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BIO 111 > Chapter 15 > Flashcards

Chapter 15 Flashcards

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Biology 101 flashcards
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

A

sister chromatids align along the metaphase plate

25
Q

anaphase of mitosis

A
  • sister chromatids separate
  • individual chromosomes move toward the poles as kinetochore microtubules shorten
  • polar microtubules lengthen and push the poles apart
26
Q

Telophase and Cytokinesis of mitosis

A
  • chromosomes decondense
  • nuclear envelope re-forms
  • cytokinesis separates mother cell into two daughter cells, which begins with a cleavage furrow in animal cells
27
Q

when the haploid sperm and haploid egg fuse…

A

a diploid fertilized egg (zygote) is produced

28
Q

meiosis.. produces sperm and eggs??

A
  • 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
Q

meiosis

A
  • haploid cells produced from originally diploid cells
  • humans: in testes and ovaires
  • replicate DNA once
  • divide the cell twice
30
Q

Meiosis- key differences

A
  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
31
Q
  1. bivalent or tetrad
A
  • homologous pairs of sister chromatids associate, form a bivalent or tetrad
  • process called synapsis
  • allows crossing over to take place
32
Q
  1. crossing over
A
  • 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
Q
  1. independent assortment
A
  • 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
Q

Prophase I of meiosis

A
  • homologous chromosomes synapse; crossing over occurs
  • chromosomes condense
  • nuclear envelope begins to dissociate into vesicles
35
Q

Prometaphase I of meiosis

A
  • the nuclear envelope completely dissociates into vesicles

- bivalents become attached to kinetochore microtubules

36
Q

metaphase I of meiosis

A
  • bivalents randomly align along the metaphase plate

- each pair of sister chromatids is attached to one pole

37
Q

anaphase I of meiosis

A

-homologous chromosomes separate and move toward opposite poles

38
Q

telophase I and cytokinesis of meiosis

A
  • the chromosomes decondense, and the nuclear envelope re-forms
  • the 2 daughter cells are separated by a cleavage furrow
39
Q

Prophase II of meiosis

A
  • sister chromatids condense, and the spindle starts to form

- the nuclear envelope begins to dissociate into vesicles

40
Q

prometaphase II or meiosis

A
  • the nuclear envelope completely dissociates into vesicles

- sister chromatids attach to the spindle via kinetochore microtubules

41
Q

metaphase II of meiosis

A
  • sister chromatids align along the metaphase plate

- each pair of sister chromatids is attached to both poles

42
Q

anaphase II of meiosis

A
  • sister chromatids separate, and chromosomes move toward poles as kinetochore microtubules shorten
  • polar microtubules lengthen and push the poles apart
43
Q

telophase II and cytokinesis of meiosis

A
  • chromosomes decondense, and nuclear envelope re-forms

- cleavage furrows separate the 2 cels into 4 cells

44
Q

life cycles

A
  • 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
Q

chromosome variation

A
  • variations of chromosome structure and/or number can have major effects on organisms
  • several human diseases
  • important in evolution of new species
46
Q

Deletions; chromosomal mutations

A
  • segment or whole
  • example: Cri-du-chat syndrome
  • “cry of the cat”
  • deletion on chromosome 5
  • abnormal brain development, small head, abnormal larynx
47
Q

duplications; chromosomal mutations

A

-section occurs 2 or more times in a row

48
Q

inversions; chromosomal mutations

A

change in direction along a single chromosome

49
Q

Simple translocations; chromosomal mutations

A

-one segment becomes attached to another chromosome

50
Q

reciprocal translocations; chromosomal mutations

A

-exchange pieces between two different chromosomes

51
Q

Aneuploidy

A
  • 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
Q

nondisjunction

A
  • 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
Q

trisomy

A
  • 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
Q

Trisomy: Sex chromosomes

A
  • 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
Q

monosomy

A
  • 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
Q

trisomy and monosomy

A
  • 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
Q

Aneuploidy in humans

A
  • 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
Q

euploid

A
  • chromosome number that is viewed as normal

- in a diploid organisms, 2 sets is normal; 2n

59
Q

polypoid

A
  • 3 or more sets of chromosomes
  • triploid 3n
  • tetraploid 4n
  • not compatible with life in humans

BIO 111 (17 decks)

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