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Principles of Inheritance > Lecture 1: Prokaryotic Genetics I > Flashcards

Lecture 1: Prokaryotic Genetics I Flashcards

1
Q

Characteristics of Eukaryotes = 5

A
  1. DNA associated with HISTONE PROTEINS enclosed in a membrane-bound nucleus
  2. have other membrane-bound organelles eg. Mitochondria, Chloroplasts, lysosomes, endoplasmic reticulum
  3. have a CYTOSKELETON
  4. Almost all MULTICELLULAR ORGANISMS
  5. Size range from 10–100 μm in diameter
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2
Q

Examples of Eukaryotic Cells = 4

Eukaryotic cells are exclusively found in plants, animals, fungi, protozoa, and other complex organisms. The examples of eukaryotic cells are mentioned below:

A
  1. Plant Cells
    The cell wall is made up of cellulose, which provides support to the plant. It has a large vacuole which maintains the turgor pressure. The plant cell contains chloroplast, which aids in the process of photosynthesis.
  2. Fungal Cells
    The cell wall is made of chitin. Some fungi have holes known as septa which allow the organelles and cytoplasm to pass through them.
  3. Animal Cells
    These do not have cell walls. Instead, they have a cell membrane. That is why animals have varied shapes. They have the ability to perform phagocytosis and pinocytosis.
  4. Protozoa
    Protozoans are unicellular organisms. Some protozoa have cilia for locomotion. A thin layer called a pellicle provides support to the cell.
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3
Q

Characteristics of Eukaryotic Cells
The features of eukaryotic cells are as follows: 7

A
  1. Eukaryotic cells have the nucleus enclosed within the nuclear membrane.
  2. The cell has mitochondria.
  3. Flagella and cilia are the locomotory organs in a eukaryotic cell.
  4. A cell wall is the outermost layer of the eukaryotic cells.
  5. The cells divide by a process called mitosis.
  6. The eukaryotic cells contain a cytoskeletal structure.
  7. The nucleus contains a single, linear DNA, which carries all the genetic information
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4
Q

Characteristics of Prokaryotes = 6

A
  1. genome located in the CYTOPLASM/ sometimes confined to REGION Called “NUCLEOID”
  2. No membrane-bound organelles
  3. ONLY membrane is the PLASMA Membrane
  4. NO CYTOSKELETON in Eubacteria but in SOME Archea
  5. Nearly ALL are UNICELLULAR
  6. SIZE 0.1 to 5.0 micrometers
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5
Q

Characteristics of Prokaryotes - 7 online

A
  1. They lack a nuclear membrane.
  2. Mitochondria, Golgi bodies, chloroplast, and lysosomes are absent.
  3. The genetic material is present on a single chromosome.
  4. The histone proteins, the important constituents of eukaryotic chromosomes, are lacking in them.
  5. The cell wall is made up of carbohydrates and amino acids.
  6. The plasma membrane acts as the mitochondrial membrane carrying respiratory enzymes.
  7. They divide asexually by binary fission. The sexual mode of reproduction involves conjugation
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6
Q

Examples of Prokaryotes 3.

A
  1. bacteria …eubacteria
  2. archaea
  3. cyanobacteria (blue-green algae)
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7
Q

Prokaryotic Genetics 3.

A
  1. They are HAPLOID
  2. Contain SMALL CIRCULAR DNA MOLECULES = “PLASMIDS” ; useful properties such as drug resistance
  3. Translation coupled to transcription: translation of RNA starts before transcription is finished
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8
Q

Eukaryote Genetics 3

A
  1. Eukaryotes (esp. multicellular ones) are often DIPLOID
    - HAVE LINEAR CHROMOSOMES, USUALLY MORE THAN 1
  2. TRANSCRIPTION of genes occurs in the NUCLEUS
  3. PROTEIN TRANSLATION occurs in CYTOPLASM
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9
Q

NOTES: Many Fungi (e.g. yeast), protozoans, algae, and mosses can exist both as haploid and diploid.

A

NOTES: Many Fungi (e.g. yeast), protozoans, algae, and mosses can exists both as haploid and diploid.

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10
Q

LOOK AND COMPARE EUKARYOTE VS PROKARYOTE GENETICS

A

LOOK AND COMPARE EUKARYOTE VS PROKARYOTE GENETICS

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11
Q

What defines a “model” organism? = 6

A
  1. Simple growth and handling
  2. easy to work with
  3. small genome
  4. fast life cycle
  5. ethical issues
  6. applicable to relevant species?
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12
Q

What makes bacteria a top “model” organism?
9 and example?

A

ADVANTAGES OF USING BACTERIA AND VIRUSES FOR GENETIC STUDIES

  1. Reproduction is Rapid
  2. Many Progenies are produced
  3. The haploid genome allows all mutations to be expressed directly
  4. Asexual reproduction simplifies the Isolation of genetically pure strains.
  5. Growth in the Laboratory is easy and requires little space.
  6. Genomes are small
  7. Techniques are available for isolating and manipulating their genes.
  8. They have medical importance
  9. They can be genetically engineered to produce substances of commercial value.

EXAMPLE = YEAST = Saccharomyces cerevisiae

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13
Q

Bacteria require nutrients to grow and divide.

What does the MEDIA for CULTURE usually contain? - 6

COMPLETE MEDIA - CONTAIN ALL SUBSTANCES REQUIRED BY ALL BACTERIA, INCLUDING AUXOTROPHIC BACTERIA

A

COMPLETE MEDIA - CONTAIN ALL SUBSTANCES REQUIRED BY ALL BACTERIA, INCLUDING AUXOTROPHIC BACTERIA

  1. Carbon Source
  2. Essential Elements, N, P, etc
  3. Vitamins
  4. Trace metals, ions, etc
  5. Oxygen if aerobic
  6. Warmth for most common bacteria (accelerate growth)
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14
Q

What does the very MINIMAL MEDIA contain for a culture? = 4

AKA SYNTHETIC MEDIUM

ONLY REQUIRED BY PROTOTROPHIC BACTERIA

A

ONLY REQUIRED BY PROTOTROPHIC BACTERIA

  1. Inorganic N, P, etc
  2. Minerals (Na, K, Mg, C)
  3. Carbon source ( Glucose or glycerol).
  4. Another important feature of MINIMAL Medium/ Synthetic medium = is that it is DEFINED
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15
Q

Properties of Escherichia coli (E.coli) = 4

A
  1. Common GI tract bacteria
  2. Grows on partially digested extracts made from YEAST and ANIMAL PRODUCTS
  3. At 37 Degrees Celcius
  4. In a normal atmosphere
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16
Q

Types of Bacterial Cultures = 2

A
  1. Liquid “broth” culture
  2. Solid Media (individual colonies)
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17
Q

What are the Properties of a Liquid “broth” culture? = 4

A
  1. Nutrients allow rapid growth
  2. Growth is in high density
  3. Easy and Cheap
  4. Example : LB (Luria-Bertani) Broth = YEAST EXTRACT, PEPTONE AND NaCl
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18
Q

What are the properties of Soild Media Cultures?

A
  1. Same nutrients as liquid culture
  2. But with AGAR = polysaccharide from seaweed,
    - Most bacteria can not digest it
  3. Can ISOLATE INDIVIDUAL BACTERIAL CELLS
    - then grow each cell up into a colony, = standard way to create a pure culture of bacteria
    - All Cells of a colony are CLOSELY RELATED TO THE ORIGINAL CELL, with only a small amount of genetic variation possible.
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19
Q

Define Wild-type:

A

Wild-type is capable of full range of metabolic activities

20
Q

Define Mutant:

A

Mutants could be defective in the synthesis of some substances . e.g. amino acid leucine (leu- strain); needs the addition of leucine in order to grow

21
Q

Phenotype Vs Genotype Explain =

A

Genotype = 3 small italics letter, eg lacZ (indicates the gene for lactose Z protein)

Phenotype = 3 letter code that ends in a +/- (Leu+ = strain that can make its own leucine, Leu-strain that cannot make its own leucine.)

22
Q

What are the 2 MECHANISMS OF MUTATION?

A
  1. Spontaneous-replication errors
  2. Induced-chemical, UV radiation, transformation
23
Q

Explain Wild-Type of bacteria = 2

A
  1. can grow on media containing simple ingredients (listed previously) = minimal media (contains the minimum nutrients for possible colony growth)
    - and these bacteria are known as PROTOTROPHS.
  2. Most wild-type bacteria are SENSITIVE TO ANTIBIOTICS

Prototrophs
- A type of wild-type bacteria
- can use simple molecules to build more complex ones

24
Q

What are PROTOTROPHS?

A
  1. A type of wild-type bacteria
  2. can use simple molecules to build more complex ones
25
Q

What are AUXOTROPHS?

A
  1. Auxotrophs are MUTANT BACTERIA
  2. Require EXTRA nutrient/s in their media

Eg, a leucine auxotroph (leucine-) needs Leucine (Leu) to be added to the growth media (minimal medium with Leu supplement or complete medium);

Whereas a prototroph is Leu+ and does not need any leu supplementation (on a defined minimal medium).

26
Q

Catabolism vs Anabolism

A

Catabolism
- is the set of metabolic pathways that break down molecules into smaller units that are either OXIDISED to release ENERGY energy or used in other anabolic reactions.

Anabolism
- is the set of metabolic pathways that construct molecules from smaller units, these reactions REQUIRE ENERGY, known as an ENDERGONIC PROCESS

27
Q

What is a Chemoauxotroph

A

A bacteria that has

  1. Mutation in a catabolism pathway
  2. Lost the ability to breakdown a certain molecule to generate energy
  3. Chemoaxutrophs are MUTANTS that can’t use some nutrient (Usually a sugar, amino acid, or vitamin) that PROTOTROPHS can use as a Food Source

e.g. lactose
lac- mutants can’t grow on lactose, but lac+ prototrophs can
- For example if a phenotype

e.g. Red cells are lac+ and can metabolize lactose, grow much faster, and change indicator dye (cell ONPG) to red
lac- mutant does not have beta-galactose activity and therefore cannot metabolize lactose and convert the indicator dye to red.

28
Q

What is an Auxotroph

A

A bacteria that has

  1. Mutation in an anabolism pathway
  2. Lost the ability to make an essential building block in the cell, e.g. an amino acid

(e.g. leucine).

29
Q

What is Random Mutagenesis: 3

A
  1. Bacteria mutants are generated in the lab
  2. by exposing them to mutagens, e.g. UV, ethyl methanesulfonate (EMS) - forward genetics
  3. unbiased approach: mutate the gene then screen for a phenotype
30
Q

What is Targeted Mutagenesis: 3

A
  1. By genetic transformation
  2. often used in reverse genetics
  3. identify a gene then modify/insert/delete the gene,
    then look at the consequences to phenotype
31
Q

What are Resistance mutants:

A
  1. confer resistance to some environmental toxins: drugs, heavy metals, bacteriophage (bacterial virus) etc.
32
Q

What does ….. mean?

amp^r

kan^r

kan^s

leu-

leu+

A

amp^r = Resistant to the antibiotic penicillin;/ampicillin

kan^r = resistant to kanamycin

kan^s = sensitive to kanamysin

leu- = required leucine added to media

leu+ = generate own leucine

don’t name with genes, only mutants

33
Q

Bacterial mutants - examples

met-

A

met- is common among Pseudomonas aeruginosa strains isolated from cystic fibrosis patients.

A requirement likely satisfied by the high concentration of amino acids in the patient’s sputum

34
Q

Why are auxotrophs/chemotrophs fundamental to research?

A
  1. Auxotrophs dictate the carbon and energy flow in endosymbiotic communities
  2. Auxotrophs/chemotrophs can be use as Marker and reporter genes with mutants pivotal for research (plasmids)
  3. Auxotrophic strains elucidated biochemical pathways (bread mold).
35
Q

What is Replica plating? - A simple technique o revolutionise science.

2

A

A simple technique o revolutionise science.

  1. A common way to find bacterial mutants is replica plating making identical copies of the colonies on a Petri dish under different conditions.
  2. Eg, to find leu- (auxotrophs), one plate would contain added leu and the other plate would not.

PROCESS

Bacteria first plated on a permissive plate, (allows both mutants and wild type to grow) i.e had leu added. After growth, a copy of the plate is made by pressing a piece of velvet onto the surface, then moving it to a fresh plate with restrictive conditions (no Leu). The velvet transfers some cells from each colony to an identical position on the restrictive plate.

36
Q

PROCESS OF REPLICA PLATING = 7

A

PROCESS

  1. Plate bacteria on medium containing leucine. Both Leu+ and leu- colonies grow
  2. Replica plate the colonies by pressing a velvet surface to the plate
  3. Cells adhere to velvet
  4. Press onto new petri plates. Cells from each colony are transferred to new plates.
  5. Leucine auxotrophs (leu-) are recovered from the colony growing on supplemented medium and cultured for further study.

CONCLUSION = A colony that grows only on the supplemented medium has a mutation in a gene that encodes the synthesis of an essential nutrient.

  1. Colonies that grow on the permissive plate,
    but not the restrictive plate are leu- (auxotrophs), because they can grow if leucine is supplied.
  2. The auxotrophs can be selected and studied - this is how many biochemical pathways were elucidated.
37
Q

Who is Esther and Joshua Lederberg?

A

Esther and Joshua Lederberg 1958 Nobel Prize ceremony

  • she developed replica plating techniques during her research on the transfer of genetic information. (Phage)
38
Q

Explain the BACTERIAL GENOME properties = 3

A
  1. Most have One circular chromosome
    - only 1 DNA molecule, several million bp.

E.coli has 4.6 million bp, 90% of which encodes proteins (only <2% in humans!)

  1. Some bacteria have multiple chromosomes, some have linear chromosomes.
  2. Bacteria can also contain plasmids - small circular DNA then can replicate.
39
Q

What are Bacterial Plasmids? = 7

A
  1. Esther and Joshua Lederberg named this CIRCULAR DNA = PLASMID
  2. Many bacteria also have SMALL, CIRCULAR DNA molecules (plasmids), usually SEVERAL 1000s bp long.
    - numbers vary - can have one, two, or many copies per cell.
  3. Plasmids CONTAIN genes that are not essential to function but play Role in the life cycle or growth of bacteria or in specific environmental/ecological niches.
  4. Plasmids have their own origin of replication and can replicate independently of chromosome
  5. Some plasmids contain genes for antibiotic resistance and are used in genetic engineering.
  6. Extra chromosome, small circular dsDNA
  7. They replicate INDEPENDENTLY OF THE BACTERIA CHROMOSOME
40
Q

Process of Bacterial PLASMIDs (5)

A
  1. Replication in a plasmid begins at the origin of replication, the oriV site
    - Origin of replication (oriV site)
    - in double-stranded DNA
  2. STRAND SEPARATION
  3. Strands separate and replication takes place in both directions…
    - newly synthesised DNA
  4. SEPARATION OF DAUGHTER PLASMID

5….Eventually producing two circular DNA molecules
- with new strand and old strand

41
Q

PLASMIDS ARE COMMONLY USED IN THE LAB

LOOK AT DIAGRAMS WITH PLASMIDS AND THE PROCEDURE

A

LOOK AT DIAGRAMS WITH PLASMIDS AND THE PROCEDURE

42
Q

PLASMIDS - EPISOME (4)

A
  1. Some plasmids can INTEGRATE into BACTERIAL CHROMOSOME = (B.chr = episome)
    - freely replicating plasmids: F (fertility) factor
  2. The term episome can be used for a plasmid or a viral genome.
  3. Episome is able to exist in an integrated form but also in an autonomous form.

Eg. F (fertility) factor - an E. coli episode that regulates transfer, replication, and insertion.

LOOK AT THE DIAGRAM AND SECTIONS OF IT

43
Q

Explain Bacterial vs Plasmid genome

A

The bacterial genome:
– Mostly single, circular DNA molecule/chromosome

– Plasmids:
* Extra chromosome, small circular dsDNA
* Episomes—freely replicating plasmids: F (fertility) factor

44
Q

How do Plasmids replicate?

A

They replicate independently of the bacterial chromosome.

45
Q

When does Genetic exchange occur?
In eukaryotes vs Bacterial

A

in eukaryote genetic exchange occurs during meiosis and mitosis via genetic recombination.

Bacterial processes are not so regular; however,
- they serve the same aim: to mix the genes from two different organisms together.

46
Q

What are the three types of processes that allow genetic exchange in bacteria? (CTT) - Explain the

A

There are three types of processes that allow genetic exchange in bacteria:

  1. conjugation: direct transfer of DNA from one bacterial cell to another (an animation is posted on LMS)
  2. transduction: use of a bacteriophage to transfer DNA between cells.
  3. transformation: naked DNA is taken up from the environment by bacteria

Principles of Inheritance (23 decks)

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