Lecture 8- Cell Division In Prokaryotes

Question 1

How long does cell division occur in Escherichia coli, and compare it to eukaryotic cells?

Answer 1

20 minutes in É coli, around 24 hours for Eukaryotic cells

Question 2

At which Carbon in the pentose sugar in DNA are the bases attached?

Answer 2

Carbon 1

Question 3

At which carbons in the pentose sugar are the phosphates added?

Answer 3

5’&3’- antiparallel

Question 4

Name the four bases in DNA

Answer 4

Adenine & Thymine Cytosine & Guanine

Question 5

How many hydrogen bonds from with the base pairs?

Answer 5

Adenine & Thymine = Cytosine & Guanine ≡

Question 6

What tell-tale sign indicates a prokaryotic cell is about to undergo cell division?

Answer 6

attachment of the chromosome to a special plasma membrane

Question 7

Describe the process of chromosome replication in prokaryotes?

Answer 7

Initiation

• Enzymes recognize the origin, and attach to it

Helicase and gyrase separates DNA strands, forming a ​replication fork​

• DNA primase adds RNA primers( short strands) to the DNA strand to be replicated(new)

Elongation

• DNA polymerase ​adds nucleotides at the 3’ end, replication is 5’–> 3’
• DNA polymerase removes RNA primers, and proofreads newly made DNA
• Replication is bidirectional (2 strands at the same time, forming a bubble)

​Termination

• DNA polymerase recognizes stop Codon
• enzymes from both sides meet and detach

Question 8

Do all cells have spindles and microtubules?

Answer 8

no! Prokaryotes do not have either spindles or microtubules

Question 9

Describe the process of cell division in prokaryotes

Answer 9

• Attachment of chromosome to special plasma membrane site, indicating cell is starting process
• preparing for binary fission by enlarging cell wall. Membrane, and overall volume
• DNA replication- producing 2 identical chromosomes cell wall and plasma membrane begin to grow inward in middle
• Chromosomes pulled apart, even distribution of cytoplasm

division complete resulting in 2 daughter cells

Question 10

What are the characteristics of plasmids in prokaryotes?

Answer 10

• much smaller than circular DNA
• self replicative
• not needed for survival under normal conditions
• give rise to genetic variation

Question 11

What are the different types of plasmids?

Answer 11

• sex or conjugation plasmid F plasmid
• Resistance plasmids- confer resistance to antibiotics
• virulence plasmids- convey pathogenic properties

plasmids can either be integrative or non-integrative

Question 12

Describe the process of conjugation

Answer 12

• A cell carrying F plasmid (F+= male) forms a bridge with a F-(female)
• One strand of the F plasmid breaks at a point and begins to move to the recipient cell (F-), donor plasmid rotates as the transfer is made,at the same time as DNA replication in both cells using the one strand as a template
• plasmid circulizes, and reproduction of pillus, bridge removed, resulting in two male cells (F+)

Question 13

What are the characteristics of a male bacterial cell?

Answer 13

contains a pillus and F plasmid F+)

Question 14

Describe the process of Transformation

Answer 14

DNA is picked up from environment, and is integrates to the chromosome

does not require pillus

Question 15

Describe the process of transduction

Answer 15

• phage infects donor bacterial cell
• phage DNA and proteins are made
• bacterial chromosome broken into pieces
• pieces of bacterial DNA are packaged along with viral DNA during its reproduction
• bacterial cell lysis and phage exits
• phage infects new recipient cell
• Recombination can occur, resulting in a different genotype for both cells, as the donor was infected initially

Question 16

What happens during plasmid transformation?

Answer 16

Free plasmids are picked up from the environment and may remain as a functional plasmid or integrate into the chromosome

Question 17

Is it true that plasmids and chromosomes are the only areas that hold DNA in a prokaryote?

Answer 17

no, there are others (don’t need to know specifics)