About the final
It will be in English,Try to answer in English as
well,The problems are given in such a way that
very short answers are needed,Chinese allowed if
you can only read English
People with language difficulty are allowed to have
extra time,for example,half an hour,and are
allowed to have dictionary,This rule does not
apply to general audience
A short test in the format of the final will be given
in 1-2 weeks online,so that students know what
they expect
Only materials that are mentioned during the
lectures will be in the exam,60 points total
Bacterial Genetics
Three kinds of genetic transfer
occur in bacteria
Transformation,donor cell releases DNA by lysis
and it is taken up by the recipient cell
Conjugation,physical contact between two
bacterial cells and transfer of DNA
Transduction,bacterial virus (phage) transfers
the DNA from donor cell to recipient cell
Gene Transfer in Bacteria
Bacterial transformation
Transformation involves uptake of DNA,followed by
either recombination of the DNA with the host
chromosome or self-replication of DNA (plasmids).
Genes that are close together on DNA can cotransform,
That is,alleles of both genes can be inserted on the
same piece of DNA.
Gene order can be determined by cotransformation.
Natural Transformation
Transformation of bacterial cells
Transformation does not naturally occur in most strains
of bacteria,including E,coli.
E,coli and other bacteria can be forced to take up DNA
by special chemical and temperature treatments
DNA can also be put into bacterial cells by first treating
the cells with a brief high voltage pulse (electroporation),
This causes a temporary production of pores in the cell
membrane,allowing the DNA to pass into the cell,
The sex factor,F
DNA transfer is mediated by F,the fertility factor,
F is a plasmid,a small self-replicating circle of
DNA.
F carries genes that direct the formation of the
conjugation tube and its replication and transfer
to the recipient
The F-factor replicates and a new copy is sent into
the F- recipient cell,The F-factor is an example of
a conjugative plasmid
Generation of an Hfr Strain
a single crossover between the F-factor and the
bacterial chromosome
This generates a high frequency recombination cell
(Hfr).
Recombination occurs at site of insertion sequence
The Hfr strain transfers a copy of the bacterial
chromosome along with the F -factor.
If mating is interrupted,only a portion of the
chromosome is transferred.
The location of a gene can be determined by
determining when it is transferred,
Genes are mapped in units of minutes of mating.
The gene closest to the inserted F-factor is
transferred first.
Many Hfr strains exist with F inserted in different
locations,
Any gene can be mapped by using several Hfr
strains
Entry times of genes depend upon their
distance from the entry point of the Hfr
F’ and partial diploids
The F-factor in a Hfr chromosome can excise out to
become an autonomously replicating plasmid.
If a segment of the chromosome becomes part of the F-
plasmid during excision,the new element is called an F’-
plasmid.
This F’-plasmid can be conjugated to another bacterial
cell to form a partial diploid.
F-plasmid
F’-plasmid
chromosome
with deletion
Recombination
point
Hfr
chromosome
a
a a
Partial Diploids in bacteria are used in
complementation analysis
a
F’ plasmid
+ Bacterial cells = (by either conjugation
or transformation)
a
a
Partial diploid
for only one region
of the chromosome
The recipient bacterial
cells are recA- to prevent
recombination and re-integraton
of the plasmid into the host
chromosome.
Bacteriophage Genetics
Phage can take two different pathways
upon infection of a bacterial cell
,lytic or lysogenic
Generalized Transduction
introduction of genes from a
donor cell
occurs with phage which can
co-package DNA (rare event)
Packaged DNA is a random
fragment
Used to measure:
co-transduction frequencies
map distances
a-
b-
c-
a+
b+
c+
recipient donor
Phage lambda
Gene
knockout in
Bacteria
Non-Mendelian genetics
Extranuclear inheritance
Maternal effect
MITOCHONDRIA AND
CHLOROPLASTS
Mitochondria are energy producing organelles in
plants and animals.
Mitochondria possess their own DNA
The chromosome is circular
The chromosome is small (15 to 250 kb/genome)
Each mitochondria has multiple copies(1-hundreds)
The chromosome has a small number of genes
The gene structure resembles that of bacterial genes.
TRANSCRIPTION AND
TRANSLATION
Mitochondrial RNA transcripts are made (no introns
are usually present) using a special RNA polymerase
The RNA transcripts are processed into individual
mRNA’s
Poly(A) tails are added
Translation occurs in the organelle,not in the
cytoplasm
The genetic code is slightly different in mitochondria.
UGA,the normal stop codon,codes for tryptophan
AGA & AGG,normal arginine codons,are stop codons
Endosymbiotic theory suggests these organelles
were once bacteria.
During evolution,these bacteria became
symbiotic with eukaryotes
The theory is supported by the fact that,
chloroplasts and mitochondria closely resemble
bacteria
They have lost many of their genes to the nucleus with
time.
ORIGIN OF CHLOROPLASTS
AND MITOCHONDRIA?
Inheritance pattern of organellar genes:
Non-Mendelian
Evidence comes from several experiments:
Reciprocal crosses are not identical
Mutations do not map to the nuclear genome
Phenotype ratios for F2 progeny are non-Mendelian (not 3:1)
The mutant phenotype persists after nuclear substitution
Example of extranuclear inheritance in Mirabilis
Variegated plants have
green leaves with yellow-
white patches
Green color in leaves is
due to chlorophyll
Yellow-White color in
leaves is due to loss of
chlorophyll from
chloroplasts
What are the possible
outcomes of crossing a
variegated plant?
Figure 7.9
Parental
plant Egg
Sperm or
pollen
Progeny
plant
White
Green
Variegated
White
Green
Green
White
Variegated
&
leukoplasts any type
any type
any typeChloroplasts
Chloroplasts
leukoplasts
mixture&
Myoclonic
epilepsy and
ragged red fiber
disease (MERRF)
has a range of
phenotypes
depending on
ratios of mutant
mitochondria in
each tissue
Mitochondria and chloroplast of C,reinhardtii
have different inheritance patterns
Some organisms exhibit Biparental
Inheritance
Maternal effects
Some phenotypes are controlled by the mother’s genes.
Example,coiling direction in snails.
Dextral = dominant,maternal effect allele,gives right-handed
coiling.
sinstral = recessive,maternal effect allele,gives left-handed
coiling.
DD and Dd mothers give right-handed coiled offspring.
dd mothers give left-handed coiled offspring.
It will be in English,Try to answer in English as
well,The problems are given in such a way that
very short answers are needed,Chinese allowed if
you can only read English
People with language difficulty are allowed to have
extra time,for example,half an hour,and are
allowed to have dictionary,This rule does not
apply to general audience
A short test in the format of the final will be given
in 1-2 weeks online,so that students know what
they expect
Only materials that are mentioned during the
lectures will be in the exam,60 points total
Bacterial Genetics
Three kinds of genetic transfer
occur in bacteria
Transformation,donor cell releases DNA by lysis
and it is taken up by the recipient cell
Conjugation,physical contact between two
bacterial cells and transfer of DNA
Transduction,bacterial virus (phage) transfers
the DNA from donor cell to recipient cell
Gene Transfer in Bacteria
Bacterial transformation
Transformation involves uptake of DNA,followed by
either recombination of the DNA with the host
chromosome or self-replication of DNA (plasmids).
Genes that are close together on DNA can cotransform,
That is,alleles of both genes can be inserted on the
same piece of DNA.
Gene order can be determined by cotransformation.
Natural Transformation
Transformation of bacterial cells
Transformation does not naturally occur in most strains
of bacteria,including E,coli.
E,coli and other bacteria can be forced to take up DNA
by special chemical and temperature treatments
DNA can also be put into bacterial cells by first treating
the cells with a brief high voltage pulse (electroporation),
This causes a temporary production of pores in the cell
membrane,allowing the DNA to pass into the cell,
The sex factor,F
DNA transfer is mediated by F,the fertility factor,
F is a plasmid,a small self-replicating circle of
DNA.
F carries genes that direct the formation of the
conjugation tube and its replication and transfer
to the recipient
The F-factor replicates and a new copy is sent into
the F- recipient cell,The F-factor is an example of
a conjugative plasmid
Generation of an Hfr Strain
a single crossover between the F-factor and the
bacterial chromosome
This generates a high frequency recombination cell
(Hfr).
Recombination occurs at site of insertion sequence
The Hfr strain transfers a copy of the bacterial
chromosome along with the F -factor.
If mating is interrupted,only a portion of the
chromosome is transferred.
The location of a gene can be determined by
determining when it is transferred,
Genes are mapped in units of minutes of mating.
The gene closest to the inserted F-factor is
transferred first.
Many Hfr strains exist with F inserted in different
locations,
Any gene can be mapped by using several Hfr
strains
Entry times of genes depend upon their
distance from the entry point of the Hfr
F’ and partial diploids
The F-factor in a Hfr chromosome can excise out to
become an autonomously replicating plasmid.
If a segment of the chromosome becomes part of the F-
plasmid during excision,the new element is called an F’-
plasmid.
This F’-plasmid can be conjugated to another bacterial
cell to form a partial diploid.
F-plasmid
F’-plasmid
chromosome
with deletion
Recombination
point
Hfr
chromosome
a
a a
Partial Diploids in bacteria are used in
complementation analysis
a
F’ plasmid
+ Bacterial cells = (by either conjugation
or transformation)
a
a
Partial diploid
for only one region
of the chromosome
The recipient bacterial
cells are recA- to prevent
recombination and re-integraton
of the plasmid into the host
chromosome.
Bacteriophage Genetics
Phage can take two different pathways
upon infection of a bacterial cell
,lytic or lysogenic
Generalized Transduction
introduction of genes from a
donor cell
occurs with phage which can
co-package DNA (rare event)
Packaged DNA is a random
fragment
Used to measure:
co-transduction frequencies
map distances
a-
b-
c-
a+
b+
c+
recipient donor
Phage lambda
Gene
knockout in
Bacteria
Non-Mendelian genetics
Extranuclear inheritance
Maternal effect
MITOCHONDRIA AND
CHLOROPLASTS
Mitochondria are energy producing organelles in
plants and animals.
Mitochondria possess their own DNA
The chromosome is circular
The chromosome is small (15 to 250 kb/genome)
Each mitochondria has multiple copies(1-hundreds)
The chromosome has a small number of genes
The gene structure resembles that of bacterial genes.
TRANSCRIPTION AND
TRANSLATION
Mitochondrial RNA transcripts are made (no introns
are usually present) using a special RNA polymerase
The RNA transcripts are processed into individual
mRNA’s
Poly(A) tails are added
Translation occurs in the organelle,not in the
cytoplasm
The genetic code is slightly different in mitochondria.
UGA,the normal stop codon,codes for tryptophan
AGA & AGG,normal arginine codons,are stop codons
Endosymbiotic theory suggests these organelles
were once bacteria.
During evolution,these bacteria became
symbiotic with eukaryotes
The theory is supported by the fact that,
chloroplasts and mitochondria closely resemble
bacteria
They have lost many of their genes to the nucleus with
time.
ORIGIN OF CHLOROPLASTS
AND MITOCHONDRIA?
Inheritance pattern of organellar genes:
Non-Mendelian
Evidence comes from several experiments:
Reciprocal crosses are not identical
Mutations do not map to the nuclear genome
Phenotype ratios for F2 progeny are non-Mendelian (not 3:1)
The mutant phenotype persists after nuclear substitution
Example of extranuclear inheritance in Mirabilis
Variegated plants have
green leaves with yellow-
white patches
Green color in leaves is
due to chlorophyll
Yellow-White color in
leaves is due to loss of
chlorophyll from
chloroplasts
What are the possible
outcomes of crossing a
variegated plant?
Figure 7.9
Parental
plant Egg
Sperm or
pollen
Progeny
plant
White
Green
Variegated
White
Green
Green
White
Variegated
&
leukoplasts any type
any type
any typeChloroplasts
Chloroplasts
leukoplasts
mixture&
Myoclonic
epilepsy and
ragged red fiber
disease (MERRF)
has a range of
phenotypes
depending on
ratios of mutant
mitochondria in
each tissue
Mitochondria and chloroplast of C,reinhardtii
have different inheritance patterns
Some organisms exhibit Biparental
Inheritance
Maternal effects
Some phenotypes are controlled by the mother’s genes.
Example,coiling direction in snails.
Dextral = dominant,maternal effect allele,gives right-handed
coiling.
sinstral = recessive,maternal effect allele,gives left-handed
coiling.
DD and Dd mothers give right-handed coiled offspring.
dd mothers give left-handed coiled offspring.
