CELS199 Exam Flashcards
1
Q
What is a cell?
A
The basic unit of structure and function for an organism, simplest collection of matter that can live and replicate itself
2
Q
3 main characteristics of a eukaryote
A
Complex internal organisation of organelles, large 10-100 micro meters, have a nucleus, uni/multi cellular
3
Q
3 main characteristics of a prokaryote
A
Simple cells, small 1-5 micro meters, no nucleus, unicellular no membrane bound organelles
4
Q
List the characteristics of life
A
Cellular organisation, reproduction, metabolism, homeostasis, heredity, responses to stimuli, growth and development, adaptation through evolution
5
Q
What type of microorganisms are viruses?
A
Acellular
6
Q
What are the 4 basic features of all living cells?
A
plasma membrane, cytosol, chromosomes, ribosomes
7
Q
What is the definition of a plasma membrane?
A
membrane boundary to the cell, selective barrier that regulates the cells chemical composition
8
Q
What is the difference between cytosol and cytoplasm?
A
cytosol is the semi fluid portion of the cytoplasm and the cytoplasm refers to the cytosol and all of the cellular structures that are bounded by the plasma membrane
9
Q
What is the definition of chromosomes?
A
a structure that carries the genetic makeup of the cell, found in the nucleus (eukaryotes) or nucleoid region (prokaryotes)
10
Q
What is the definition of ribosomes?
A
complex of ribosomal RNA and proteins that function as a sit of protein synthesis, have large and small subunit
11
Q
What kingdoms are in the domain Eukarya?
A
plantae, animalia, fungi, protist kingdoms (bacteria and archaea are prokaryotes)
12
Q
What are the common organelles found in most eukaryotic cells?
A
Nucleus, mitochondrion, sER, rER, golgi
13
Q
What organelle is only found in animal cells and what organelles are only found in plant cells?
A
animal - lysosome
Plant - chlorplast and central vacuole
14
Q
Common structure found in some eukaryote cells?
A
flagella
15
Q
Structures only found in plant cells?
A
cell wall, plasmodesmata
16
Q
What size are mitochondria and chloroplasts?
A
M - 1-10 micrometers
C - 2-5 micrometers
17
Q
What are the four main biological molecules found in cells?
A
carbohydrates, lipids, proteins, nucleic acids (all polymers except lipids)
18
Q
Wha is the order the number of higher order structures?
A
building blocks, macromolecules, supramolecular assemblies, organelles
18
Q
What are the components of the building blocks?
A
Amino acids, simple carbohydrates, nucleotide bases, lipids
19
Q
What are the components of macromolecules?
A
proteins, DNA, RNA (nucleic acids), complex carbohydrates
20
Q
What are the components of super molecular assemblies?
A
membranes, ribosomes, chromatin
21
Q
What are the components of organelles?
A
nucleus, mitochondria, golgi, ER
22
Q
What is the monomer subunit for carbohydrates?
A
monosaccharides, for complex its polysaccharides
23
Q
What are the functions of carbohydrates?
A
- Recognition 2. Energy 3. Structure (cellulose)
24
What are the monomer subunits of nucleic acids?
nucleotides (DNA, RNA), polynucleotides
25
What is the basic structure of a nucleic acid?
A sugar, nitrogenous base, and a phosphate group
26
What is the basic structure of a carbohydrate?
hexose or Pentose or cellulose strand things
27
What are the functions of nucleic acids?
DNA = inheritance (chromosomes), informational molecule, RNA controls protein synthesis
28
What is the monomer of proteins?
amino acids, different R group
29
Definition and functions of proteins?
molecules by which cells perform their functions in the whole organism, structural = collagen, regulatory = insulin, contractile = actin, myosin, protective = antibodies
30
4 key characteristics of a lipid
Don’t form polymers, smaller than other macromolecules, heterogenous (very different structures), all are hydrophobic (not soluble in water)
31
What are the functions of lipids?
Structural (phospholipid and cholesterol in the cell membrane), regulatory, energy (TAG)
32
What must a cell do?
manufacture cellular materials, obtain raw materials, remove waste, generate required energy, control all of the above
33
What are the 3 main things organelles do?
form concentration gradients, package for transport or export, protect vital parts of the cell
34
What are the 3 main parts of the phospholipid bilayer?
hydrophilic phosphate heads, hydrophobic fatty acid tails, integral membrane proteins
35
What does cholesterol do in the phospholipid bilayer?
aids fluidity in animal cells, buffer to changes in temperature, at higher temps it interacts with the hydrocarbon tails for the membrane to be less fluid, at lower temps it limits how tightly the hydrocarbon tails pack together to retain fluidity
36
What diffuses through the phospholipid bilayer?
Lipid soluble (hydrophobic) molecules like steroid hormones, gases (CO2), can occur in either direction
37
What does the phospholipid bilayer restrict movement of?
water soluble molecules (hydrophilic) and charged molecules like glucose, water, ions
38
Explain facilitated diffusion
Movement of specific hydrophilic molecules requires membrane proteins (channel or carrier proteins), passive, water uses aquaporins (osmosis, high to low)
39
What are proton pumps an example of?
active transport, have internal concentration different to its surroundings
40
What is signal transduction?
protein changes shape when a chemical messenger binds, this transfers a signal from on side of the membrane to another (hormone)
41
What is cell recognition?
some glycoproteins act as a identification tag
42
What is intercellular joining?
membrane proteins of adjacent cells may hold them tight together (gap and tight junctions)
43
What do membrane proteins link and help do?
link the cytoskeleton and Extracellular matrix, helps maintain cell shape and coordinate Extracellular and intracellular changes
44
Explain the process of synthesis of secretory proteins
Synthesised on the surface of the rER, as they are synthesised they enter the lumen, membrane then surrounds the proteins forming a transport vesicle, they are processed via the Endomembrane system, same process for membrane bound proteins and those going to be excreted from the cell.
45
What is the golgi complex?
series of membrane sacs and associated proteins, has polarity (direction), cis (arrive) and trans (leave) face, in cells that are specialised for secretion
46
What are the functions of the golgi complex?
glycosylation of proteins (add/modify of carbos to proteins, imp for cell surface proteins), synthesis of many polysaccharides that are secreted, sorting proteins, directing vesicle trafficking
47
What is constitutive exocytosis?
continuous/unregulated, e.g. Extracellular matrix proteins
48
What is regulated exocytosis?
regulated/in response to stimulus e.g. hormones and neurotransmitters
49
What is phagocytosis?
transport of large particulate substances into the cell, forms a phagocytic vacuole around it, cell eating, non selective
50
What is pinocytosis?
uptake of Extracellular fluid and solutes, uptake is non selective, cell drinking
51
What is receptor mediated Endocytosis?
Specialised type of pinocytosis, take up specific molecules which are often in low concentration outside of the cell (cholesterol), receptors on cell surface bind to specific molecules, selective
52
What are lysosomes made by? And what type of enzymes do they contain
rER and Golgi body, contain hydrolytic enzymes
53
What is the functions of a lysosome?
they degrade proteins, lipids, carbohydrates and nucleic acids and release breakdown products into the cell, digest and recycle unwanted cellular materials (autophagy)
54
What is the cytoskeleton and what is its function?
3-dimensional interconnected network within a cell and provides structure, important role in cell movement and transport, 3 components are microtubules, microfilaments, intermediate filaments
55
Microtubules
form a tube, composed of tubular subunits, resist compression, can be dismantles and reassembled, provides cell motility, example of motility is flagella, allow things to be transported to specific targets
56
Microfilaments
double chain of actin subunits, resist tension, forms linear strands and 3-d networks, actin and myosin interactions
57
Intermediate filaments
made of various proteins like keratin, bearing tension, help shape and ancho some organelles, make up the nuclear lamina
58
Tight Junctions
Prevent movement of fluid between cells, neighbouring cells are tightly pressed together and held by proteins, form continuous seal
59
Gap Junctions
Communication between cells, point of cytoplasmic contact between 2 cells, ions and molecules can pass cell to cell, rapid communication
60
Desmosomes
Anchor and hold cells together, interacting with intermediate filaments, act like rivets, anchoring junctions, intermediate filaments anchor desmosomes to the cytoplasm
61
Collagen in the ECM
Most abundant glycoprotein, strong fibres, great tensile strength
62
What do fibronectins and integrins do?
attach cells to collagen in the ECM (Fibronectins), provide a communication link, connect ECM to cytoskeleton (integrins)
63
is there a ECM in plant cells?
no, cells held together by middle lamella (pectin), intercellular communication via plasmodesmata
64
What is a protoplast?
all of the cell structures inside the cell wall
65
Order of cell wall structure
Plasma membrane, secondary cell wall, primary cell wall, middle lamina
66
Phase 1 of synthesis of the primary cell wall
Crystalline microfibrillar phase, synthesised at the plasma membrane by an enzyme called cellulose synthase
67
Phase 2 of synthesis of the primary cell wall
Non crystalline matrix - hemicellulose and pectin synthesises in the golgi by constitutive exocystosis, extensin synthesised in rER
68
How does the cell wall regulate shape?
influences cell morphology, provides structural support (protoplast), prevents excessive water uptake
69
What is the secondary cell wall made of?
more cellulose, less pectin and lignin (complex polymer). And microfibrils in each layer have different orientations
70
What is the vacuoles function?
regulation of turgor
71
What is the process of energy generation?
cellular respiration
72
What does the mitochondrion contain?
mitochondrial DNA and ribosomes, it is semi-autonomous, 2 membranes
73
What are the 3 main stages of cellular respiration? And where do they occur?
1. Glycolysis in the cytosol 2. Citric acid cycle in the mitochondrial matrix 3. Oxidative phosphorylation in the inter membrane space across the inner membrane
74
What happens during glycolysis (stage 1) and what does it generate?
glucose is converted into 2 smaller molecules of pyruvate. Generates ATP and electrons are transferred to high energy carrier NAD+ making NADH
75
What happens during pyruvate oxidation and citric acid cycle (Stage 2) and what are the outputs?
Pyruvate is converted into Acetyl CoA and that enters the citric cycle and is further processed into CO2, other outputs are ATP and NADH and FADH2
76
What happens in the first part of Oxidative phosphorylation (stage 3) and what are the outputs?
ETC, electron carriers shuttle high energy electrons to inner mito membrane, they move along proteins embedded in the inner membrane, as they move protons H+ are pumped across the inner membrane to the inter membrane space, proton gradient formed
77
What happens during chemiosmosis (part 2 of oxidative phosphorylation stage 3) and what does it generate?
Inner mitochondrial membrane contains ATP synthase, protons move down concentration gradient though this, powers ATP synthase, generates ATP
78
What are the 3 membranes and 3 compartments in a chloroplast?
membranes - outer, inner, thylakoid. Compartments - intermembrane space, stroma, thylakoid space
79
Where do light reactions take place?
thylakoid membrane
80
Where does carbon fixation occur?
stroma
81
What is the purpose of the light reactions? And what proteins does it use?
produce ATP and NADPH for the Calvin cycle, uses specialised membrane proteins called photo systems
82
What are photosystems?
pigment protein complexes that are found in the thylakoid membrane, contain chlorophyll, there are 2 photosystems (ll is for water splitting and l is for NADPH producing) (connected by ETC)
83
What does photosystem ll provide a source of?
electrons, H+ ions, O2, electrons form this move into photosystem l
84
What does the Calvin cycle use and produce?
uses ATP and NADPH from light reactions, produces 3 carbon sugar (G3P) that is converted to glucose, also referred to as light independent reactions, ‘fix’ carbon
85
How do molecules move in and out of the nucleus?
small molecules (ions) diffuse through, large molecules (proteins) are actively transported
86
What does the nuclear pore complex control?
movement of molecules in or into the nucleus. OUT - mRNA, tRNA, and ribosomal subunits IN controls signals, building materials and energy like when to turn a gene on or off
87
What does mRNA do?
carries information from a gene to a ribosome in the cytoplasm
88
What is the inner surface of the nuclear envelope lined by and what is it composed of and helps to do?
nuclear lamina, intermediate filaments, helps maintain shape of nucleus and helps organise the packing of DNA
89
When is the nucleolus visible and what does it make?
during interphase and is a ribosome factory, makes large and small sub units of the ribosomes
90
Heterochromatin
densely packed, genetically inactive
91
Euchromatin
not as dense, genetically active
92
Endosymbiont theory steps
1. Large felled prokaryote (host)
2. In folding of plasma membrane forming internal compartments
3. Large host cel engulfed an aerobic prokaryote
4. Eventually the aerobic prokaryote evolved into a semi autonomous organelle - mitochondrion
5. Large host cell engulfed a photosynthetic prokaryote
6. Eventually the photosynthetic prokaryote evolved into a semi-autonomous organelle - chloroplast
93
Evidence of the endosymbiont theory
all eukaryotes have mitochondria, only plants and some protists have chloroplasts, characteristics of mito and chloroplast suggest the were one free living prokaryotic organisms (semi autonomous, have 2 membranes surrounding them, similar size to prokaryote, contain “prokaryote like” ribosomes and DNA and they divide by binary fission
94
What are the 3 key features of a hereditary molecule?
encodes and stores information, mechanism for replication, transmissible
95
How are nucleotide units linked together?
through the phosphate groups, forming the backbone of the molecule, phosphodiester bonds
96
What are purines?
nitrogenous bases, double ring structure, A and G
97
What are pyrimidines?
nitrogenous bases, single ring structure, C U and T
98
What end is the phosphate group attached to?
carbon 5 (5’ carbon)
99
What is the OH group attached to?
carbon 3 (3’ carbon)
100
Explain the steps of replication
helicase unwinds, Enzyme called primase attaches an RNA primer (short sequence of RNA nucleotides) then DNA pol lll attaches, it joins new nucleotide to newly synthesised strand of DNA in the 5’ to 3’ direction, DNA pol l removed RNA primer, DNA ligase seals the gap.
101
What binds to a strand to stop it from winding back together?
Single-strand binding protein
102
What does topoisomerase do?
cut and rejoin double stranded DNA ahead of the replication fork and relieves pressure caused as the strands unwind
103
What does mitosis and meiosis produce?
mitosis - genetically identical somatic cells used for growth and repair
Meiosis - produces genetically distinct gametes for sexual reproduction
104
Definition of diploid cell
Cells that contain pairs of homologous chromosomes
105
Definition of haploid
Cells that contain one copy of each chromosome (no pairs)
106
Explain interphase
Longest part of cell cycle
G1 - cells grow and produce proteins and organelles
S - synthesis phase, DNA replication occurs, chromosomes replicate
G2 - cells prepare for cell division
107
What does everything look like at the end of interphase?
DNA/chromosomes are replicated but not condensed, nuclear envelope is present, nucleolus is visible, centrosomes have duplicated
108
Describe prophase of mitosis
replicated chromosomes begin to condense, centrosomes move to opposite poles and form spindle, single microtubules attach to the centromere of each replicated chromosome, nuclear membrane breaks down
109
Describe the 2 types of mitotic spindles
Kinetochore microtubules - attach to the kinetochore proteins at the centromere of each chromosomes
Nonkinetochore microtubules - do not attach to chromosomes, they elongate during anaphase
110
Describe metaphase in mitosis
Spindle microtubules are fully formed, replicated chromosomes move to the centre of the cell, centromeres lie on the metaphase plate
111
Describe anaphase in mitosis
Kinetochore microtubules retract and seperate the sister chromatids, chromosomes move to opposite ends of poles, cell elongates due to nonkinetochore microtubules
112
Describe telophase of mitosis
nuclear envelope beings to form at either end of the cell, chromosomes start to decondense (unwind), spindle disappears, nucleolus reappears
113
Describe cytokinesis of mitosis
Cytoplasm divides between the 2 cells
114
Definition of a karyotype
ordered, visual representation of the pairs of chromosomes in a cell
115
What happens during prophase 1 meiosis 1?
Chromosomes begin to condense, homologous pairs of chromosomes pair up (synapse), crossing over occurs
116
What happens during metaphase 1 meiosis 1?
pairs of homologous chromosomes move to metaphase plate, chiasmata align along the plate, chromosomes are attached to the microtubules attached to the centromere.
117
What happens during anaphase meiosis 1?
homologous pairs of chromosomes are separated, each replicated chromosome moves to opposite poles of the cell
118
What happens during telophase and cytokinesis meiosis 1?
Go to each pole, spindle disappears and nuclear envelope reforms, then cytokinesis
119
What does everything look like at the end of meiosis 1?
resulting cells contain one copy of each chromosome, haploid, cells are genetically different
120
What does everything look like at the end of meiosis ll?
4 cells, each cell contains one copy of each chromosome, haploid, genetically different
121
What does non-disjunction during meiosis l anaphase 1 result in?
n+1, n+1, n-1, n-1
122
What does non-disjunction during meiosis ll result in?
n+1, n-1, n, n
123
what is gene dosage?
number of copies of a particular gene present in a cell of an organism
124
What is the definition of deletion?
loss of a part of a chromosome, affected chromosome is then missing certain genes, deletion affect the number of copies of the gene involved
125
What is the definition of duplication in regard to chromosomal rearrangements?
segment is repeated
126
What is the definition of inversion in regard to chromosomal rearrangements?
segment of chromosome is detached and then reattached in opposite orientation, affects gene expressions and regulation
127
What is the definition of translocation in regard to chromosomal rearrangements?
segment of one chromosome attaches to another non-homologous chromosome, swap fragments
128
General outline transcription
It is the synthesis of messages RNA, RNA polymerase synthesises mRNA by catalysing the formation of phosphodiester bonds between ribonucletides, selects the correct nucleotides to incorporate into mRNA based on the sequence being transcribed, transcribes from the template strand
129
Outline initiation of transcription
binding of RNA polymerase to transcription factors at the promoter region TATA, unwinding of DNA, reading of the template strand and starting the synthesis of the RNA strand
130
Outline elongation of transcription
RNA pol used the template strand as a template and inserts complementary RNA nucleotides
131
Outline the termination sequence of transcription
terminates RNA synthesis, RNA polymerase detached from DNA strand and RNA strand is released
132
What happens to mRNA before it leaves the nucleus for transcription ?
addition of 5’ G cap and Poly-A tail, splicing of introns
133
What is translation?
synthesis of proteins by ribosomes using mRNA as a set of instructions
134
What is tRNA?
‘Adaptor’ molecule, each one has a region that can bind an amino acid and a region which can interact with mRNA, when bound to a tRNA it is charges
135
Outline initiation in regard to translation
5’ end of the mRNA binds to the small ribosomal subunit at a specific sequence, ensures mRNA is in the right frame to be read, large ribosomal subunit attaches
136
Outline elongation in regard to translation
charged tRNA with the anticodon that matches the next codon on the mRNA binds to the A site of the ribosome, ensures correct amino acid is brought into frame, ribosome catalyses the formation of peptide bonds, ribosome breaks bond between polypeptide chain in the P site and joint it to the amino acid in the A site, tRNA in P site is now uncharged
137
Outline termination in regard to translation
Stop codons are coded for by proteins (release factors) not tRNA, when it bind the ribosome separates and releases mRNA and polypeptide chain, it goes on to form protein
138
Definition of a gene
Unit of heredity, codes for a specific trait
139
What is Mendels first law?
the law of segregation - genes seperate at meiosis so that each gamete contains only one of the two possessed by the parent
140
What is Mendels second law?
The law of independent assortment - alleles of different genes assort independently during gamete formation
141
What is the phenotypic cross of a mono hybrid ratio?
3:1
142
What is the phenotypic cross of a dihybrid ratio?
9:3:3:1
143
How do you calculate the probability of parents producing a specific genotype?
Do a small punnet square of each letter, if its 2/4 it will be 0.5, after getting them all then times them together
144
What are the 3 ways there could be a deviation from Mendel? With brief explanations
Polymorphic genes - one gene having many alleles
Incomplete dominance - like a white and red flower making a pink flower
Co-dominance - 2 alleles affect genotype in seperate ways
145
What is polygenic inheritance?
When many genes affect one trait, like skin colour
146
What is a autosome?
all other chromosomes that aren’t sex linked genes
147
What do most genes on the Y chromosome control?
characteristics related to determining sex
148
Fathers can pass X-linked genes on to? And mother can pass X-linked genes on to?
fathers- only daughters
Mothers - sons and daughters
149
If a disease is X-linked dominant who can express the disease?
males and females
150
If a disease is X-linked recessive who can express the disease?
all males, only females if they carry 2 copies of the disease causing allele
151
If a female has an X-linked dominant disease she will pass her affected X chromosome on to what percent of her children?
50% regardless of sex
152
If a female has an X-linked recessive disease she will pass an affected X chromosome onto what percent of her children?
100%
153
What X linked diseases (dominant or recessive) are more common in which gender? And who does Y-linked diseases affect?
X-linked dominant is more common in females, X-linked recessive is more common in males, Y-linked is rare and only affects males
154
What ratio will a dihybrid individual produce 4 gametes at?
1:1:1:1
155
In what situation could a gene not assort independently?
if they are on the same chromosome
156
What is complete linkage? And what outcome is the ratio?
when 2 genes are very close together on the same chromosome and crossing over does not occur between them, 1:1
157
What is incomplete linkage? And what outcome is the ratio?
2 genes on the same chromosome and crossing over occasionally happens between them, unequal ratios because more parental than recombinant types
158
What is the measure of distance between 2 genes? And how do you calculate the recombination frequency?
Centrimorgans which is recomb freq X 100, recomb freq = # of recombinant divided by total # of offspring
159
Definition of a population
a group of interbreeding individual of the same species in the same location that produce fertile offspring
160
Definition of a gene pool
The sum of all the alleles, at every locus on every chromosome, in all members of a population, at one time
161
What does it mean if a allele is fixed?
there is only one allele for a gene in a population, all individuals will be homozygous for that allele
162
What does the Hardy-Weinburg principle state and what can it be used to determine?
that frequencies of alleles and genotypes in a population will remain constant from generation to generation, can be used to determine in natural selection or other factors are causing changes of allele frequencies in a population
163
What 2 reason why we might need to estimate frequencies of genotypes in a population?
1. To predict how many individuals will inherit a genetic disease
2. To estimate the proportion of individuals who are carriers of a genetic disease
164
How do allele frequencies change?
genetic drift (3 types), gene flow or migration, natural selection, non random mating, mutation
165
What is random genetic drift?
a random change in allele frequencies over generations due to change events
166
What is the bottleneck effect?
occurs when a population has reduced dramatically as a result of natural disaster, disease or human actions, reduce genetic diversity so resulting allele frequencies are not representative of original population
167
What is the founder effect?
When a few individuals of a larger population become founders of anew population
168
What 4 things do you require for natural selection?
variance, inheritance, selection, time
169
What is stabilising selection?
selection against both extremes, graph os one peak in the middle, reduced variation but does not change the mean
170
What is directional selection?
changes the mean towards one extreme, graph is towards one side
171
What is disruptive selection?
Favours the 2 extremes, results in 2 peaks
172
What is frequency dependant selection?
A type of natural selection where the fitness of a phenotype depends on the frequency of that phenotype in the population
173
Outline what a phylogenetic tree is
Represents a hypothesis about the evolutionary relationships, characteristics shared between organisms are used, physical or DNA
174
What is a genome?
the complete set of DNA of an organism including all of its genes, includes nuclear and mitochondrial DNA
175
What is a SNP?
single nucleotide polymorphism, most common type of genetic variation in humans, most don’t do anything and are just inherited variations, can be outside or inside a gene
176
What is a STR?
repeats of 2-5 nucleotides found in specific regions of the genome
177
What are InDels?
second most common variant type in human genome (cystic fibrosis), can cause frame shifts (changes entire DNA sequence after the mutation)
178
What is CNVs?
Copy number variants, chunks of DNA that are present a variable number of times in different people
179
What are things in common when comparing genomes called?
conserved
180
What are mutations called that are inherited and passed on via gametes?
germline mutations
181
Is a loss of function mutation recessive or dominant and why?
often recessive, a normal copy exists on the other chromosome and replaces the lost function
182
Is a gain of function mutation recessive or dominant and why?
often dominant, effect of the gain of function in not masked by the normal copy on the other chromosome
183
Do dominant diseases skip generations?
no
184
Do recessive diseases skip generations?
They can
185
What is an example of a autosomal dominant disease?
huntingtons disease
186
Do autosomal diseases affect males or females more?
Affects them equally
187
Difference between monogenic and polygenic diseases?
Monogenic diseases are caused by a single gene, polygenic diseases are caused by multiple genes and can also be affected by the environment
188
How do you use CRISPR-CAS9 to edit genes?
cas9 enters the nucleus and finds target sequence in genome that matches the guide RNA, after DNA is cut there is 2 options, 1. If no DNA repair template in provided DNA repair enzymes will try to patch up the cut which often results in errors and small InDels are created at the target site, 2. If a DNA repair template is provided it can be used to ‘edit’ the DNA sequence at this cut sight
189
What are the 3 ways to find out what a gene does?
study mutations, trangenesis, deliberately break a gene and see what happens (gene knockout, like using CRISPR-Cas9 without a template), all these are called functional molecular genetics
190
Can we fix genetic disease?
yes, but only if we know what causes it and have a way to correct the defect, best candidate are single gene disorders and using gene therapy like gene editing
191
What is differentiation?
the process by which a cell becomes specialised in structure and function
192
An embryo begins as a small number of ? Cells? Give definition too
Totipotent, unspecialised cells with total potential - can develop into all cells of the embryo and the placenta
193
At the blastocyst stage we see 2 types of cells. The outer cells become ? And the inner mass cells are ?
outer - placenta
Inner - embryonic stem cells (pluripotent)
194
embryonic stem cells are still ? And can give rise to ?
unspecialised and give rise to all cell types except the placenta
195
When differentiated cells divide by mitosis they can only ?
divide to become the same type of cell
196
Control genes make proteins called ? That ‘switch on” other genes in the cell
Transcription factors
197
What does switching on a gene mean?
that it is transcribed into RNA and then translated to make proteins, once its on its fate has become determined
198
Why are stem cells different?
Can divide without limit, undifferentiated, give rise to both stem cells and cells which will go on to differentiate into functional tissue cells
199
Are embryonic stem cells multi potent or pluripotent ?
human ones are pluripotent
200
Are adult (tissue) stem cells multi potent or pluripotent ?
multi potent
201
Blood stem cells or haematopoiteic stem cells are what type of stem cells?
adult, important for tissues and used for transplants
202
What are iPS cells?
induced pluripotent stem cells, genetically identical to source skin cells, as they are pluripotent they can be cultures to generate into any cell type
203
Prokaryotic cells are characterised by what 4 things?
unicellular, no nucleus, no membrane bound organelles, small size
204
What is the 2 functions of the bacterial cell wall?
rigid structure that provides strength to cell maintaining shape, provides physical protection (prevents cell losing/bursting due to osmotic stress)
205
What is transpeptidase?
enzyme that cross links the peptidoglycan chains to form rigid cell walls
206
Is the layer of peptidoglycan around gram positive bacteria thick or thin, and what colour is the gram stain?
thick, positive which is purple
207
Is the layer of peptidoglycan around gram negative bacteria thick or thin, and what colour is the gram stain?
thin, negative which is pink
208
What is the function of glycocalyx?
Prevents desiccation, and allows adhesion, in pathogenic bacteria it can help the cell avoid the hosts immune system and it increases resistance to phagocytosis
209
What is the structure and function of fimbriae?
Short, sticky and made of protein, shorter than flagella, function is adhesion and joining cells together to form biofilms, like Velcro
210
What is the structure and function of Pili?
filamentous projections from surface of cell made of protein, longer than fimbriae and shorter than flagella, involved in conjugation, 1-10 per cell
211
What is the nucleoid region?
location of bacterial chromosome which is a single large loop of DNA associated with proteins
212
What is a plasmid and what is its function?
short circular loop of DNA, can carry resistance genes and are involved in gene transfer via a pilus
213
What is the structure and function of a endospore?
original cell makes a copy of chromosome and surrounds it in a tough cell wall and metabolism stops, very resistant cells produced during adverse condition e.g. lack of nutrients, allows DNA to resist things
214
What are the 4 steps of binary fission?
1. Chromosome replication begins
2. One copy of the origin is now at each end of the cell
3. Replication finishes
4. 2 daughter cells result
215
What are the 3 things needed for microbial growth ?
energy source, carbon source, reducing power
216
What is cryptic growth?
when organisms survive by consuming components of other dead cells within a culture
217
What is an auxotroph?
species that lack one or more essential genes and therefore cannot grow unless that specific factor is supplied
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How do auxotrophs survive in nature?
by cross feeding which is when one species gains the metabolic products of another species
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What is the definition of a microbiome?
the complete collection of microorganisms, and their genes, within a particular environment
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Pros and cons of culture dependant approaches?
pros - can study phenotype, can manipulate the culture conditions to see response of organism
Cons - many species can’t be cultured, too many to try and culture, doesn’t match real world conditions
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Pros and cons of culture independent approaches?
Pros - study many organisms at once to build a picture of their communities, provides genotype
Cons - provides no information on how they grow and condition required, expensive and complex methods
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Why do bacteria need an energy source to grow?
needs ATP for catabolic and anabolic reactions, catabolic reactions breaks large molecules into smaller molecules and therefore release energy, anabolic reaction synthesis large molecules from small molecules and therefore us energy
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Why do bacteria need a carbon source to grow?
needs to be able to generate macromolecules and therefore needs building blocks, can be organic or inorganic
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Why does bacteria need reducing power to grow?
needs carriers of electrons NAD+/NADP+, for redox reaction
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What makes something a auto or hetero troph?
autotroph uses a carbon source - inorganic/CO2 and a heterotroph does not
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Definition of microbiota
Individual microbial species in a biome
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What are the 4 phyla that dominate the human microbial communities ?
firmicutes, bacteroidetes, actinobacteria, proteobacteria
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What are some known functions of the human microbiome?
priming the immune system, moderating energy intake, synthesis of compounds such as vitamins
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Definition of probiotics?
live microorganisms
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Definition of prebiotics?
an ingredient that beneficially nourishes the food bacteria already in the large bowel or colon, stimulate growth of probiotics, fertiliser
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Viruses are referred to as? And why?
particles or acellular R obligate parasites because they do not have ribosomes, a plasma membrane or cytosol
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All viruses consist of?
nucleic acid and a capsid which provides protection and is made up of subunits called capsomeres
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What are the 4 categories for classification of viruses?
type of nucleic acid, presence or absence of envelope, capsid symmetry/shape, target host
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What are the 3 types of symmetry of viruses?
helical, icosahedral, complex
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List the 6 steps of viral infection
1. Attach - to receptor proteins on cell surface
2. Penetrate
3. Uncoat - capsid uncoats
4. Gene expression and genome replication - uses host cell enzymes to synthesis
5. Assembly - new virus particles assemble
6. Release - from the cell
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Morphology of bacteriophages
head - capsid and nucleic acid
Tail - attached to receptor proteins on bacterial wall and acts like a hypodermic needle to puncture through
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What viruses are eukaryotic cells infected by?
naked or enveloped viruses
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Vertical gene transfer
between generations, in prokaryotes this is via binary fission, creates genetic diversity
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Horizontal gene transfer
from one bacteria to another within same generation, transformation, transduction, conjugation, generates genetic diversity
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What is transformation in regard to generating genetic diversity?
competent cells take up DNA from environment, DNA binding proteins on their surface allows the cell to be selective about what DNA it takes up, if it integrates the DNA it becomes a recombinant cell
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What is transduction in regard to generating genetic diversity?
transfer of bacterial DNA carried from one host cell to another by bacteriophages, remember that bacteriophages infect bacteria, same general process as Lytic cycle, creates a transducting phage
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What is conjugation in regard to generating genetic transfer?
direct transfer of plasmid DNA between 2 cells that are temporarily joined by a conjugation pilus
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What features can be transferred via horizontal gene transfer?
virulence factors, antibiotic resistance
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What are Koch’s postulates criteria ? (4)
1. The organism must be present in every case of the disease
2. The organism must be isolated from the host with the disease and grown in pure culture
3. The specific disease must be reproduced when a pure culture of organisms are inoculated into a healthy host
4. The organisms must be recoverable from the experimentally infected host after disease develops
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What are the exceptions to Koch’s postulates criteria ? (4)
1. Some organisms cannot be isolated and cultured under laboratory conditions
2. Some disease are due to a combination of organisms
3. Some pathogens are found in healthy hosts
4. Some carriers are asymptomatic
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What are 3 medically important pathogens and examples?
viruses (influenza), Protozoa (malaria parasites), bacteria (anthrax)
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What are the 4 key stages to microbial pathogenesis (disease development)?
1. Adherence to host - e.g. fimbriae and adhesions
2. Invasion of host tissues - e.g. flagella
3. Replication within host tissues - e.g. capsule, siderphores
4. Disease causing damage to host tissues - e.g. exotoxins and endotoxins
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What is virulence ?
a measure of ability of a microbe to infect and cause disease, does not relate to severity of disease
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Why do not all bacteria have the same level of virulence and what is it called when they cannot attach to the host?
due to their ability to produce virulence factors which increase the virulence of a pathogen, avirulent
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Name virulence factors and what they do?
adhesions - allow microorganisms to attach, motility (chemotaxis) - some pathogens with flagella can move through mucus and therefore invade host cells, capsules (glycocalyx) - polysaccharide coating around cells which prevents phagocytosis by host immune cells, siderophores - iron binding proteins allow pathogens to remove iron from the blood stream and transport it to their own cells, endotoxins - lipopolysaccharides, exotoxins
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What are the 3 targets of exotoxins?
cytotoxins, neurotoxins, enterotoxins
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What is selective toxicity?
more toxic to pathogen that to its host and therefore target structural or metabolic differences between microorganism and host cell
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Definition of an antibiotic
antibacterial agent including naturally and synthetically produced compounds excluding agents with antiviral and anti fungal activity, selectively toxic
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Difference between antibacterial and antimicrobial?
antibacterial is only against bacteria, antimicrobials act gains bacteria, virus, fungi and protozoa
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How does penicillin work?
acts by preventing the formation of peptide cross links in the cell wall by binding to and inhibiting the enzyme transpeptidase
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How does penicillin resistance happen?
some bacteria produce an enzyme which degrades/breaks down penicillin by targeting the B-lactam ring, called penicillinase or B-lactamase, breaks the bond
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How does antibiotic resistance occur? General and the 4 steps
original change arises from a mutation, if it’s beneficial it will be selected for, resistance genes can spread from one cell to another by horizontal gene transfer
1. Some bacteria in the human body become drug resistant
2. Antibiotics kill bacteria but not those resistant to drugs
3. Resistant bacteria then have space to multiply
4. Bacteria can transfer their drug resistance to other bacteria
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How do you prevent antibiotic resistance occurring? (4)
decrease utilisation, improve diagnostics, identify new targets, combination therapys
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Describe the 5 stages of an infectious disease?
1. Incubation period - time between infections and occurrence of first symptoms, pathogen attaches and beings to replicate, length of this stage depends on virulence, immune response, sit of infection
2. Prodromal period - as pathogen levels being to increase general symptoms are seen, a short period of mild symptoms that occur before illness
3. Illness - characteristic symptoms of illness, most severe stage, immune responses not yet helpful, most infectious stage, highest concentration of pathogen
4. Decline - immune response or medical treatment starts to decrease pathogen numbers, symptoms lessen
5. Convalescence - recovery, tissue repairs, length depends on amount of tissue damages, nature of pathogen, infection site, patient health, and there’s a low level of pathogen
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What are the 6 steps of the chain of infection?
1. Causative pathogen - what pathogen is causing the disease like virus bacteria parasite
2. Source where pathogen is found
3. Means for exiting the source and therefore infection another host
4. Mode of transmission
5. Entry point (way into host body)
6. Host that is at risk of infection
All comments must be present for infection to spread
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What is epidemiology?
the study of disease transmission
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What is the incidence of a disease?
the number of new cases of the disease in a given period of time
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What is the prevalence of a disease?
the total number of new and existing cases in a population in a given time
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Endemic
always present at stable levels within a given population or area
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Sporadic
a disease that occurs infrequently and irregularly
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Epidemic
an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area
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Pandemic
An epidemic that has spread over several countries or continents, usually affecting a large number of people
