Microbiology Chapter 7

What composed DNA?

made of nucleotides

What composed a mononucleotide?

phosphate group, a pentose sugar, and nitrogenous base

How many strands are there in a DNA molecule?

two strands

What is meant by antiparallel?

the two strands run in opposite directions

Describe the structure of a DNA molecule

• double helix

• sides are made of pentose and phosphate group

• middle is made up of pairs of nitrogenous bases

• Adenine pairs with Thymine

• Guanine pairs with Cytosine

Compare number of chromosomes of bacteria with the human cell

Bacteria are haploid (single copy) and humans are diploid (23 chromosomes from each parent)

What types of nucleic acid make up the genome of bacteria?

circular or linear DNA

Where can DNA be found in bacteria?

in the nucleoid

Where can DNA be found in plant and animal cells?

in the nucleus

What is the shape of bacterial chromosomes?

circular

how are bacterial chromosomes packaged inside the cell?

in loops back and forth

what is a nucleoid

bundled DNA

What composed the plasmid?

DNA molecules

What is the shape of plasmids?

circular

What is the size of plasmids in relation to the bacterial cell?

0.1 - 10% the size of a chromosome

What are the functions of plasmids?

• can replicate independently of chromosome

• carry genes for selective advantage: antimicrobial resistance and heavy metal resistance

What are the 4 steps in DNA replication in bacteria?

• begins at origin of replication 

• unwinding of the DNA

• RNA primer formation

• elongation of the leading and lagging strand

What are the enzymes involved in DNA replication?

• Helicase

• RNA primase

• DNA Polymerase I

• DNA Polymerase III

• DNA ligaments

What is the function of helicase?

unwinds the two strands of DNA

What is the function of RNA primase?

synthesizes RNA primer

What is the function of DNA polymerase I?

removes RNA primers and replaces them with DNA; adds nucleotides

What is the function of DNA polymerase III?

adds nucleotides and proof reads

What is the function of DNA ligaments?

joins short segments of DNA

How many origin of replication is there?

only 1

How many replication forks are formed when a molecule of DNA replicates?

two

What is semi-conservative method of DNA replication?

an old strand of DNA and a new strand of DNA

Where does DNA replication begin at?

origin of replication

The two strands of DNA separate forming ____________ and ____________

Replication bubble; replication fork

What is the replication fork?

the Y-shaped regions of replicating DNA molecules where new strands are growing.

What enzyme catalyzes the formation of RNA primer?

RNA primase

Elongation of the leading strand is:

continuous

What is the direction of the process of the leading strand?

towards the replication fork

How many primers are needed for the leading strand?

one

Name the enzymes that catalyze the elongation of new DNA at a replication fork

DNA polymerase I and III

What end does DNA polymerase III add nucleotides to?

3 OH

in the leading strand, how is DNA synthesized?

as a single polymer

How many primers are needed for the lagging strand?

depends of the size of DNA

What is the direction of the process of the lagging strand?

away from the replication fork

What are Okazaki fragments?

short DNA fragments produced in the lagging strand

What are the enzymes that remove RNA primers and replace them with DNA?

DNA polymerase I and DNA ligase

What is gene expression?

process by which DNA directs protein synthesis

what are the two processes involved in gene expression?

translation and transcription

what is transcription?

synthesis of RNA from DNA

what is translation?

synthesis of proteins from mRNA

where does transcription take place in prokaryotes?

cytoplasm

where does transcription take place in eukaryotes?

nucleus

where does translation take place in prokaryotes?

ribosome in the cytoplasm

where does translation take place in eukaryotes?

cytoplasm

What are the different RNAs produced by the cell?

• Messenger RNA (mRNA)

• Transfer RNA (tRNA)

• Ribosomal RNA (rRNA)

what does the template strand of DNA do in transcription?

provides a template for ordering the sequence of complementary nucleotides in an RNA transcript

What is the function of mRNA?

carries genetic information from DNA in nucleus to cytoplasm where proteins are to be synthesized

What is the function of tRNA?

carries amino acids from amino acid pool to mRNA

What is the function of rRNA?

structural component of ribosomes

What is the saying for nitrogenous bases pairing?

Apples in the Tree, Cars in the Garage

What is genetic code?

set of rules by which the sequence of nucleotides in DNA or RNA determines the sequence of amino acids in proteins

How many total codons are there?

64 codons

How many codons code for amino acids?

61 codons

What is a codon?

sequence of 3 nucleotides in DNA or RNA that codes for a specific amino acid

What is an anticodon?

sequence of 3 nucleotides on a tRNA molecule that is complementary to a codon on mRNA

What is the start codon?

AUG

What are the stop codons?

• UAA

• UAG

• UGA

What amino acids are coded by AUA codon?

Ile

What amino acids are coded by CAC codon?

His

What amino acids are coded by AUU codon?

Ile

What amino acids are coded by GCG codon?

Ala

What amino acids are coded by AAC codon?

Asn

During translation, what does each codon specify to be placed at each corresponding position along a polypeptide?

amino acids

What is gene transfer?

mechanisms for uptake of DNA to create variability

What are the two types of gene transfer?

• Vertical transfer

• Horizontal transfer

What are the three processes of horizontal gene transfer in bacteria?

• transformation

• transduction

• conjugation

What is transformation?

uptake of “naked” DNA from environment

What is transduction?

via bacteriophage aka “phage”

What is conjugation?

Direct cell to cell; sex pilus

What are required in bacterial transformation?

competent cells, DNA to introduce, and a method to help DNA enter the cells

What is a competent cell?

a cell that is able to integrate the gene for capsule formation and synthesis

describe the process of bacterial tranformation

• uptake of ‘naked’ DNA from environment (lysed bacterial cells)

• dead bacterium DNA from a donor binds to protein in a living, competent recipient and the donor DNA gets taken up and changes the recipient

What is vertical transfer?

from mother to daughter; think triangle

What is horizontal transfer?

from cell to cell of the same generation; think straight line

Describe the experiment of Griffith

• injected mic with different forms of pneumonia bacteria

  • living smooth strain resulting in mouse dying

  • dead smooth strain resulting in mouse living

  • living rough strain resulting in mouse living

• When the living rough strain and dead smooth strain were mixed and injected, the mouse died

• a culture of streptococcus pneumoniae from the dead mouse was taken and living smooth strain was present

• concluded that living rough strain transformed into living smooth strain by taking up DNA from dead smooth strain

What is transduction?

the transfer of DNA from one bacterium to another with the use of a bacteriophage

What are the two primary types of bacteriophages?

• lytic bacteriophages

• temperate bacteriophages

How does lytic bacteriophage replicate?

by lytic life cycle

How does temperate bacteriophage replicate?

by lysogenic life cycle

Describe lytic life cycle

Describe lysogenic life cycle

Describe generalized transduction

What is a prophage?

Wha tis required in transduction?

What is a transducing phage?

What is bacterial conjugation?

Discuss the process of plasmid transfer or F+ conjugation

After F plasmid transfer, what happens to the donor cell (F+ or F-)?

After F plasmid transfer, what happens to the recipient cell (F+ or F-)?

Discuss R plasmid conjugation

Discuss the process of chromosomal transfer conjugation or Hfr conjugation?

What is an Hfr?

How is an Hfr formed?

After chromosomal transfer, what happens to the donor cell (F+ or F-)?

After chromosomal transfer, what happens to the recipient cell (F+ or F-)?

What are the requirements for transformation, transduction, and conjugation?