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Biology 2311-- Fall 2022 > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

Prokaryotic cell division occurs as ______

A

binary fission

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2
Q

What is the genetic information in a prokaryote called?

A

Nucleoid

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3
Q

Where does copying begin in prokaryotes?

A

Replication origin

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4
Q

What direction does copying proceed in for prokaryotes?

A

Bi-directionally

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5
Q

Describe the process of binary fission

A
  1. Bacterial cell has an origin of replication
  2. Replication begins at origin and proceeds in opposite directions
  3. Replicated origins move to two ples of the cell as replication continues
  4. Plasma membrane grows inward, new cell wall is synthesized
  5. Cell cuts in two
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6
Q

How many chromosomes are in humans?

A

46 (23 nearly identical pairs)

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7
Q

How many chromosomes do eukaryotes tend to have?

A

10-50

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8
Q

What are the three parts of a cell’s life cycle?

A

Cell growth, including DNA replication
Nuclear division/mitosis
Division of the cytoplasm in cytokinesis

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9
Q

What is mitosis?

A

DNA is equally and precisely divided, generating daughter cells that are genetic copies of the parent cells. This occurs with almost perfect fidelity and is facilitated by the mitotic cytoskeleton.

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10
Q

What is meiosis?

A

Daughter nuclei with half the number of chromosomes are produced; the arrangement of genes on chromosomes are different from parent cells

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11
Q

What are chromosomes?

A

Linear DNA molecules combined with proteins.

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12
Q

The complex of DNA and all its proteins is called ____

A

Chromatin

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13
Q

What proteins pack DNA into a shorter length?

A

Histone proteins

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14
Q

What is the structure of a nucleosome?

A

An 8-protein nucelosome core particle forms when DNA winds around 2 molecules each of H2A, H2B, H3, and H4

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15
Q

What segment connects nucleosomes?

A

A linker segment

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16
Q

What is the 10-nm chromatin fiber?

A

Compacts DNA by a factor about 7

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17
Q

30-nm chromatin fiber

A

Forms when Histone H1 attaches, which causes the structure to coil

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18
Q

Complex of DNA and all associated proteins is called

A

Chromatin

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19
Q

What is the solenoid model?

A

It predicts that the nucleosomes spiral helically with about six nucleosomes per turn

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20
Q

Euchromatin vs heterochromatin

A

Euchromatin is more loosely packed and more highly expressed in comparison to heterochromatin regions

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21
Q

What are sister chromatids?

A

Replicated chromosomes connected to eachother at the centromere- held together via sister chromatid adhesion (cohesion) until mitosis separates them

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22
Q

What holds sister chromatids together?

A

Cohesin

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23
Q

The equal distribution of chromosomes into each of two daughter nuclei is called

A

Chromosome segregation

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24
Q

What is the difference between sister chromatids and homologous chromosomes?

A

Sister chromatids are identical, homologous chromosomes code for same genes but have different alleles

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25
Q

What is ploidy?

A

The number of chromosome sets in a cell or species

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26
Q

If an organism has only one copy of each chromosome type, it is a ____

A

haploid

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27
Q

Most eukaryotes have two copies of each type of chromosome, making them

A

Diploids

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28
Q

What is polyploidy?

A

When species have 3 or more of each type od chromosome

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29
Q

The two chromosomes of each pair in a diploid cell are called homologous chromosomes because

A

One is from the mother, one is from the father, and they have the same genes in the same order

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30
Q

What does a karyotype show?

A

An individual’s array of chromosomes

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31
Q

How are cells prepared for a karyotype?

A

Sample is added to a culture medium that has a stimulator for growth and division of cells incubated at 37 C
Cell is stained so chromosomes are visible
Chromosomes are photographed

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32
Q

What are the steps of interphase?

A

G1 (primary growth, longest phase)
S (DNA replication)
G2 (organelles replicate, microtubules organize)

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33
Q

Eukaryotic cell cycle

A

Interphase (G1,S,G2), Mitosis, Cytokinesis

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34
Q

T or F: G1 varies in length

A

True

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35
Q

What is special about the G1 phase?

A

Here, many cells stop dividing and are instead put in a G0 phase, where some never resume the cell cycle

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36
Q

What happens in G1?

A

G1 is a period of growth where RNA, proteins, and molecules needed for S phase are created

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37
Q

S phase

A

DNA is replicated and copies are held together

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38
Q

G2 phase

A

No DNA synthesis, but protein and RNA synthesis continues to prepare for mitosis

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39
Q

How many hours spent in each stage?

A

G1- 10 hrs
S- 9 hrs
G2- 4 hrs
Mitosis- 1 hr

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40
Q

What are the checkpoints in the cell cycle?

A

G1/S
G2/M
Mitotic spindle checkpoint

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41
Q

Mitosis divided into 5 phases

A

Prophase
Prometaphase
Metaphase
Anaphase
Telophase/cytokinesis

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42
Q

Mitosis requires the formation of

A

a spindle

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43
Q

Centrosome

A

The main microtubule organizing center of animal cells and protists

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44
Q

What happens to the centrosome in mitosis

A

Centrosome has centrioles that are duplicated and divided

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45
Q

Microtubles extending from the centrosomes produce

A

Arrays/asters at the tips that form the poles of the spindle

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46
Q

What is the spindle

A

Separated centrosomes and the mass of microtubules in between them

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47
Q

G1

A

Chromosomes are unreplicated and extend through nucleus

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48
Q

S

A

DNA replication

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49
Q

G2

A

DNA condensation using cohesins which align the sister chromatids tightly- centriole has also doubled

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50
Q

Prophase

A

Individual condensed chromosomes first become visible
Condensation continues
Spindle apparatus assembles and centrosomes move to opposite poles, generating the spindle as they separate
Nuclear envelope starts to disintegrate and nucleolus disappears

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51
Q

Prometaphase

A

Transition occurs after disassembly of nuclear envelope
Spindle microtubules grow from centrosomes at opposite spindle poles towards the center of the cell
A kinetochore forms on each sister chromatid at the centromere
Kinetochore microtubules bind to kinetochores
Nonkinetochore microtubules from opposite sides overlap at the spindle point
Chromosomes begin to move to center of cell in a process called congression (facilitated by motor proteins at kinetochores and assembly/disassembly of microtubules)

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52
Q

Metaphase

A

Spindle microtubules move chromosomes into alignment at the spindle midpoint/metaphase plate
Condensation gives each chromosome a characteristic shape
Karyotypes formed here according to size and shape

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53
Q

Anaphase

A

Centromeres split, cohesin protein is removed from all chromosomes
Sister chromosomes pulled to opposite sides (microtubules shorten)
Separase enzyme

54
Q

Anaphase A

A

Motor proteins at the spindle poles pull kinetochore microtubules polewards, and the microtubule disassembles into tubulin subunits

55
Q

Anaphase B

A

Nonkinetochore microtubules elongate the cell as motor proteins walk in opposite directions- grow in length as they slide along

56
Q

Telophase

A

Spindle apparatus disappears, chromosomes decondense, returning to extended state, muclear envelope forms around cromosomes which uncoil, nucleolus reappears and RNA transcription resumes

57
Q

Cytokinesis

A

Animals, protists, fungi: a furrow/contractile ring of microfilaments slide together girdles the cell and deepens until it cuts the cytoplasm into two
Plants: cell plate forms and grows laterally until cytoplasm divides in two

58
Q

T or F: mitosis occurs within the nucleus in some organisms

A

T, fungi and protists

59
Q

What determines the plane of cytoplasmic division

A

Microtubules at spindle midpoint

60
Q

What is the contractile ring made from

A

Actin and myosin

61
Q

Cytokinesis in plant cells

A
  1. Vesicles with material collect in the plane
  2. More vesicles added and fuse togehter, dumping contents into an expanding wall which separates cell into two by a continuous wall
62
Q

What is cell division?

A

One cell divides to form two new cells- daughter cells

63
Q

What kinds of processes happen within cells before they divide?

A

Growth period- protein synthesis, cell growth, ER synthesizes phospholipids and membrane proteins and the ER increases in surface area, and other organelles grow or become more numerous
Afterwards, DNA replication occurs, followed by mitosis

64
Q

What does cenocytic mean?

A

Many nuclei are interspersed throughout cytoplasm- cytokinesis does not occur

65
Q

How is eukaryotic dna stored?

A

Linear chromosomes containing a single DNA molecule with 2 strands of DNA

66
Q

How many nucelotides in an eukaryotic chromosome?

A

1 million- some human chromosomes are over 100 million nucleotides long

67
Q

Chromatin

A

A dna protein complex

68
Q

what are histones?

A

a class of small dna proteins that bind dna

69
Q

nucleosome

A

the complex of dna and histones

70
Q

nucleosome core particles

A

the histones that the dna wraps around

71
Q

What are the five types of histones?

A

H1, H2A, H2B, H3, and H4

72
Q

what histones make up the nucleosome core particle?

A

h2a, h2b, h3, h4 (2 molecules each to make an 8-protein complex)

73
Q

how many base pairs of dna in a nucleosome?

A

150 base pairs

74
Q

what is a linker?

A

a short segment of about 50 dna base pairs that extends between one nucleosome and the next

75
Q

10 nm chromatin fiber

A

a series of nucleosomes connected by linkers- is about 7 times shorter than dna

76
Q

H1 histone

A

one H1 molecule binds both to the nucleosome and to the linker dna, causing the nucleosomes to form a coiled 30 nm structure called the 30 nm chromatin fiber, which has about 6 nucleosomes per turn

77
Q

solenoid model

A

6 nucleosomes coiled together to form the h1 protein- this is the chhromosome in the metaphase stage of the cell in mitosis (the most compact form of a chromosome)

78
Q

what do chromosomes look like in cells not in mitosis?

A

chromatin fibers are loosely packed in some regions and densely packed in others

79
Q

euchromatin

A

loosely packed region

80
Q

heterochromatin

A

densely packed region

81
Q

nonhistone proteins

A

proteins other than chromatin needed for higher level coiling of chromatin

82
Q

condensins

A

a nonhistone protein that binds dna at two sites and holds together two parts of a chromosome positioned next to eachother

83
Q

topoisomerase

A

adjusts the twisting of the two strands of dna which causes the dna to form loops

84
Q

The two identical copies of each chromosome that are produced in DNA replication are called

A

sister chromatids

85
Q

how are sister chromatids held together?

A

sister chromatid cohesion- ring-shaped proteins called cohesins circle the sister chromatids along their length

86
Q

how many chromosomes in a human egg cell?

A

23

87
Q

for each of the 23 chromosomes in an egg cell, there is a ______ in the sperm cell

A

homologous chromosome

88
Q

what is a diploid?

A

cells that contain homologous pairs of chromosomes

89
Q

what are haploids?

A

only have one homolog for each chromosome

90
Q

what is the ploidy of human cells?

A

2n=46

91
Q

G1

A

period of growth before the dna replicates, the cell synthesizes proteins, rna, and molegules

92
Q

s phase

A

cell duplicates chromosomes, chromosomal proteins

93
Q

g2

A

continued synthesis of dna molecules and rna molecules, and it continues to grow

94
Q

which is the phase that usually varies in length?

A

g1

95
Q

how long do s and g2 phases last?

A

10-12 hours for s and 4-6 for g2 and 1 hour or less for mitosis

96
Q

what is the g0 phase?

A

A phase where cells not destined to divide enter- cell performs normal functions but stops growing and does not replicate its dna- for example, organs and neurons

97
Q

what is the centromere?

A

a specialized chromosomal region that connects sister chromatids and attaches them to the mitotic spindle

98
Q

when do the centrosomes first separate?

A

s phase

99
Q

what is an aster?

A

radiating array produced by microtubules

100
Q

spindle poles

A

centrosomes at either end

101
Q

what is the kinetochore?

A

a structure consisting of proteins attached to the centromere that mediates attachment and movement of chromosomes along the mitotic spindle

102
Q

describe the orientation of a sucessfully attached chromosome

A

attached to microtubules extending from each spindle pole

103
Q

nonkinetochore microtubules

A

overlap those from the opposite spindle pole

104
Q

metaphase plate

A

the midpoint where chromosomes align

105
Q

what enzyme is activated during anaphase

A

separase

106
Q

furrow

A

girdles the cell and deepens until it cuts the cytoplasm in two

107
Q

cell plate

A

a new cell wall that forms between the daughter nuclei until it divides the nuclei in two - formed by vesicles containing cell wall material

108
Q

describe gorbsky’s experiment

A

bleached region of kinetochore microtubule remained the same length, indicating that the bleached region remained the same distance from the pole as the chromosomes moved toward the pole- microtubule disassembles as kinetochore walks over it

109
Q

why does a dividing cell elongate?

A
  1. motor proteins on overlapping protein nonkinetochore microtubules walk in opposite directions, reducing the amount of overlap present, which pushes the spindle poles further apart.
  2. the nonkinetochore microtubules push the poles apart by growing in length as they slide along
110
Q

why is yeast an ideal organism to study?

A

single celled and easy to manipulate- rapidly reproduces

111
Q

key checkpoints in a cell

A

g1/s, g2/m, mitotic spindle

112
Q

what does the g1/s cdk do?

A

phosphorylates target proteins for g1/s transition and commits cell to dna replication

113
Q

s-phase cdk

A

phosphorylates target proteins for initiation of dna replication and progession through s

114
Q

mitotic cyclin/m cdk

A

phosphorylates proteins for g2/m transition and progression through mitosis

115
Q

most important checkpoint in a cell

A

g1/s checkpoint, because once the cell replicates its dna, it is committed to completing the rest of the cell cycle

116
Q

what is the major determinant of whether cell is ready to divide?

A

cell size, so growth factors are an important molecule present in cell growth

117
Q

cells with more chromosomes tend to grow ______ before cell division

A

larger

118
Q

contact inhibition

A

inhibition of movement or proliferation of normal cells that result from cell-cell contact - shunts cell into the g0 phase

119
Q

g2/m checkpoint

A

determines whether cell is ready to begin mitosis- senses errors in dna replication, inhibits passage through g2/m

120
Q

mitotic spindle checkpoint

A

assesses whether chromosomes are all attached properly to the mitotic spindle- marks transition from metaphase to anaphase- senses the absense of tension in the cohesion rings

121
Q

g1 cyclins

A

bind to g1 cdks before the g1/s transition to increase expression of the gi/s and s cyclins. g1 cyclins do not change rapidly at cell cycle transitions and instead are activated by signal transduction pathways.

122
Q

g1/s cyclins

A

bind to gi/s cdks to form complexes that increase expression of s cyclins- facilitate the transition from g1 to s

123
Q

s-phase cyclins

A

bind to s-phase cdks to activate dna replication

124
Q

mitotic cyclins

A

bind to mitotic cdks in g2 to form a complex that is required for the transition from g2 to m and progression of the cell through mitosis. also known as the m phase promoting factor, which activates the anaphase promoting complex

125
Q

anaphase promoting complex (apc)

A

degrades an inhibitor of anaphase, leading to separation of sister chromatids

126
Q

describe the unique cell division properties of cancer cells

A

divide continuously and uncontrollably, producing a tumor, and in metastasis, they break loose and grow into new tumors in other body regionss. many of their proteins code for components of the cyclin/cdk system, and others regulate gene expression or receptors. oncogenes encode altered versions of these products.

127
Q

what is the structure of dna in a proakaryote?

A

one circular chromosome packed and coiled into an irregularly shaped mass called the nucleoid. many bacterial cells also contain plasmids which are circular dna molecules

128
Q

how long does it take for the cell cycle in prokaryotes

A

about 20 minutes

129
Q

describe the process of dna replication in bacteria

A
  1. replication starts at the ori
  2. proceeds in opposite directions
  3. the two replicated origins migrate to the two ends of the poles as replication continues
  4. replication is complete and a new cell wall is synthesized
130
Q

T or F: mitosis evolved from binary fission

A

T

Biology 2311-- Fall 2022 (12 decks)

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