BIO 111 > Chapter 15 > Flashcards

Chapter 15 Flashcards

(59 cards)

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1
Q

Cell division

A
  • highly regulated series of events
  • 2 types
    1. mitosis
    2. meiosis
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2
Q

chromosomes

A
  • different species have different numbers of chromosomes
  • eukaryotic chromosomes usually found in pairs
  • humans have 46 (23 pairs)
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3
Q

haploid

A
  • one

- which cells are haploid?

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4
Q

diploid

A
  • 2

- which are diploid

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5
Q

Cytogenetics (eukaryotic chromosomes)

A
  • involves examination of chromosomes and cell division
  • when cells prepare to divide, chromosomes become very compact
  • easily viewed with light microscope
  • karyotype
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6
Q

homologous chromosomes

A
  • in diploid organisms (including humans), chromosomes come in matched pairs
  • one from each parent
  • not exact copies, same genes (but maybe different versions
  • each pair= homologous chromosomes
  • slight differences provide variation in gene function
  • red hair vs. blonde hair; brown eyes vs. blue eyes
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7
Q

chromosomes in humans

A
  • 23 pairs (46 total)
  • first 22= autosomes
  • lower #- larger, more genes
  • pair #23= sex chromosomes
  • X and Y male, not homologues
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8
Q

cell cycle

A
  1. G1- first gap
  2. S- synthesis of DNA
  3. G2- second gap
  4. mitosis and cytokinesis
    - first 3 are interphase
    - G0- substitute for G1 for cells postponing division or never dividing again (neurons)
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9
Q

G1 phase of cell cycle

A
  • growth phase
  • signaling molecules can help cell progress to next phase
  • if cell passes restriction point (G1 checkpoint), can move on to S phase
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10
Q

S phase of cell cycle

A
  • replication
  • afterward, two copies stay joined as sister chromatids
  • human cell in G1 has 46 chromosomes
  • same cell in G2 has 46 pairs of sister chromatids or 92 chromatids total
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11
Q

G2 phase of cell cycle

A

-cell makes proteins necessary for mitosis and cytokinesis

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12
Q

Mitosis and Cytokinesis

A
  • division of one cell nucleus into two, with separation of sister chromatids
  • cytokinesis- follows mitosis to divide the cytoplasm into two daughter cells
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13
Q

Checkpoints

A
  • cyclins or cyclin-dependent kinases (cdks) responsible for advancing a cell through the phases of the cell cycle
  • after G1, G2 and M phase
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14
Q

mitotic cell division

A
  • end product- two daughter cell
  • genetically identical to original mother
  • used for:
    1. Asexual reproductions
    2. Growth and development
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15
Q

preparation for cell division

A
  • DNA replicated (what phase)
  • sister chromatids
  • tightly associated at centromere
  • used as attachment site for kinetochore
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16
Q

mitotic spindle

A
  • apparatus responsible for organizing and sorting the chromosomes
  • composed of microtubules
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17
Q

Centrosomes (mitotic spindle)

A
  • microtubule organizing centers (MTOCs)
  • duplicate at beginning of M phase
  • each composed of two centrioles
  • each defines a pole
  • plants and fungi- use different MTOCs
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18
Q

Astral microtubules

A

position spindle in cell

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19
Q

polar microtubules

A

separate 2 poles

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20
Q

kinetochore microtubules

A

attached to kinetochore bound to centromeres of each chromosome

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21
Q

phases of mitosis

A

prophase -> pro metaphase -> metaphase -> anaphase -> telophase

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22
Q

prophase of mitosis

A
  • sister chromatids condense
  • mitotic spindle starts to form
  • nuclear envelope begins to dissociate
  • nucleolus is no longer visible
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23
Q

prometaphase of mitosis

A
  • nuclear envelope completely dissociates into vesicles
  • mitotic spindle is fully formed
  • sister chromatids attach to the spindle via kinetochore microtubules
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24
Q

metaphase of mitosis

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A

sister chromatids align along the metaphase plate

25
anaphase of mitosis
- sister chromatids separate - individual chromosomes move toward the poles as kinetochore microtubules shorten - polar microtubules lengthen and push the poles apart
26
Telophase and Cytokinesis of mitosis
- chromosomes decondense - nuclear envelope re-forms - cytokinesis separates mother cell into two daughter cells, which begins with a cleavage furrow in animal cells
27
when the haploid sperm and haploid egg fuse...
a diploid fertilized egg (zygote) is produced
28
meiosis.. produces sperm and eggs??
- if we produced sperm and eggs by mitosis, each gamete would have 46 chromosomes - sperm (46) + egg (46) -> offspring with 92 chromosomes - grandchildren would have 184 chromosomes - sperm (92) + egg (92) - clearly does not happen
29
meiosis
- haploid cells produced from originally diploid cells - humans: in testes and ovaires - replicate DNA once - divide the cell twice
30
Meiosis- key differences
1. homologous pairs form a bivalent or tetrad 2. crossing over -> "gene swapping" 3. independent assortment of chromosomes - overall effect- increase genetic possibilities in offspring
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1. bivalent or tetrad
- homologous pairs of sister chromatids associate, form a bivalent or tetrad - process called synapsis - allows crossing over to take place
32
2. crossing over
- overlapping sections of tetrad can exchange genetic material - increases the genetic variation of a species - chiasma- arms of the chromosomes tend to separate but remain adhered at a crossover site
33
3. independent assortment
- random movement of chromosomes into daughter cells - metaphase I of Meiosis I - homologous chromosomes randomly assort to either side of metaphase plate - humans have 23 pairs of chromosomes - 2^23 different ways chromosomes could line up in meiosis - 8 mill different ways - 8 mill genetically diff eggs - 8 mill genetically diff sperm - 64 trillion genetically diff offspring - NOT including variation due to crossing over
34
Prophase I of meiosis
- homologous chromosomes synapse; crossing over occurs - chromosomes condense - nuclear envelope begins to dissociate into vesicles
35
Prometaphase I of meiosis
- the nuclear envelope completely dissociates into vesicles | - bivalents become attached to kinetochore microtubules
36
metaphase I of meiosis
- bivalents randomly align along the metaphase plate | - each pair of sister chromatids is attached to one pole
37
anaphase I of meiosis
-homologous chromosomes separate and move toward opposite poles
38
telophase I and cytokinesis of meiosis
- the chromosomes decondense, and the nuclear envelope re-forms - the 2 daughter cells are separated by a cleavage furrow
39
Prophase II of meiosis
- sister chromatids condense, and the spindle starts to form | - the nuclear envelope begins to dissociate into vesicles
40
prometaphase II or meiosis
- the nuclear envelope completely dissociates into vesicles | - sister chromatids attach to the spindle via kinetochore microtubules
41
metaphase II of meiosis
- sister chromatids align along the metaphase plate | - each pair of sister chromatids is attached to both poles
42
anaphase II of meiosis
- sister chromatids separate, and chromosomes move toward poles as kinetochore microtubules shorten - polar microtubules lengthen and push the poles apart
43
telophase II and cytokinesis of meiosis
- chromosomes decondense, and nuclear envelope re-forms | - cleavage furrows separate the 2 cels into 4 cells
44
life cycles
- most animals are diploid-dominant - are there haploid-dominant eukaryotes? - many fungi, some plants and algae - haploid cells fuse to form diploid zygote, immediately use meiosis to make 4 haploid spores
45
chromosome variation
- variations of chromosome structure and/or number can have major effects on organisms - several human diseases - important in evolution of new species
46
Deletions; chromosomal mutations
- segment or whole - example: Cri-du-chat syndrome - "cry of the cat" - deletion on chromosome 5 - abnormal brain development, small head, abnormal larynx
47
duplications; chromosomal mutations
-section occurs 2 or more times in a row
48
inversions; chromosomal mutations
change in direction along a single chromosome
49
Simple translocations; chromosomal mutations
-one segment becomes attached to another chromosome
50
reciprocal translocations; chromosomal mutations
-exchange pieces between two different chromosomes
51
Aneuploidy
- alterations in number if a particular chromosome pair - total number not an exact multiple of a set - usually has detrimental consequences - often results from non-disjunction
52
nondisjunction
- common cause of aneuploidy - chromosomes do not sort properly during cell divisions - gametes with too many or too few chromosomes - if used during reproduction, effects every cell of offspring
53
trisomy
- third copy of a chromosome - 2n+1 (47 in humans) - due to non-disjunction: 10% in sperm; 90% in egg - down syndrome: three copies of chromosome 21 - 0.1% of all live births - various morphological and behavioral effects - short stature, reduced life span, infertility in males, heart defects
54
Trisomy: Sex chromosomes
- XXY (Klinefelter Syndrome) - male external appearance - dysfunctional testicles - tall stature - some feminine features - normal intelligence; some verbal cognitive difficulties - reduced fertility - may require hormonal treatment at puberty
55
monosomy
- missing one of normal copies of a chromosome - 2n-1; (45 total in humans) - ex: Turner's Syndrome: - XO genotype - random error (not heritable) due to non-disjunction - normal female external appearance, but fertility may be affected by abnormal ovaries - short stature with folds of skin at neck - normal intelligence, with some spatial and memory deficits
56
trisomy and monosomy
- trisomic and monosomic individuals have imbalance in the level of genes - increased or decreased expression of these genes can interfere with proper cell function
57
Aneuploidy in humans
- 5-10% of all fertilized human- abnormal chromosome number - approx. 50% of all spontaneous abortions (miscarriage) due to chromosomal abnormality - we can survive some abnormalities - trisomies or abnormalities in sex chromosome number
58
euploid
- chromosome number that is viewed as normal | - in a diploid organisms, 2 sets is normal; 2n
59
polypoid
- 3 or more sets of chromosomes - triploid 3n - tetraploid 4n - not compatible with life in humans
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