Gentics Module 3 (Jenna)

Created by mia_petrucci9 on Quizlet :)

Bacteria

Single-celled organism lacking a nucleus (or any membrane-bound organelles)

Virus

An infectious agent composed of DNA or RNA and proteins. Requires a host to reproduce

Prokaryotes

Unicellular and lack a membrane-bound nucleus and membrane-bound organelles

3 Characteristics of bacteria

1. Diverse shapes and sizes
2. Some are photosynthetic
3. Replication occurs prior to binary fission (dividing in two)

9 Advantages of using bacteria and viruses for genetic studies

1. Rapid reproduction
2. Many progeny produced
3. Haploid genome allows all mutations to be expressed directly
4. Asexual reproduction simplifies isolation of genetically pure strands
5. Growth in lab easy
6. Techniques available for isolating and manipulating genes
7. Genome small
8. Have medical importance
9. Can be genetically engineered to produce substances of commercial value

The bacterial genome

Mostly comprised of a single, circular DNA molecule/ chromosome

Plasmids

An extra chromosome of small circular DNA

Episomes

freely replicating plasmids: F (fertility) factor

Where does replication of plasmid begin?

origin of replication (ori site)

Does plasmid replication occur in one or both directions?

Both directions

Separation of daughter plasmids creates what

Two circular DNA molecules

F-factor

Donor bacteria carries a DNA sequence called the fertility factor that allows donor to produce a pilus to contact the recipient

R-factor

Drug resistant plasmid; a group of conjugative plasmids that promote the bacterial most resistance to specific antibiotics

3 ways bacteria exchange DNA

conjugation, transformation, transduction

Conjugation

Direct transfer of DNA via connection tube from donor cells to recipient cells (not a reciprocal exchange)

F+ Cells

donor cells containing F factor

F- Cells:

Recipient cells lacking F factor

F' (F prime) Cells:

Contain F plasmid carrying some bacterial genes

Sex pilus

Thin strand that connects F+ and F- cells during bacterial conjugation

How do you determine the positions of the genes on chromosomes?

The amount of time required for individual genes to be transferred from the Hfr "High Frequency" to the F- cells indicate the relative positions

Where does antibiotic resistance come from?

The actions of the genes located on R plasmids that can be transferred naturally.

How long have the R plasmids evolved and why?

They have evolved in the past 60 years since the beginning of widespread use of antibiotics.

is the transfer of R plasmids restricted to bacteria of the same or related species?

No

Transformation

Bacterium takes up free DNA from the medium. Recombination takes place between introduced genes and the bacterial chromosome.

When the transformed cell replicates and divides what does it make?

One transformed cell and one non transformed cell

How we manipulate bacteria into transformation?

Applying heat to the bacteria to weaken the cell wall, so that the DNA can enter from the environment

Component Cells

Cells that can take up DNA from the environment

Transformed cells

Cells that received genetic material

Co-transformed cells:

Cells that are transformed by two or more genes

How big is the bacterial genome?

1-4 million base pairs of DNA

Horizontal gene transfer

Genes can be passed between individual members of different species by nonreproductive mechanisms

What are 4 Bacterial Restriction-modification systems?

1. CRISPR-Cas system
2. CRISPR ARRAY
3. CRISPR-CAS FUNCTION
4. PAM Sequences

What are the three steps of CRISPR-Cas Bacterial immunity?

1. Adaptation
2. Expression
3. Interference

CRISPR-Cas Bacterial Immunity: Adaptation

Bacteria captures foreign DNA from viruses or plasmids and integrates their genome into its own CRISPR array.

CRISPR-Cas Bacterial Immunity: Expression

Transcription of CRISPR array occurs into a long RNA (pre-crRNA) and is processed into smaller CRISPR RNAs, each matching a spacer

CRISPR-Cas Bacterial Immunity: Interference

crRNA guide the Cas proteins to the invading DNA and the Cas proteins cut the DNA, neutralizing the threat

When was CRISPR gene editing made

2012

What does CRISPR provide?

A synthesized version of a guide RNA (gRNA) complementary to a target DNA strand

Virus

A simple replicating structure (DNA/RNA) plus a protein coat

Bacteriophage

Bacterial infection virus

Virulent phage

Reproduce through the Lytic cycle and always kill the host cells

Temperature phage

Phage DNA integrates into bacterial chromosome, where it remains as inactive prophage

Viruses come in different structures and sizes, like...

DNA/RNA, Linear/ Circular, Single stranded/ Double stranded

Bacteriophages have two alternative life cycles:

lytic and lysogenic cycles

Lytic Cycle

Viral replication process leading to the destruction of the host cell

Steps of the Lytic cycle

1. Virus attaches to host cell
2. Viral DNA/ RNA enters host cell
3. Host cell machinery produces viral components
4. New viral particles are assembled
5. Host cell bursts open releasing new viruses to infect other cells

Lysogenic Cycle

Viral replication process where viral DNA integrates into the host genome and replicates with it.

steps of lysogenic cycle

1. Virus binds to host cell
2. Viral DNA enters host cell
3. Viral DNA integrates into host genome as a prophage
4. Host cell replicates normally, copying viral DNA
5. Prophage exists in host genome and switches to the Lytic cycle (optional)

Generalized Transduction

any gene may be transferred

Specialized Transduction

Only a few genes are transferred

Retrovirus

RNA virus has been integrating into the host genome by using reverse transcriptase to synthesize DNA from RNA or DNA template strand

What are the three main types of influenza viruses?

Influenza A, Influenza B, Influenza C... A is most common

Coronaviruses

These viruses have ribonucleic acid (RNA) as their genetic material. This family of viruses causes many forms of the common cold (SARS, MERS)

What are examples of RNA viruses?

Influenza, AIDS, Coronavirus, Ebola, Hepatitis C

What are examples of DNA viruses?

HSV, HPV, Hepatitis B, VZV (Chickenpox/Shingles)

Similarities between DNA and RNA viruses

Both infect host cell, Both cause disease, Both require host machinery

Differences between DNA and RNA viruses

DNA: Uses DNA as genetic material, replicate in nucleus of host, more stable (less mutations), Double-stranded

RNA: Uses RNA as genetic material, replicates in cytoplasm of host, High mutation rates, typically single stranded

Why do new strains of influenza viruses appear?

Due to antigenic drift and antigenic shift

Antigenic drift

Occurs when mutations are continually introduced into the genome of the viral strain

Antigenic shift

Occurs when new viral genomes are created through the reassortment of RNA molecules of different strains

Transduction

Bacterial viruses take DNA from one bacterium to another. Usually occurs between bacteria of the same or closely related species