Neil Flashcards
Expression vector
A plasmid or virus designed for gene expression in cells. Used to introduce specific gene into target cell and lead to protein synthesis
Shuttle vector
A plasmid designed so it can propagate in two different host species
Describe the two mechanisms of protein evolution
Gradual accumulation of mutations that in some way enhance the protein
Recombination which results in chimeras (hybrid proteins) with enhanced properties
An example of a virus with a single stranded DNA genome is:
M13 bacteriophage
An example of an organism with a double stranded RNA genome is
Blue tongue virus
A retrovirus has a _______ genome
Single standard RNA
E. Coli had a ___________________ genome
Circular double stranded
Humans have a _______________
Linear double stranded DNA genome
Give an example of an organism with a linear single stranded DNA
Parovirus
Give an example of an organism with a circular single stranded DNA genome
Porcine circovirus (PCV)
Describe gene expression in viral RNA genomes.
In many viruses genes are encoded by RNA not DNA
RNA can be D-S or S-S
In many cases RNA is reverse transcribed into DNA and then translated normally
Describe the effect of orientation on translation of single stranded RNA genomes
Positive sense: can be directly translated even in the absence of a cap or poly A tail
Antisense: first converted into a positive sense ssRNA molecule by RNA dependent RNA pol.
Ambisense: parts can be translated directly but other parts have to be converted to positive sense first
Enhancers can occur in a variety of positions with respect to genes:
Up/downstream
Distal
Adjacent
Internal
Need direct contact between _________ and _________ for activation
Enhancer
Promoter
What role do snRNAs play?
Found in splicing speckles
Involved in processing of pre mRNA
Always associated with snRNPs
Twintrons
Intron within an intron
Removed in a two step process
Describe the role of small nuclear RNAs (snoRNA)
Involved in chemical modification of rRNAs
Pan-editing: insertion of uracil
Methylation
Describe micro RNAs (miRNA)
Control gene expression: fold back RNA to form stem loops, cut into individual loops by drosha. Cut again by dicer
Silence endogenous mRNAs so there are not translated
C value
Total amount of DNA in haploid genome
C value paradox
Apparent lack of correlation between organisms c value and morphological complexity due to variations in repetitive DNA
In bacteria, genome size is related to _________ and _________
Complexity
Environmental
In viruses and bacteria __________ is proportional to ________
Genome size
Gene number
How many chromosomes do bacteria have?
Most have one but some contain additional replicants that can be considered to be either mega plasmids or mini chromosomes
A few have more than one true chromosome
Chromosome copy number size variation
Genes closer to origin can have high copy number (up to 4) in dividing cells due to multiple initiations
Operons
Genes transcribed together but translated separately
Overall gene function can be investigated by _____________:
______________
______________
_______________
Gene inactivation by
Homologous recombination
Transposon mutagenesis
RNA interference
Differential splicing
Means that one gene can produce more than one protein
E.g. Human slo gene contains 35 exons and generates 500 mRNA species. Encoded protein involved in sound reception in cochlea, variants detect different frequencies
RNA editing can:
Result in multiple proteins from a single message
Repeated genes/clusters
Multiple similar genes. Normally occurs when genes required in high frequencies.
Eg. rRNAs
Multigene family
Multiple different genes
Eg. Haemoglobin needs to be expressed in different forms over lifetime
Describe the two types of pseudogenes
Conventional: mutations have occurred in a gene sequence and caused it to become non functional
Processed: gene sequence contains neither introns or promoters. Derived from DNA copies of mRNA which have become incorporated into the genome
