Bacterial Genetics (BE #5) Flashcards
Name the 3 parts of a nucleotide
- sugar
- phosphate group
- nitrogenous base
What is the building block of nucleic acid?
nucleotide
What does DNA stand for?
deoxyribose nucleic acid
In the ladder analogy of DNA structure, what kinds of molecules make up the sides of the ladder?
sugars & phosphates
What kinds of molecules make up the rungs of the ladder?
nitrogenous bases
What part of the nucleotide spells out the genetic message or code int he DNA molecule?
nitrogenous base
Name the 4 nitrogenous bases in DNA molecule.
- Adenine
- Thymine
- Guanine
- Cytosine
Describe complimentary base pairing (what pairs with what?).
A - T
G - C
Describe the prokaryotic chromosome.
single
circular chromosome
contains essential genes
Describe a plasmid.
circular
can be multiple plasmids
an extra chromosome that has nonessential genes
Why is a plasmid not considered another chromosome?
contains nonessential genes
Name 2 cellular processes that involve DNA (what does cell do with it?)
- replication
2. protein synthesis
What do genes code for
proteins
We say that DNA controls everything that is going on in the cell. How?
Through the production of enzymes, which are proteins. Enzymes catalyze chemical reactions, so help the DNA control cellular activities.
Briefly describe DNA replication.
an enzyme causes the hydrogen bonds between the 2 DNA strands to “unzips” & they separate. Each strand acts as a template directing the synthesis of a new complementary strand along its length. A-T, G - C
Why is DNA replication referred to as “semi conservative?”
This replication keeps half of the original strand & adds a new strand to it.
What would conservative replication look like?
Duplicating the DNA molecule with 2 completely new strands.
What are the 2 major events in protein synthesis?
Transcription
Translation
During the 2 major events in protein synthesis, what gets made in each event and what kinds of nucleic acids are involved in the event (DNA, mRNA, rRNA, and/or tRNA)?
Transcription - make mRNA, DNA & mRNA involved
Translation - make protein (assemble amino acids); mRNA, tRNA & rRNA are involved.
What does RNA stand for?
ribonucleic acid
How is transcription different in eukaryotes vs. prokaryotes?
B/c prokaryotes don’t have the noncoding sequences like eukaryotes, they don’t have to do the extra step of getting rid of them before the mRNA can be translated into protein.
What are the 3 types of RNA & what is the function of each in protein synthesis?
- mRNA - copy of the DNA molecule; contains the code for the amino acid sequence in the protein.
- tRNA - transfers amino acids to the ribosome to be assembled into the protein; very specific for the amino acid it transfers; has an anitcodon at one end.
- rRNA - reads the mRNA & directs the assembly of the protein.
List 3 differences between DNA & RNA.
- Different sugars (ribose vs. deoxyribose)
- RNA is single stranded; DNA is double stranded
- RNA uses uracil; DNA uses thymine (both pair with adenine)
Why do we call the second major event of protein synthesis “translation?”
synthesis of proteins (polypeptides) translates information from nucleic acid code to amino acids.
When does the translation process terminate or stop?
When the ribosome reaches a stop codon
Where does transcription take place in eukaryotic & prokaryotic cells?
prokaryotic - cytoplasm
eukaryotic - nucleus
Where does translation take place in eukaryotic & prokaryotic cells?
prokaryotic - cytoplasm
eukaryotic - cytoplasm
Why is each codon specific for only one amino acid?
Otherwise the ribosome wouldn’t know which amino acid to put in the protein. If it picks the wrong one, that could change the structure of the protein, which would change its function.
What is meant by “universal genetic code?”
all organisms and viruses use the same genetic code
What is an operon?
What’s the advantage of an operon?
a cluster of related genes involved in similar function and are often found in a contiguous array so all are transcribed & translated at the same time.
veyr efficient
T or F
Many ribosomes can translate a mRNA transcript at one time.
true
continuous synthesis (a type of operon)
- enzymes are synthesized continuously regardless of available nutrients.
- example is glucose metabolism
repressible operon
- end product binds to some part of pathway and entire pathway shuts down
- ex.
inducible operon
- enzymes are synthesized depending on presence or absence of a particular substrate.
- ex. is lactose metabolism
What does the Lac Operon consist of?
Promoter (for RNA polymerase to bind to) + Operator (for repressor to bind to) + Structural genes for lactase enzymes
Name the enzyme produced by the lac operon.
What is the enzyme’s substrate?
Lactase
Lactose
Lac Operon - lactase is synthesized
- when lactose is present
- lactose binds to repressor protein
- repressor protein is released from binding to DNA
- transcription can take place
Lac Operon - lactase is NOT synthesized
- when lactose is ABSENT
- the repressor binds to DNA
Define mutation.
Are they good or bad for the organism?
A mutation is any change in a cell’s genotype that may or may not lead to changes in a cell’s phenotype (specific characteristics displayed by the organism). Mutations can be good or bad.
Define:
- point mutation
2. frameshift mutation
- changes only a single codon (base substation)
2. base deletion or base addition
Which has greater consequences - point or frameshift mutation? Why?
Frameshift - They don’t affect just one codon. Since they shift the organization of the codons, they can result in many changes in amino acids in the protein.
During what process do spontaneous mutations generally occur?
Spontaneous mutations can occur during DNA replication, transcription & translation, but mostly occur in DNA replication.
Name a chemical mutagen.
sodium nitrite, mustard gas
Name a physical mutagen.
UV light, x-rays
Is heat mutagenic to DNA?
only slightly; it breaks the hydrogen bonds causing the strands to separate, but it doesn’t mutate the code.
Describe dimers.
2 adjacent bases on the same strand that bond. Result is a gap in replicated DNA which stops transcription process.
What causes dimers?
UV radiation
T or F
Bacteria can repair UV damage to their DNA?
True
What are 3 ways genetic information can be transferred from one bacterium to another?
- conjugation via pili
- transformation
- transduction
Conjugation
transfer of genetic material (DNA) from one bacterial cell to another via pili.
What does “R” stand for in R plasmid?
drug resistant
What does “F” stand for in F plasmid?
fertility
Do F(+) cells have pili?
yes
Transformation
a genetic change in which extracellular DNA is taken into another bacterial cell by endocytosis. It may then become incorporated into the chromosome. (mouse example)
Transduction
during viral replication in a bacterial cell, a fragment of the bacterial DNA can be taken into a new viral cell which can then “infect” another bacterial cell. The virus is a “vector/carrier” of the bacterial DNA.
bacteriophage
a virus that infects bacteria.
