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H2 Biology > Cell Division > Flashcards

Cell Division Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What happens to DNA before DNA replication?

A

DS DNA associated with histone proteins and exist as long, thin threads known as chromatin

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2
Q

What happens to DNA after DNA replication?

A

DNA molecules are held together at the centromere and known as identical sister chromatids. Proteins bind to the centromere and form the kinetochore complex which becomes the site of attatchment for spindle fibres during prophase. Chromatin condenses into thick, short x-structures known as visibile chromosomes.

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3
Q

What explains the structure of a chromosome?

A

Two identical sister chromatids are joined at the centromere. Each sister chromatid consists one DS DNA molecule.

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4
Q

What are homologous chromosomes?

A

Homologous chromosomes are chromosomes derived from the two parents which have the same length, same sequences of genes and same locus but different alleles.

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5
Q

What are the 2 advantages of being diploid?

A

Increased genetic variation due to mixture of characteristics inherited from both parents due to presence of two different alleles

2 alleles provided for the same gene - if one allele on the chromosome of a pair is faulty, the other allele of a homologous pair will be a backup

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6
Q

What are the 3 phases of interphase?

A

G1, S and G2 Phase

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7
Q

What occurs at the G1 checkpoint?

A

assesment of cell growth

checking for the presence of growth factors to stimulate cell division.

check for cell size and DNA damage

check that nutrients are sufficient

progression delayed until DNA damage is repaired/conditions are favourable

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8
Q

What are the 5 points of the G2 checkpoint?

A

assesment of DNA replication

check if DNA is replicated without any damage

prevents initation of mitosis after s phase by ensuring that incompletely replicated DNA are not distributed to the daughther cells

apoptosis → irreparable DNA damage

proteins will signal cell to begin molecular processes for the cell to divide once checkpoint has passed

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9
Q

Name the two regulatory proteins involved in the stop and go checkpoints?

A

Cyclins and cyclin-dependent kinases

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10
Q

Highlight the importance of the mitotic cell cycle.

A

it produces 2 genetically identical daughter cells

it conserves the ploidy of cells by equally allocating replicated chromosomes to each of the daughter nuclei

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11
Q

What are occurs during prophase?

A

condensation of chromatin into thick, condensed chromosomes, appearing as two sister chromatids held together at the centromere.

centrioles move to two opposite poles of the cell

spindle fibres form and attach to the kinetochore complex on both sides of the chromosome at the centromere

nuclear envelope disintegrates

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12
Q

what is the chiasmata?

A

Chiasmata is the site of exchange of corresponding alleles between non-sister chromatids of homologous chromosomes

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13
Q

what is crossing over?

A

it is the breakage and reunion of two non-sister chromatids at each site

alleles from one chromosome may swap with its corresponding allele from another chromosome

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14
Q

What occurs during metaphase 1?

A

bivalents arrange along the metaphase plate at the right angle of the spindle axis

independent assortment occurs where each homologue arranges itself on either side of the plate, independently of the other pairs of homologous chromsomes

pole to pole spindle fibres form

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15
Q

what happens during anaphase 1?

A

centromeres does not divide

spindle fibres pull chromosome towards opposite poles of the cell

chiasmata breaks and each chromosome now contains a segment of genetic material from its corresponding homologue

homologous chromosomes separate into 2 haploid sets, one set at each end of the spindle

pole to pole spindle fibres lengthen to push the poles apart

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16
Q

What happens in telophase 1 and to the ploidy and amount of DNA relative to parent cell at the end of telophase 1?

A

Chromosomes decondense back into chromatin.

Spindle fibres disintegrates.

Nuclear envelope reforms around chromatin at opposite poles.

Nucleolus reappears.

Ploidy is halved. Amount of DNA remains the same.

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17
Q

are cytokinesis in mitosis and cytokinesis 1 in meiosis the same?

A

yes. However, plant cells passes straight from anaphase 1 to prophase 2

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18
Q

what is the difference/similarity between interphase 1 and interphase 2?

A

difference - DNA only replicates in interphase 1

similarity - centrioles replicate

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19
Q
  • what does chromatin condenses into at prophase 2?
A

condenses into chromosomes with 2 non geneticall identical sister chromatids held at the centromere

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20
Q

which stage of meiosis leads to genetic variation and how?

A
  • prophase 1 -crossing over, exchange of corresponding alelles, new combination of parental and maternal alellesmetaphase 1 - independent assortment of homologous chromosomes, different combinations of parental chromosomes
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21
Q

what happens to ploidy and amount of DNA at the end of telophase 2? (relative to parent cell)

A

ploidy is halved and DNA amount is halved

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22
Q

what is the significance of s phase of interphase? (3)

A

semi conservative DNA replication requires parental DNA to be the template to form copies of daughter DNA

DNA replication occurs before disappearance of protective nuclear membrane so as to minimise mutations

DNA replication occurs prior to equal division of genetic material

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23
Q

what is the significance of prophase in mitosis?

A

Coiling of long, thin chromatin into thick, condensed chromosomes prevents entanglement of chromatin and breakage during separation of DNA

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24
Q

what is the significance of metaphase and anaphase?

A

alignment of chromosomes in a single file along the metaphase plate to ensure each daughter cell will have the complete diploid set of chromosomes

anaphase: division of centromeres and separation of sister chromatids by spindle fibres

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25
Q

what is the significance of telophase?

A

formation of nuclear envelope prevents entanglement of chromatin

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26
Q

what is the significance of mitosis?

A

Maintain genetic stability

Growth of cells

Replacement of cells

Regeneration of tissues

Asexual reproduction

Production of stem cells

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27
Q

what is the significance of prophase 1?

A

Formation of bivalents for crossing over to occur to give to rise to new combination of paternal and maternal alleles. Thus, rise in genetic variation

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28
Q

what is the significance of metaphase 1?

A

Independent assortment of homologous chromosomes which give rise to different combination of paternal and maternal chromosomes in the gametes formed

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29
Q
  • what is the significance of interphase 1?
A

DNA replicates only once so that it is immediately followed by two successive nuclear divisions to produce haploid cells

30
Q

What is the significance of metaphase and anaphase 1?

A

alignment of paired homologues along the metaphase plate and segregation of homologues so that chromosomes are equally distributed in two daughter cells which leads to the halving of the ploidy in each of the two haploid daughter cells

31
Q

What is the significance of metaphase and anaphase 2?

A

alignment of chromosomes along the metaphase plate and segregation of sister chromatids so that chromatids are equally distributed into each daughter cell which leads to the halving of the amount of DNA in the four haploid daughter cells as compared to the original parent cell

32
Q

what is gene mutation

A

It is the change in the structure of DNA which occurs at a single locus on a chromosomes which may lead to the formation of new alleles

33
Q

what is gene mutation caused by (4)

A
  • It is caused bySubstitutionInsertionDeletionInversion
34
Q

how does cancer arise?

A

when cells escape from control mechansims that normally regulate cell growth and division

35
Q

why are genes expressed differently?

A

genes are mutated which changes the way certain genes are expressed

36
Q

what are the two types of mutations that lead to uncontrolled cell division (not cancer)

A

gain of function
loss of function

37
Q

what is an example of a gain of function mutation?

A

proto oncogene

38
Q

how is the new product of a gain of function mutation different than a normal product?

A

the protein is hyperactive

produced in excess

resistant to degradation

39
Q

what is the production of a gene that has undergone loss of function mutation?

A

gene product that is not functional or not produced

40
Q

difference between loss of function and gain of function mutation? (dominant/recessive)

A

both copies of gene undergone LOF must be mutated so functional (mutated) gene product can be produced to result in abnormal cell proliferation.

only one mutant copy of the two for GOF is sufficient for abnormal cell proliferation since it increases rate of cell division

41
Q

why must both copies o fgene undergo LOF mutation to result in abnormal cell proliferation?

A

if only one copy of the gene is mutated/lost, cell cycle remains normal as other copy of the gene is still able to produce sufficient quantity of normal gene product to regulate normal cell cycle

42
Q

what are proto-oncogenes? what are its functions?

A

They code for proteins which stimulate normal cell division and control cell differentiation

43
Q

Proto-oncogenes contain different types of protein with essential functions. What are the proteins? (5)

A

Growth Factors which signals cells to divide

Growth factors receptors -membrane proteins that bind to growth factors

transcription factors - bind to DNA to control rate of transcription

protein kinases - enzyme which add phosphate group to other proteins, activating them.

apoptosis inhibitor - reduced rate of cell death
44
Q

how are proto-oncogenes converted to oncogenes?

A
  • Translocation
  • Gene amplification
  • Point mutation
    > within coding region
    > within control element
45
Q

example of an oncogene

A

ras gene

46
Q

what is the function of a ras gene?

A

it codes for a ras protein (G protein) involved in signal transduction. explain the process of signal transduction

47
Q

what does a tumour suppressor gene do?

A
48
Q

what is chromosomal aberration?

A

It is the departure from the normal chromosomal structure or number, such as deletion, inversion, translocation, duplication trisomy

49
Q

what are the two types of chromosomal mutation?

A

change in structure of chromosome

change in number of chromosomes

50
Q

how are changes in chromosome structure brought about?

A
  • Deletionbreaks at two points of the chromosome and the middle portion is lost
  • Inversionbreaks occur at two points of a chromosome. Middle portion rates 180 degress before rejoining
  • Translocationsection of chromosome breaks off and attaches to a non-homologous chromosomes
  • Duplication

section of chromosome replicates. set of gene loci is repeated

51
Q

what is the overall effect of chromsomal aberration?

A

reshuffling of alleles on the chromosome

52
Q

what changes are resulted from the change in the number of chromosomes?

A

Non-disjunction during mitosis or meiosis

53
Q

what does non-disjunction refer to?

A

the failure of sister chromatids to separate during anaphase/anaphase 2 or the failure of homologous chromosomes to separate during anaphase 1

it can occur on one, several or all chromsomes within the nucleus

54
Q

how does non-disjunction occur?

A

Non-disjunction occurs due to problems in the formation of spindle fibres

55
Q

what if non-disjunction occurs in a somatic cell?

A

It results in daughter cells having one or more, missing or extra chromosome

56
Q

What is the impact of non-disjunction on an individual?

A

Unstable ploidy

Effect wont be passed down to offspring though

57
Q

how does non-disjunction in a somatic cell compare with the impact of non-disjunction in a germ cell?

A

the effect of having one or more, missing or extra chromosome may be passed down to the offspring upon fusion of gametes during fertilization

58
Q

how does non-disjunction in a somatic cell compare with the impact of non-disjunction in a germ cell?

A

the effect of having one or more, missing or extra chromosome may be passed down to the offspring upon fusion of gametes during fertilization

59
Q

what is aneuploidy?

A

Aneuploidy is a condition of the nucleus where there are one or several chromsomes, more than or less than the diploid number of chromosomes

60
Q

What is aneuploidy caused by?

A

formation of abnormal gametes by non-disjunction of one or several pairs of homologous chromosomes during anaphase 1 or non-disjunction of chromatids of one or several chromsomes during anaphase 2

the fusion of a normal haploid gamete with abnormal haploid gamete with non-diploid number of chromosomes

61
Q

what is an example of aneuploidy?

A

Down syndrome (Trisomy 21)

62
Q

What is Down Syndrome caused by?

A

The extra chromosome 21 which resulted from the non-disjunction during gamete production from one of the parents

63
Q

what is polyploidy?

A

It is a chromosomal alteration in which organism possesses more than two complete chromosome sets.

64
Q

What is polyploidy caused by

A

It can be resulted from the non-disjunction of all homologous pairs during anaphase 1 / non-disjunction of chromatids of all chromosomes during anaphase 2.

Followed by fusion of a diploid gamete with a haploid gamete to give a triploid nucleus

or fusion of two diploid gametes to give a tetraploid nucleus

65
Q

what are the factors that contribute to cancer?

A

ionising radiation

loss of immunity

viral and bacterial infection

chemical carcinogens

UV light

hereditary disposition

66
Q

what are the observable differences between normal cells and cancer cells?

A

cancer cells lack density-dependent inhibition and lack anchorage dependence

67
Q

What is density-dependent inhibition?

A

Cells which grow on a surface (laboratory vessel) in a single layer, dividing until they touch other, when then cell division stops.

It is related to the availability of growth factors. Cell division stops when the supply of growth factors is used up.

68
Q

What is anchorage dependence?

A

Normal cells do not divide if they are not in contact with a solid surface, i.e a liquid medium.

Even if growth factors are in abundance.

When cells are anchored to a solid surface, they will divide immediately.

This keeps cells from dividing uncontrollably if the cells ever become separated from their normal surroundings.

69
Q

what are the malignant properties which differentiate cancer cells from benign tumours?

A

They are able to invade and destroy surrounding tissues

They are able to promote angiogenesis

They are able to metastasise

70
Q

what is angiogenesis?

A

It is the proliferation of a network of blood vessels that connect to the cancerous growth which supplies oxygen and nutrients while also removing waste product

71
Q
  • what is metastasis?
A

Metastasis is a process in which a cancerous growth is able to spread to other distant locations in the body via lymph or blood vessels, forming a secondary tumour.

H2 Biology (3 decks)

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