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Genetics > Cell Division > Flashcards

Cell Division Flashcards

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Biology 101 flashcards
1
Q

Cell cycle

A

controls cell division

Consisting of interphase (G1 phase, S phase, and G2 phase) and M phase (mitosis or meiosis) in cells

  • the life cycle cells must pass through to replicate their DNA and divide

The transition from one phase to the next is controlled by protein-based interactions.

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2
Q

interphase

A

consists of:
G1 phase
S phase
G2 phase

duplicate everything the cell has (if you want to make 2 cells you need 2 ribosomes etx)
increase in cell size
major chunk of cell cycle
does not involve cell division

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3
Q

G1 phase

A

“Gap 1”, Gene expression is high

activity gene expression (genes are actively transcribed and translated while normal cells carry on function) and cell activity preparation for DNA synthesis

4-6 hrs

cell grows increasing in size

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4
Q

s phase

A

Synthesis” phase, DNA replication occurs here

Doubles the DNA content by creating two sister chromatids (chromosomal duplication)

10- 12 hrs- done with high level of accuracy
- if something is recopied wrong this could have major consequences

  • in chromatin phase at the start of s phase at the end each chromosome has 2 sister chromatids
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5
Q

G2 phase

A

“Gap 2”,
cell prepares to divide

Chromosomes are diffuse and not visible (called chromatin)

Chromosomes are duplicated (already went through S-phase)

Nuclear envelope still encloses the nucleus

Two centrosomes are in the cytoplasm

Microtubules begin the to extend

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6
Q

M phase

A

is the short segment during the cell cycle in which cells divide
follows interphase

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7
Q

mitosis

A

is the process that creates two genetically identical daughter cells
Occurs in somatic cells
Responsible for growth and tissue repair, replacing dead cells

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8
Q

meiosis

A

process of cell division that occurs in germ line cells

produces 4 haploid gametes

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9
Q

prophase

A

Chromosomes begin to condense and become visible

Sister chromatids attached via centromeres visible

Pair centrosomes move to the poles

Microtubules extend from centrosomes to form mitotic spindle

Nucleolus disappears

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10
Q

Prometaphase

A

Nuclear envelope breaks down

Mitotic spindle attaches to kinetochores of the sister chromatids

Microtubules begin exerting pulling forces in both directions

Chromosomes begin to move to center of the cell

Cohesion proteins bind sister chromatids together

Resists premature separation

Non kinetochore and astral microtubules stabilize the cell

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11
Q

metaphase

A

Chromosomes fully condensed

Chromosomes align to metaphase plate

Sister chromatids are still attached to kinetochore microtubules extended from centrosomes

Mitotic spindle fully developed

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12
Q

anaphase

A

Sister chromatids separate (disjunction)

Cohesion proteins break down

Kinetochore microtubules depolymerize

Daughter chromosomes move towards opposite poles and congregate at centrosomes

Non kinetochore and astral microtubules polymerize, elongating the cell

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13
Q

telophase

A

Nonkinetochore microtubules continue polymerising, elongating the cell

Nuclear envelope redevelops

Chromosomes decondense

reverse of prophase

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14
Q

cytokinesis

A

divides the cytoplasmic contents equally between the daughter cells

Forms a cell plate in plants

Forms a contractile ring and cleavage furrow in animals

Nucleolus reforms

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15
Q

diploid

A

If organisms have 2 copies of each gene

2n

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16
Q

haploid

A

If organisms only have 1 copy of each gene

n

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17
Q

homologous chromosome

A

Chromosomes that synapse (pair) during meiosis. Chromosomes with the same genes in the same order
Also known as homologs

Each chromosome carries many genes, and homologs carry genes for the same traits in the same order on each member of the pair.

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18
Q

sister chromatids

A

The identical DNA duplexes that are produced by DNA replication (s phase) and are temporarily joined to one another during the early stages of cell division(prophase)

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19
Q

recombination

A

i

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20
Q

crossing over

A

The breakage and reunion of homologous chromosomes that results in reciprocal recombination.

crossing over of genetic material between nonsister chromatids of homologous chromosomes.

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21
Q

disjunction

A

Sister chromatids separate

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22
Q

nondisjunction

A

failed chromosomal separation

Chromosomes pulled to the wrong pole

Occurs in meiosis I or meiosis II

Leads to aneuploidy

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23
Q

aneuploidy

A

missing or extra chromosomes
Extra chromosomes result in excessive gene product

Causes miscarriage since most aneuploid cells are inviable  Trisomy 21 (Down Syndrome) occurs in 1 of 1000 births

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24
Q

Genes

A

are the physical units of heredity, that collectively control gene transcription of DNA to RNA and therefore translation to proteins

-code for various functions within cells

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25
Q

what is the central dogma of biology?

A

(DNA -> RNA -> protein)

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26
Q

chromosomes

A
  • consisting of single long molecules of double-stranded DNA contained within the nucleus and is inherited through cell division
  • contain genes
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27
Q

polyploid

A

Some organism have more than 2 copies

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28
Q

Cytoplasmic inheritance

A

used to identify the random distribution of the mitochondria and chloroplasts among daughter cells during cytokinesis

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29
Q

Where else can genetic info be carried in?

A

Genetic information (DNA and RNA) can also be contained within chloroplasts (plants) and mitochondria (plants and animals)

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30
Q

Genotype

A

is the genetic make-up of the organism

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31
Q

Phenotype

A

is the observable traits dictated by the genotype

Controlled by variations in genes called alleles

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32
Q

What are the 3 main subdisciplines of genetics?

A

Transmission genetics
Evolutionary genetics
Molecular genetics

33
Q

Transmission genetics

A

“Mendelian” genetics -> transmission of traits and characteristics between successive generations (inheritance)

34
Q

Evolutionary genetics

A

Studies the origins of and genetic relationships between organisms and the evolution of traits and genes/genomes

35
Q

Molecular genetics

A

Studies inheritance and variation in nucleic acids (DNA and RNA), proteins, and genomes and connects them to inherited variation and evolution in organisms

36
Q

somatic cells

A

structural cells of the body

ex- liver nervous muslce skin cells

23 homologous pairs of chromosomes- 22 autosomal and 23rd is sex linked

37
Q

G0

A

some cells enter after G1

Some specialized cells enter this phase and do not go on to cell division

Gene expression continues

No longer progress through the cell cycle - very rarely leave and resume cell cycle

most G0 cells maintain their specialized function until they enter programmed cell death

Ex. Bone cells, eye cells

38
Q

Describe the movement of eukaryotic chromosomes during the cell
cycle.

A

Kinetochore microtubules move chromosomes

Non kinetochore microtubules elongate and stabilize the cell

Astral microtubules stabilize the cell

39
Q

What are the 4 main checkpoints in cell division?

A

G1 checkpoint: Pass if cell size is adequate, nutrients availability is good, presence of growth factors

S-phase checkpoint: Pass if DNA replication is complete and base-pair mismatches/errors are removed

G2 checkpoint: Pass if cell size is adequate, chromosome replication is complete

Metaphase checkpoint: Pass if all chromosomes are attached to the mitotic spindle

Mutations that alter the cell cycle or checkpoints can lead to cancer, and other diseases

40
Q

daughter cells

A

The genetically identical cells produced by mitotic cell division

41
Q

What are somatic cells in humans? How many chromosomes are in human cells?

A

Each somatic cell within a typical mammal is 2N (diploid)

Human cells contain 23 unique chromosomes, so in the diploid state 2N = 46 chromosomes

42
Q

What are gametes in human cells?

A

Human gametes are 1N (haploid), so N = 23 chromosomes

43
Q

germ-line cells

A

produce gametes- egg and sperm
divide by meiosis

23 in total (not pairs)

1-22 are autosomal and 23rd= X or Y

44
Q

what happens if mitosis doesn’t occur? or if too much occurs

A

an organism may fail to develop at all or have morphological abnormalities

growth of structures beyond the boundaries leading to morphological abnormalities even death

45
Q

What are the 5 stages of mitosis?

A 
prophase 
prometaphase 
metaphase 
anaphase 
telophase and cytokinesis
46
Q

chromatin

A

The complex of nucleic acids and proteins that compose eukaryotic chromosomes

DNA + protein

47
Q

karyokinesis

A

Part of telophase, the process of nuclear division between daughter cells.
equal partitioning of the chromosomal material in the nucleus of the parental cell between the nuclei of the 2 daughter cells

48
Q

when cells enter mitosis are they diploid of haploid?

A

diploid

49
Q

centromere

A

A specialized DNA sequence on eukaryotic chromosomes that is the site of kinetochore protein and microtubule binding.

50
Q

centrosomes

A

A cytoplasmic region, containing a pair of centrioles (90 degrees to each other) in many eukaryotic species, from which the growth of microtubules forms the spindle apparatus during cell division

site of spindle assembly

51
Q

kinetochore

A

The site of attachment of multiple proteins that connects a spindle fiber microtubule to the centromeric region of a chromosome
Forms during M phase of cell division

52
Q

List the basic similarities presented in the notes between meiosis and mitosis

A

Germ-line cells have identical interphase as somatic cells

Structures such as centrosomes, spindle fibres are the same

Germ-line cells are replenished via mitosis, but undergo meiosis to produce gametes

53
Q

How does meiosis differ than mitosis?

A

2 main divisions, with no DNA replication in between

Meiosis I – homologous chromosomes separate, ploidy level reduces by half

Ie. 2N -> 1N

Meiosis II – sister chromatids separate

Duplicated chromosomes reduce to single chromosomes (ie no sister chromatids)

54
Q

What are the 3 hallmark events during meiosis 1?

A
  1. Homologous chromosome pairing

Chromosome synapsis

  1. Crossing over between homologous chromosomes

results in recombination at cross-over sites called chiasmata

  1. Segregation (separation) of homologous chromosomes (ploidy level reduced by half)
55
Q

What are the stages of meiosis 1?

A

Prophase I -> homologous pairing and cross-over

Metaphase I -> aligning to the centre of the cell

Anaphase I -> separation of homologous chromosomes

Telophase I and cytokinesis -> end of first division

56
Q

what are the stages within prophase 1?

A 
Leptotene  
 Zygotene  
Pachytene  
Diplotene  
Diakinesis
57
Q

Leptotene

A

Chromosomes are duplicated (having passed Sphase)

Chromosomes condense, but not visible

Centrosomes migrate to poles

Spindle fibers produced from each centrosome

58
Q

Zygotene

A

Chromosomes continue condensing

Homologous pairs enter synapsis, forming the synaptonemal complex

Meiotic spindle forms

Nuclear envelope beings to break down

59
Q

synaptonemal complex

A

3 layer structure that forms during prophase I

Tightly binds non-sister chromatids of homologous chromosomes

The function is to properly align homologous chromosomes before their separation and then to facilitate recombination between homologous chromosomes.

60
Q

Pachytene

A

Chromosome condensation partially complete

Synapsed homologs are seen as bivalents (tetrads)

Crossing over occurs between non-sister chromatids, formation of chiasmata

Kinetochore microtubules attach to the kinetochores

Nuclear envelope breakdown continue

61
Q

Diplotene

A

Crossing over is complete

Synaptonemal complex dissolves but chiasmata remain

Tetrads completely visible

Nuclear envelope fully dissolved

62
Q

Diakinesis

A

Meiotic spindle established

Homologous chromosomes tethered to poles via spindle fibres

Nuclear envelope fully degraded
Tetrads move to cell middle

63
Q

Metaphase I

A

Tetrads align to metaphase plate

Homologous pairs tethered to opposite poles

Kinetochores od sister chromatids are attached to the same centromere, joined by cohesion proteins to prevent premature separation

Chiasmata linking non -sister chromatids broken

Allows recombination via independent assortment

2 (n -1) possible combinations, where n = number of homologous pairs

64
Q

Anaphase I

A

segregation of alleles) 

Kinetochore microtubules depolymerise

Disjunction occurs, pulling homologs to opposite poles

Sister chromatids remain attached by cohesion

Ploidy level has now been reduced by half

65
Q

Telophase I

A

Nuclear membrane re-form around chromosomes

Chromosomes partially decondense

66
Q

Cytokinesis

A

Cytokinesis divides the cytoplasmic contents, which may be unequal

Progeny cells are now haploid (n)

67
Q

Prophase II

A

Nuclear envelope breaks down

Centrosomes duplicate and migrate to poles

Microtubules form

Chromosomes recondense

68
Q

Metaphase II

A

Sister chromatids attached to kinetochore

Align at metaphase plate

69
Q

Anaphase II

A

Sister chromatids separate, breakdown of cohesion proteins

Kinetochore microtubules depolymerize

Sister chromatids move to opposite poles

Non kinetochore microtubules elongate the cell

70
Q

Telophase II and Cytokinesis

A

Chromosome migration complete

Chromosomes decondense

Nuclear envelope reforms

Cytokinesis divides the cytoplasm

71
Q

synapsis

A

The close approach and contact between homologous chromosomes during early prophase I in meiosis.

72
Q

Nonsister chromatids

A

are chromatids belonging to different members of a homologous pair of chromosomes.

73
Q

chiasmata

A

they are located along chromosomes where crossing over has occurred

mark the locations of DNA-strand exchange between nonsister chromatids of homologous chromosomes.

74
Q

Which part of meiosis is similar to mitosis and how?

A

meiosis II
kinetochore microtubules from opposite centrosomes attach to the kinetochores of sister chromatids

the chromosomes align randomly along the metaphase plate

sister chromatid separation is accompanied by cohesin breakdown, the action of motor proteins, and depolymerization of microtubules

Cytokinesis takes place at the end of telophase II

75
Q

What are the different stages within interphase?

A

G1 S and G2

76
Q

metaphase plate

A

the cell midline along which chromosomes align in the middle of the cell

77
Q

Describe how DNA content changes or stays the same throughout mitosis

A

if we start with 2 ng of DNA in 2N=46 at G1 then:

After S phase, the DNA content doubles: 4 ng DNA content

After anaphase (M phase), the DNA content is halved: 2ng DNA content

78
Q

Describe DNA content during meiosis

A

If we start with 2 ng of DNA in 2N=46 at G1 then:

After S phase, the DNA content doubles: 4 ng DNA content, with duplicated chromosomes

Ie 2 chromatids per chromosome

After anaphase I, the DNA content is halved: 2 ng DNA content, but chromosomes are still duplicated

Twice the number of chromatids still

After anaphase II, the DNA content is halved again, and chromatids no longer doubled

79
Q

Why does aneuploidy occur?

A

Reduced cohesion of sister chromatids

Reduced connection between homologous chromosomes

Reduced recombination

Environmental factors:

Maternal age

Smoking, oral contraceptives, radiation exposure

Genetics (12 decks)

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