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Cell cycle Flashcards

1
Q

Chromosome structure

A

Made of DNA and protein - histone
DNA- double helix, running length of chromosome- sections along length: genes
Chromosomes only visible when chromatin condenses prior to cell division after DNA replication
Two copies - sister chromatids, lie parallel along length, joined at Centromere

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2
Q

Chromatid

A

One of the two identical copies of a chromosome joined at the central mere prior to cell division

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3
Q

chromosome

A

Long thin structure of DNA and protein, in the nucleus, carrying genes

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4
Q

Centromere

A

specialised region of a chromosome which two chromatids join and to which microtubules of spindle attach at cell vision

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5
Q

Haploid

A

Having one complete set of chromosomes

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6
Q

homologous

A

Chromosomes in homologous pairs are identical in size and shape and they carry the same gene- loci.
One chromosome of each pair comes from each parent
Same pairs of sex chromosomes eg. X,Y are different sizes on and not homologous pairs

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7
Q

diploid

A

Having two complete sets of chromosomes

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8
Q

ploidy level

A

Number of complete sets of chromosomes in an Organism

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9
Q

polyploid

A

Organisms with more than two complete sets of chromosomes

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10
Q

Mitosis

A

Cell division in which two daughter cells have the number of chromosomes and are genetically identical with each other and the parent cell
4 stages

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11
Q

Cell cycle

A

Sequence of events that take place between the cell division and the next

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12
Q

interphase

A

Period of synthesis and growth
Longest phase of the Southside core with much metabolic activity
Made up of G1, G2, S phase, mitosis and cytokinesis

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13
Q

G1

A

Organelles are replicated, if the cell possesses restriction points it must divide
If it doesn’t, it can differentiate and become locked in G1
Stem cells are temporarily out of cycle and are in G0

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14
Q

G2

A

Organelles needed for division are replicated
Energy reserves are built up as ATP is needed for division

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15
Q

stages of mitosis

A

Prophase
metaphase
Anaphase
Telophase

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16
Q

Prophase 1
mi

A
  • chromosomes condense, coil and gets shorter and thicker.
    become visible as long thin threads
    become distinguishable as pairs of chromatids
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17
Q

Prophase 2
mi

A

Centrioles present in animal cells separate and moves to opposite ends (poles) of cell
organises a partner as they move. by the time they reached the poles they are in pairs again

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18
Q

prophase 3

mi

A

Protein microtubules form, radiating from each centriole making the spindle. Spindle Fibre extend from pole to pole to the centromere of each chromosome

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19
Q

Prophase 4

mitosis

A

towards the end of prophase, nuclear envelope disintegrates and the nucleolus disappears
Pair of chromatids can clearly be seen lying free in cytoplasm

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20
Q

Metaphase

A

Each chromosome is a pair of chromatids joined at the centromere
Centromere attaches to the Spindle fibres so that chromosomes are aligned at the equator

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21
Q

Anaphase

rapid stage

A

Rapid stage
Spindle fibres shorten and centromere separate, pulling the now seperated chromatids to the poles, centromere first

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22
Q

Telophase

A

Chromatids reach poles of cells - chromosomes
Chromosomes uncoil and lengthen
Spindle fibres breakdown
Nuclear envelope reforms, nucleolus reappears

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23
Q

cytokinesis

A

Division of nucleus by mitosis is followed by cytokinesis which is a division of cytoplasm to make two cells

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24
Q

cytokinesis in animal cells

A

Occurs by construction of the parent cell around the equator from the outside inwards
cleavage furrow

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25
cytokinesis in plant cells
droplets of cell wall material, a cell plate, form across the equator of the parent cell from the centre outwards and they extend and join to form the new cell wall
26
Difference between mitosis in animal and plant cells Shape, centrioles, cytokinesis, spindle, occurrence
shape: A- cell becomes rounded before mitosis P- No shape change Centrioles: A- present P- Absent from higher plant cells Cytokinesis: A- cleavage Furrow develops from outside inwards P- Cell plate develops from centre outwards Spindle: A- Degenerates at telophase P- Remains throughout new cell wall formation Occurrence: A- In mammals, epithelia, born marrow, hair folicles, nail beds for cell replacement. Other sites for tissue repair P- meristems
27
significance of mitosis- chromosome number
Mitosis produces two cells that have the same number of chromosomes as the parents cell and as each other Daughter cell is exact replica of parental cell Mitosis produces genetically identical cells- giving genetic stability
28
significance of mitosis- growth
producing new cells - and grows, repairs tissues and replaces dead cells
29
Significance of mitosis- asexual reproduction
asexual reproduction produces complete offspring genetically identical to parent
30
# controlled genes length of cell cycle
Controlled by genes - ensuring mitosis occurs appropriately allowed timely replacement of cells and repaired tissues in adults and correct development in embryos
31
Meiosis
Two stage cell division in sexually reproducing organisms that produce four genetically distinct haploid gametes each with half the number of parent cell
32
number of chromosomes in meiosis | diploid to haploid
In meiosis, diploid number has halved into haploids. Haploids gametes fuse art fertilisation, zygote formed has two complete sets of chromosomes- one from each gamete Restoring diploid condition Without halving, number would double every generation
33
if genes are damaged
Sell me fail to divide or divide too much at the wrong time Radiation, some chemicals and viruses can mutate DNA and DNA sequencing can identify specific gene mutations that affect this time of cell cycle
34
tumour suppressor genes
Gene controls the cell cycle by acting as a brake preventing cell cycle from repeating continually Called tumour suppressor genes as they prevent rapid replication, which could lead the tumours
35
Formation of a tumour
If genes are mutated - break is damaged and cell may go immediately from one round of mitosis to the next and cells replicate too fast In solid tissue, tumour forms In bone marrow, immature blood cells accumulate that they spill out into general circulation as blood cancers
36
proto-oncogenes
genes that have the potential to cause cancer If they become mutated or sellers infected with a virus
37
oncogenes
Genes that once altered and able to cause cancer
38
cancer
uncontrolled mitosis
39
2 divisions of meiosis
Meiosis 1 Meiosis 2 Each division goes through the same sequence of steps as meiosis Between two divisions there is no more DNA replication. Only happens once before meiosis 1.
40
Meiosis 1 summary
Homologous pairs separate. Daughter cell has half the initial number of chromosomes, but each chromosome comprises two chromatids
41
meiosis 2 summary
Chromated separate. Store to sell has the half initial number of chromosomes, each with only one chromatid
42
Prophase 1 | of meiosis
Parental and maternal chromosomes come together in homologous pairs. Pairing called synapsis, each homologous chromosome pair is a bivalent Chromosones coil app, condensing, shorter and thicker. Visible as two chromatids Centrioles separate and move to the poles of the cells Centrioles organise the polymerisation of microtubules, which radiates out of them, spindle forms
43
how does prophase 1 differ from prophase in mitosis
Homogeneous chromosomes associates in their pairs- bivalent Chromatids wrap around each other and partially repel but remain joined at Chiasmata
44
prophase 1- at chiasma
A segment of DNA from one chromatid may be exchanged with equivalent part from a chromated of homologous chromosome Swapping is called crossing over and is a source of genetic variation - mixes jeans from two parents in one chromosome
45
genetic recombanation- prophase 1
Produces new combinations of alleles Single crossover occurring during meiosis 1 results in four haploid gametes having different compositions Crossing over can happen at several places along chromatid therefore huge numbers of genetic combinations
46
end of prophase 1 | meiosis
Nuclear envelope disintegrated and nucleolus has disappeared
47
metaphase 1
Pair of homologous chromosomes arrange themselves at equator of Spindle Lie at equator randomly, with either one facing either Pole
48
Independent assortment
Either of a pair of homologous chromosomes faces to either Poel at Metaphase one of meiosis, independently of the chromosomes of other homologous pairs Either of a pair of chromatids faces to either pull at metaphase two independently of the chromatids of other chromosomes
49
Anaphase 1 | chromo in each biv
Chromosomes in each by bivalent separate Spindle fibres shorten Each pair is pulled to one pole and the other to the opposite pole Each poem receives only one of each homologous pair of chromosomes and because of random arrangement at the metaphase 1, there is a random mixture of maternal and parental chromosomes
50
Telophase 1 | in some
In some species, the nuclear envelope reforms around the haploid group of chromosomes and the chromosomes decondense and are no longer visible. In many species, the chromosomes stay in their condensed form
51
Cytokinesis 1
Division of cytoplasm occurs, making two haploid cells
52
Prophase 2 ## Footnote centrioles seperate organise
central separate and organised a new spindle at right angles to the old spindle
53
metaphase 2 | b cen
Chromosomes line up on the equator with each chromosome attached to a spindle fibre by its centromere Independent assortment happens because chromatids of chromosomes can face either pole
54
Anaphase 2/ | meiosis
Spindle Fibre shorten and centromere separate, chromatids to opposite poles
55
Telophase 2
At the poles, the chromatids lengthen and can no longer be distinguished in the microscope Spindle disintegrates and the nuclear envelope and nucleoli reform Cytokinesis takes place, producing four haploid daughter cells
56
significance of meiosis
Keeps chromosome number constant from one gen to the next gen Genetic variation in the gummy the zygotes that they produce.
57
Two ways genetic variation occurs
- Crossing over during prophase 1 - independent assortment at: Metaphase 1, so that daughter cells contain diff combos of maternal and parental chromosomes Metaphase 2, so daughter cells have diff combis of chromatids In order for species to survive in constantly changing environments and to colonise new ones
58
comparison of meiosis 1 and meiosis 2 1‘ | prophase, metaphase, anaphase
Meiosis 1: Prophase- follows DNA replication and crosses over Metaphase- homologous pairs aligned either side of equator and independent assortment of homologous chromosomes Anaphase- chromosomes separate, 2 daughter cells, haploid
59
comparison of meiosis 1 and meiosis 2 2'
Meiosis 2: Prophase- doesn't follow DNA replication and doesn't cross over Metaphase- chromosomes aligned at equator and chromatids are independently assorted Prophase- separation of chromatids, 4 daughter cells, haploid
60
comparison of mitosis and meiosis Mitosis
Mitosis: One number of divisions Two daughter cells Same chromosome number in daughter cells as parent cell Diploid daughter cells Absent chiasmata No genetic crossing over No independent assortment Genetic composition is genetically identical with parent cell and each other
61
Comparison of mitosis and meiosis Meiosis
Meiosis: Two number of divisions Four daughter cells Chromosome number in daughter cells is half the number of parents Haploid Present chiasmata Independent assortment in metaphase 1 &2 Genetic crossing over in prophase 1 Genetically different genetic composition
62
s phase
DNA is synthesised Amounts of DNA doubles and after DNA replicated it now consists of two identical strands joined at a centromere. Each strand is a chromatid

Biology🔬🧬 (11 decks)

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