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Topic 2: Cells, viruses and reproduction of living things > Eukaryotic cell cycle and division > Flashcards

Eukaryotic cell cycle and division Flashcards

1
Q

cell cycle

A

interphase - the time taken between divisions
mitosis - separation of the chromatids of each chromosome to form two new nuclei
cytokinesis - division of the cytoplasm

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2
Q

Interphase

A

G1 - first growth phase
- organelles replicate protein synthesis cell size grows - respiration
S - synthesis
- DNA replication
- each chromosome becomes two chromatids attached at the centromere
G2 - second growth phase
- G1 + error checking

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3
Q

State the cell divisions in mitosis

A

prophase, metaphase, anaphase and telophase

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4
Q

Prophase

A
  • replicated chromosomes super coil ( shorten and thicken )
  • nuclear envelope breaks down and disappears
  • centrioles divide into two and each daughter centriole moves to form a spindle
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5
Q

Metaphase

A
  • chromosomes line up and move to the central region of the spindle known as the equator
  • each chromosome becomes attached to the spindle thread by its centrosome
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6
Q

Anaphase

A
  • replicated sister chromatids that make up the chromosome separate from each other when the centromere holding them splits
  • each of the sisters becomes an individual chromosome
  • spindle fibre shorten
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7
Q

Telophase

A
  • as the separated sister chromatids reach the poles of the cell, a new nuclear envelope forms around each cell
  • the spindle breaks down and disappears
  • chromosomes uncoil, so you can no longer see them under a light microscope
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8
Q

Cytokinesis - after mitosis

A
  • the whole cell now splits to form two new cells, each one containing a full set of chromosomes identical to that found in original parent cell
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9
Q

where is mitosis commonly observed ?

A

mammals: tissues - epithelial tissues such as the skin and the lining of the intestine
plants: meristems - the actively growing tips of shoots and roots

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10
Q

In prokaryotic cells, cell division ..

A

occurs by a process known as binary fission

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11
Q

In eukaryotic cells, cell division ..

A

part of a regulated process called the cell cycle

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12
Q

what is asexual reproduction ?

A

the formation of new organisms that does involve the fusion of gametes

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13
Q

gene

A

a base sequence of DNA that codes of the amino acid sequence of a polypeptide or a functional RNA molecule

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14
Q

allele

A

versions of genes

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15
Q

chromosome

A

structure in a cell that contains genetic material also known as DNA

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15
Q

chromatid

A

one of the two identical halves of a chromosome that has been replicated in preparation for cell division

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16
Q

centromere

A

a constricted region of a chromosome to which the microtubules of the spindle attach during cell division

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17
Q

chromatin

A

a mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms

DNA + histone = chromatin

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18
Q

how many daughter cells does meiosis produce ?

A

4 daughter cells

19
Q

differences between mitosis and meiosis

A

meiosis:
- have half the number of chromosomes as the parent cell
- genetically different

mitosis:
- same chromosomes complement as the parent cell
- genetically identical to each other - clones

20
Q

where does meiosis occur in humans ?

A

occurs in the gonads - testes and ovaries - and results in the formation of haploid gametes that fuse at fertilisation to form a diploid zygote

21
Q

what is a haploid ?

A

contains only one chromosome from each of its homologous series

22
Q

overview of meiosis

A

in meiosis 1, homologous chromosomes are separated
in meiosis 2, the chromatids of each chromosome are separated

23
Q

Meiosis 1

A
  • prophase 1 (early )
  • prophase 1 ( mid )
  • prophase 1 ( late )
  • metaphase 1
  • anaphase 1
  • telophase 1
24
Q

prophase 1 ( early )

A

during interphase the chromosomes replicate into chromatids held together by a centromere ( the chromatids are not visible ). NOW, the chromosomes condense ( shorten and thicken ) and become visible

25
Q

prophase 1 ( mid )

A

homologous chromosomes pair up
( becoming bivalents ) as they continue to shorten and thicken. Centrioles duplicate.

26
Q

prophase 1 ( late )

A

Homologous chromosomes repel each other. Chromosomes can now be seen to consist of chromatids. Sites where chromatids have broken and rejoined, causing crossing over, are visible as chiasmata

27
Q

metaphase 1

A

nuclear membrane breaks down. Spindle forms. Bivalents line up at the equator, attached by centromeres

28
Q

anaphase 1

A

homologous chromosomes separate. Whole chromosomes are pulled towards opposite poles of the spindle, centromere first ( dragging along the chromatids )

29
Q

telophase 1

A

nuclear membrane re-forms around the daughter nuclei. The chromosome number has been halved. The chromosomes start to decondense

30
Q

Meiosis 2

A

prophase 2
metaphase 2
anaphase 2
telophase 2

31
Q

prophase 2

A

the chromosomes condense and the centrioles duplicate

32
Q

metaphase 2

A

the nuclear membrane breaks down and spindle forms. The chromosomes attach by their centromere to spindle fibres at the equator of the spindle

33
Q

anaphase 2

A

the chromatids separate at their centromeres and are pulled to opposite poles of the spindle

34
Q

telophase 2

A

the chromatids ( now called chromosomes ) decondense. The nuclear membrane re-forms . The cells divide

35
Q

what is meiosis a major source of ?

A

genetic variation in organisms

36
Q

the cells produced by meiosis are genetically different because of two different reasons :

A

independent assortment and crossing over

37
Q

Independent assortment

A

bivalents line up at the equator of the spindle in meiosis 1 entirely at random

38
Q

Crossing over

A

exchange in DNA between chromatids of homologous chromosomes

39
Q

w/hat is a chromosome mutation ?

A

a change in the number or the sequence of genes can be brought about in a number of different ways

40
Q

chromosome translocation

A

part of a chromosome breaks and re-joins a completely different chromosome

41
Q

chromosome non disjunction

A

the members of a homologous pair fail to be separated during meiosis

42
Q

polysomy

A

a zygote with more copies of this chromosome than usual

43
Q

monosomy

A

a zygote with only one copy of this chromosome

44
Q

Turner’s syndrome - monosomy

A
  • only one case of full monosomy in humans
  • Women have only one X chromosome rather than the normal two (represented XX)
45
Q

Down’s syndrome - polysomy

A

non disjunction of chromosome 21 during gamete production - total of 47 chromosomes

Topic 2: Cells, viruses and reproduction of living things (9 decks)

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