Module 1 Flashcards
pre-existing cells divide to form new cells
Cell Division / Cell Reproduction
the entire sequence of events happening from the end of one nuclear division to the beginning of the next.
Cell cycle
DNA synthesis alternates with mitosis
Chromosome cycle
Cell growth alternates with cytokinesis
Cytoplasmic cycle
cytoplasmic and chromosome cycle require the centrosome to be inherited and duplicated precisely to form mitotic spindle
Centrosome cycle
four phases of cell cycle
G1, S, G2, M
cells that
- have distinct nuclei complete with intact nuclear envelope
- chromosomes occur in the form of diffused, long, coiled and indistinctly visible chromatin fibers
- DNA amount becomes double during this time
- nucleolus size is greatly increased
Interphase cells
loose DNA coiled around histones
look like beads on a string
Nucleosomes
coiled nucleosomes
is organized tighter by protein scaffold to form the condensed chromosome
Solenoid fiber
loose, thin and long; a DNA
Chromatin
condensed chromatin to make the process of segregation possible during M phase
Chromosomes
first order of DNA packaging in the nucleus
Chromatin Primary Structure
is a histone octamer composed of 2 copies of H2A, H2B, H3 and H4
is composed of 146 base pairs (bp) of superhelical DNA
nucleosome
are proteins which are rich in lysine and arginine residues and are thus positively-charged, the main reason that they can bind tightly to the negatively-charged phosphates in DNA
responsible for tightening the binding of the DNA
Histones
between nucleosomes
approximately 20 to 90 bp and varies among different species, tissues, and even fluctuates within a single cellular genome.
linker DNA
what structure
- solenoid fiber
driven by salt and intrinsic nucleosome-nucleosome and
nucleosome DNA interactions and is stabilized by linker histones.
Chromatin Secondary Structure
what structure
-is formed from interactions between discrete secondary chromatin structures
Chromatin Tertiary Structure
Parts of Chromosome
centromere, telomere, arm
a region of repetitive nucleotide sequences at each end of a chromatid
protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes
Telomere
Type of chromosome
centromere is in the middle and the chromosome arms are of equal length.
When a chromosome of this type is pulled to one pole during cell division, it appears V-shaped.
Metacentric
Type of chromosome
near the middle and the chromosome arms slightly vary in length
When pulled to one pole, this type of chromosomes appeared L-shaped
submetacentric
type of chromosome
centromere is near one end and the arms clearly vary in length; thus, p and q arms are easily distinguishable.
When a chromosome of this type is pulled to one pole during cell division, it appears J-shaped
acrocentric
type of chromosome
centromere is at one end and there is only 1 chromosome arm.
Thus, when pulled to one pole, this chromosome appears I shaped.
telocentric
what chromosomes belong in
- large metacentric
- large submetacentric
- medium submetracentric
- medium acrocentric
- short submetacentric
- short metacentric
- short acrocentric
A: 1-3
B: 4,5
C: 6-12, X
D: 13-15
E: 16-18
F: 19-20
G: 21-22 and Y
- a resting phase
- first gap phase since no DNA synthesis
- also called first growth phase
- synthesis of RNA, proteins and membranes
- leads to the growth of nucleus and cytoplasm of each daughter cell
- transcription of three types of RNAs, namely rRNA, tRNA and mRNA
- 30-50 total time
G1 phase
Terminally differentiated somatic cells that no longer divide, are arrested usually in the G1 stage; such a type of G1 phase is called _________
G0 phase
- synthetic phase
- replication of DNA
- synthesis of histone proteins
- occupies roughly 35 to 45 percent of cell cycle.
S phase
- a second gap or growth phase or resting phase
- synthesis of RNA and proteins continues
-10 to 20 percent time
G2 phase
is a short period of chromosome condensation, segregation and cytoplasmic division.
occurs in the somatic cells and it is meant for the multiplication of cell number during embryogenesis and blastogenesis of plants and animals
M phase or Mitotic phase
what stage in mitotic phase
- Chromosomes condense and become visible
- Spindle fibers emerge from the centrosomes
- Nuclear envelope breaks down
- nucleolus disappers
prophase
what stage in m phase
• Chromosomes continue to condense
• Kinetochores appear at the centromeres
• Mitotic spindle breaks down microtubules attach to kinetochores
• Centrosomes move toward opposite poles
prometaphase
- mitotic spindle is fully developed, centrosomes are at opposite poles of the cell
- chromosomes are lined up at the ____________ plate
- each sister chromatid is attached to a spindle fiber originating from opposite poles
metaphase
- cohesin proteins binding the sister chromatids together break down
- sister chromatids (now called chromosomes) are pulled toward opposite poles
- Non-kinetochore spindle fibers lengthen, elongating the cell
anaphase
- chromosomes arrive at opposite poles and begin t o decondense
- nuclear envelope material surrounds each set of chromosomes
- the mitotic spindle breaks down
telophase
animal cells: a cleavage furrow separates the daughter cells
plant cells: a cell plate separates the daughter cells
cytokinesis
primary point at which cell must choose whether or not to divide
checks for cell size, availability of nutrients, DNA damage or replication errors
G1 checkpoint
checks if cells already have all the requirements for division
checks for DNA damage and whether DNA replication has really been completed
G2 checkpoint
checks if all chromosomes are properly attached to the mitotic spindle
M checkpoint or spindle checkpoint
—the constriction of cytoplasm into two separate cells
- usually begins in anaphase and continues through telophase and into interphase.
The first sign of cleavage in animal
cells is puckering and furrowing of the plasma membrane during
anaphase.
Cytokinesis or cytoplasmic division
During cytokinesis, the cytoplasm divides by a process, called
cleavage
is the longest stage of the meiotic division
first prophase
Prophase I includes following substages (5)
Leptotene/leptonema
Zygotene/zygonema
Pachytene/pachynema
Diplotene/diplonema
Diakinesis
In the ___ substage of prophase I, chromosomes become more uncoiled and assume a long thread-like shape.
Along each chromosome are ___, localized condensations that resemble beads on a string.
Leptotene/Leptonema
chromomeres
In the ___ substage of prophase I, The pairing of homologous chromosomes takes place. These chromosomes come from the mother (___) and father (___).
This pairing is known as ___.
Zygotene/Zygonema
Oocyte
Sperm
Synapsis
Types of synapsis (3)
Proterminal synapsis
- end to centromeres
procentric synapsis
- centromeres to ends
localized pairing / random synapsis
- various points
The homologous chromosomes are joined by a roughly 0.2um thick protein-containing framework called a ___.
synaptonemal complex (SC)
upon completion of
zygonema that the paired homologs are
referred to as ______________
bivalents or tetrads
Organisms in which crossing over does not occur and therefore has no synaptonemal complex
Drosophila melanogaster
In the ___ substage of prophase I, the pair of chromosomes continue to coil and shorten and further development of the synaptonemal complex.
This is where the important genetic phenomenon called “___” takes place. Reshuffling and redistribution and mutual exchange of hereditary material.
Pachytene / Pachynema
Crossing over
In pachytene,
Chromatids may divide transversely by the help of an enzyme called the ___.
Broken chromatid segments are united by the enzyme ___.
Endonuclease
Ligase
In the ___ substage of prophase I, The synaptonemal complex disassembles and the homologous chromosomes begin to move apart.
The ___ shows the result of crossing-over. This is where homologous chromosomes are very tightly associated.
Diplotene/Diplonema
Chiasma
___ is followed rapidly by the remaining stages of meiosis. However, in many animals the oocytes can remain in that form.
Diplonema
In the ___ substage of prophase I, the chromosomes condense even more making it now posssible to see the four members of the tetrads
The chiasmata are clearly visible at this stage.
The nucleolus detaches and disappears. Nuclear envelope breaks down.
diakinesis
In diakinesis, Chiasma moves from centromere towards the end of the chromosomes and the immediate chiasmata diminish, this is called ___.
Chromatids remain connected to the terminal chiasmata up until metaphase
Terminalization
T or F: The synapsis and crossing-over phenomena applies only to homologous chromosomes the autosomes.
False, this can also apply to the Y chromosome of eutherian (placental) mammals.
This is due to their PARs or (Pseudo-autosomal regions) which is very important otherwise it will make the man sterile.
During the ___ stage, the microtubules of the spindle are attached to the ___ at the ___ of the homologous chromosomes of each tetrad, aligning chromosomes at the equator.
Centromere is directed towards the opposite poles. The repulsive forces between the homologous chromosomes increase greatly and the chromosomes become ready to separate
Metaphase I
kinetochores
centromeres
During the ___ stage, homologues are freed from each other due to the shortening of chromosomal fibers or microtubules.
Chromosomes with less terminal chiasmata separate more frequently.
The two chromatids of a chromosome do not resemble each other genetically
Anaphase I
During the ___ stage, a haploid set of chromosomes arrive at each pole.
Nuclei are then reassembled.
___ forms near the nuclear envelope around the chromosomes and the chromosomes become uncoiled.
The ___ reappears and thus two daughter ___ are formed.
Karyokinesis and cytokinesis occur and two haploid cells are formed.
Short interphase occurs
Telophase I
endoplasmic reticulum
Nucleolus
Nuclei
During the ___ stage, each centriole divides into two and thus two pairs of it are formed. Each pair migrates to the opposite pole, microtubules form a spindle again.
Nuclear membrane and Nucleolus disappear
Prophase II
During the ___ stage, chromosomes arrange themselves on the equator. Chromosome produces two monads or daughter chromosomes. Spindle attach to centromere through kinetochore.
Metaphase II
During the ___ stage, daughter chromosomes move towards the opposite poles due to the shortening of the ___ and stretching of ___ of the spindle.
Anaphase II
chromosomal microtubules
interzonal microtubules
During the ___ stage, endoplasmic reiculum forms nuclear envelope around chromosome and nucleolus reappears. Karyokinesis and cytokinesis occur and Four haploid cells are formed.
Telophase II
Significance of meiosis (2)
- definite number of chromosomes in organisms
- Crossing over allows exchange of genes thus variation
Q
Meiosis occurs in the ___ cells of sexually reproducing organisms. And these cells are localized in the ___.
Germ
Gonads
___ or ___ is found in animals and a few lower plants. Meiotic division occurs immediately before the formation of gametes or gametogenesis.
Meiosis takes place in the gonads and results in the formation of gametes
Terminal or Gametic meiosis
During this type of life cycle, a reproductive cell reproduces haploid gametes (egg and sperm) to make zygote.
Gametic life cycle
___ or ___ is characteristic of flowering plants. Just before flowering or between fertilization and formation of gametes. It is involved in the production of ___ in ___ (___) and ___ in ___ or ___(___)
Intermediary or sporic meiosis
microspores in anthers (microsporogenesis)
megaspores in ovary or pistil (megasporogenesis)
Long dominant diploid and multicellular generation :
Short, multicellular haploid generation:
Sporophyte
Gametophyte
___ or ___ occurs in some algae, fungi, and diatoms. Meiotic division occurs immediately after fertilization. The most simple sexual life cycle is called the ___.
These organisms are ___ during most of their life cycle. The zygote is the only ___ phase.
Initial or zygotic meiosis
zygotic life cycle
Haploid
Diploid
Applications of Genetics (7)
Agriculture
Production of transgenic organisms
Medicine
Legal applications
Industries
Humans
Environment
Selective breeding has been practiced for a while now. Fruits have longer shelf life. Animals are bigger, can give more meat and can produce more milk. All of these can be translated as an increase in food
production.
agriculture
These are organisms that are formed by combining the genes of different organism.
are resistant to pests and diseases
can be produced with inserted genes for human growth hormone (HGH) to make them grow large very fast, shortening the developmental period and increasing yield and
income at a shorter time.
The production of transgenic organisms
Genetics has been used in the accurate diagnosis of
diseases, especially in the case of inherited diseases. The use of
genetics in medicine has also led to the identification of drug
sensitivities, prevention of use of medicine or even disease
prevention.
medicine
This includes the use of gathering samples and
doing DNA testing on them to identify the possible perpetrators of a crime, or to check parentage of a child.
Legal applications.
Genetics has provided some synthetically produced raw materials for industries. For example, the brewing industry may use geneticists to improve the strains of yeast that product the
alcohol. The pharmaceutical industry has developed strained of molds, bacteria and other microorganisms which have high antibiotic yield.
industries
All of the benefits mentioned above benefit humans
______ can also address deficiencies by having corrections done to the baby’s genetic structure.
Life span of humans have also been increased due to availability of vaccines,
medications and vitamins, among others.
In humans.
Gene therapy
The environment has benefited from the availability of genetically modified microorganism which have the capability to
degrade waste materials rapidly.
The process of ______________
which refers to the use of either naturally occurring or deliberately
introduced microorganisms or other forms of life to consume and
break down environmental pollutants, in order to clean up a polluted
site.
Environment;
bioremediation
