48 Questions
Which enzyme stabilizes the unwound parental DNA during replication?
Proteins
What polymerase is responsible for synthesizing a short RNA primer on the lagging strand?
RNA polymerase
Which enzyme is involved in continuously synthesizing the leading strand?
DNA polymerase
What is the role of DNA ligase in DNA replication?
Joins fragments of the lagging strand
Which fragments are formed on the lagging strand during DNA replication?
Okazaki fragments
Which process involves the synthesis of RNA from a DNA template?
Transcription
What does DNA stand for?
deoxyribonucleic acid
How are the nitrogenous bases adenine and thymine connected in DNA?
By two hydrogen bonds
Which component is not a part of a nucleotide?
Lipids
What is the direction of the DNA strand on the left side of the double helix diagram?
5' to 3'
What type of sugar is found in DNA?
Deoxyribose
Which enzyme is responsible for unwinding the DNA strands during DNA replication?
DNA Helicase
In E. coli, approximately how long is the DNA relative to the cell?
1000 times longer
Which enzyme is responsible for extending the RNA primer during replication on the lagging strand?
DNA Polymerase
What percentage of the total cell volume does the DNA take up in E. coli?
10%
Which of the following base pairings is correct in the structure of DNA?
A-T
Which enzyme is involved in the transcription process?
RNA Polymerase
What is the function of tRNA?
To transfer amino acids to the ribosomes for protein synthesis
Which type of RNA contains the codons?
mRNA
During transcription, in which direction is the mRNA synthesized?
5' to 3'
Which of the following is NOT a component involved in the transcription process?
Ribosome
How many amino acids are coded by the genetic code?
20
How many possible combinations of 3-base codons exist?
64
What is the term used to describe genes that are always turned on?
Constitutive
Which of the following bases is NOT found in RNA?
T
What role do codons play in the genetic code?
They code for a specific amino acid
Which type of mutation does not alter the function of the protein?
Silent (neutral)
Which process involves the uptake of naked DNA from the environment by a bacterium?
Transformation
Which of the following is necessary for evolution in bacteria?
Genetic variation
Genetic transfer in bacteria does NOT occur through which of the following methods?
Mitosis
Which process of genetic transfer in bacteria involves a virus?
Transduction
What happens to the DNA of bacterial cells when they die?
It is released into the surrounding medium.
Which process involves DNA being transferred from one bacterium to another by a virus?
Transduction
In conjugation, what structure is used to pass DNA between bacteria?
Sex pilus
During bacterial transformation, where does a living bacterium obtain new DNA?
From the surroundings
Which of the following terms best describes a virus that infects bacteria?
Bacteriophage
What are the causes of genotypic variation in bacteria?
Mutation
Which type of mutation involves the substitution of one nitrogenous base for another?
Substitution
What is an example of a transversion mutation?
Substitution of adenine with thymine
Which statement is true about genotypic variations?
They are heritable among bacterial generations
By what mechanisms can a gene mutation be induced?
UV light
What occurs in a deletion mutation?
A base is removed
What is a characteristic of phenotypic variation in bacteria?
It is influenced by environmental conditions.
Which substance interferes with the bacterial development of flagella?
Phenol
What happens to bacterial cells with irregular staining when transferred to a fresh medium?
They return to normal morphology.
Which factor influences the formation of capsules and spores in bacteria?
Composition of medium
What is the relationship between young multiplying bacterial cells and their susceptibility to disinfectants?
Young multiplying cells are more susceptible.
When does Escherichia coli synthesize the enzyme beta-galactosidase?
When grown in a medium containing lactose.
Study Notes
DNA Replication
- Occurs at the replication fork (5' to 3')
- Enzymes unwind the parental double helix
- Proteins stabilize the unwound parental DNA
- Leading strand is synthesized continuously by DNA polymerase
- Lagging strand is synthesized discontinuously by RNA polymerase and DNA polymerase
- RNA primer is digested and replaced with DNA
- DNA ligase joins the discontinuous fragments of the lagging strand
DNA Structure
- Double-stranded (double helix)
- Polymers of nucleotides
- 5' to 3' (strands are anti-parallel)
- Complimentary base pairing:
- A-T
- G-C
DNA and RNA
- DNA: deoxyribonucleic acid
- RNA: ribonucleic acid
- Nucleotides consist of:
- Phosphate group
- Pentose sugar
- Nitrogenous base
Genetic Code
- Codons code for a specific amino acid
- 20 amino acids
- 3-base code (4^3 = 64 possible combinations)
- Amino acids are coded for by more than one codon
Transcription
- One strand of DNA is used as a template to form a complementary strand of mRNA
- 3 ways RNA differs from DNA
- Promoter, RNA polymerase, and termination site are involved
- 5' to 3' direction
Types of RNA
- mRNA: contains codons
- rRNA: found in ribosomes (70S)
- tRNA: transfers amino acids to ribosomes for protein synthesis
- Anti-codon
Mutations
- Can be harmful, lethal, beneficial, or silent (neutral)
- Examples: UUU - Phe, UUC - Phe
Genetic Transfer in Bacteria
- Results in genetic variation, necessary for evolution
- 3 ways genetic transfer can occur in bacteria:
- Transformation
- Conjugation
- Transduction
Transformation
- Genes are transferred from one bacterium to another as naked DNA
- Bacterial cells uptake free DNA from the surrounding medium
Conjugation
- One bacterium passes some DNA (in a plasmid) to another bacterium
Transduction
- DNA is transferred from one bacterium to another by a virus (bacteriophage)
Genetic Variation
- Phenotypic variation:
- Changes in bacterial characters in response to environmental conditions
- Reversible when the environmental cause is removed
- Not heritable (no genetic changes)
- Genotypic variation:
- Changes in the bacterial characters due to changes in the genetic constitution of the bacterial cell
- Irreversible
- Heritable among bacterial generations
- Causes:
- Mutation
- Gene transfer
Learn about the processes of transformation and conjugation in bacterial genetics, including how DNA is released and taken up by bacterial cells.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
