Download 16.1 Genetic variation in bacteria

16.1 Genetic variation in
bacteria
Learning objectives:
• Describe the genetic material in bacteria
• List the ways variation may occur in
bacteria
• Define the term mutation
• Describe how conjugation occurs
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Bacteria- prokaryote
Sketch the structure of a simple rod shaped bacteria
Label the following parts:
cell wall, plasma membrane, plasmid, DNA, cytoplasm, 70s ribosomes,
capsule, mesosome, flagellum
Why is the
genetic
material not
identified as a
chromosome?
What is a
plasmid?
Change over time
Write a sentence or two describing the link
between
adaptation mutation variation
Which comes first?
Definitions
recombining mutation survive DNA increases
adaptation sexual changing
Natural selection a process where a species
(group of organisms) adjusts to suit a
………….. environment over time. This is called
……………. . It …………. the long term
reproductive success of a species as it enables
its members to ………... long enough to breed.
Variation or diversity occurs by
a) changing the quantity or structure of the …..,
known as ………… or
b) ……………… existing DNA of two individuals
during …………reproduction.
Variation in bacteria
A. Mutations: Changes in bases sequences:
CATGATTAGTAC
Addition e.g. ………………………………….
Deletion e.g. …………………………………
Substitution e.g. …………………………….
Explain how each of these types of
mutations affect the primary structure of a
polypeptide and the tertiary structure of a
protein. Which could have the greatest effect
on the functioning of a globular protein such
as an enzyme? Give your reasoning.
B. Conjugation is the transfer of DNA from one
bacterial cell to another. Draw sequence of events
1. Conjugation tube
produced by one cell
2. Donor cell plasmid
replicates
3. Circular plasmid
breaks and linear
DNA passes down tube
4. Linear DNA enters
recipient cell
5. Linear strand forms
new plasmid
A. Circular
plasmid
breaks
C.Linear DNA
enters
recipient cell
B. Donor cell
plasmid
replicates
E. Linear
DNA passes
down tube
D. Conjugation
tube
produced by
one cell
F. Linear
strand forms
new plasmid
Conjugation is a ………..event with only
some of the donor cell DNA being
transferred.
The recipient cell will acquire new
………………… from donor cell DNA
This method of DNA transfer is known as
……………. gene transmission, i.e.
between two individuals of different
species.
Where genes are passed from one
generation to the next is known as
………………….. gene transmission.
Test yourself: summary Q p219
In which two ways goes genetic diversity occur
in living organisms?
2. What is a mutation?
3. Albinism can be caused by a mutation that
results in organisms being unable to produce
an enzyme involved in the manufacture of a
chemical called melanin. Suggest a possible
sequence of events, starting with a mutation
and ending with cells being unable to produce
melanin.
4. Distinguish between horizontal and vertical
gene transmission.
1.
Discovering conjugation in bacteria
Strain 1 in medium
+ methionine and
biotin required
growth
supplements
Minimal medium
Strain 2 in medium
+ threonine and
leucine required
growth
supplements
Minimal medium
Medium plus all
four supplements
Strain 1 and 2 in
medium +
threonine, leucine
methionine and
biotin
Minimal medium
Which strains of Escherichia coli should grow on
the medium that contained all the missing
nutrients?
2. Which strains of E. coli would you expect to grow
on the minimal medium?
3. What information had the DNA from the donor
strain transferred to the recipient strain?
4. These further experiments were carried out to
disprove explanations other than conjugation.
Suggest one alternative explanation that might
account for the growth of a few colonies on the
minimal medium.
1.