Molecular Genetics Flashcards
What is SLC2682?
Gene which results in issues producing cartilage.
What is BRCA1/2?
Gene that when mutated can cause breast cancer.
How does Herceptin contribute to the treatment of cancer?
- binds to receptors in the breast (HER2) and blocks info which tells cells to divide.
What are the 4 theories in where we came from?
Ovism - tiny humans already in the egg/sperm
Spontaneous Generation - generate spontaneously
Panspermism - not already formed, comes from particles in the body
Maupertuis - suggested we were a result of both mother and father particles together
Who first observed cells in 1600?
Leewenhock
Who proposed all organisms made out of cells in 1830?
Schleiden and Schwann
Who proved microbes couldn’t spontaneously occur?
Louis Pasteur
Who and in what year proved DNA was the heritable molecule?
Oswald Avery 1944
How did Avery prove DNA was the heritable molecule?
- Isolated molecular components of heat killed pneumococci serotype
- smooth capsule trait from heat killed cells was picked up by cultures of rough cells when DNA wasn’t degraded
Is bacteria’s genome stored in the nucleus?
No, stored as operons
- single circular chromosomes with a single replication origin
What is a plasmid?
Small circular DNA molecules which contain a reduced number of genes
- can be transferred between bacteria of same species or between species
What are the features of Plasmids?
- 1000’s - 100000’s bp long
- can exist in multiple copies within a cell
- many diff plasmids inhabit one species
- some promote genetic exchange between bacteria
Features of E.Coli
- lives in gut causing no harm
- Glucose is its main food source
- can also feed of lactose
- must break down lactose –> galactose and glucose (using lactase)
What happens when lactose is available in E.coli?
- It will pass through enzyme permease
- beta galactosidase will transfer some lactose to allolactose, some also transferred to galactose and glucose
Features of a Lac Operon
- Promotor Region
- Operator Reion (where protein binds to)
- 3 structural genes
What happens in the absence of lactose in the Lac Operon?
- Repressor protein binds to operator
- So RNA polymerase cannot bind
- NO TRANSCRIPTION occurs
What happens in the presence of lactose in the Lac Operon?
- Beta galactosidase binds to lactose and changes some to allolactose
- allolactose binds to active regulator protein so itll no longer bind to operator site
- TRANSCRIPTION OCCURS
- RNA polymerase can bind to operator
What is an operon and what is the regulatory region and molecule which binds to it called?
A single transcriptional unit that includes a series of structural genes, a promotor and an operator.
- transcription is under control of a single regulatory region (located upstream of gene) called cis-acting
- molecule that bind to this are called transacting
What is and inducible operon?
- Transcription normally off and needs to be turned on
- an inducer is a small molecule which turns on transcription
What is a repressible operon?
- Transcription normally on and needs to be turned off
- co-repressor is small molecule which binds to repressor making it incapable of binding to operator, thus turning off transcription.
In inducible operons, what is negative control?
- Transcription occurs only when the inducer binds to the repressor and makes it inactive
- therefore repressor cant bind to operator so transcription can occur
In inducible operons, what is positive control?
- Regulatory protein is an activator so inducer must bind with it to make it active
- then transcription can occur
In repressible operons, what is negative control?
- Transcription blocked when co-repressor binds to regulator allowing it to bind to DNA and block trancription
In repressible operons, what is positive control?
- regulatory protein is an activator
- transcription is blocked when co repressor binds to regulator
- then it cant bind to promotor regulator so RNA polymerase is not recruited
What occurs when Extracellular osmolarity is low?
- the ompF mRNA is translated to produce ompF protein (serves as a passive chanel for small polar molecules)
What occurs when Extracellular osmolarity is high?
- the micF gene is activated and micF RNA produced
- the micF pairs with the 5’ end of ompF RNA blocking ribosome binding site.
- no ompF protein produced
What is a riboswitch found in a prokaryote?
A regulatory sequence of mRNA molecules where molecules can bind and affect gene expression by influencing secondary structure formation in mRNA.
What happens in a riboswitch when the regulatory protein doesn’t bind?
- riboswitch assumes an alternative secondary structure that makes the ribosomes binding site available so translation occurs.
What is a ribozyme?
Can catalyse biochemical functions
- but when bound to small molecules can induce the cleavage of degradation of RNA, PREVENTING TRANSLATION
Who produced insulin producing beta pancreatic cells?
Douglas Melton
What does a nuclear membrane allow?
- allows other steps to process RNA between transcription and translation
What do Histones allow?
- dna to be more compact and thus have higher quantities of it
What do multiple linear chromosomes allow?
- cells to hold more DNA and add more regulatory genes to genome
What does single gene transcription allow?
- control of how much each gene is expressed
What are the 3 types of RNA Polymerase in eukaryotes?
Polymerase I - rRNAs
Polymerase II - pre mRNAs, snoRNAs, some miRNAs and snRNAs
Polymerase III - tRNAs, smallRNAs, miRNAs, and some snRNAs
What must eukaryotes DNA do before transcription?
- unwind from the histone
What occurs in post transcriptional modification?
- addition of a 5’ cap added
- splicing
What do coactivator do?
- bind to other molecules not the promotor itself
How is transcription initiated in Eukaryotic promotor?
1) Promotor has a TATA box
2) one strand as template, transcription factors bind to DNA promotor region and transcription initiation complex forms
3) some transcription factors after transcription started
What is an insulator?
- DNA sequence that blocks / insulates the effect of enhancers
What is transcriptional stalling?
- extra layer of regulation of heat shock proteins and genes
- good for genes that have been transcribed at short notice
- transcription elongation blocks released and transcription proceeds
Altering the chromatin structure by Chromatin Remodelling
- repositioning of nucleotides results in a change in structure
- allows transcription factors to bind to DNA and initiate transcription
- chromatin remodelling complexes bind to specific DNA sites
2 Types of histone modification?
- Methylation
- aceylation
What is DNA methylation?
- Methyl group binds to nucleotide, makes less easy for transcription factors to bind as it becomes more tightly wrapped around the histone protein.
Which way does polymerase go along template strand?
3’-5’ direction - but synthesis in other
In post transcriptional modifications what is RNA degradation?
- 5’ cap removal
- shortening of poly A tail
- degradation of 5’ UTR coding sequence and 3’ UTR
In post transcriptional modifications what is the purpose of addition of a Poly Adenine Tail?
- polyAtail added to 3’ end
- it bends over to 5’ end to stabilise ribosome
In post transcriptional modifications what is the purpose of RNA splicing?
- you don’t get a protein that may be harmful and you don’t waste energy on translation
In post transcriptional modifications what is DNA - RNA mismatch / RNA processing?
- Colinearity - 2 strands of genetic material perfectly align to each other
In post transcriptional modifications what is Alternative splicing?
- allows a single gene to produce several protein products
- introns can be used as regulatory mechanisms
- eg. Alt Spli of tra gene
In flies how is Sex determined by post transcriptional modifications?
Males - upstream splice site is used, inclusion of premature stop codon so no functional tra protein produced.
Females - presence of SxI protein causes downstream splice of 3’ site to be used, termination codon spliced out so functional tra protein produced.
What is RNA interference?
- inhibition of translation
- altering chromatin structure
- used to reduce expression of target genes
siRNA and microRNAs functions and purpose
- 22 nucleotides long, both prevent mRNA’s being translated
- double stranded RNA cleavage
- siRNA can lead to degradation of mRNA by cleavage
- microRNA can form complexes with proteins, bind with mature RNA and will block translation
- some miRNAs methylate histones
- siRNA’s can treat cancer, reduction of liver tumours.
Key features of mitochondria and Chloroplasts
- both have outer and inner membranes
- both DNA and ribosomes
- both provide energy to the cell
- contain their own genomes
- endosymbiotic theory
- their genes migrated to the nucleus
Features of only mitochondria
- 6kbp - millions of bp
- resp and ox phosphor
- most of proteins encoded in nucleus translated in cytoplasmic ribosomes then into mitochondria
- mitochondrial DNA inherited from mother
- dependent on nuclear transcription
- used for phylogenetic studies
Features of only chloroplast
- 80000-600000 bp
- circular double stranded DNA
- highly coiled
- no histone proteins
- rRNAs and tRNAs
- genes in operons
- transcription and lation similar to eubacteria
- DNA evolves slower than mitochondria
- used to asses phylogenetic relationships among plant species
How can mitochondria be different in TAXA?
- huge genome size variation
- plant mit have multiple circular DNA
- linear in some species
Features of the Human mitochondrial genome
- 16000bp
- no UTR
- single promotor per strand
- 2 long transcripts are cleaved
Features of Yeast mitochondrial genome
- 78000bp
- high non coding DNA content
- many introns
- UTR’s and intergene spacers
Features of plant mitochondrial genome
- variation in size of genome
- multiple circular genomes
- high repeat DNA content
Who started the Human Genome project and what was diff between first and second one/The shotgun sequencing technique used by Craig Venter differed from the strategy used by the public funded sequencing consortium in that…
- Craig Venter
- private funding
- shotgun sequencing involved sequencing shorter fragments of DNA
- shotgun sequencing did not involve the construction of a detailed map of genetic markers
- shotgun sequencing did not require cloning of very large chromosome fragments in a yeast vector
What was the goal of the HGP?
Obtain the entire sequence of the haploid human genome
What were the HGP expectations and what did it actually reveal?
- understand functions of genes
- understand genomic basis of diseases and cure them
- revealed only a fraction of the genes present that we thought 20-22k
What is comparative genomics?
Comparing genomes of diff species
What is functional genomics?
Using techniques to assess RNA levels
What is structural genomics?
Determines DNA sequence of entire genomes
What is a Transposon?
- short sequences along DNA which can change position
- mechanisms for copies
What is Homologus? (comparative genomics)
- genes that are evolutionarily related
What is Orthologs?(comparative genomics)
- homologus genes in diff species that evolved from same gene in common ancestor
What is Paralogs?(comparative genomics)
- Homologus genes arising by duplication of a single gene in same organism.
What is a transcriptome? (functional genomics)
- all RNA molecules transcribed from a genome
What is Proteome? (functional genomics)
- all proteins encoded by a genome
What is transcriptomics? (functional genomics)
- assessment of gene activity of many genes at a time
siRNAs and miRNAs are produced by
The cutting and processing of double-stranded RNA by Dicer enzymes
What is the difference between a structural gene and a regulator gene?
- Structural genes encode proteins or functional RNAs not involved in gene expression regulation; regulator genes control the transcription of structural genes
What genes is found in all bacterial transposable elements?
A transposase gene
Mitochondria have been linked to ageing because
Oxidative phosphorylation in mitochondria generates free radicals
In a negative repressible operon, the regulator protein is synthesized as…
An inactive repressor
A haplotype refers to
A particular set of polymorphisms in a chromosome
What does the term heteroplasmy mean?
Cells with a variable mixture of normal and abnormal organelles
