Molecular Biology Wk 2 Flashcards
Describe the structure of prokaryotic cells
Typically, spherical rod like or corkscrew shaped
They often have a protective coat or cell wall surrounding the plasma membrane which encloses single compartment containing the cytoplasm and the dna
However, under optimal conditions many prokaryotic cells can duplicate in as little as 20 mins
In 11 hours by repeated divisions a single prokaryote can give rise to more than 8 billion progeny ( exceeds the total number of humans on earth)
What are the two main domains of prokaryotic cells
Bacteria
Archaea - members of archaea are more closely related to eukaryotes than they are to the other groups of prokaryotes ( bacteria)
What are archaea
They are best known to live in extremely inhospitable environments and they are often referred to as extremophiles
Included among the archaea are…
Methanogens- capable of producing co2 and h2 gases into methane gas
Halophiles - prokaryotes that live in extremely salty environments such as the Dead Sea or certain deep seas brine pools
Acidophiles- acid loving prokaryotes that thrive at a ph of as low as 0 such as those found in in drainage fluids or abandoned mine shafts
Thermophiles- prokaryotes that live at very high temperatures
Hyperthermophiles - live in hydrothermal vents of the ocean floor
What are domain bacteria
Includes the smallest known cells called mycoplasma which lack a cell wall and contain a genome with fewer than 500 genes
What is Cyanobacteria
Most complex of all prokaryotes
Contain elaborate arrays of cytoplasmic membranes, which serve as a site for photosynthesis
As in plants, photosynthesis of Cyanobacteria is accomplished by the splitting of water molecules which releases molecular oxygen
Where is an unusual place for Cyanobacteria bacteria to live
In the hairs of polar bears
What are Cyanobacteria also capable of
Nitrogen fixation - conversion of nitrogen gas into reduced forms of nitrogen ( such as ammonia NH3)
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Types of eurkayotic cells
The most complex eukaryotic cells are not found in plants and animals but in unicellular protists
All of these complex activities such as sensing the environment, trapping food, expelling excess fluid and evading predators is all confined in this one cell- (amoebas, euglena, plasmodium)
What are the characteristics of protists
They are eukaryotic which means they have a nucleus
Most have mitochondria
They can be parasites
Prefer moist and aquatic environments
Describe the process of cell differentiation
An alternative pathway has led to the evolution of multicellular organisms in which different activities are conducted by different types of cells -
Specialised cells are formed for a process called differentiation
Describe the process of differentiation in a fertilised human egg
Embryonic development will lead to the formation of approx 250 distinct types of differentiated cells
The pathway of differentiation depends primarily on the signals received from the surrounding environment - this determines the position of the embryo
Name the six model organisms
A bacterium (prokaryote)
(Eukaryote)
Budding yeast
Flowering plants
A nematode
A fruit fly
A mouse
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Explain the studying of a human disease for example Colton cancer using E. coli
Basic steps of DNA repair are the same in both organisms and a gene involved in dna repair (mutL IN E. coli and MLH1 in humans is found in both organisms
E. coli has an advantage of being easier to grow and researchers can easily study new mutations in the bacterial mutL gene in order to figure out how it works
Found on chromosome 3
Health conditions related to genetic changes in MLH1 gene
Lynch syndrome - hereditary nonpolypopis colorectal cancer
Ovarian cancer
What diseases is the fruit fly being used for
Mutant genes in the fruit fly produce phenotypes with structural abnormalities of the NS and adult on set degeneration of the NS
Huntingdon disease
Machado- Joseph disease
Myotonic dystrophy
Alzheimer disease
What is Huntington disease
Is a progressive brain disorder that causes uncontrolled movements, emotional problems and loss of thinking ability
Mutations on the HTT gene cause this disease
HTT provides instructions for making a protein called huntingtin
Located on chromosome 4
What is Machado Joseph disease
- is a condition characterised by progressive problems with movement. People usually experience problems with coordination and balance (ataxia). Other early signs and symptoms include speech difficulties, uncontrolled muscle tensing (dystonia), muscle stiffness (spasticity), rigidity, tremors, bulging eyes, and double vision.
This results from a mutation in the ATXN3 gene know as trinucleotide repeat expansion. The mutation increases the length of the repeated CAG segment in the gene.
Located on chromosome 14
What is myotonic dystrophy
Part of a group of inherited disorders called muscular dystrophies
Characterised by progressive muscle wasting and weakness.
What are the two types of myotonic dystrophy
Type 1 and 2
Muscle weakness associated with type 1 particularly affects lower legs, hands and neck and face
Muscle weakness in type 2 primarily involves the muscles of the neck, shoulders, elbows and hips
Different types are caused by mutations in different genes
Mutations of myotonic dystrophy
Type 1 is caused by mutations in the DMPK gene while type 2 results from mutations in the CNBP gene.
CNBP- located on chromosome 3
DMPK- located on chromosome 19
What is Alzheimer’s disease (ad)
Approx. 10 percent of familial ad exhibits autosomal dominant inheritance ; the remainder exhibits multifactoral inheritance.
Defects of the beta amyloid precursor protein metabolism cause neuronal dysfunction and death observed with AD.
Presenelin 1,2 gene, when any gene is altered large a sounds of toxic protein fragment called amyloid beta peptide are produced in the brain- leads to death of nerve cells
People with Down syndrome have an increased risk of getting AD
What disease is nematode being used to study
Diabetes
Insulin dependent diabetes mellitus (IDDM)
Insulin resistant diabetes
What causes IDDM type 1
- autoimmune destruction of islet beta cells in the pancreas
- auto reactive Tcells lead to the destruction of the islet cells in the pancreas
- the destruction of islet beta cells causes an insulin deficiency and thereby the dysregulation of anabolism and catabolism resulting in metabolic changes
What are the two units of linear measure
- micrometers
- nanometers
Size of the nucleus in diameter
5-10 micrometer
Size of mitochondria
- is 2 micrometers in length
Size of prokaryotic cells
1 to 5 micrometer in length
Size to eukaryotic cells
About 10 to 30 micrometer
What features are viruses characterised by
Particles composed of an internal core containing either dna or rna (but not both) covered by a protective protein coat
Obligate intracellular parasites
Viruses replicate in a manner different from that of cells
One virus can replicate to produce hundreds of progeny viruses
How are the shapes of virus particles determined
Arrangement of repeating subunits formed by the protein coat of the virus
Most viruses appear as spheres or rods in the EM
20 to 300 nm in diameter
What is insulin resistant diabetes type 2
Antibodies to insulin receptors have demonstrated that interfere with insulin binding
Symptoms of diabetes
Blurred vision
Weight loss
Lethargy
Nausea
Vomiting
