Chap 2- Meiosis and Mitosis Flashcards
In living organisms, what is the genetic material made up of?
Nucleic acid DNA
What units are DNA organized into? What do these units do?
DNA is organized in units called genes. Genes direct metabolic activities of cells.
What does the transmission of genetic material in Eukaryotic cells involve?
Meiosis and Mitosis
What is Mitosis?
The production of two different cells (2n). The two cells contain the same number of chromosomes and chromatid as their parent.
What is Meiosis?
The production of gametes. Half the number of chromosomes are produced (n).
When are chromosomes visible as condensed structures?
During Meiosis and Mitosis
What is chromatin?
It is uncoiled chromosomes that diffuse network with the nucleus.
What are the two main type of cells?
Eukaryotic (bacteria, archae) and Prokaryote (Protisist, plants, fungi, animal)
What are the common features shared in cells?
DNA, Plasma membrane, ribosome
What are cells surrounded by? What is its purpose?
Cells are surrounded by a semipermeable membrane. It’s purpose is to protect/ create a boundary, delimit the cell from its environment, surround by a covering (glycocalyx),
(Plants have a cell wall composed of cellulose).
What is glycocalyx?
Defines the biochemical identity of each cell
What does the nucleus contain?
DNA (proteins into thin fibers- chromatin) and nucleolus (rRNA synthesized and assembled)
During Mitosis and Meiosis, what happens to chromatin?
It coils and condenses to form chromosomes
What is the eukaryotic cell enclosed by, except nucleus?
Cytoplasm
What is the purpose of cytoskeleton?
Provides structure to cytoplasm.
Maintains shape, mobility, and anchors organelles
Made up of microtubules and microfilaments
What is the purpose of the endoplasmic reticulum (ER)>
compartmentalizes the cytoplasm
What is the purpose of smooth ER?
Site of lipid synthesis
What is the purpose of Rough ER?
Studded with ribosomes, sites of protein synthesis
What is the purpose of Golgi Apparatus?
Receives, refines, and distributes products from the ER.
( Like an EMT picking up, making sure, and leaving the injured to the ER )
What is the purpose of mitochondria?
The site of cell respiration, found in both plants and animal cell
It is also the site of ATP synthesis
POWERHOUSE OF THE CELL.
What is the purpose of chloroplast in plant, algae and some protozoan?
The site of photosynthesis
What do mitochondria and chloroplast both contain?
DNA similar to prokaryotic DNA
Where are centrioles in the cytoplasm located?
In the centrosome in animal cells
What is the purpose of centrioles?
To organize spindle fibers for movement of chromosomes during meiosis and mitosis
When do somatic cells contain the same number of chromosomes?
for members of the same species
Where do chromosomes exist?
In homologous pairs in diploid organisms
What are homologous chromosomes?
Similar copies of each other; One chromosome of the homologous pair is from the father (via the sperm) and the other from the mother (via the egg)
Alleles
different versions of the same gene
What is karyotype?
The creation of a photographed, cutting and matching a mitotic chromosome
What is each chromosome structurally made up of?
Two sister chromatids connected at the centromere
What is the purpose of Mitosis?
Asexual reproduction for many single-celled organisms such as protozoan, fungi, algae.
In multicellular, it is responsible for wound healing, cell replacement, and growth
What happens in mitosis for genetic material?
It divides into two nuclei (karyokinesis)
After karyokinesis, what follows?
cytoplasmic division (cytokinesis)
What is the cell composed of?
Interphase (G1, S, G2) and mitosis
Where does the S phase occur?
In the nucleus, where DNA is duplicated
Where do G1 and G2 occur?
In the cytoplasm
By the end of G2, what occurs?
Cell has doubled in size (DNA duplicated, mitosis initiated)
Where is G0?
In G1- cells withdraw from the cell cycle and enter nondividing, metabolically active state
What happens in G1 Phase?
The first “gap” phase. Size and protein content of the cell increase and prepare for S phase. Many regulatory proteins are made and activated.
What occurs in S phase?
“Synthesis” phase, entire DNA in the nucleus of the cell is replicated
What occurs in G2 Phase?
Second “gap phase”, cell prepared for mitosis and cytokinesis
What occurs in G0 phase?
No active preparation taking place but within G1, in a way. This phase is present in all cell types that do not actively divide.
Example: Muscle, eye, nerve cells, etc.
What are sister chromatids?
Two parts of each chromosome. They are identical and visibly connected at centromere
What is cohesion?
Protein complex that holds sister chromatids together. Formed during S phase.
Stages in mitosis?
Prophase, Prometaphase, Metaphase, Anaphase, Telophase
What occurs in Prophase?
Chromosomes: Condense and become chromosomes
Centrosomes: radiate microtubules and migrate to opposite poles
Nuclear envelope: Breaks down
What occurs in prometaphase?
Microtubules of spindle attach to chromosomes
What are kinetochore?
Where spindle fibers attach to kinetochore (protein layers) and move chromosomes
During Prometaphase/Metaphase, what occurs to the structure of chromatic, etc?
-Cohesion is degraded by enzyme separase
- Sister chromatid arms disjoin except at centromere
Enzyme shugoshin prevents degradation of cohesion at centromere
What occurs during metaphase?
Chromosomes align in the center of the cell
What occurs during anaphase?
Centromeres split and sister chromatids separate from each other (disjunction); they are no longer chromatids, but daughter chromosomes
In anaphase, how do we know complete disjunction has occurred?
-Shugoshin degards
-Cohesion complex is cleaved by separase
- Sister chromatids are pulled toward opposite poles of cell
What occurs during Telophase?
The final stage of two complete sets of chromosome, one set at each pole.
- Cytokinesis partitions the cytoplasm, (cell plate in plants, furrow in animal)
- Chromosomes uncoil
-Nuclear envelope re-forms and so does the nucleolus
-Spindle fibers disappear
END OF MITOSIS.
What is the cell cycle genetically regulated by? What happens if it is not regulated?
Three major checkpoints. If not regulated, it can lead to uncontrolled cell division characterizing malignancy.
What are kinases?
Enzymes that serve as a “master control”
What do kinases bind to?
Cyclins (protein). It activates them at appropriate times during the cell cycle.
What does Meiosis do?
reduces the amount of genetic material by half. It produced haploid gametes or spores containing one member of each homologous pair of chromosomes.
What does Meiosis maintain?
Genetic continuity from generation to generation and gives rise to genetic variation in gametes by crossing over, and unique combination (independent assortment)
What does fertilization restore?
The diploid number
What does Meiosis begin with?
A diploid cell (DNA duplicated during interphase, chromosomes made up of sister chromatids)
What is the unique full structure of Meiosis?
It comprises two division: Meiosis I (Reduction division) and Meiosis II
What is the exception for mitotic prophase and Meiosis to not be similar?
homologous chromosomes pair up (synapsis)
What is the purpose of synapsis?
gives rise to a tetrad (two pairs of sister chromatids) with overlapping nonsister chromatids (chiasma)
- exchange of genetic material through recombination
What do the tetrad attach to?
spindle fibers
What occurs in Prophase I of Meiosis I?
-Chromosomes become visible as thin threads. DNA replication is already complete
-Homologous chromosomes continue to condense and undergo synapsis (gene for gene pairing)
-After synapsis tetrads are formed. Each chromosome consists of two sister chromatids
- Chromosomes continue to shorten and thicken and chiasmata b/w non-sister chromatids become apparent
-Nuclear envelope begins to break down and spindle is forming
What occurs in Metaphase I of Meiosis?
Homologous pairs of chromosomes orient randomly, chiasma are visible holding nonsister chromatids together
What does crossing over produce?
recombinant chromosomes, combine DNA inherited from each parent
-Begins in prophase I as homologous chromosomes pair up gene by gene
-Homologous portions of two nonsister chromatids trade places
-Contributes to genetic variation by combining DNA from two parents into a single chromosome
What occurs in prophase II of Meiosis II?
Chromosomes are composed of one pair of sister chromatids attached by a common centromere, nuclear envelope breaks down
What occurs during Metaphase II during Meiosis II?
Centromere is positioned at the metaphase plate
What occurs during Anaphase II during Meiosis II?
Centromeres divide; sister chromatids are pulled to opposite poles
What occurs during Telophase II during Meiosis II?
Cytokinesis results in four haploid gametes with equal cytoplasm, containing a combination of maternal and paternal genes
Where does spermatogenesis take place?
Testes
Where does Oogenesis take place?
Ovary
What is spermatogonium and what does it become?
An undifferentiated germ cell that enlarges to become a primary spermatocyte
What does the primary spermatocyte undergo?
Meiosis I to produce haploid secondary spermatocytes
What does secondary spermatocytes undergo?
Meiosis II; producing a total of four haploid spermatids that undergo developmental changes and become highly specialized, motile spermatozoa or sperm
What is oogonium and what does it become?
An undifferentiated germ cell that enlarges to become a primary oocyte
What is polar body?
The cell with little to almost no cytoplasm; it will ultimately disintegrate
What does secondary oocyte receive?
the bulk of the cytoplasm
What does the secondary oocyte undergo?
Meiosis II, produced two haploid cells
-1st polar body may or may not divide
-All polar bodies will eventually disintegrate with only one function cell remaining
