Pharmaceutical Biotechnology Lecture 9

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Questions and Answers

What type of spores are formed from the fragmentation of septate hyphae into single, thickened cells?

Chlamydospores

Sporangiospores

Blastospores

Arthrospores (correct)

Which type of spore is formed externally on a base of basidium?

Zygospores

Chlamydospores

Basidiospores (correct)

Ascospores

What characteristic differentiates Fungi from Bacteria in terms of their cell wall composition?

Peptidoglycan layers

Chitin and glucans (correct)

Mycolic acid

Presence of ergosterol

Which reproductive method is characteristic of Fungi Imperfecti (Deuteromycetes)?

Asexual reproduction only Signup and view all the answers

Which type of spores are produced in a sac-like structure called an ascus?

Ascospores Signup and view all the answers

What is a common pathogenic effect caused by certain fungi in humans?

Liver cancer due to mycotoxins Signup and view all the answers

Which of the following types of fungi reproduces by budding?

Candida albicans Signup and view all the answers

In what way do fungi contribute to the food industry?

Production of yeast for bread and beer Signup and view all the answers

What is the primary component of the fungal cell wall?

Chitin Signup and view all the answers

Which type of fungi can only grow on specific living hosts?

Biotrophic fungi Signup and view all the answers

What is a defining feature of yeast morphology?

Unicellular and oval or spherical shape Signup and view all the answers

What is the optimal pH range for fungal growth?

4.5-6.5 Signup and view all the answers

Which of the following is a method of asexual reproduction in fungi?

Budding Signup and view all the answers

What characterizes dimorphic fungi?

Exhibit two forms based on environmental conditions Signup and view all the answers

What type of spores do fungi produce that are arranged in chains?

Conidiospores Signup and view all the answers

Which organelles are specifically mentioned as being part of the fungal structure?

Endoplasmic reticulum and vacuoles Signup and view all the answers

What is the primary role of histones in relation to DNA?

They package DNA and help regulate gene expression. Signup and view all the answers

How many chromosomes are present in a typical human cell?

46 Signup and view all the answers

Which of the following correctly describes the structure of RNA?

Single-stranded with ribose sugar. Signup and view all the answers

Which type of RNA carries genetic information from DNA to ribosomes for protein synthesis?

Messenger RNA (mRNA) Signup and view all the answers

What distinguishes eukaryotic genes from prokaryotic genes?

Presence of both introns and exons. Signup and view all the answers

In which cellular compartment does ribosomal RNA (rRNA) primarily function?

Cytoplasm Signup and view all the answers

Which statement accurately reflects a difference between DNA and RNA?

DNA contains deoxyribose sugar, whereas RNA contains ribose sugar. Signup and view all the answers

What is the function of the A site in a ribosome?

It is the binding site for new tRNA with amino acids. Signup and view all the answers

What is the correct order of processes in the Central Dogma of Life?

Replication, Transcription, Translation Signup and view all the answers

What molecule does DNA polymerase III use to initiate the synthesis of a new strand?

RNA primer Signup and view all the answers

During DNA replication, what role does DNA helicase perform?

Separates DNA strands Signup and view all the answers

What is a primary difference between the leading strand and the lagging strand during DNA replication?

The leading strand is synthesized continuously, while the lagging strand is in short segments. Signup and view all the answers

Which enzyme is responsible for joining Okazaki fragments together?

DNA ligase Signup and view all the answers

What is the role of single-strand binding proteins (SSB) during DNA replication?

Stabilize separated DNA strands Signup and view all the answers

What does the semi-conservative model of DNA replication imply?

Each new DNA molecule consists of one old strand and one newly synthesized strand. Signup and view all the answers

Which process does NOT occur in the Central Dogma of Life?

Protein to DNA synthesis Signup and view all the answers

What is the primary function of the TATA box in transcription?

It provides a binding site for RNA polymerase. Signup and view all the answers

In which direction does transcription occur on the DNA template?

3' to 5' Signup and view all the answers

What happens during the elongation phase of transcription?

The RNA strand is synthesized and separates from DNA. Signup and view all the answers

What role does the cap and tail play in mRNA processing?

They increase mRNA stability and help in its release from the nucleus. Signup and view all the answers

What occurs during the initiation phase of translation?

mRNA binds to the small ribosomal subunit. Signup and view all the answers

What triggers the termination of translation?

A stop codon reaching the ribosome’s A site. Signup and view all the answers

What is the function of the RNA polymerase during transcription termination?

It detaches from both RNA and the gene. Signup and view all the answers

What is transformation in the context of bacteria gaining genetic material?

Bacteria take up DNA from their environment. Signup and view all the answers

What occurs during the process of transformation in bacteria?

Naked DNA is taken up by a competent recipient bacterium. Signup and view all the answers

What is a key characteristic of competent cells?

They can bind and take up DNA from their environment. Signup and view all the answers

Which bacteria are known to exhibit natural competence?

Streptococcus pneumoniae and Neisseria gonorrhoeae Signup and view all the answers

What is the primary function of the sex pilus in bacterial conjugation?

It forms a connection for DNA transfer. Signup and view all the answers

What is the significance of conjugation in bacteria?

It transfers genetic traits, including antibiotic resistance. Signup and view all the answers

During generalized transduction, how does a bacteriophage acquire host DNA?

Through packaging errors during viral DNA assembly. Signup and view all the answers

Which of the following statements about transformation is true?

It can involve degraded DNA from dead bacteria. Signup and view all the answers

What is one way artificial competence can be achieved in bacteria?

By exposure to high concentrations of calcium ions. Signup and view all the answers

Signup and view all the answers

Study Notes

Level 5, Semester 1 Pharmaceutical Biotechnology, Lecture 9

Lecture covered microbial genetics, focusing on transcription and translation.
This lecture discussed the central dogma of molecular genetics, which describes the flow of genetic information from DNA to RNA to protein.
DNA serves as the template for RNA synthesis (transcription).
mRNA is a sequence of codons, which are translated into chains of amino acids (polypeptides).
A codon is a sequence of three nucleotides.

Microbial Genetics

Lecture summary included transcription and translation.

Protein Synthesis

DNA → mRNA → Protein
Transcription
Translation

Triplet Code

DNA serves as a template for RNA synthesis.
A codon is a sequence of three nucleotides that codes for an amino acid.
Codons are translated into chains of amino acids (polypeptides).

The Genetic Code

mRNAs consist of codons that code for amino acids.
The Genetic Code contains 64 codons (4³) corresponding to 20 amino acids.
An amino acid can be coded for by more than one codon.

Stop Codons

Three stop codons exist (UAA, UAG, UGA).
They signal the end of translation.
AUG is the start codon, coding for methionine.

Transcription

One strand of DNA (template strand, 3' to 5') is used to create a complementary mRNA strand (5' to 3').
The other strand of DNA is called the sense strand and is complementary to the mRNA strand (except T is replaced by U).
Transcription begins at a promoter region (with a TATA box) and ends at the terminator site
Components of Transcription:
- Promoter
- RNA Polymerase
- Termination Site
The process of mRNA production from a DNA template.

Transcription in Eukaryotes

RNA splicing involves removing introns (noncoding sequences) and joining exons (coding sequences)
A cap and tail are added to the mRNA to facilitate release from the nucleus, stabilize the mRNA, and aid ribosome binding.
- Cap: single G nucleotide
- Tail: 50-250 A nucleotides.

Translation

mRNA translation begins at the start codon (AUG) and terminates at a stop codon (UAA, UAG, or UGA).
Translation involves three main steps:
- Initiation
- Elongation
- Termination

Initiation (Translation)

mRNA binds to the small ribosomal subunit.
Initiator tRNA binds to the start codon (AUG).
Initiator tRNA carries the amino acid methionine (Met).
Large ribosomal subunit joins the small subunit.
Initiator tRNA fits into the P site of the ribosome.
The other tRNA-binding site (A site) is empty, awaiting the next amino acid-carrying tRNA.

Elongation (Translation)

New tRNA carrying an amino acid binds to the A site on the ribosome.
Peptide bond formation between the amino acid at the P site and the amino acid at the A site, releasing the previous tRNA from the P site.
The ribosome moves along the mRNA
The P site tRNA leaves the ribosome and the ribosome translocates the tRNA in the A site to the P site.

Termination (Translation)

A stop codon reaches the ribosome's A site.
Stop codons do not code for amino acids; they signal the end of translation.
The completed polypeptide is released from the last tRNA.
The ribosome subunits separate.

Transfer of Genetic Elements

Transformation: DNA uptake from the environment.
Conjugation: DNA transfer between bacteria (often through a pilus).
Transduction: DNA transfer mediated by a bacteriophage.

Transformation

Genes are transferred as "naked" DNA from one bacterium to another.
Frederick Griffith (1928)
Recipient cell becomes competent by binding special proteins.

Griffith's Experiment

Used two strains of Streptococcus pneumoniae (one with a capsule, one without).
Demonstrated genetic material transfer, key step in understanding bacterial transformation.

1- Transformation Process

A fragment of donor DNA attaches to a competent recipient cell
Internal DNA processes bind the DNA for replication.

Competence

A cell able to absorb and utilize foreign DNA from the environment.

Natural Competence

Special proteins like RecA facilitate DNA uptake in some bacteria.
Examples include Streptococcus pneumoniae, Bacillus subtilis, Hemophilus influenza, and Neisseria gonorrhoeae.

Artificial Competence

Induced competence through high concentrations of calcium ions, creating pores in cell membranes.

Conjugation

Donor bacteria transfers DNA plasmid (usually) to a recipient bacterium via a sex pilus.
Donor cell must have the F+ factor (plasmid).

Transduction

DNA transfer between bacteria mediated by a bacteriophage (virus).
Generalized transduction: packaging of host DNA instead of viral DNA.
Generalized transduction can lead to recombination with the recipient cells DNA.

Importance of Conjugation

Allows bacteria to acquire new genes and genetic traits.
Important in the transfer of antibiotic resistance.

Importance of studying fungi

Pathogenicity: some fungi cause human diseases.
Toxin production: mycotoxins harm humans.
Metabolic activity: damages food and structures.
Plant diseases: fungi cause many plant diseases.
Food and pharmaceutical applications: used in food and medicine.

Fungi

Heterotrophic eukaryotes
Cell walls contain chitin, mannan, and/or glucan.
Key types:
- Yeasts
- Molds
- Dimorphic

Fungal Morphology

Yeasts: Unicellular, oval/spherical cells
Molds: Filamentous mycelium, hyphae
Dimorphic: Mold or yeast forms depending on conditions

Fungal Reproduction

Asexual:
- Conidiospores
- Sporangiospores
- Arthrospores
- Chlamydospores
- Blastospores
Sexual:
- Zygospores
- Basidiospores
- Ascospores

DNA Replication

Semi-conservative model (Watson & Crick): DNA molecules consist of one parental strand and one new strand.
Locations: starts at replication bubbles (single origin in prokaryotes, multiple in eukaryotes).
Enzyme Overview:
- DNA gyrase (a topoisomerase): Relaxes supercoiled DNA
- DNA helicase: separates the 2 DNA strands.
- Single-Strand Binding proteins (SSBs): Keeps separated DNA strands apart
- Primase: synthesizes short RNA primer, allowing DNA polymerase to start replication.
- DNA polymerase III: adds nucleotides in the 5' to 3' direction. It is termed "proofreading" or "error correction", as it removes mismatched base pairs.
- The leading strand (5’ to 3’) is synthesized continuously from the replication fork.
- The lagging strand (3’ to 5’) is synthesized discontinuously in short segments called Okazaki fragments. Gaps filled by DNA polymerase I and sealed via DNA ligase.

RNA (Structure and Types)

RNA is a single-stranded polynucleotide.
RNA contains ribose as the sugar moiety.
RNA contains Uracil (U) instead of Thymine (T).
Types Include:
- mRNA
- tRNA
- rRNA

Differences between DNA and RNA

DNA: double helix; deoxyribose sugar A-T and G-C base pairs
RNA: single-stranded; ribose sugar, U replaces T in hydrogen bond pairs, migrates out of the nucleus.

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Description

This lecture focuses on microbial genetics, detailing transcription and translation processes. It explains the central dogma of molecular genetics, the flow of genetic information, and the role of codons in protein synthesis. Gain insights into the mechanisms of DNA, RNA, and protein interactions.