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Biology EXAM 8 > Biology 8 Exam > Flashcards

Biology 8 Exam Flashcards

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1
Q

Q: What are the main functions of cell division?

A

Reproduction, growth, and repair.

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2
Q

How do unicellular organisms reproduce?

A

By cell division.

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3
Q

What two processes does cell division involve in eukaryotes?

A

Mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm).

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4
Q

What is the difference between asexual and sexual reproduction?

A

Asexual reproduction involves a single parent producing genetically identical offspring, while sexual reproduction involves two parents and produces genetically unique offspring.

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5
Q

What type of cell division occurs in bacteria?

A

Binary fission.

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6
Q

What type of cell division produces human gametes?

A

Meiosis.

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7
Q

Why is DNA partitioned among chromosomes in eukaryotic cells?

A

DNA is partitioned among chromosomes to make it easier for the eukaryotic cell to replicate and distribute its large amounts of DNA during cell division.

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8
Q

What do chromosomes consist of, and how do they change during mitosis?

A

Chromosomes consist of chromatin, a complex of DNA and protein that condenses during mitosis. When chromosomes replicate, they form identical sister chromatids, which separate during mitosis to become the chromosomes of the new daughter cells.

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9
Q

What is binary fission, and how does it differ from mitosis?

A

Binary fission is the process of bacterial division, which is simpler and not the same as mitosis in eukaryotic cells.

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10
Q

What is asexual reproduction, and how does it occur in single-celled and multicellular organisms?

A

In asexual reproduction, a single individual passes copies of all its genes to its offspring, resulting in genetically identical offspring.

Single-celled organisms, such as bacteria, and multicellular organisms, like hydras, reproduce asexually. Hydras can reproduce by budding to form genetically identical offspring.

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11
Q

How does mitosis enable asexual reproduction?

A

Mitosis allows for asexual reproduction by producing cells that carry the same genetic information as the parent cells, making the offspring genetically identical to the parent.

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12
Q

How does sexual reproduction increase genetic variation compared to asexual reproduction?

A

Sexual reproduction produces greater genetic variation because offspring inherit a unique combination of genes from two parents, making them genetically distinct from both their parents and siblings.

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13
Q

What are human somatic cells, and how many chromosomes do they have?

A

Human somatic cells are diploid, meaning they have two sets of 23 chromosomes, for a total of 46 chromosomes.

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14
Q

What type of cell division occurs in the ovaries and testes, and what does it produce?

A

Meiosis occurs in the ovaries and testes, producing haploid gametes (eggs and sperm) that carry only one set of 23 chromosomes each.

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15
Q

What happens during fertilization in humans?

A

During fertilization, a haploid sperm cell combines with a haploid egg cell to form a diploid zygote with 46 chromosomes. This zygote develops into a sexually mature diploid adult.

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16
Q

What is the alternation of diploid and haploid stages in sexual life cycles?

A

In sexual life cycles, diploid organisms produce haploid gametes through meiosis, and fertilization produces diploid zygotes, maintaining the alternation between diploid and haploid stages.

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17
Q

What are the main stages of mitosis, and how do they alternate with interphase in the cell cycle?

A

prophase, metaphase, anaphase, and telophase, followed by cytokinesis. Mitosis alternates with interphase, which includes the G1, S, and G2 phases. DNA replication occurs during the S phase.

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18
Q

What is the mitotic spindle, and what is its function?

A

The mitotic spindle is an apparatus of microtubules that controls chromosome movement during mitosis, ensuring proper distribution to daughter cells.

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19
Q

What is the role of centrosomes and centrioles in mitosis?

A

Centrosomes, which include centrioles in animal cells, are organelles that help organize the mitotic spindle during cell division.

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20
Q

What happens to chromatids during metaphase and anaphase?

A

During metaphase, chromatids align at the metaphase plate, and during anaphase, sister chromatids separate and move toward opposite poles of the cell.

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21
Q

How do kinetochore microtubules and motor proteins function during anaphase?

A

Kinetochore microtubules, with the help of motor proteins, shorten to pull chromatids to opposite poles. Nonkinetochore microtubules slide past each other, elongating the cell.

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22
Q

How does cytokinesis differ between animal and plant cells?

A

In animal cells, cytokinesis occurs through the formation of a cleavage furrow that pinches the cell in two. In plant cells, a cell plate forms to divide the cytoplasm and create two daughter cells.

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23
Q

What is contained within the cytoplasm of a cell in late interphase?

A

Two centrosomes, each with centrioles, and chromosomes in the nucleus as loose chromatin. Nucleoli are also present.

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24
Q

What are the five phases of mitosis?

A

prophase, prometaphase, metaphase, anaphase, and telophase.

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25
Q

What happens to chromatin fibers during prophase?

A

The chromatin coils into chromosomes, each made of two sister chromatids.

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26
Q

What initiates the formation of the mitotic spindle?

A

Microtubules grow out from centrosomes to form the spindle.

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27
Q

What is the metaphase plate?

A

It’s an imaginary line in the middle of the cell where chromosomes align.

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28
Q

What event marks the beginning of anaphase?

A

The centromeres split, separating the sister chromatids.

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29
Q

What happens to the spindle microtubules during anaphase?

A

Spindle microtubules pull chromosomes to opposite sides, and the cell stretches out.

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30
Q

What reforms around the chromosomes during telophase?

A

Nuclear envelopes form around the chromosomes at each pole

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31
Q

How does cytokinesis differ between animal and plant cells?

A

In animal cells, a cleavage furrow pinches the cell in two. In plant cells, a cell plate forms to separate the two cells.

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32
Q

What is binary fission?

A

It’s the simple cell division in bacteria, where the cell splits in two.

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33
Q

What drives the cell cycle?

A

Proteins called cyclins and Cdks control the timing of the cell cycle.

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34
Q

What are cyclins?

A

Cyclins are proteins whose levels rise and fall during the cell cycle.

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35
Q

What do cyclin-dependent kinases (Cdks) do?

A

Cdks are enzymes that need cyclins to be active and help move the cell through different stages.

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36
Q

What is the role of the anaphase-promoting complex (APC)?

A

The APC helps separate sister chromatids and destroys cyclins to end mitosis.

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37
Q

What happens as G1-cyclins rise?

A

G1-cyclins bind to their Cdks, signaling the cell to prepare chromosomes for replication.

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38
Q

What does the S-phase promoting factor (SPF) do?

A

SPF, which includes cyclin A and Cdk2, enters the nucleus to prepare the cell for DNA duplication and centrosome replication.

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39
Q

What occurs during DNA replication in terms of cyclins?

A

Cyclin E is destroyed, and the levels of mitotic cyclins increase during G2.

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40
Q

What does the M-phase promoting factor (MPF) initiate?

A

MPF initiates the assembly of the mitotic spindle, breakdown of the nuclear envelope, and condensation of chromosomes.

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41
Q

What does MPF activate at metaphase?

A

MPF activates the anaphase promoting complex (APC).

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42
Q

What role does the APC play in cell division?

A

The APC allows sister chromatids to separate during anaphase and destroys mitotic cyclins, starting the next cycle with G1 cyclin synthesis.

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43
Q

What is the purpose of checkpoints in the cell cycle?

A

Checkpoints monitor the cell cycle to stop it if something goes wrong.

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44
Q

What does the S phase checkpoint monitor?

A

It checks for the presence of Okazaki fragments during DNA replication before the cell can continue.

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45
Q

Where do DNA damage checkpoints occur?

A

DNA damage checkpoints occur before entering S phase (G1), during S phase, and after DNA replication (G2).

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46
Q

What do spindle checkpoints detect?

A

They detect issues with spindle fibers not attaching to kinetochores, blocking the cell from entering anaphase (M checkpoint).

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47
Q

What happens if there is improper spindle alignment?

A

The cell will block cytokinesis and may trigger apoptosis if the damage is severe.

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48
Q

What is the consequence of mutations in checkpoint proteins?

A

Mutations can lead to cancers since they allow damaged cells to continue dividing.

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49
Q

What is the role of checkpoints in the cell cycle?

A

Checkpoints monitor the cell cycle and can stop it if something goes wrong.

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50
Q

What does the S phase checkpoint monitor?

A

It checks for Okazaki fragments during DNA replication and won’t allow the cell to continue until they are gone.

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51
Q

What do spindle checkpoints do?

A

They detect problems with spindle fibers not attaching to kinetochores and can halt the cell cycle at metaphase (M checkpoint).

52
Q

Where are DNA damage checkpoints located?

A

They are found before S phase (G1), during S phase, and after DNA replication (G2)

53
Q

How does the spindle checkpoint ensure proper attachment?

A

They detect problems with spindle fibers not attaching to kinetochores and can halt the cell cycle at metaphase (M checkpoint).

54
Q

What happens if there is improper spindle alignment?

A

The cell blocks cytokinesis and may trigger apoptosis if the damage is severe and cannot be repaired.

55
Q

Why are mutations in checkpoint proteins concerning?

A

Mutations can lead to cancers because they allow damaged cells to keep dividing instead of stopping.

56
Q

What does growth factor depletion explain?

A

It explains density-dependent inhibition, where crowded cells stop dividing.

57
Q

What is anchorage dependence?

A

It means that most animal cells need to be attached to a surface (like the extracellular matrix) to divide.

58
Q

What is anchorage dependence?

A

It means that most animal cells need to be attached to a surface (like the extracellular matrix) to divide

59
Q

How do cancer cells differ from normal cells in terms of division?

A

Cancer cells do not follow the normal rules; they can divide uncontrollably and do not exhibit density or anchorage dependence.

60
Q

What are some characteristics of cancer cells?

A

They are often undifferentiated (unable to perform specific functions) and have properties similar to embryonic stem cells, like immortality and mobility.

61
Q

What is a malignant tumor?

A

A malignant tumor invades surrounding tissues and can spread (metastasize) to other parts of the body.

62
Q

What does it mean for cancer cells to be “immortal”?

A

It means they do not undergo programmed cell death like normal cells, which typically divide only 50-60 times before aging and dying.

63
Q

What are carcinogens?

A

Carcinogens are agents that can cause cancer, such as UV light, radiation, cigarette smoke, certain viruses, and some food additives.

64
Q

How can personal lifestyle affect cancer risk?

A

Your lifestyle choices can increase exposure to carcinogens, which may raise the risk of certain types of cancer.

65
Q

How do offspring acquire genes from their parents?

A

Offspring inherit genes from their parents by receiving chromosomes.

66
Q

What is genetics?

A

Genetics is the study of heredity and the variation of genes.

67
Q

What is the specific location of a gene on a chromosome called?

A

The specific location of a gene is known as its locus.

68
Q

What is asexual reproduction?

A

Asexual reproduction is when a single individual produces offspring by passing on copies of all its genes

69
Q

Give an example of asexual reproduction.

A

An example is hydra, which can reproduce by budding to create genetically identical individuals.

70
Q

How does mitosis contribute to asexual reproduction?

A

Mitosis allows organisms to reproduce asexually by creating cells that are genetically identical to the parent cells

71
Q

What is the difference between asexual and sexual reproduction in terms of genetic variation?

A

Sexual reproduction produces greater genetic variation, while asexual reproduction creates genetically identical offspring.

72
Q

How do offspring inherit genes in sexual reproduction?

A

Each offspring inherits a unique combination of genes from two parents, making them different from their siblings and parents.

73
Q

What process occurs in the ovaries and testes to produce gametes?

A

Meiosis occurs in the ovaries and testes to produce haploid gametes (eggs and sperm).

74
Q

How many chromosomes do haploid gametes carry?

A

Haploid gametes carry one set of 23 chromosomes each.

75
Q

What happens during fertilization?

A

Fertilization combines an egg and a sperm, producing a diploid zygote with 46 chromosomes.

76
Q

What is a diploid zygote?

A

A diploid zygote is the fertilized egg that contains two sets of chromosomes (one from each parent).

77
Q

How does the life cycle progress after fertilization?

A

The zygote develops into a sexually mature diploid adult, which then produces haploid gametes.

78
Q

What is the relationship between diploid and haploid stages in sexual life cycles?

A

Sexual life cycles involve alternating between diploid (two sets of chromosomes) and haploid (one set of chromosomes) stages.

79
Q

How many chromosomes do normal human somatic cells have?

A

Normal human somatic cells have 46 chromosomes.

80
Q

What two processes alternate in sexual life cycles?

A

Fertilization and meiosis alternate in sexual life cycles.

81
Q

What is a karyotype?

A

A karyotype is an ordered display of an individual’s chromosomes, often prepared using lymphocytes.

82
Q

How many pairs of chromosomes are shown in a human karyotype?

A

A human karyotype shows 23 pairs of chromosomes.

83
Q

What are homologous chromosomes?

A

Homologous chromosomes are pairs of chromosomes that have the same length, centromere position, and staining pattern, and usually carry genes for the same inherited characters.

84
Q

How are the 23 pairs of chromosomes categorized in humans?

A

In humans, there are 22 pairs of autosomes and 1 pair of sex chromosomes.

85
Q

How do we inherit chromosomes?

A

We inherit one chromosome of each homologous pair from each parent.

86
Q

What are sex chromosomes, and what is the exception in humans?

A

Sex chromosomes determine an individual’s sex. In humans, females have a homologous pair of X chromosomes (XX), while males have one X and one Y chromosome (XY). The Y chromosome has fewer corresponding genes compared to the X chromosome.

87
Q

What do sperm cells and ova (gametes) contain?

A

Sperm cells and ova each have one set of chromosomes, consisting of 22 autosomes and either an X or a Y chromosome.

88
Q

What is a haploid cell?

A

A cell with a single set of chromosomes is called haploid

89
Q

What is the haploid number of chromosomes for humans?

A

The haploid number of chromosomes for humans is 23 (n = 23).

90
Q

What happens during fertilization?

A

A haploid sperm fuses with a haploid ovum, forming a fertilized egg (zygote) that contains two haploid sets of chromosomes.

91
Q

What is the chromosome count for a diploid cell?

A

The diploid number of chromosomes for humans is 46 (2n = 46).

92
Q

What are the only haploid cells in sexual reproduction?

A

The only haploid cells in sexual reproduction are gametes, produced by meiosis.

93
Q

How does the timing of meiosis and fertilization vary?

A

The timing of meiosis and fertilization varies among species, but the life cycle of humans and other animals is typical of one major type.

94
Q

What is the role of gametes in reproduction?

A

Gametes fuse to form a diploid zygote, which divides by mitosis to create a multicellular organism.

95
Q

What characterizes the life cycle of most fungi and some protists?

A

The zygote is the only diploid stage. It undergoes meiosis to create haploid cells, which then develop into haploid multicellular adults

96
Q

How do plants and some algae reproduce?

A

They have a life cycle with both haploid (gametophyte) and diploid (sporophyte) stages. Spores from the sporophyte become gametophytes, which produce gametes.

97
Q

How does sexual reproduction create genetic diversity?

A

It introduces variation through independent assortment, crossing over, random fertilization, and mutations.

98
Q

What is independent assortment?

A

It’s the random arrangement of chromosomes during meiosis, leading to different combinations in gametes.

99
Q

How many combinations can arise from independent assortment in humans?

A

With 23 chromosomes (n = 23), humans can have about 8 million combinations due to independent assortment.

100
Q

What is crossing over?
A7: Crossing over occurs when?

A

Crossing over occurs when homologous chromosomes exchange genetic material, creating new combinations of genes.

101
Q

What is crossing over?

A

It’s when chromosomes swap DNA segments during meiosis, mixing traits from parents.

102
Q

Why is crossing over important?

A

It creates genetic variety in offspring.

103
Q

How often does crossing over happen in humans?

A

It occurs 2 to 3 times for each pair of chromosomes.

104
Q

What is random fertilization?

A

It’s when any sperm can combine with any egg, making each zygote unique.

105
Q

How many combinations can a human zygote have?

A

A human zygote can have about 70 trillion possible combinations.

106
Q

What do mutations do?

A

Mutations add new genetic variations to a population.

107
Q

What is the main job of meiosis?

A

Meiosis reduces chromosomes from 46 to 23 and produces four daughter cells.

108
Q

How is meiosis different from mitosis?

A

Meiosis includes chromosome pairing and crossing over, while mitosis does not.

109
Q

What happens during prophase I of meiosis?

A

Homologous chromosomes pair up and exchange genetic material.

110
Q

What occurs during anaphase I?

A

The pairs of chromosomes separate and move to opposite ends of the cell.

111
Q

What do the two divisions of meiosis produce?

A

They produce four haploid daughter cells from one diploid cell.

112
Q

What occurs in prophase I of meiosis?

A

Each chromosome duplicates and pairs with its homolog, forming sister chromatids. This is when crossing over can occur, allowing genetic material exchange.

113
Q

What occurs in telophase I?

A

Two daughter cells form, each with one chromosome from each homologous pair.

114
Q

Describe anaphase I.

A

Homologous chromosomes separate, but sister chromatids remain together and move to opposite poles of the cell

114
Q

What happens during metaphase I?

A

Homologous chromosomes align at the equatorial plate of the cell.

115
Q

Is there DNA replication before prophase II?

A

No, DNA does not replicate before prophase II

116
Q

What happens during metaphase II?

A

Chromosomes line up at the equatorial plate again, similar to metaphase in mitosis.

117
Q

Describe anaphase II.

A

The centromeres divide, and sister chromatids move to opposite poles.

118
Q

What is the result of telophase II?

A

Four haploid daughter cells are formed, each genetically different from the parent cell.

119
Q

Where does mitosis occur?

A

Mitosis occurs in body cells.

120
Q

Where does meiosis take place?

A

Meiosis occurs in reproductive organs.

121
Q

How many division events occur in mitosis?

A

Mitosis has one division event.

122
Q

How many division events occur in meiosis?

A

Meiosis has two division events.

123
Q

What is the result of mitosis in terms of daughter cells?

A

Mitosis produces two daughter cells that are diploid (2N) and identical to the parent.

124
Q

What is the result of meiosis in terms of daughter cells?

A

Meiosis produces four daughter cells that are haploid (N) and genetically different from the parent.

Biology EXAM 8 (1 decks)

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