Cell cycle, Mitosis, and Meiosis Flashcards
What are the stages of the cell cycle?
Interphase- G1, S, G2
M phase
Cytokinesis
What happens in Interphase?
grows and makes a copy of its DNA- (90% of the cycle)
What occurs in G1?
cell grows larger, copies organelles and makes molecular building blocks
What occurs in S phase?
synthesizes a complete copy of the DNA( copies chromosomes) and duplicates the centrosomes
What occurs in G2?
grows more, makes proteins and organelles, and reorganizes for mitosis; ends when mitosis begins
What occurs in M phase?
formation of two new cells; divides DNA and cytoplasm
What occurs during cytokinesis?
cytoplasm of the cell split into two cells
G1 checkpoint description & what it checks for
whether the cell is prepared for division- most important
Checks for size, nutrients, and DNA damage; if not met it will not go into S phase
G2 checkpoint description and what it checks for
Mitotic phase
Checks for cell size, protein reserves, and all chromosomes have been replicated and DNA damage
- If problems exist→ cell either completes DNA replication or repairs DNA
M checkpoint description and what it checks for
near the end of metaphase of karyokinesis
- Checks if all the sister chromatids are correctly attached to the spindle microtubules
What is G0?
a resting state; not actively prepare dot divide
- Cells that do not receive go-ahead signal
- Can be a permanent state for some cells or temporary for some cells who can start division if they have the right signals
Describe CDKs?
enzymes that activate or inactivate other proteins by phosphorylating them; to be active they must bind to a cyclin
What is an MPF?
cyclin and CDK complex
Triggers cell passage past the G2 checkpoint and into M phase
Cyclins and CDKS bind in G2- phosphorylate proteins→ mitosis
What do peaks of MPF activity correspond with?
corresponds with cycling concentration; rise during S and G2 phases;falls during M phase
Why does MPF switches off?
destruction of its own cyclin
Difference between Somatic cells and Gametes?
Somatic Cells- 46 chromosomes- diploids cells
Gametes- 23 chromsomes- haploid cells
Difference between sister chromatids and chromosomes
Sister chromatids: are two indenticial strands of DNA that are attached by the centromere
Chromosomes: composed of chromatids
Stages of mitosis
prophase, metaphase, Anaphase, telophase
Describe what occurs in prohase?
-Nucleolus disappears
-chromatin condenses into chromosomes
-Separation of centrosomes
-Formation of mitotic spindle
Describe what occurs in prometaphase?
-Nuclear envelope disassembles
-Chromosomes form 2 kinetochores at the centromere
-Microtubules attach to the chromosomes
Describe what occurs at metaphase
Chromosomes align in the metaphase plate
What occurs during anaphase?
Chromatids move apart to separate poles
What occurs during telophase?
Nuclear envelope forms
Chromosomes unfold back into chromatin
Nucleoli reappear
Cell continues to elongate
Cytokinesis in plants and animals
plants- cell plate
animals- cleavage furrow- cell pinches together
Binary Fission
bacteria replicate circular chromosomes and then cytoplasm divides through cytokinesis.
Chromosomes number in daughter cells vs. mother in binary fission
Daughter cells have the same chromosome number as the mother cell
How is there more genetic vartiation in sexual reproduction compared to asexual?
Law of segregation
Law of Independent Assortment
Random Fertilization
Define Law of Segregation
separation of alleles during gamete formation
Each gamete has 1 allele for each gene; varied combinations of alleles
define Law of Independent Assortment
alleles of two (or more) different genes get sorted into gametes independently
How is there genetic variation in random fertilization?
random unique egg gets fertilized by unique sperm
Define karyotype
individual’s complete set of chromosomes
Define autosomes
chromosomes other than sex chromosome
Define sex chromosomes
XX and XY- determine the person’s gender
Exception to homologous chromosomes
Define diploid cells
2 set of chromosomes
Define haploid cell
1 set of chromosome
Define homologous chromosomes
are a set of maternal and paternal chromosomes that pair up in a cell during fertilization
Define tetrads
consists of two homologous chromosomes with a total of 4 sister chromatids
what is the purpose of meiosis?
the creation of gamete cells
Prophase 1
- Synapsis occurs: maternal and paternal chromosomes(homologous chromosomes) wrap up tightly
-Crossing Over: through synapsis, swap parts of chromsomes
Describe metaphase 1
-Independent Orientation: ligning up at metaphase plate
-Spindals attaches to centromere of each homologous chromosome
Describe Anaphase 1
Homologous chromosomes are pulled apart to opposite ends
Describe telophase 1
Divide cell with cytokinesis
Describe prophase 2
-No crossing over
-Chromosomes condense
-Nuclear envelope breaks down
-Spindle forms
Describe metaphase 2
Chromosomes line up along the metaphase plate
Describe Anaphase 2
Sister chromatids separate and are pulled towards opposite poles of the cell
Describe telophase 2
-Nuclear membranes form around each set of chromosomes and chromosomes decondensed
-Cytokinesis continues
Describe ploidy during meiosis?
During Meiosis, cells go from diploid → haploid (by end of MI→)haploid (end of MII)
What are the type of cells in which meiosis takes place?
Spermatocyte and oocyte
Describe spermatogenesis?
Germ cell→spermatogonial→spermatogonium→primary spermatocyte→secondary spermatocyte→spermatids→sperm
Describe oogenesis?
Germ cell→oogonium→primary oocyte→secondary oocyte→fertilization→meiosis 2 is completed→ fertilized egg (zygote)
End result of meiosis (comparison of daughter cells with mother cell in terms of number of daughter cells and chromosome makeup)
Chromosomal makeup: results half as many as the parent cell for each haploid daughter cell
4 daughter cells
Spermatogenesis compared to Oogenesis
Spermatogenesis is equal and oogenesis is unequal and produces two polar bodies
