Lecture 8: Mitosis and Meiosis Flashcards
In eukaryotes, the hereditary information within the nucleus is distributed among individuals called?
linear DNA molecules
What are three things DNA molecules can do?
- combine with proteins that stabilize the DNA molecules
- assist in packaging DNA during cell division
- influence the expression of individual genes
In a cell, each chromosome is composed of one what?
DNA molecule an its associated proteins
What is the chromosome complement?
the complete set of chromosomes of eukaryotic organism
The nucleus of each somatic contains a ___ number of chromosomes typical of the particular species
fixed
T or F: the number of chromosomes vary tremendously among species and have little relationship to the complexity of the organism
True
What phases are in interphase?
G1, S, G2
What does G1 stand for, and what is a basic description?
primary growth phase, and it is the longest phase. It also stands for gap phase 1
What does S phase stand for and what is a basic description?
Synthesis, and replication of DNA
What does G2 phase stand for and what is a basic description?
Gap phase 2, organelles replicate, microtubules organize
How many phases is mitosis divided into?
5
What is cytokinesis?
the separation into 2 new cells
T or F: the time it takes to complete a cell cycle varies greatly?
True
In G2, what are three things besides the basic description that occurs?
- chromosomes coil more tightly using motor proteins
2.centrioles replicate - tubulin synthesis
What are centromeres?
the point of constriction
T or F: each sister chromatid has a centromere
True
How do chromatids stay attached at the centromere?
by cohesin
What protein replaces cohesins?
condensins (in multicellular animals)
What are the five phases of mitosis?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
What continues throughout prophase?
condensation
When does the spindle apparatus assemble?
prophase
When does the nuclear envelope breaks down?
prophase
When do individual condensed chromosomes first become visible with the light microscope?
prophase
When does prometaphase occur?
The transition occurs after disassembly of nuclear envelope
What is called when chromosomes begin to move to center of cell, and what phase is it in?
congression, prometaphase
What is metaphase?
The alignment of chromosomes along the metaphase plate
In what phase do the centromeres begin to split, and cohesin proteins from all chromosomes is removed, and sister chromatids are pulled to opposite poles?
Anaphase
What is anaphase A?
kinetochores pulled toward poles
What is anaphase B?
the poles move apart
In what phase does the spindle apparatus dissambles and the nuclear envelope forms around each set of sister chromatids?
Telophase
In what phase are the sister chromatids called chromosomes?
Telophase
When do the chromosomes begin to uncoil?
telophase
What is the sexual life cycle composed of?
meiosis and fertilization
When does the nucleolus reappear in each new nucleus?
telophase
What cells are diploid?
somatic
What cells are haploid?
gametes
What do offspring inherit from 2 parents?
genetic material
In most animals, with sexual reproduction, what state dominates?
diploid state
Single - cell diploid zygote undergoes mitosis to produce___ cells?
somatic
Some diploid cells undergo meiosis to produce ____ gametes
haploid
How many rounds of division are in Meiosis?
two rounds
What is synapsis?
It occurs in early prophase I, and homologous chromosomes become closely associated, and it includes formation of synaptonemal complexes
What are synaptonemal complexes also called?
tetrads or bivalents
When does crossing over?
prophase I
What are the sites for crossing over called?
chiasmata
What is the first meiotic division termed?
reduction division
T or F: No DNA replication between meiotic divisions
True
What does the first meiotic division result in?
daughter cells that contain one homologue from each chromosome pair
What does the second meiotic division result in?
it separates the sister chromatids for each homologue
What is crossing over?
the genetic recombination between non-sister chromatids
T or F: after crossing over, alleles of genes that were formerly on separate homologues can now be found on the same homologue
True
What happens in Metaphase 1?
1.paired homologues locked together following crossing over,
2. microtubules from opposite poles attach to each homologue
3. homologues are aligned at the metaphase plate side-by-side
T or F: the orientation of each pair of homologues on the spindle is random
True
In what phase do
1. microtubules of the spindle shorten (chiasmata break)
2. homologues are separated from each other and move to opposite poles (sister chromatids remain attached at centromeres)
3. each poles has a complete haploid set of chromosomes
4. independent assortment of maternal and paternal chromosomes
anaphase 1
In what phase does the nuclear envelope re-forms around each daughter nucleus
telophase 1
What happens in prophase II?
nuclear envelopes dissolve and new spindle apparatus forms
What happens in metaphase II?
chromosomes align on metaphase plate
What happens in anaphase II?
sister chromatids are separated from each other
What happens in telophase II?
nuclear envelope re-forms around 4 sets of daughter chromosomes; cytokinesis follows
What is the final result of meiosis?
four cells containing haploid sets of chromosomes
What is nondisjunction?
failure of chromosomes to move to opposite poles during meiotic division
What are aneuploid gametes?
gametes with missing or extra chromosomes
What are the two key differences between meiosis and mitosis?
- maintenance of sister chromatid cohesion at the centromere during all of meiosis I
- loss of cohesion from the chromosome arms during anaphase I
T or F: Sister kinetochores attach to the same pole during meiosis I
True
T or F: Meiosis produces cells that are not indentical
True
How does meiosis produce cells that are not identical?
random orientation in first division and crossing over
