Ch. 2 chromosomes and cellular reproduction Flashcards
what are histones?
it is a type of protein found in chromosomes
- chromatin wraps around it and DNA
what is the advantage of having histones?
it allows you to have more DNA in a smaller space
where did mitochondria come from? and how are they inherited genetically?
- mitochondria evolved from bacteria that was engulfed by a eukaryotic cell and they started to evolve together.
- mitochondria come from the mother
Diploid v haploid
- diploid organisms have two homologous copies of each chromosome
- in haploid organisms/cells the chromosomes are unpaired
what is a sister chromatid?
pairs of identical copies of DNA joined at a point called the centromere
What are the parts of a chromosome?
- telomere - protective caps on chromosomes that protect DNA further in
- centromere - middle of the chromosome where the sister chromatids are connected
- Origin of replication - where the copying of DNA starts
- kinetochore - large protein assemblies that connect chromosomes to microtubules of the mitotic and meiotic spindles
- spindle microtubules - responsible for chromosome movement
Chromosome v chromatid V chromatin
Chromosomes - chromatin condenses to form a chromosome ( X)
chromatid - chromosomes that have divided into two identical strands
chromatin - a substance found in the cell nucleus that’s composed primarily of DNA and proteins
what are checkpoints in cellular reproduction and why are they important?
Checkpoints make sure cell replication is only happening when it should, and that there are no mistakes being let through the entire process
What is interphase?
the longest period of the cell cycle (everything that isn’t mitosis or meiosis)
- for growth, development, and cell cycle checkpoints
What is the G1 phase (gap 1)?
- for cell growth and protein synthesis necessary for cell division
- mammalian cells typically spend ~ 10 hours in G1
what is the G0 phase?
-where cells will stay performing their daily functions
- can stay here indefinitely or return to G1 phase if needed
what is the G1/S checkpoint?
- checkpoint before cell enters S phase
- determines if all enzymes that are necessary for cell division are present
what is S phase?
- DNA synthesis stage (duplication of chromosomes)
- DNA synthesis MUST precede mitosis
- at the end of S phase sister chromatids made and are held together by cohesin
- mammalian cells typically spend ~9 hours in this phase
what is G2 phase (gap 2)?
- biochemical reactions
- final prep for cell division takes place
- mammalian cells typically spend ~4 hours in G2
what is the G2/M checkpoint?
- checks to make sure the DNA is completely replicated correctly
difference between mitosis and meiosis?
Mitosis - 1 division; from Diploid -> diploid
meiosis - 2 divisions; diploid -> haploid then haploid -> haploid
What are the key events in prophase?
- condensation of chromosomes ( sister chromatids)
- formation of the mitotic spindle
what are the key events in prometaphase?
- disintegration of the nuclear envelope
- anchoring of chromosomes to both centromeres ( via the microtubules of the mitotic spindle)
- biorientation happens (chromosomes are getting pulled from both sides of the cell by spindle fibers so they can later separate)
What are the key events in metaphase?
- chromosomes alight on metaphase plate (straight up and down)
- chromosomes center at spindle poles
- spindle- assembly checkpoint ensures that sister chromatids are pulled in opposite directions
what are the key events in anaphase?
- sister chromatids separate (cohesin broken down by separase)
- daughter chromosomes move to opposite spindle posed due to disassembly of tubulin molecules ( molecular motors remove tubulin)
what are the key events of telophase?
- chromosomes arrive at spindle poles
- Nuclear membrane reforms -> 2 nuclei at one cell
- chromosomes relax/lengthen
-cytokinesis often happens too
(ploidy level still diploid)
What are the key events in metaphase 1?
- Homologs are lined up side by side on the metaphase plate
- cross over happens
what are the key events in anaphase 1?
-sister chromatids are pulled apart
- cohesin at chromosome arms breaks down, shugosin protects it at the centromere
what are the key events in telophase 1?
- chromosomes arrive at the spindle poles
- cells divide
- interkinesis comes next
what are the key events in prophase 2?
- interkineses is reversed
(stage can be skipped by some cells)
what are the key events in metaphase 2?
- chromosomes align on the metaphase plate (end to end similar to mitosis)
what are the key events in anaphase 2?
- shugosin has broken down and chromatids separate from one another
what are the key events in telophase 2?
- chromosomes arrive at spindle poles
- nuclear envelope reforms
- cytoplasm divides
- chromosomes relax
-results in 4 cells (haploid)
what is the process of spermatogenesis?
spermatogonium (diploid) –meisosi to prophase 1 –> primary spermatocyte (diploid) –completion of meiosis 1–> secondary spermatocyte (haploid) –meiosis 2–> spermatids (haploid) –maturation –> sperm (haploid)
what is the process of oogenesis?
- oogonium (diploid) –meiosis to prophase 1–> primary oocyte (diploid) – completion of meiosis 1–> secondary oocyte and polar body (haploid) – meiosis 2–> ovum and polar body (haploid)
- primary oocyte arrest in prophase 1until puberty
