Chapter 9-10 quiz Flashcards
Why is cell division important to multicellular organisms?
It enables them to develop from a single cell and, once fully grown, to renew, repair, and replace cells as needed
What is the continuity of life based on?
cell division
What best distinguishes living and nonliving organisms?
The ability of something to produce their own
What is the cell cycle?
the life of a cell from the time it is first formed from a dividing parent cell until its own division into 2 daughter cells
What is the most common result of cell division?
The distribution of identical genetic material(DNA) to two daughter cells
What is a genome?
All the DNA in a cell
What are chromosomes?
What DNA is packaged into in cells, consisted of DNA associated with proteins to maintain structure
What is chromatin?
A complex of DNA and protein that make up Eukaryotic chromosomes
What are somatic cells?
nonreproductive cells that have 2 sets of chromosomes
What are gametes?
reproductive cells(sperm and eggs) that have one set of chromosomes
What are sister chromatids?
joined, identical copies of the original chromosome
What is the centromere?
Where the chromatids are most closely attached, joined by proteins that are bound to the centromeric DNA sequences
What, in short, is done in preparation of cell division?
DNA is replicated and chromosomes condense
How/when do sister chromatids become chromosomes?
Once the sister chromatids have moved and separated into two nuclei, they are chromosomes
When are mitosis and meiosis used?
Mitosis is used in Eukaryotic cell division, meiosis is used to produce gametes
What does meiosis yield?
nonidentical daughter cells with only one set of chromosomes, half as many as he parent cell
What is the interphase?
The phase of the cell cycle including cell growth and copying of chromosomes in preparation for cell growth
What phases is the interphase divided into?
- G1 phase-“first gap”, growth
- S phase-“synthesis”, growth and duplication
- G2 phase-“second gap”, growth
What are the phases of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
How many chromosomes so gametes and somatic cells have?
Somatic: 46
Gametes: 23
What is cytokinesis?
The division of the cytoplasm immediately following mitosis
What happens in G2 of interphase?(mitosis)
- Nuclear envelope forms
- 2 centrosomes have formed by duplication of a single centrosome. The centrosome organize the microtubules of the spindle in animal cells
- Chromosome duplicated in the S phase have NOT condensed
What happens in the prophase(mitosis)?
- Chromosomes begin to condense
- Each duplicated chromosome appears as identical sister chromatids joined at their centromeres
- Mitotic spindle forms
- Centrosomes move away
- nucleoli appear
What happens in the prometaphase?(mitosis)
- Nuclear envelope disappears
- Microtubules enter the nuclear area
- Chromatids condense further
- Each pair of chromatids now has a kinetochore
- Some microtubules attach to the kinetochores
- Nonkinetochores interact with those from the opposite side of the spindle
What happens in the metaphase of mitosis?
- Centrosomes have moved to opposite poles
- Metaphase plate forms
- All kinetochore microtubules are connected to kinetochore microtubules coming from opposite poles
What happens in the anaphase of mitosis?
- Phase begins when cohesion proteins are broken, separating chromatids and making chromosomes and bringing the new daughter chromosomes to opposite ends of the cell
- Cell elongates due to kinetochores
- By the end of this phase the two ends of the cell are equivalent and have complete collections of chromosomes
What happens in the Telophase of Mitosis?
- 2 daughter nuclei form and nuclear envelopes form from fragments of the parent’s nuclear envelope and other portions of the endomembrane system
- Nucleoli reappear
- Chromosomes become less condensed
- Any remaining spindle microtubules are depolymerized
- Mitosis is complete after this phase
What happens in cytokinesis(mitosis)?
- Starts during late telophase
- Cleavage furrow develops in animal cells, cell is pinched in two
- In plant cells, a cell plate forms
What is the mitotic spindle?
A structure made of fibers made of microtubules and associated proteins that controls chromosome movement during mitosis. In animal cells, their assembly begins in the centrosome
What is an aster?
A radial array of short microtubules extending from each centrosome
What are the parts of the mitotic spindle?
Centrosomes, spindle microtubules, and he asters
What are kinetochores?
Protein complexes that assemble on sections of DNA at centromeres
What are centrosomes?
A subcellular region containing material that functions throughout the cell cycle to organize the cell’s microtubules
What is responsible for elongating a cell in anaphase? how does this work?
nonkinetochore microtubules, they overlap extensively during the metaphase, and motor protein attached to the microtubules walk them away from each other and push the spindle poles apart
What causes a cleavage furrow to form and pinch into two parts?
actin microfilaments interact with myosin molecules to form a ring around the cleavage furrow and contract and pull like a drawstring
How is a cell plate formed?
Vesicles derived from the golgi apparatus move along microtubules to the middle of the cell where they coalesce, forming a cell plate.
How to prokaryotes reproduce?
Binary fission(asexual)
What is the likely origin of mitosis and why? what supports this hypothesis?
Binary fission, because prokaryotes evolved before eukaryotes. The fact that some proteins used in binary fission are related to eukaryotic mitosis proteins support this
What is the origin of replication?
The site in binary fission where the single chromosome replicates, resulting in 2 daughter cells that end up dividing
What controls the frequency if cell division?
regulation at the molecular level
What drives the cell cycle?
specific signaling molecules present in the cytoplasm
What are checkpoints?
specific points where the cell cycle stops until a go-ahead signal is recieved
What is the G1 phase checkpoint important?
If the cell receives a go ahead at this checkpoint, it will complete the S, G2 and M phases and divide. If not, it will enter the G0 phase
What is the cell cycle regulated?
A set of regulatory proteins and protein complexes including kinases and proteins called cyclins
What is the internal signal that occurs at the M phase checkpoint?
Anaphase does not begin if any kinetochores remained unattached to spindle microtubules. Attachment of all kinetochores activates a regulatory complex which activates the enzyme separase that allows sister chromatids to separate, triggering the anaphase. This ensures daughter cells dont end up with missing or extra chromosomes
What are growth factors?
Proteins released by certain cells that stimulate other cells to divide, external signals
What is density-dependent inhibition?
Crowded cells stop dividing
What is anchorage dependence?
An external most animal cells exhibit where they must be attached to a substratum in order to divide
How is a normal cell converted to a cancerous cell?
A process called transformation, where cancer cells not eliminated by the immune system form tumors
What are malignant tumors and what do they do?
Tumors that invade surrounding tissues and they metastasize, exporting cancer cells to other parts of the body, where they may form other additional tumors
What is heredity?
The transmission of traits from one generation to the next
What is variation?
The differences in appearances that offspring show from parents and siblings
How are genes passed to the next generation?
Gametes(sperm and eggs)
What is a locus?
A gene’s position in a chromosome
What is asexual reproduction?
A single individual passes genes to its offspring without fusion of gametes
What is a clone?
A group of genetically identical individuals from the same parent
What is sexual reproduction?
Two parents give rise to offspring that have unique combinations of genes inherited from the two parents
What is a life cycle?
The generation-to-generation sequence of stages in the reproductive history of an organism
What is karyotype?
An ordered display of the pairs of chromosomes from a cell
What are homologous chromosomes?
Aka homologs, they are the two chromosomes in each pair
What are the characteristics of chromosomes in a homologous pair?
They are he same length and shape and carry genes controlling the same inherited characters. Each pair includes one chromosome from each parent
What are sex chromosomes? what makes a male or female?
Sex chromosomes determine the sex of an individual, they are called x and y. Females have XX and males have XY
What are autosomes?
The 22 pairs of chromosomes that arent sex cells
What is a diploid cell?
(2N) a diploid cell has two sets of chromosomes(46 in humans)
What is a haploid cell?
(n) a gamete containing a single set of chromosomes(23 in humans)
What is fertilization?
The union of gametes(sperm and egg)
What is a zygote?
A fertilized egg that has one set of chromosomes from each parent
What is special about the production of gametes?
They are the only types of human cells produced through meiosis rather than mitosis
What are gametes supposed to do once they are produced?
Fuse with another gamete to form a diploid zygote that divides by mitosis to develop a multicellular organism
How are gametes produced?
The develop from specialized germ cells in the ovaries in females or testes in males.
Why are gametes produced through meiosis?
To counterbalance the doubling of the number of chromosomes that happens during fertilization
What is the alternation of generations?
Experienced by plants and some algae, it is a cycly where a multicellular diploid stage called a sporophyte produces a haploid cell called a spore. The spores divide mitotically to produce gametophytes, which give rise to gametes by mitosis. The two haploids fuse into a diploid sporophyte through fertilization and the cycle continues
What is the third type of life cycle?
Carried out by most fungi and some protists, gametes fuse to form a diploid zygote, the go through meiosis without a multicellular diploid offspring developing. The meiosis produces either haploid unicellular organisms or a haploid multicellular adult organism
What happens during prophase 1?
- Chromosomes begin to condense, homologs loosely pair along their lengths
- Synapsis crossing over takes place
- Synaptonemal complex dissembles in mid-prophase, chromosomes in each pair move apart slightly
- Chiasmata form
- Centrosome movement, spindle formation, nuckear envelope breakdown just like in mitosis
What is crossing over?
A genetic rearrangement between nonsister chromatids occurs involving the exchange of corresponding segments of DNA molecules
What are chiasmata?
X shaped regions the point where a crossover has occurred. Sister chromatids are held together but one of them is part of the other homolog
What happens during metaphase 1?
- Homologous chromosomes are arranged at the metaphase plate with one chromosome in each pair facing the pole
- Both chromatids of one pair are attached to kinetochore microtubules from one pole, the chromatids of the other homolog are attached to the opposite pole
What happens in Anaphase 1?
- Breakdown of proteins responsible for sister chromatid cohesion in the arms allows homologs to separate
- Homologs move toward opposite poles, guided by spindles
- Sister chromatid cohesion persists at centromere, causing them to move toward the pole as a unit
What happens during telophase 1/cytokinesis?
- At the beginning, each half of the cell has a complete haploid set of duplicated chromosomes, each chromosome consists of 2 sister chromatids. One or both chromatids contain regions of nonsister chromatid DNA
- Cytominesis occurs simultaneously, forming 2 haploid daughter cells
- Animal cells form cleavage furrows, plant cells form cell plates
- In some species chromosomes decondense and nuclear envelopes form
- No chromosome duplication occurs between Meiosis 1 and 2
What happens during prophase II?
- Spindle apparatus forms
* Later in this phase, chromosomes(still composed of 2 sister chromatids) move towards metaphase II plate
What happens during metaphase II?
- Chromosomes are positioned on metaphase plate
- The two sister chromatids are notidentical bc of crossing over in meiosis 1
- Kinetochores of sister chromatids are attached to microtubules extending from opposite poles
What happens during anaphase II?
•Breakdown if proteins holding the sister chromatids together at the centromere allows chromatids to separate, chromatids move toward opposite poles as individual chromosomes
What happens during telophase II/cytokinesis?
- Nuclei form, chromosomes decondense, cytokinesis occurs
- 4 daughter cells, each with a haploid(unduplicated) set of chromosomes is the result
- The 4 daughter cells are genetically different from each other and the parent cell
What is synapsis?
A state where paired homologs become physically connected to each other along their lengths by the synaptonemal complex
What are the differences between meiosis and mitosis?
- Meiosis reduces number if chromosome sets from 2 to 1, mitosis conserves the number
- Meiosis produce genetically different daughter cells, mitosis producers genetically identical cells
What 3 events occur in meiosis that are unique to it?
- Synapsis and crossing
- Homologous pairs at metaphase plate(individual chromosomes in mitosis)
- Separation of homologs(sister chromatids separate in mitosis)
What are 3 mechanisms that contribute to the genetic variation arising from sexual reproduction?
- Indepedent assortment of chromosomes: In metaphase one, homologs align themselves on the metaphase plate and which chromosome faces which pole is random(50% chance of paternal/fraternal)(2^n)
- Crossing over: Crossing over produces chromosomes that carry genes derived from 2 parents.
- Random fertilization: fusion of male and female gametes gives even more combination of genetic variation
When do chromosomes become visible in mitosis?
Prophase
