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[h] IB DP Biology HL D2.1 Cell and nuclear division Flashcards
[q] Parent Cell
[a] original cell/mother cell before cell division and produces two daughter cells
[q] Daughter Cell
[a] The product of cell division.
[q] Cytokenesis
[a] The splitting of the cytoplasm of a parent cell to form two daughter cells.
Each nucleur division is followed by cytokenesis.
[q] Cleavage Furrow
[a] The area of the cell membrane that pinches in and eventually separates the dividing cell using myosin and actin
[q] Cell plate
[a] Cytokenesis in plants form vesicles of carbohydrates from the Golgi apparatus along the equator of the cell and fuse to form a cell plate and forms two separate cells, cellulse is secreted into the cell plate to form the cell wall of the new cells.
[q] Oogenesis
[a] Formation of eggs in females.
Oogenesis involves unequal division of cells during meiosis to produce one large egg cell
[q] Budding
[a] In yeast, it is a form of asexual reproduction where a small daughter cell buds off a larger cell by cytokenesis
[q] Mitosis
[a] Nuclear division which produces two genetically identical daughter nuclei.
Parent cells undergoes Cytokenesis after mitosis.
[q] Mitosis is required for?
[a] growth and development (including embryological development)
Tissue repair as new cells are produced to replace dead cells
Asexual reproduction in unicellular (one cell) eukaryotic (with nucleus) organisms.
[q] Meiosis
[a] Nucleur division which produces four daughter cells, each with half the number of chromosomes as the parent cell.
It is required for he production of gametes for sexual reproduction.
[q] Gametes
[a] Produced by meiosis, sex cells (egg and sperm)
[q] Spores
[a] Produced by meiosis. Grow into haploid organisms by mitosis.
[q] Zygote
[a] a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.
[q] Anucleate Cell
[a] A cell without a nucleus
[q] DNA Replication
[a] The production of two identical copies of a DNA molecule.
Must occur before mitosis and meiosis and held together by a centromere.
[q] Sister chromatids
[a] Two identical copies of a duplicated chromosome;
seperated during Anaphase of mitosis and Anaphase II of meiosis to form individual chromosomes
[q] Condensation of Chromosomes
[a] Chromatin condenses to form visible chromosomes, with sister chromatids during prophase of mitosis and prophase I and II of meiosis.
During condensation, DNA coils around historic proteins to form nucleosomes.
The nucleosomes coil around each other to form chromosomes with sister chromatids.
Condensation of chromosomes allows for segregation of chromosomes during mitosis and meiosis
[q] Microtubules
[a] Spiral fibres of protein molecules that form a tubelike structure and attach to the centromeres of chromosomes by kinetochore during prophase of mitosis and meiosis.
[q] Microtubule motors
[a] on kinetochores and move the chromosomes to the poles during anaphase
[q] Interphase
[a] the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis.
[q] Nucleosome
[a] repeating subunit of chromatin fibers, consisting of DNA coiled around histones
[q] Histone protein
[a] A simple protein bound to DNA, involved in the coiling of chromosomes
[q] spindle fibers
[a] Protein structures which move the chromosomes during cell division.
[q] Prophase (mitosis)
[a] Chromosomes condenses to form chromosomes which are visible under a light microscope.
The chromosomes are composed of two identical sister chromatids attached to a centromere and the nucleur membrane breaks down.
The centrioles move towards the poles producing spindle fibres, then the chromosomes attached to the spindle fibres at the centromeres.
[q] Metaphase (mitosis)
[a] The chromosomes line up along the equator of the cell attached to spindle fibres
[q] Anaphase (Mitosis)
[a] The spindle fibers seperate the sister chromatids at the centromere to form single stranded chromosomes.
The microtubule motors on the kinetochore, attached to centromeres, move chromosomes to opposite poles of the cell.
[q] Telophase (mitosis)
[a] Chromosomes arrive at the poils of the cell.
Nucelur membranes form around the set of chromosomes at each pole.
The chromosomes uncoil to form chromatin.
Two genetically identical nuclei are produced.
Cytokenesis begins during telophase to produce two genetically identical daughter cells.
[q] Diploid
[a] 2 sets of chromosomes (2n).
A diploid cell has a nucleus with two sets of chromosomes.
Each chromosomes will have a matching homolog (similar in position, structure, and evolutionary origin but not necessarily in function.)
[q] Haploid
[a] having a single set of unpaired chromosomes
[q] Reduction division
[a] Meiosis is known as a reduction division as the parent cell is diploid and the daughter cells are haploid and meiosis reduces the number by half, in the nucleus of the daughter cells.
[q] Homologous chromosomes
[a] Chromosomes that have the same sequence of genes and the same structure by may have different alleles
[q] Bivalents
[a] The paired chromosomes that result from the pairing of homologous pair.
The non-sister chromatids cross over during the formation of bivalents, exchanging sections of non-sister chromatids.
[q] Meiosis 1
[a] Segregates the homologous chromosomes to produce two haploid cells
[q] Meiosis II
[a] Segregates the sister chromatids producing four haploid cells
[q] Prophase I (meiosis 1)
[a] Homologous chromosomes pair-up to form bivalents.
Crossing over occurs where alleles switch between non-sister chromatids.
Chromatin condenses to form sister chromatids (after crossing over).
The centrioles move towards the poles ad start to produce spindle fibres.
The nuclear membrane breaks down.
[q] Metaphase I (meiosis I)
[a] Spindle fibers move the bivalents to the equator of the cell.
Sister chromatids are attached to the spindle fibres at the centromere.
The maternal and paternal homologous chromosomes are randomly assorted as they line up along the equator of the cell.
[q] Anaphase I (meiosis I)
[a] Homologous chromosomes from the bivalents separate and are pulled towards the poles of the cell by the spindle fibers.
The microtubule motors on the kinetochore, attached to centromeres, move chromosomes to opposite poles of the cell.
[q] Telophase I (meiosis I)
[a] The chromosomes, as sister chromatids, arrive at the poles and uncoil.
A nuclear membrane forms around the sister chromatids at each pole, producing two haploid nuclei.
Cytokensis occurs to produce two haploid cells.
[q] Prophase II (Meiosis II)
[a] Chromosomes, as sister chromatids, super coil and appear in both haploid cells.
The centrioles move towards the poles, producing the spindle fibres microtubules.
The chromosomes (sister chromatids attach to the spindle fibres at the centromere.
[q] Metaphase II (Meiosis II)
[a] Chromosomes line up along the equator of the cells, attached to the spindle fibre by the centromere.
Bivalents dont line up only single chromosomes.
[q] Anaphase II (Meiosis II)
[a] Sister Chromatids are pulled apart (at the centromere) producing single stranded chromosomes.
Those chromosomes are moved towards the poles by the microtubule motors on the kinetochore
[q] Telophase II (Meiosis II)
[a] The chromosomes reach the poles of each cell.
The chromosomes uncoil.
A nuclear membrane forms around each set of chromosomes.
Cytokenesis occurs forming 4 cells with haploid nuclei with are not identical.
[q] Non-disjunction
[a] The failure of one or more pairs of homologous chromosomes or sister chromatids to separate fully during nuclear division.
Can occur during Anaphase I if homologous chromosomes dont separate correctly, or Anaphase II of meiosis if sister chromatids dont seperate correctly or if it produces gametes with an extra chromosome or a missing chromosome.
[q] Down Syndrome (Trisomy 21)
[a] A genetic disorder caused by the presence of all or part of a third copy of chromosome 21.
Often caused by non disjunction during meiosis.
The zygote will have 47 chromosomes with three copies of chromosome 21.
[q] Cell Proliferation
[a] The process by which a cell grows and divides to produce two daughter cells.
Cell proliferation leads to an exponential increase in the number of cells is a rapid mechanism for tissue growth and repair
[q] What are examples of Cell proliferation?
[a] Embryological development: early embryos grow by cell proliferation through mitosis and cytokenesis
Plant meristems: Meristems are groups of undifferentiated cells which reproduce and differentiate to produce plant issues and organs.
Tissue replacement and healing: Dead and damaged tissue is replaced by cell proliferation. Skin cells are lost and replaced throughout an animal’s life
[q] Meristems
[a] Meristems are groups of undifferentiated cells which reproduce and differentiate to produce plant issues and organs.
[q] Cell Cycle
[a] interphase, mitosis, cytokinesis
[q] Interphase (HL)
[a] Cell spends most of its life cycle in interphase.
Transcription and translation occurs during interphase.
The numbers of chloroplasts and mitochondria increase as the cell grows and during G1 and G2 phases of interphase.
[q] G1 Phase
[a] First stage of interphase.
Cell grows after mitosis and cytokinesis.
There is a lot of protein synthesis allowing the cell to grow and build new organelles.
[q] S Phase
[a] 2nd stage of interphase.
DNA replication occurs to produce chromosomes with sister chromatids.
[q] G2 Phase
[a] Last stage of interphase.
Cell prepares for mitosis by growing and replicating organelles.
[q] Cyclins
[a] A group of four proteins which control the movement of a cell through the cell cycle.
A treshold level of a specific cyclin is required to pass each checkpoint in the cycle.
Concentrations of different cyclins increase and decrease during the cell cycle.
[q] Cyclin-dependent kinases (CDKs)
[a] enzyme to which cyclin binds during interphase and mitosis, triggering and controlling activities during the cell cycle
[q] Mutations
[a] Any change to the DNA or RNA base sequence of a cell or virus.
[q] Tumour suppressor genes
[a] Tumour suppressor genes regulate cell division, as they normally inhibit cell proliferation and tumor development.
Mutations to a tumour suppressor gene will cause the genes functions to be lost and uncontrolled cell division may occur.
[q] Proto=oncogenes
[a] Genes involved in regulating normal cell growth.
Mutations to a proto-oncogene may cause it to become an oncogene
[q] Oncogenes
[a] Oncogenes are genes that change a cell into a tumour cell which can lead to cancer
[q] Tumours
[a] abnormal proliferation of cells, either benign or malignant.
[q] Primary tumour
[a] first tumour produced throughout the body
[q] Metastasis
[a] The spread of cancer cells beyond throughout the body to form secondary tumours
[q] secondary tumours
[a] result from the metastasis of cancer cells throughout the body
[q] cancer
[a] uncontrolled cell division
[q] Benign tumours (tumour by abnormal cell growth)
[a] Non-cancerous and grow slowly and do not invade neighbouring tissue or undergo metastasis
[q] Malignant Tumours (tumour by abnormal cell growth)
[a] Cancerous, grow quickly and do undergo metastasis to spread to other parts of the body.
[q] Mitotic Index
[a] Ratio of cells in mitosis to the total number of cells and can be expressed as a percentage.
A high mitotic index strongly suggests cancer is present in the tissue.
[q] D2.1.1—How are new cell generated in living organisms?
[a] In all living organisms, a parent cell;
often referred to as a mother cell;
divides to produce two daughter cells;
via cell division
through mitosis; and cytokinesis;
[q] D2.1.2—How do the new cells split the cytoplasm between them?
[a] In animal cells a ring of contractile actin and myosin proteins; pinches a cell membrane together to split the cytoplasm;
in plant cells;
vesicles assemble sections of membrane;
and cell wall to achieve splitting;
[q] D2.1.3—When is division of cytoplasm even?
When is it uneven?
What happens with mitochondria for the new cells?
[a] The division of cytoplasm is usually even;
and that both daughter cells must receive at least one mitochondrion and any other organelle that can only be made by dividing a pre-existing structure;
however in egg formation in humans (and other animals);
called oogenesis;
it is uneven, with one cell getting almost all the cytoplasm;
and budding in yeast is also uneven;
[q] D2.1.4—What is the a brief role of mitosis and meiosis in eukaryotes?
[a] Nuclear division is needed before cell division to avoid production of anucleate cells;
cells without a nucleus;
Mitosis maintains the chromosome number and genome of cells;
whereas meiosis halves the chromosome number and generates genetic diversity;
[q] D2.1.5—What is required before both mitosis and meiosis (in terms of genetic information)?
What is the form of the genetic information at the start of these processes?
[a] DNA replication comes first;
after replication, each chromosome consists of two elongated DNA molecules;
called chromatids;
held together until anaphase;
[q] D2.1.6— What are shared features between meiosis and mitosis in terms of movement and packaging of DNA?
[a] Both include supercoiling of DNA;
using histones proteins;
in the condensation of DNA by supercoiling;
and the use of microtubules and microtubule motors;
to move chromosomes;
[q] D2.1.7—What are the phases of mitosis in order?
What is ultimately produced by mitosis?
[a] Prophase:
Supercoiling (condensation) of chromosomes;
breakup of nuclear membrane;
growth of microtubules;
attachment of microtubules to chromosomes;
Metaphase – Chromosomes line up at the equator
Anaphase – division of centromeres;
sister chromatids move to opposite poles;
Telophase – reformation of nuclear membranes around chromosomes at each pole;
[q] D2.1.8—What does prophase look like?
[a] Supercoiling (condensation) of chromosomes;
breakup of nuclear membrane;
growth of microtubules;
attachment of microtubules to chromosomes;
[q] D2.1.8—What does metaphase look like?
[a] Chromosomes line up at the equator
[q] D2.1.8—What does anaphase look like?
[a] division of centromeres;
sister chromatids move to opposite poles;
[q] D2.1.8—What does telophase look like?
[a] reformation of nuclear membranes;
around chromosomes at each pole;
[q] D2.1.9— Why is meiosis necessary in sexually reproducing organisms?
What does diploid mean? Haploid?
[a] Diploid means two sets of each chromosome; 2n;
they are in pairs;
haploid means one set of chromosomes;
meiosis involves two divisions of a diploid cell;
to produce four haploid nuclei;
in meiosis chromosome pairs (a pair of the same chromosomes) separate in the first division and sister chromatids are pulled apart in the second;
[q] Stages of meiosis essay from IB
[a] prophase I; chromosomes condense during (homologous) chromosomes pair up crossing over happens as chiasmata form metaphase I;
movement of pairs of chromosomes known as bivalents to the equator in random assortment of chromosomes along equator; anaphase I;
movement of half of the chromosomes to each pole telophase I,
chromosomes uncoil;
reduction of chromosome number to haploid;
metaphase II (double-stranded) chromosomes line up on the equator and are attached to both poles at the centromere;
anaphase II;
sister chromatids move to opposite poles in telophase II;
decondensation and uncoiling in reformation of nuclear membranes;
cytokinesis then occurs;
tetrad of haploid daughter cells formed.
[q] D2.1.10—What is disjunction? How does Down syndrome result from it?
[a] Non-disjunction is when chromosomes and or chromatids do not separate correctly;
and therefore go to the same pole;
non-separation of (homologous) double-stranded chromosomes during anaphase I;
also known as bivalents;
due to incorrect spindle attachment;
ALSO due to non-separation of chromatids during anaphase II;
due to centromeres not dividing;
occurs during gamete formation;
less common in sperm than egg formation;
Down syndrome due to extra chromosome 21;
called trisomy 21;
sperm or egg receives two chromosomes of same type; offspring has three chromosomes of same type;
[q] D2.1.11—Why is meiosis a source of genetic diversity?
When do the events responsible happen?
[a] due to crossing over;
during prophase I;
leading to new combinations of alleles/genes on chromosomes;
random orientation of chromosomes during metaphase I;
leading to different chromosomes (maternal or paternal) being selected for each gamete;
almost infinite variety created;
[q] HL ONLY – D2.1.12—What is cell proliferation?
How is it used for growth, cell replacement and tissue repair?
[a] proliferation (making more cells) is used for growth within plant meristems;
the regions of growth at the end of shoot tips and root tips;
and early-stage animal embryos;
in skin, cell proliferation is used during routine cell replacement;
and during wound healing;
[q] HL ONLY – D2.1.13—What is the cell cycle?
What are the phases?
[a] Cell cycle is the period between one cell division and the next;
Interphase is what happens between mitosis;
Composed of G1, G2 and S;
G1: the cell grows; duplicates organelles
e.g. mitochondria and extra cytoplasm including enzymes;
synthesises proteins;
S: The stage during which DNA is replicated
G2: more growth
[q] HL ONLY – D2.1.14— How does the cell grow during interphase?
[a] interphase is a metabolically active period;
there is biosynthesis of cell components including proteins and DNA;
Numbers of mitochondria and chloroplasts increase;
through growth and division of these organelles;
[q] HL ONLY – D2.1.15—How is the cell cycle controlled?
[a] Cyclins are proteins that control the movement through different phases of the cell cycle;
e.g. from G1 to S;
the concentration of different cyclins increases and decreases during the cell cycle;
and a threshold level of a specific cyclin is required to pass each checkpoint in the cycle.;
if this doesn’t happen, the division will stop;
[q] HL ONLY – D2.1.16—How can mutations in genes that control the cell cycle caused cancer?
[a] mutations in proto-oncogenes;
convert them to oncogenes;
which lead to tumour formation;
and mutations in tumour suppressor genes;
which normally stop tumour formation;
result in uncontrolled cell division;
known as cancer;
[q] HL ONLY – D2.1.17 — How are tumour cells different than normal ones?
How do they spread?
Which tumours are not usually harmful?
Which are?
[a] benign tumours are not normally harmful as they do not spread, invading other tissues;
malignant tumours however can spread and invade other tissues;
a primary tumour is the site of the first cancer;
a secondary tumour is one that has moved to a different site;
[q] HL ONLY – D2.1.17 — What is a mitotic index?
[a] The mitotic index is the number of cells in mitosis (prophase, metaphase, anaphase, telophase and cytokinesis); divided by the total number of cells;
gives an indication of how many cells out of the total are in a state of cell division;
high mitotic index in root tips;
and other regions of cell division;
or tumours;
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