Ch. 2 chromosomes and cellular reproduction

Question 1

what are histones?

Answer 1

it is a type of protein found in chromosomes
- chromatin wraps around it and DNA

Question 2

what is the advantage of having histones?

Answer 2

it allows you to have more DNA in a smaller space

Question 3

where did mitochondria come from? and how are they inherited genetically?

Answer 3

• mitochondria evolved from bacteria that was engulfed by a eukaryotic cell and they started to evolve together.
• mitochondria come from the mother

Question 4

Diploid v haploid

Answer 4

• diploid organisms have two homologous copies of each chromosome
• in haploid organisms/cells the chromosomes are unpaired

Question 5

what is a sister chromatid?

Answer 5

pairs of identical copies of DNA joined at a point called the centromere

Question 6

What are the parts of a chromosome?

Answer 6

• 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

Question 7

Chromosome v chromatid V chromatin

Answer 7

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

Question 8

what are checkpoints in cellular reproduction and why are they important?

Answer 8

Checkpoints make sure cell replication is only happening when it should, and that there are no mistakes being let through the entire process

Question 9

What is interphase?

Answer 9

the longest period of the cell cycle (everything that isn’t mitosis or meiosis)
- for growth, development, and cell cycle checkpoints

Question 10

What is the G1 phase (gap 1)?

Answer 10

• for cell growth and protein synthesis necessary for cell division
• mammalian cells typically spend ~ 10 hours in G1

Question 11

what is the G0 phase?

Answer 11

-where cells will stay performing their daily functions
- can stay here indefinitely or return to G1 phase if needed

Question 12

what is the G1/S checkpoint?

Answer 12

• checkpoint before cell enters S phase
• determines if all enzymes that are necessary for cell division are present

Question 13

what is S phase?

Answer 13

• 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

Question 14

what is G2 phase (gap 2)?

Answer 14

• biochemical reactions
• final prep for cell division takes place
• mammalian cells typically spend ~4 hours in G2

Question 15

what is the G2/M checkpoint?

Answer 15

• checks to make sure the DNA is completely replicated correctly

Question 16

difference between mitosis and meiosis?

Answer 16

Mitosis - 1 division; from Diploid -> diploid
meiosis - 2 divisions; diploid -> haploid then haploid -> haploid

Question 17

What are the key events in prophase?

Answer 17

• condensation of chromosomes ( sister chromatids)
• formation of the mitotic spindle

Question 18

what are the key events in prometaphase?

Answer 18

• 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)

Question 19

What are the key events in metaphase?

Answer 19

• 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

Question 20

what are the key events in anaphase?

Answer 20

• 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)

Question 21

what are the key events of telophase?

Answer 21

• chromosomes arrive at spindle poles
• Nuclear membrane reforms -> 2 nuclei at one cell
• chromosomes relax/lengthen
  -cytokinesis often happens too
  (ploidy level still diploid)

Question 22

What are the key events in metaphase 1?

Answer 22

• Homologs are lined up side by side on the metaphase plate
• cross over happens

Question 23

what are the key events in anaphase 1?

Answer 23

-sister chromatids are pulled apart
- cohesin at chromosome arms breaks down, shugosin protects it at the centromere

Question 24

what are the key events in telophase 1?

Answer 24

• chromosomes arrive at the spindle poles
• cells divide
• interkinesis comes next

Question 25

what are the key events in prophase 2?

Answer 25

• interkineses is reversed
  (stage can be skipped by some cells)

Question 26

what are the key events in metaphase 2?

Answer 26

• chromosomes align on the metaphase plate (end to end similar to mitosis)

Question 27

what are the key events in anaphase 2?

Answer 27

• shugosin has broken down and chromatids separate from one another

Question 28

what are the key events in telophase 2?

Answer 28

• chromosomes arrive at spindle poles
• nuclear envelope reforms
• cytoplasm divides
• chromosomes relax
  -results in 4 cells (haploid)

Question 29

what is the process of spermatogenesis?

Answer 29

spermatogonium (diploid) –meisosi to prophase 1 –> primary spermatocyte (diploid) –completion of meiosis 1–> secondary spermatocyte (haploid) –meiosis 2–> spermatids (haploid) –maturation –> sperm (haploid)

Question 30

what is the process of oogenesis?

Answer 30

• 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