Cell Divisions Flashcards
What is the result of cell growth + cell division
2 daughter cells
What is the first phase of the cell cycle?
Interphase
What are 3 major things that happens in the G1 phase?
-Accumulates building block of chromosomal DNA
-Accumulates energy to complete the task of replicating
-metabolically active + cell growing
What is the main principle of S phase?
Synthesis DNA
What are the two most important things occurring during S phase?
1-DNA replicates — formations of sister chromatids attach to the centromeric regions
2-Centrosome duplicates — Mitotic spindle
What is the function of Mitotic spindle?
Give movement of chromosomes during mitosis
What are the 4 important things occurring in G2 phase?
-Synthesizes proteins necessary for chromosome manipulation
-centrosome replicates
-cytoskeleton dismantled
-mitochondria and chloroplasts divide
What is the result of mitosis?
Division of the cell nucleus
What are all the phases of mitosis?
-Interphase
-prophase
-prometaphase
-métaphase
-anaphase
-telophase
What are 2 things that happens in G2 interphase?
-chromosomes + centromeres duplicates
-mitochondria duplicates + nucleolus dissapears
What are 3 things that happens in prophase?
-chromosomes coil up
-centrosomes move to poles
-nuclear membrane breaks down
What are two things that happens in prometaphase?
-chromosomes become even more condensed and discrete
-sister chromatids face opposite poles
What are two things that happens in metaphase?
-centrioles makes spindle fibres
-centrioles moves to the equator
What are 2 things that happens in anaphase?
-centromere break down
-sister chromatids are pulled apart moving towards opposite poles
What are 4 thing that happens in telophase?
-nuclear membrane reforms
-chromosomes uncoil
-nucleoli reform
-CELL DIVIDES in two
What would be the last phase of the cell cycle that does not always happen?
Cytokinesis
What is the function of cytokinesis?
«cell motion» physical separation of the cytoplasmic components
Label the diagram of the cell cycle
Draw and label stages of mitosis
DNA double helix is wrapped around what type of protein?
Histone protein
What is the main function of meiosis?
Nuclear division of sexual chromosomes (divide sets by half)
The interphase of meiosis consist which phases?
G1, S and G2
What is the name of the protein that helds together sister chromatids?
Cohesin protein
In what phase the tetrad are formed?
Prophase 1
What occurs during prophase 1?
-Chromosomes condense
-Nuclear enveloppe fragments
-Synapsis
-cross over
What is the synapsis?
-Tight paring of the homologous chromosomes
-genes are aligned precisely with each other
-forming a tetrad
What is the principle of cross over?
Exchanging segments of DNA to produce genetically recombined chromosomes
Where occurs the cross over?
At the chiamasta
What are the two main things occurring in Prometaphase 1?
-homologous chromosomes are attached to spindle microtubules at the end of kinetochore shared by the sister chromatids
-nuclear membrane has broken down entirely
Are homologous chromosomes identical if not what is the explanation?
No — contains different version of the same gene
What are the two main event occurring in metaphase 1?
-homologous chromosomes are arranged at the metaphase plate
-tetrads line up at the midway point between the two poles of the cell to form metaphase plate
In which phase does the indépendant assortment is done?
Metaphase 1 — Radom assortments of tetrads on the metaphase plates
What is the result of random assortment in metaphase 1?
Produces a unique combinations of maternal and paternal chromosomes that will make their way into gametes
In what phase does the cross over occur in meiosis?
Prophase 1
How recombinant chromatids with new combinations of maternal and paternal genes is made?
By crossover event between non-sister chromatids of each homologous pair of chromosomes
What are the 3 main events occurring in Anaphase 1?
-Spindle microtubules pull the homologous chromosomes appart
-sister chromatids are still attached at the centromere
-chiamasta are broken
What is the two main event occurring in telophase 1?
-sister chromatids arrive at opposites poles — are decondense
-nuclear envelope forms around each nucleus and the cytoplasm
What is the two main event occurring in telophase 1?
-sister chromatids arrive at opposites poles — are decondense
-nuclear envelope forms around each nucleus and the cytoplasm
What is the result of the first meiosis?
2 haploid cells (only one chromosome set)
What is the ultimate goal of meiosis 2?
That the 2 cell produced in meiosis one go through meiosis 2 and form 4 new haploid gametes
What are the 3 things that occurs in prophase II?
-sister chromatids condense again
-spindle begin to form
-nuclear envelope start to fragment
What are the two main things occurring in Prometaphase II?
-nuclear enveloppe completely broken
-each sister chromatids forms individual kinetochore
What happens during Metaphase II?
Sister chromatids line up at the metaphase plate
What happens during anaphase II?
-Sister chromatids are pulled apart by the shortening of the kinetochore
What occurs during telophase II?
-chromosome arrive at poles and decondense
-nuclear envelope surrounds the four nuclei
how does the two cells divide into 4 haploid cell during cytokinesis of meiosis 2?
By cleavage furrow
Name 3 major difference between Mitosis and Meiosis?
Mitosis:
-One cell division
-result = 2 nuclei (genetically identical)
Meiosis:
-2 cell division
-result = 4 nuclei haploid (each one unique combination)
**Crossing over during Meoisis 1
When does segregation happens in meiosis?
Anaphase I and II
What are two characteristics of homologous chromosomes?
-same length
-specific nucleotide segments (genes exactly at the same location)
what is aneuploidy?
Individual with an error in chromosome number
What is monosomy?
Individual losing one chromosome
What is trisomy?
Individual gaining an extraneous chromosome
What are autosomes?
Non-ses chromosomes
What is the major difference between haploid and diploid cells?
Haploid cells have a single set of chromosomes
Diploid cells have two sets of chromosomes that will
Are gametes haploid or diploid cells?
Haploid
What are the arrangement of chromosomes within humain body?
22 homologous pairs of autosomes + 1 homologous pair of sex chromosomes
What is the role of apoptosis?
Allows cell to die in a controlled manner that prevents the release of potentially damaging molecules
What can initiate apoptosis?
-abnormalities
-external signaling
What is the advantage of apoptosis for the immune system?
Helps eliminating infected, aged cells
What is the consequence of monosomic zygote missing one copy of an autosome?
-Fail to develop to birth
-lack essentials genes
How many chromosomes does human somatic cells contains?
46 chromosomes
How aneuploidy occurs in meiosis?
By nondisjunction of chromosomes, they fail to separate — don’t complete the process of cell division
What is the law of segregation?
Paired unit factors must be segregate equally into gametes such that offsprings have equal likelihood of inheriting either factors
What is the law of indépendant assortment?
Genes do not influence each other with regard to the sorting of alleles into gametes
What are dominant allele?
Expressed exclusively — only need one allele to be expressed
What are recessive allele?
«Latent» allele — only be expressed by offspring if they have two copies of this allele
