DNA base sequence.
When are Mutations most likely to arise and why
Often arise spontaneously during DNA replication, Most likely here due to exposed bases or base sequence errors
What are Insertion and Deletion Mutations?
- Where one or more nucleotides (bases) are either inserted or deleted from the DNA sequence.
- More likely to be either harmful or beneficial, due to frame shift which means the entire amino acid sequence will be different
What is a Substitution Mutation?
- When a nucleotide in the DNA sequence is replaced by another.
- More likely to be a neutral mutation, meaning no change occurs in the amino acid sequence.
How is gene expression regulated at the transcriptional level?
Transcription factors. These are proteins (or no coding RNA pieces) that can either initiate or inhibit the transcription of genes, so that only certain parts of the DNA are expressed.
What are Introns and Exons
Introns are NON coding pieces of DNA
Exons are coding pieces of DNA
What is the function of the Lac operon
a group of genes in E.coli that allows it to metabolise lactose instead of glucose as a respiratory substrate(if no glucose, but lactose present)
What is the function of
Lactose permease
Lactose permease allows lactose to pass through the bacterial cell wall(permeate)
What is the function of B-galacotsidase
B galacotsidase hydrolyses lactose to its monomers, glucose and galactose
What does Lac I code for
Lac I codes for repressor protein that binds to lac o and prevents lac Z&Y being transcribed
What does Lac O do
O for operator, is where repressor protein binds to, preventing trancription
What do Lac Z, and Lac Y code for
code for B-galactosidase(Z)
and lactose permease(Y)
How does Lactose Induce the Lac Operons activity
Lactose binds to Lac I altering the shape of the represor protein it produces and preventing it binding to the operator, allowing lac Z&Y to be made
Describe the function of the Lac Operon in low lactose concentrations.
When lactose concentration is low, the repressor proteins bind to the the operator preventing transcription of genes(Z&Y)
Describe the function of the Lac Operon in high lactose concentrations.
Lactose binds to the repressor protection, causing it to change shape and unattach from the operator. Allows RNA polymerase to bind and the genes (Z&Y) to be transcribed
How is gene expression regulated at the Post-Transcriptional level?
Splicing.
Primary mRNA contains both coding regions (exons) and non-coding regions (introns). The introns are removed to produce mature mRNA ready for translation.
How is gene expression regulated at the Post-Translational level?
Activation of proteins, such as adrenaline. When adrenaline binds to a receptor, an enzyme is activated which converts ATP to cyclic AMP. Prompts further enzyme reactions, which activates the protein.
What’s a Homeobox sequence?
180 base pairs(exons) that regulate patterns of development in animals,fungi &plants
How is development controlled by Homeobox genes?
They code for transcription factors that activate genes when they’re needed during development of a zygote.
What’s a Hox gene?
subset of homebox genes ONLY found in animals(bilaterians) that are involved in formation of body parts in the correct locations
How is development controlled by Mitosis?
Mitosis (cell replication) is the primary mechanism of growth. Genes regulating mitosis respond to various stimuli, both internal and external, in order to control rate of growth.
What is Apoptosis, what does it do?
Programmed cell death. It is highly controlled and keeps cell division at a constant rate so as to prevent cancer.
What’s a Nonsense mutation
a mutation where a stop codon is made and the strand is cut off early resulting in a truncated, non-functional protein
What’s a Missense mutation?
a codon change which results in the production of a different amino acid, thus resulting in altered tertiary structure of the protein
What’s a Silent mutation?
due to DNA’s degenerative code multiple codons make the same amino acid so this base change has NO effect on the final protein
What does it mean to “Sequence” a genome?
to read the order of base sequences
Why must Apoptosis be highly controlled?
too much leads to cell loss & degeneration.
Not enough can lead to tumors and Cancer
Briefly summarize the cAMP Post translation regulation example
1.signalling molecule binds to target cells plasma membrane receptors
2. activates trans membrane protein which activates G protein which activates adenyl cyclase enzymes
3. enzymes catalyse formation of cAMP from ATP
4 cAMp activate protein kinase which may phosphyrlate another protein that enters the nucleus and acts as a transcription factor
What does ‘Frame shift’ mean
The whole DNA sequence is moved by space(s) and can result in a new sequences
Define operon
a group of genes under the same regulatory mechanism, transcribed as a single unit
How might cells diffrentiate/specialise
transcription factors bind to sections of DNA, activating or supressing gene transcription leading to differential expression
