Chapter 2
chromosomes and cellular reproduction
2
.I Prokaryotic and eukaryotic cells differ in a number of
genetic characteristics
unicellular cell structure
prokaryotes are
organisms with simple
·
a
↳ two bacteria and
groups : archaea
eukaryotic cells have compartmentalized organelles and nucleus that separates
·
a
DNA from the rest of the cell
↳ in histones
eukaryotes the INA is closely associated with to form chromosomes
>
Complex of DNA and histones is called chromatin
histones and DNA fit
regulate the accessibility of INA enable to
-
to enzymes
into the nucleus
in located molecules
eukaryotes multiple DNA
·
genes are on
↳ need a mechanism to ensure a copy of each chromosome is transmitted
. I Cell reproduction
2 of
requires the
copying genetic material ,
separation of the copies, and cell division
for cell to reproduce three fundamental events must take place
any
·
.
3
1 the
genetic information must be copied
2) the copies must be separated from each other NB !
3) the cell must divide
prokaryotic cells reproduce via
binary fission
·
eukaryotic cells undergo complex reproduction due the of
·
more to presence
Multiple chromosomes
↳ each cell must end up with one copy of every chromosome
L the Nuclear Matrix maintains precise spatial regions among the components of the
nucleus
-
takes part in DNA replication and gene modification
, gene expression ,
each
eukaryotic species has number of chromosomes
·
a characteristic
↳ most of
eukaryotic cells have two sets
chromosomes (characteristic of sexual
reproduction)
-
one set is maternal (mom) and the
other set is paternal (dad)
>
each chromosome has a
corresponding
chromosome in the other set
together form a homologous pair
-
<
homologs are alike in structure and size
and info codes for the of
the
genetic same set
hereditary characteristics
-
each copy of
pene
a is calledan allele but alleles do not have to
be exactly the same
,·
cells that
carry two gets of information diploid
genetic are
↳
reproductive cells contain one get of
genetic information and are haploid
more than of genetic information called
polyploid
-
two sets is
·
ChromosomeStructure
↳ each unreplicated chromosome consists of one piece of DNA
DNA coils
tightly around histone proteins Schromatin)
-
>
a functional chromosome has three essential elements
1) Centromere serves as an attachment site for microtubules
2) telomeres provide chromosome stability
3)
origins of replication are where protein synthesis begins
<
when chromosomes replicate ,
two identical copies of DNA are formed
called
I
sister chromatics
-
held together at a centromere at various positions :
·
metacentric =
middle/central centromere
>
-
telocentric has position
P-arm only bottom
·
=
-q-arm acrocentric =
most of chromosome is below centromere
·
The cell cycle and mitosis
↳
the cell cycle information
allows for genetic to pass from parent to
Daughter cells
divides
one parent cell to form I
daughters
-
progression through the cell regulated
>
is
cycle
at transition points called checkpoints
prevent damaged cells or cells with incorrect
-
chromosomes from multiplying
·
there cell
are two
major phases in the
cycle :
interphase and the M(mitotic) phase
Interphase is extended period of
growth and development between divisions
·
the
↳ three phases of interphase : G .. S and G
G cell and proteins for cell division
grows
-
:
are synthesized. Ends at G /5 , checkpoint
-
cells can enter the Go non-dividing phase
before the G. /5 checkpoint
-
S :
TNA synthesis where chromosomes are
duplicated
-
G2 :
biochemical events necessary for mitosis .
Cell must
pass G2/M checkpoint to divide
·
M-phase is where sister chromatids are separated
↳ the M-phase has 6 phases the 5 of
:
stages
mitosis(prophase prometaphase metaphase, , ,
er
anaphase and telophase) and cytokinesis
as a cell enters prophase the chromosomes
-
condense -
condensin proteins help condense
, ·
the mitotic spindle forms from centromeres
in prometaphase the nuclear envelope starts to
disintegrate and spindle
-
fibers enter the nuclear
region
·
spindle microtubules are made of tubulin which makes the
microtubules grow and shrink
microtubules attach Kinetochore of sister
·
to the one
chromatic
during metaphase the chromosomes line up on the Metaphase plate and the
-
centromeres center at the poles
·
a
spindle-assembly checkpoint ensures all chromatids are attached and
aligned. Tension must be put on the microtubules to
get past the checkpoint
-
in anaphase the connection between sister chromatids breaks down and the
chromatids separate and move towards opposite poles
in telophase the chromatids are considered chromosomes
-
separate
nuclear membrane reforms forming Nuclei where chromosomes
·
two separate the
relax
in cells is
many cytokinesis simultaneous with telophase
-
,
. 3 Sexual
2 reproduction produces genetic variation through the
process of meiosis
by shuffling the genetic information from two parents genetic variation increases
·
,
↳ meiosis results in
gametes that are haploid and then haploid gametes fuse during fertilisation
·
meiosis
↳ consists of two divisions where formed cells have half the
newly chromosome
number and all
are
genetically different
·
meiosis includes G ,
S and G2 like mitosis But has the two
distinct processes of meiosis I and meiosis It
-
meiogig I is the reduction division because the number of
chromosomes is reduced by half
-
meiosis #I can be termed the equatorial division
·
meiosis It's events are similar to that of Mitogis
·
meiosis I -
reduction division
homologous begin Synapsis (a very
↳
prophase I :
chromosomes pair up and close
pairing association)
-
each
homologous pair of
synapsed chromosomes are called a bivalent or tetrad
and consists of four chromatids
, - the 5 stages of
prophase I
know the names ,
·
order and the basic
events
lepotene chromosomes condense and become visible
-
:
like people Zebras
zypotene :
synapsis of homologs which forms bivalents or tetrads
-
die dramatically
pachytene forms and takes
:
synaptonemal complex crossing over place
-
-
diplotene : centromeres move apart and the chiasmate are visible
-
diakinesis : further chromosome condensation with chiasma terminalisation
>
crossing over is where homologs exchange genetic information in prophase I
creates
penetic variation and is essential the and
for proper alignment separation
-
of
homologs
-
the location where two chromosomes cross is called the Chiasma (plural chiasmatal
when the centromeres of the paired chromosomes apart homologs
·
move ,
the
remain attached at each chiasma
& b
⑧
A D
A B
· cut/cleared
B
by enzymes
AA
crossing
& Bb
B- After
>
metaphase I is where the homologous pairs of chromosomes line up along the metaphase plate
<
anaphase I separates the homologous chromosomes
<
telophase I the chromosomes arrive at the poles and the cytoplasm splits
-
the two cells have half the number of chromosomes as the
original cell
·
meiosis I -
equatorial division
↳ the meiosis [ and meiosis It called interkinesis
period between is where the nuclear membrane
reforms around the chromosomes at each pole and the spindle dissolves
< the cells prophase I
then move through where the effects of interkinesis are reversed
-
chromosomes recondense nuclear ,
membrane breaks down , spindle reforms
<
metaphase II is similar to metaphase in mitosis where the replicated chromosomes line
up on the metaphaphase plate
- in anaphase II the Sister chromatids separate and are pulled to opposite poles
in
>
telophase It nuclear membrane reforms and the
the around the chromosomes
cytoplasm
divides
·
sources of genetic variation in meiosis are crossing over and the random separation of
homologous chromosomes
↳ form of recombination
crossing over is a
chromosomes and cellular reproduction
2
.I Prokaryotic and eukaryotic cells differ in a number of
genetic characteristics
unicellular cell structure
prokaryotes are
organisms with simple
·
a
↳ two bacteria and
groups : archaea
eukaryotic cells have compartmentalized organelles and nucleus that separates
·
a
DNA from the rest of the cell
↳ in histones
eukaryotes the INA is closely associated with to form chromosomes
>
Complex of DNA and histones is called chromatin
histones and DNA fit
regulate the accessibility of INA enable to
-
to enzymes
into the nucleus
in located molecules
eukaryotes multiple DNA
·
genes are on
↳ need a mechanism to ensure a copy of each chromosome is transmitted
. I Cell reproduction
2 of
requires the
copying genetic material ,
separation of the copies, and cell division
for cell to reproduce three fundamental events must take place
any
·
.
3
1 the
genetic information must be copied
2) the copies must be separated from each other NB !
3) the cell must divide
prokaryotic cells reproduce via
binary fission
·
eukaryotic cells undergo complex reproduction due the of
·
more to presence
Multiple chromosomes
↳ each cell must end up with one copy of every chromosome
L the Nuclear Matrix maintains precise spatial regions among the components of the
nucleus
-
takes part in DNA replication and gene modification
, gene expression ,
each
eukaryotic species has number of chromosomes
·
a characteristic
↳ most of
eukaryotic cells have two sets
chromosomes (characteristic of sexual
reproduction)
-
one set is maternal (mom) and the
other set is paternal (dad)
>
each chromosome has a
corresponding
chromosome in the other set
together form a homologous pair
-
<
homologs are alike in structure and size
and info codes for the of
the
genetic same set
hereditary characteristics
-
each copy of
pene
a is calledan allele but alleles do not have to
be exactly the same
,·
cells that
carry two gets of information diploid
genetic are
↳
reproductive cells contain one get of
genetic information and are haploid
more than of genetic information called
polyploid
-
two sets is
·
ChromosomeStructure
↳ each unreplicated chromosome consists of one piece of DNA
DNA coils
tightly around histone proteins Schromatin)
-
>
a functional chromosome has three essential elements
1) Centromere serves as an attachment site for microtubules
2) telomeres provide chromosome stability
3)
origins of replication are where protein synthesis begins
<
when chromosomes replicate ,
two identical copies of DNA are formed
called
I
sister chromatics
-
held together at a centromere at various positions :
·
metacentric =
middle/central centromere
>
-
telocentric has position
P-arm only bottom
·
=
-q-arm acrocentric =
most of chromosome is below centromere
·
The cell cycle and mitosis
↳
the cell cycle information
allows for genetic to pass from parent to
Daughter cells
divides
one parent cell to form I
daughters
-
progression through the cell regulated
>
is
cycle
at transition points called checkpoints
prevent damaged cells or cells with incorrect
-
chromosomes from multiplying
·
there cell
are two
major phases in the
cycle :
interphase and the M(mitotic) phase
Interphase is extended period of
growth and development between divisions
·
the
↳ three phases of interphase : G .. S and G
G cell and proteins for cell division
grows
-
:
are synthesized. Ends at G /5 , checkpoint
-
cells can enter the Go non-dividing phase
before the G. /5 checkpoint
-
S :
TNA synthesis where chromosomes are
duplicated
-
G2 :
biochemical events necessary for mitosis .
Cell must
pass G2/M checkpoint to divide
·
M-phase is where sister chromatids are separated
↳ the M-phase has 6 phases the 5 of
:
stages
mitosis(prophase prometaphase metaphase, , ,
er
anaphase and telophase) and cytokinesis
as a cell enters prophase the chromosomes
-
condense -
condensin proteins help condense
, ·
the mitotic spindle forms from centromeres
in prometaphase the nuclear envelope starts to
disintegrate and spindle
-
fibers enter the nuclear
region
·
spindle microtubules are made of tubulin which makes the
microtubules grow and shrink
microtubules attach Kinetochore of sister
·
to the one
chromatic
during metaphase the chromosomes line up on the Metaphase plate and the
-
centromeres center at the poles
·
a
spindle-assembly checkpoint ensures all chromatids are attached and
aligned. Tension must be put on the microtubules to
get past the checkpoint
-
in anaphase the connection between sister chromatids breaks down and the
chromatids separate and move towards opposite poles
in telophase the chromatids are considered chromosomes
-
separate
nuclear membrane reforms forming Nuclei where chromosomes
·
two separate the
relax
in cells is
many cytokinesis simultaneous with telophase
-
,
. 3 Sexual
2 reproduction produces genetic variation through the
process of meiosis
by shuffling the genetic information from two parents genetic variation increases
·
,
↳ meiosis results in
gametes that are haploid and then haploid gametes fuse during fertilisation
·
meiosis
↳ consists of two divisions where formed cells have half the
newly chromosome
number and all
are
genetically different
·
meiosis includes G ,
S and G2 like mitosis But has the two
distinct processes of meiosis I and meiosis It
-
meiogig I is the reduction division because the number of
chromosomes is reduced by half
-
meiosis #I can be termed the equatorial division
·
meiosis It's events are similar to that of Mitogis
·
meiosis I -
reduction division
homologous begin Synapsis (a very
↳
prophase I :
chromosomes pair up and close
pairing association)
-
each
homologous pair of
synapsed chromosomes are called a bivalent or tetrad
and consists of four chromatids
, - the 5 stages of
prophase I
know the names ,
·
order and the basic
events
lepotene chromosomes condense and become visible
-
:
like people Zebras
zypotene :
synapsis of homologs which forms bivalents or tetrads
-
die dramatically
pachytene forms and takes
:
synaptonemal complex crossing over place
-
-
diplotene : centromeres move apart and the chiasmate are visible
-
diakinesis : further chromosome condensation with chiasma terminalisation
>
crossing over is where homologs exchange genetic information in prophase I
creates
penetic variation and is essential the and
for proper alignment separation
-
of
homologs
-
the location where two chromosomes cross is called the Chiasma (plural chiasmatal
when the centromeres of the paired chromosomes apart homologs
·
move ,
the
remain attached at each chiasma
& b
⑧
A D
A B
· cut/cleared
B
by enzymes
AA
crossing
& Bb
B- After
>
metaphase I is where the homologous pairs of chromosomes line up along the metaphase plate
<
anaphase I separates the homologous chromosomes
<
telophase I the chromosomes arrive at the poles and the cytoplasm splits
-
the two cells have half the number of chromosomes as the
original cell
·
meiosis I -
equatorial division
↳ the meiosis [ and meiosis It called interkinesis
period between is where the nuclear membrane
reforms around the chromosomes at each pole and the spindle dissolves
< the cells prophase I
then move through where the effects of interkinesis are reversed
-
chromosomes recondense nuclear ,
membrane breaks down , spindle reforms
<
metaphase II is similar to metaphase in mitosis where the replicated chromosomes line
up on the metaphaphase plate
- in anaphase II the Sister chromatids separate and are pulled to opposite poles
in
>
telophase It nuclear membrane reforms and the
the around the chromosomes
cytoplasm
divides
·
sources of genetic variation in meiosis are crossing over and the random separation of
homologous chromosomes
↳ form of recombination
crossing over is a
