Chromosome and Cell Division Flashcards
Life depends on the ability of cells to store, retrieve, and translate the genetic instructions required to make and maintain a living organism. This hereditary information can be passed on from a cell to its daughter cells during ___ ___
cell division
its genetic material is usually concentrated in a specific clear region of the cytoplasm called nucleiod.
prokaryotes
The prokaryotic (bacteria) genetic material is usually concentrated in a specific clear region of the cytoplasm called
nucleoid
is a single, circular, double stranded DNA molecule mostly attached to the plasma membrane.
bacterial chromome
characteristics of The bacterial chromosome
single
circular
dsDNA
the bacterial chromosome is mostly attached to the ___
plasma membrane
does bacterial chromosome have histone protein?
no
Besides the chromosomal DNA many bacteria may also carry extra chromosomal genetic elements in the form of small, circular and closed DNA molecules, called
plasmids
extra chromosomal genetic elements in the form of small, circular and closed DNA molecules
plasmids
plasmids are extra chromosomal genetic elements in the form of ___ , ___and ___DNA molecules
small
circular
cclosed
These generally remain floated in the cytoplasm and bear different genes.
plasmids
While the ___cell has genetic material in the form of genomic DNA enclosed within the nucleus.
eukaryotic
Genes or the hereditary units are located on the chromosomes which exist as ___ ___in the non-dividing cell/interphase.
chromatin network
revealed that during cell division the nuclear material organize themselves into visible thread like structures which were named as chromosomes which stains deep with basic dyes
Walter Flemming
Walter Flemming in the early 1880s revealed that during cell division the nuclear material organize themselves into visible thread like structures which were named as
chromosomes
chromosomes are stained with basic/acidic dyes
basic
The term chromosome was coined by
W. Waldeyer-Hartz
Chrome in chromosome means
coloured
soma in chromsome means
body
chromosome literally means
colored bodies
can be defined as higher order organized arrangement of DNA and proteins.
chromosomes
It contains many genes or the hereditary units, regulatory elements and other nucleotide sequences.
chromosomes
Chromosomes also contain DNA-bound proteins called
histones
which serve in packaging the DNA and control its functions
histones
reported that the number of chromosomes in each species is constant
Benden
Bovery
suggested that chromosomes are the physical structures which acted as messengers of heredity in 1902
Walter Sutton
Theodor Boveri
Each of the chromosomes is composed of ___ chromatids
sister
Each of the chromosomes is composed of sister chromatids. It has a “waist line” called
centromere or primary constriction
the site where the kinetochore proteins attach
centromere or primary constriction
is the site of the spindle fiber attachment.
kinetochore
The centromere occupies a middle position with reference to the length of the chromosome.
metacentric
The two arms thus resulted are almost equal in length.
metacentric
During anaphasic movement in cell division, metacentric chromosomes appear ‘__’ shaped.
V
When the centromere is located some distance away from the middle region of the chromosome, one chromosome arm will be shorter than the other.
submetacentric
During anaphasic movement, sub metacentric chromosomes appear ‘___’ shaped.
L
In this case, the centromere is situated almost near one end of the chromosome.
acrocentric
As a result, one arm of the chromosome will be extremely short and the other very long.
acrocentric
The centromere is said to occupy a subterminal postion.
acrocentric
When the centromere is situated exactly at one end, the chromosome will be having only one long arm.
telocentric
chromosomes that are very rare
telocentric
There are normally ___copies of each chromosome present in every somatic cell.
two
The number of unique chromosomes (n) in such a cell is known as its
haploid number
the total number of chromosomes (2n) is its
diploid number
‘ploid’ means
sets
is also known as the genome.
haploid set
In a ___cell, there are two of each kind of chromosome (termed homologous chromosomes) except the sex chromosomes
diploid
In humans there are ___pairs of homologous chromosomes (2n=46). T
23
non-sex chromosomes, termed ___
autosomes
one pair of homomorphic chromsome called
sex chromosome
of the same or similar form.
homomorphic
occurring in two or more different forms, especially at different stages in the life cycle.
heteromorphic
is a series of events that takes place in a cell as it grows and divides.
cell cycle
A cell spends most of its time in what is called
interphase
and during this time it grows, replicates its chromosomes, and prepares for cell division.
interphase
The cell then leaves interphase, undergoes mitosis, and completes its division. The resulting cells, known as ____ each enter their own interphase and begin a new round of the cell cycle.
daughter cells
Nucleus at ___is very distinct and enclosed by a define nuclear membrane
interphase
Within the nucleus are one or more small round dense bodies called ___ and a granular network of darkly stained material called ____
INTERPHASE
nucleoli
chromatin
At interphase, there are three stages that are not morphologically distinguishable but biochemically distinct.
gap 1
synthesis phase
g2
The nucleus and cytoplasm are enlarging toward mature size.
what stage of interphase
g1
The cell increases in volume by imbibing water & nutrients and building of new protoplasm.
what stage of interphase
g1
what cytoplasmic organelles are formed
endoplasmic reticulum
golgi apparatus
mitochondria
chloroplast
The DNA content C becomes 2C after this phase.
s phase
Each ___ fiber is replicated or doubled in s phase
chromatin
There is active synthesis of RNA and proteins necessary for chromosome synthesis.
what stage
G2
Mitotic spindles are also formed.
G2
The double chromatin fiber is packed to form
a chromosome, the colored bodies during cell division.
what stage
G2
The double chromatin fiber is packed to form
a \_\_\_, the colored bodies during cell division.
chromosome
is undergone by all somatic cells and sex cells.
mitosis
In multicellular organisms, it is a means of increasing the number of cells by replacing worn out tissues.
mitosis
In unicellular organisms, it is simple a mode of reproduction
mitosis
four distinct stages of mitosis
prophase
metaphase
anaphase
telophase
The chromosomes shorten, thicken and become visible as thick rods.
prophase
The chromosomes are ___double, each half is a chromatid in prophase
longitudinally
Nucleoli and nuclear membrane completely disappear by what stage of prophase.
late
In animal cell, this divides and spindle radiates from the aster during prophase.
centriole
The nuclear membrane disappears and spindle fiber soon appears.
what stage of mitosis
metaphase
The chromosomes which are maximally condensed align at the equatorial plane.
metaphase
The spindle fibers attach on the opposite sites of the centromeres.
metaphase
The centromeres become functionally double
anaphase
The chromatids of the chromosomes begin to move towards the opposite poles.
anaphase
The poleward movement of the chromosomes is due to the ___of the spindle fibers attached to the centromeres.
depolymerization
Upon reaching the opposite poles, the chromosomes regroup into two nuclear structures.
telophase
The chromosomes begin to uncoil & lengthen and finally lose their visible identity.
telophase
usually follows mitosis.
cytokinesis
In ____, the cytoplasm is divided by cell plate formation where separation starts from the inside of the cell towards the periphery
plants
In plants, the cytoplasm is divided by cell plate formation where separation starts from the ___ of the cell towards the ___
inside
periphery
In ____, cell cytokinesis occurs by furrowing or cleavage formation that starts from the periphery.
animals
In animals, cell cytokinesis occurs by furrowing or cleavage formation that starts from the ___.
periphery
In animals, cell cytokinesis occurs by ___ or ___formation that starts from the periphery.
furrowing
cleavage
is also preceded by G1, S and G2 of the cell cycle. It consists of two divisions which follow each other in rapid sequence.
meiosis
also referred to as reductional division, involves the separation of homologous chromosomes resulting in two cells with haploid chromosome number.
meiosis I
involving only the separation of chromatids producing four haploid cells. This is also known as equational division.
meiosis
Prophase I has five distinct substages:
leptotene
zygotene
pachytene
diplotene
diakinesis
The chromosomes appear as long threads with many bead-like structures (chromomeres) along their length.
leptotene
In some plants, the chromosomes are clumped on one side of the nucleus
leptotene
the chromosomes are clumped on one side of the nucleus a phenomenon called
synizesis
while in some animals, it tends to be drawn towards the part of the nuclear membrane close to the centriole during leptotene
choromosome
Synapsis or pairing of homologous chromosomes begins.
zygotene/zygonema
The paired chromosomes form a ___consisting of four chromatids.
bivaent
The paired chromosomes form a bivalent consisting of four chromatids.
zygotene
is very precise so that homologues pair side by side during zygotene
synapsis
is formed in between homologous pair that is essential in crossing over.
synaptonemal complex
is a meiosis-specific protein structure that forms between homologous chromosomes during prophase I of meiosis, mediating synapsis and facilitating meiotic recombination and crossover formation.
synaptonemal complex
The chromosomes are thicker due to further coiling.
what stage of meiosis I
pachytene
The two chromosomes in a bivalent are closely appressed.
pachytene
Chromatid breaks and their repair occur along the chromosome.
pachytene/pachynema
Repairing of breaks may entail exchange of segments between sister and non-sister chromatids in a bivalent.
what stage in prophase I
pachytene
This is known as crossing-over which is cytologically observed through formation of chiasma at the point of exchange. Crossing-over generates variation in the population.
pachytene
With the synaptonemal complex no longer functional, the longitudinal separation of homologues in a bivalent starts from the centromere and proceeds toward both ends except at the chiasma
what stage of prophase I
diplotene
Bivalents are maximally condensed and distributed throughout the nucleus
what stage in prophase I
diakinesis
By the end of this stage, nucleolus and nuclear membrane have disappeared, the spindle has formed and Prophase I is completed.
diakinesis
The bivalents align at the equatorial plane.
metaphase I
The bivalents are so oriented that each homologue is on each side of the metaphase plane with their centromeres attached at the spindle fibers.
metaphase I
The univalent (or homologue) in each bivalent separate from each other.
anaphase I
Movements of the univalent to the opposite poles is due to depolymerization of the spindle fibers.
what stage of Meiosis
anaphase I
The homologues segregate from one another so that each ___ group is composed of haploid number (n) chromosomes
anaphase
This process accounts for the reductional phase of Meiosis I.
anaphase I
The chromosomes regroup and their structures begin to relax.
telophase I
The nuclear membrane as well as nucleolus reappear forming two haploid daughter cells.
Telophase I
In some species, no ___happens after Meiosis I.
cytokinesis
A brief transitional stage called ____ occurs before the cell proceeds to the next stage.
interkinesis
The division proceeds in a manner similar to mitosis except that there are two haploid cells (from meiosis I) that undergo each stage.
meiosis II
The chromosomes begin to condense. The nucleus and nuclear member disintegrate in Meosis II
prophase II
Spindle fibers are formed and the chromosomes align at the equatorial plane in meiosis II
metaphase II
Sister chromatids of a univalent separate and proceed to the opposite poles as individual chromosomes in Meiosis II
anaphase II
Chromosomes uncoil and lengthen, nuclear membrane and nucleolus reappear in Meiosis II
telophase II
follows, forming four cells with haploid chromosome number.
cytokinesis
the production of sperm and eggs
gaemetogenesis
During meiosis, two cell divisions separate the paired chromosomes in the nucleus and then separate the chromatids that were made during an earlier stage of the cell’s life cycle, resulting in gametes that each contain __the number of chromosomes as the parent.
half
he production of sperm is called
spermatogenesis
and the production of eggs is called
oogenesis
study how to count gametogeness
+1
