Cellular Control Flashcards
What is a mutation ?
- A change in DNA base sequence caused by mutagens.
What is a mutagen ?
- Outside factors that increase the rate of mutations
What are the types of mutations ?
- Point Mutations
- Indel mutations
What are the point mutations ?
- Only affects one base
- Substitution
- Insertion
- Deletion
What causes a frameshift mutation? What is it?
- Insertion and Deletion disrupts triplet code reading .`
Substitution definition
-A form of gene mutation in which one nucleotide base is exchanged for
another. This may change an amino acid or produce the same amino acid (due to the
degeneracy of the genetic code).
Insertion defintion
-A form of gene mutation in which one or more nucleotide bases are added to a
DNA sequence. This may lead to a frameshift mutation, changing every successive codon.
Deletion definition
- Deletion: A form of gene mutation in which one or more nucleotide bases are removed from a DNA sequence. This may lead to a frameshift mutation, changing every successive codon.
What are the effects of a mutation
- Silent/Neutral - no effect (DNA degenerate)
- Beneficial - Enhanced function of protein (rare)
- Damaging/Harmful - Malfunctioning protein made
What are the types of mutations ?
- Nonsense - codon due to particular mutation has changed into a stop codon
- Missense - particular amino acid change - degenerate coding has changing
Explain how genes are ?
- Genes are switched on and off
- DNA carry the same genes but the structure and function of different cell varies
- This is because not all the genes are expressed (selectively switched on )
- They determine the cell structure and control cell processes.
What levels can genes be controlled at ?
- Transcriptional
- Post- transcriptional
- Post translational level
How is gene expression controlled at a transcriptional level ?
- Gene expression can be controlled at the transcriptional level by altering the rate of transcription of genes - e.g - increased transcription produces more mRNA which can be used to make more protein
- This can be controlled by transcription factors
- The shape of a transcription factor determines whether it can bind to DNA or not and can sometimes be altered by the binding of some molecules, e,g hormones and sugars
- This means the amount of certain molecules in an environment or a cel can control the synthesis of some proteins by affecting transcription factors binding
What is the difference between eukaryotes and prokaryotes at a transcriptional level ?
- In eukaryotes, transcription factors bind to specific DNA sites near the start of their target genes - the genes control the expression of.
- In prokaryotes control of gene expression often involves transcription factors binding to operons.
What is a transcription factor ?
- They are proteins that bind to DNA and switch genes on or off by by increasing or decreasing the rate of transcription. Factors that increase the rate are called activators and those that decrease the rate are repressors.
What is an operon ?
- A section DNA that contains a cluster of structural genes, that are transcribed together as well as control elements and sometimes a regulatory gene.
What do structural genes code for ?
- They code for useful proteins such as enzymes
