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IB HL Biology I > Unit 6 > Flashcards

Unit 6 Flashcards

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1
Q

When would a cell divide? (4)

A
  • growth of multicellular organism
  • replacement of damaged cells
  • embryonic development
  • asexual reproduction in prokaryotes
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2
Q

What is the name of the cell division for a prokaryote?

A

binary fission

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3
Q

Why don’t eukaryotes divide by binary fission?

A

Eukaryotic cells are more complex and have more DNA

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4
Q

Cell Cycle

A

series of events that take place in a eukaryotic cell as it grows and divides

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5
Q

What are the phases of interphase? (3)

A
  • G1
  • Synthesis (S)
  • G2
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6
Q

What happens in G1? (3)

A
  • organelles produced
  • proteins made (for DNA synthesis)
  • growth
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7
Q

What happens in S phase? (2)

A
  • DNA replication
  • Sister chromatids form (chromatin form)
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8
Q

What happens in G2?

A

-proteins made for (nuclear and cytoplasmic division)

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9
Q

Sister Chromatid

A

either of two identical copies of DNA (made during S phase) attached to one another by a centromere

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10
Q

Centromere

A

attaches sister chromatids

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11
Q

Chromatin

A

DNA wrapped around histone proteins

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12
Q

Mitosis

A

division of the eukaryotic nucleus

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13
Q

What are the 4 stages of mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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14
Q

What happens in prophase? (3)

A
  • centrosomes move to opposite poles of the cell and form spindle fibers
  • Sister chromatids (chromatin) condenses into replicated chromosomes
  • nuclear membrane breaks down
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15
Q

Replicated Chromosome

A

two, identical sister chromatids attached by a centromere

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16
Q

What happens in metaphase? (2)

A
  • Spindle fibers attach to kinetochores
  • Contraction of the spindle fibers causes the replicated chromosomes to line up along the center of the cell
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17
Q

What happens to sister chromatids in anaphase?

A

They become single chromosomes

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18
Q

What happens in anaphase? (2)

A
  • Continued contraction of the spindle fibers causes separation of sister chromatids
  • Single chromosomes move to opposite poles of the cell
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19
Q

What happens in telophase? (4)

A
  • nuclear membranes form
  • fibers disappear
  • Chromosomes arrive at poles
  • Chromosomes uncoil
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20
Q

Cytokinesis

A

division of the eukaryotic cytoplasm to form 2 daughter cells

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21
Q

What is seen as cytokinesis occurs in an animal cell?

A

cleavage

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22
Q

Cleavage (2)

A
  • contractile proteins pinch cell apart
  • cleavage furrow appears
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23
Q

What is seen as cytokinesis occurs in a plant cell?

A

cell plate

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24
Q

Cell Plate

A

material deposited from vesicles to form cell plate and then cell wall

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25
Q

How does prophase ensure that daughter nuclei are genetically identical?

A

Chromatin condenses so DNA doesn’t get lost/damaged

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26
Q

How does metaphase ensure that daughter nuclei are genetically identical?

A

replicated chromosomes line up at equator with one copy facing each pole

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27
Q

How does anaphase ensure that daughter nuclei are genetically identical?

A

Chromatids are pulled apart/the right # are pulled in each direction

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28
Q

How does telophase ensure that daughter nuclei are genetically identical?

A

chromosomes reach poles and newly forming nuclei allow the cell to divide while ensuring no chromosomes are caught on the wrong side

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29
Q

When do cells stop dividing? (2)

A
  • when detached from a surface
  • when they touch/get crowded and competition increases
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30
Q

What triggers cells to divide? (2)

A
  • size
  • growth factor
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31
Q

Size

A

large cells divide (SA:Volume too low)

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32
Q

Growth Factor

A

chemicals released by cells that encourage other cells to divide

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33
Q

What controls the cell cycle and division?

A

cyclins

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34
Q

Cyclin

A

proteins released in the cell in response to growth factor binding that control the cell cycle

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35
Q

How many cyclins are there for the cell cycle?

A

4

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36
Q

What do cyclins do during the cell cycle?

A

rise and fall

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37
Q

What do high levels of cyclin do?

A

activate target molecules that move cells into the next stage of the cycle

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38
Q

How do cyclins control the the cell cycle? (4)

A

1) Cyclins bind to enzymes called cyclin-dependent kinases (Cdk’s)
2) Cdk’s phosphorylate proteins (add phosphate) in the cell
3) Phosphorylation activates proteins to carry out tasks (specific to one of the phases of the cell cycle)
4) Cyclins is broken down (cyclin level falls)

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39
Q

What makes cancer cells different?

A

they do not respond to normal cell cycle regulation

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40
Q

What causes cancer?

A

damaged/mutated genes

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41
Q

Mutation

A

change in the base sequence of a gene

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42
Q

Mutagen

A

agents that cause gene mutations

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43
Q

Carcinogens (2)

A
  • agents that cause cancer
  • mutagens or other factors that accelerate cell division
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44
Q

What are examples of mutagens? (3)

A
  • high energy radiation
  • short-wave ultraviolet light
  • viruses
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45
Q

What do proto-oncogenes and tumor suppressor genes control?

A

the cell cycle by coding for cyclins, CDKs, or other proteins

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46
Q

What happens when proto-oncogenes and tumor suppressor genes are mutated?

A

the cell cycle is disrupted

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47
Q

Oncogene

A

mutated gene that contributes to the development of a tumor

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47
Q

Tumor

A

abnormal growth of tissue

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48
Q

Benign (4)

A
  • less harmful
  • won’t spread
  • fewer mutations
  • retain normal functions
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49
Q

Malignant (3)

A
  • harmful/cancerous
  • can spread
  • cell mutations accumulate
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50
Q

Primary Tumor

A

a malignant tumor growing at the site where the abnormal growth first occurred

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51
Q

Metastasis

A

the movement of cells

52
Q

Secondary Tumors

A

The circulating cancerous cells invade tissues at a different locations and develop

53
Q

How does a primary tumor become a secondary tumor? (4)

A

1) A primary tumor grows at the site where the abnormal growth first occurred
2) Cancerous cells can detach from the primary tumor
3) Cancerous cells gain penetrate the walls of lymph or blood vessels and circulate around the body
4) Cancerous cells invade tissues at different locations and develop, by uncontrolled cell division, into a secondary tumors

54
Q

Asexual Reproduction

A

offspring produced with DNA from one parent

55
Q

Prokaryotic Cells

A

reproduction is asexual using binary fission

56
Q

Sexual Reproduction

A

offspring produced with DNA from two parents who contribute half each

57
Q

What is another name for sex cells?

A

gametes

58
Q

What is formed at the result of the union of gametes?

A

a zygote

59
Q

Diploid Cell

A

two complete sets of chromosomes (2n)

60
Q

What are examples of diploid cells? (2)

A
  • Zygotes
  • Body Cells
61
Q

What is another name for a body cell?

A

somatic cell

62
Q

Haploid Cell

A

one complete set of chromosomes (n)

63
Q

What are examples of haploid cells? (2)

A
  • Sperm
  • Egg
64
Q

Meiosis

A

special type of cell division in reproductive organs that forms haploid sex cells (half the # of chromosomes) from diploid body cells

65
Q

Meiosis I

A

homologous chromosomes are pulled apart (reduction phase)

66
Q

Meiosis II

A

separates sister chromatids (separation phase)

67
Q

How many haploid cells come from diploid cells in meiosis?

A

4

68
Q

Interphase (Meiosis)

A

DNA is replicated before meiosis to produce 2 copies of genetic info each from the female and male parent

69
Q

Prophase I (5)

A
  • Chromatin condenses
  • synapsis
  • nuclear envelope disappears
  • spindle microtubules form
  • centrosomes move to opposite poles
70
Q

Synapsis

A

pairing of homologous chromosomes to form a tetrad

71
Q

Tetrad

A

two homologous chromosomes (four chromatids) joined together

72
Q

Metaphase I (2)

A
  • spindle microtubules attach to centromeres
  • Tetrads align at metaphase plate
72
Q

Anaphase I

A
  • Homologous chromosomes separate and move toward opposite poles of the cell
73
Q

Telophase I (4)

A
  • Chromosomes reach poles
  • Chromosomes decondense
  • nuclear membrane may reform
  • Cytokinesis occurs with telophase I and two haploid cells are formed
74
Q

Why is meiosis II similar to mitosis?

A

sister chromatids of each chromosome separate

75
Q

What does sexual reproduction allow for? (2)

A
  • characteristics from both parents to appear in offspring
  • leads to varied offspring/genetic diversity
76
Q

What is the benefit of genetic diversity?

A

it favors survival of a species in a changing environment

77
Q

What do the variations in Meiosis accomplish?

A

producing gametes which are all different

78
Q

How is variation accomplished in Meiosis? (2)

A
  • crossing-over
  • independent assortment
79
Q

Crossing over (prophase I)

A

parts of nonsister homologous chromatids break and then swap alleles when homologous chromosomes form tetrads

80
Q

Chiasma (4)

A
  • a site of crossing over
  • an X-shaped structure
  • visible when homologous chromosomes unpair
  • holds homologs together until anaphase
81
Q

Recombination

A

production of gene combinations different from those carried by original chromosomes

82
Q

Parental Chromosome

A

same combination of alleles as parent

83
Q

Recombinant Chromosome

A

different combination of alleles from parent

84
Q

Independent Assortment (Metaphase I)

A

tetrads are randomly arranged in the center of the cell during metaphase I and meiosis independently/randomly distributes chromosomes into cells

85
Q

What does the “n” represent in 2^n?

A

haploid #

86
Q

What does 2^n represent?

A

The total # of combinations of chromosomes that meiosis can package into gametes

87
Q

What does the fusion of gametes result in?

A

genetic variation

88
Q

True or False: the gametes in an individual are genetically different?

A

true

89
Q

How do karyograms organize chromosomes? (3)

A
  • size
  • DNA staining pattern
  • location of centromeres
90
Q

When are pictures for karyograms taken?

A

metaphase of mitosis

91
Q

What are two ways to get fetal cells to detect disorders before birth?

A
  • amniocentesis
  • chronic villus sampling
92
Q

Amniocentesis (mainly used) (2)

A
  • removes amniotic fluid
  • 2nd trimester
93
Q

chorionic villus sampling (CVS) (2)

A
  • removes piece of chorionic villi (placenta)
  • 1st trimester
94
Q

What are the advantages of amniocentesis? (2)

A
  • it can detect nearly all chromosomal abnormalities
  • lower risk
95
Q

What are the advantages of chronic villus sampling? (2)

A
  • nearly all chromosomal abnormalities are detected
  • can be performed earlier
96
Q

When is a woman a candidate for genetic testing?

A

at age 35 or older

97
Q

Why is an older women a candidate for genetic testing?

A

The possibility of having a baby with a chromosomal defect increases with the age.

98
Q

Trisomy

A

individual/cell has an extra chromosome

99
Q

Monosomy

A

individual/cell lacks a chromosome

100
Q

What is an example of a trisomy?

A

down syndrome

101
Q

Down Syndrome

A

pair 21 has 3 chromosomes instead of 2 (trisomy 21)

102
Q

Turner Syndrome

A

females lack second X chromosome

103
Q

What do errors in meiosis lead to?

A

gametes with abnormal numbers of chromosomes

104
Q

Nondisjunction

A

failure of chromosomes or chromatids to separate during meiosis

105
Q

What happens with nondisjunction during meiosis I?

A

Homologous pairs fail to separate in meiosis I due to incorrect spindle fiber attachment

106
Q

What happens with nondisjunction during meiosis II?

A

Sister chromatids fail to separate during meiosis II due to centromeres not dividing

107
Q

clone

A

group of genetically identical organisms or cells.

108
Q

What is a naturally occurring cloning system in prokaryotic cells?

A

binary fission (asexual)

109
Q

What is a naturally occurring cloning system in eukaryotic cells? (3)

A
  • budding
  • fragmentation
  • vegetative propagation
110
Q

Budding

A

Cells split off to make organism

111
Q

Fragmentation

A

organisms grow from fragment of parent

112
Q

Vegetative Propagation

A

small pieces of plants are induced to grow independently
tubers or runners

113
Q

What can the rooting of stem cuttings produce?

A

clones

114
Q

Stem cutting

A

growing plants using portions of stems

115
Q

How can sexually reproducing organisms create clones?

A

Monozygotic (identical) twins

116
Q

What are two ways animals can be cloned through biotechnology?

A
  • embryo splitting
  • nuclear transfer
117
Q

embryo splitting

A

breaking up multicellular embryo into more than one group of cells at an early stage of development to generate “twins”

118
Q

Why is embryo splitting possible?

A

Embryonic cells retain pluripotency (can become any type of tissue) at early stages (8 cells or less)

119
Q

Somatic Nuclear Cell Transfer (SCNT)

A

creates embryo from a differentiated somatic cell and an egg cell

120
Q

What are the steps of SCNT? (4)

A
  • Diploid somatic cells are removed from a donor
  • The nucleus of an unfertilized egg (haploid) is removed
  • The egg cell is fused with the diploid nucleus
  • The new diploid cell is implanted in a surrogate’s uterus
121
Q

How does SCNT differ from the natural way of making an embryo? (2)

A
  • Natural: sperm and egg join to produce zygote with 2 sets of chromosomes (diploid)
  • SCNT (reproductive cloning): 2 sets of chromosomes in zygote come from somatic cell donor
122
Q

What are the 2 main purposes of SCNT?

A
  • reproductive cloning
  • therapeutic cloning
123
Q

Reproductive Cloning

A

If the embryo is implanted into the uterus of a surrogate, a new cloned organism will develop

124
Q

Therapeutic Cloning

A

involves producing embryos from which embryonic stem cells can be harvested for medical use

125
Q

What are arguments in support of therapeutic cloning? (4)

A
  • any procedure that reduces pain and suffering is justified
    -stem cells can be used to replace organs/tissues that have been lost/damaged in a patient
    -pain and suffering can be reduced/lives can be saved
    -cells are removed when no pain is felt by the embryo
126
Q

What are arguments against therapeutic cloning? (4)

A

-there is danger of embryonic stem cells developing into tumor cells/harmful effects are not yet known;
-every human embryo is a potential human with the right to development;
-more embryos may be produced than can be used and so some would be killed;
-any procedure that harms a life/kills is unethical

IB HL Biology I (10 decks)

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