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Biology A level > Cell division, cell diversity and cellular organisation The cell cycle and mitosis > Flashcards

Cell division, cell diversity and cellular organisation The cell cycle and mitosis Flashcards

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1
Q

What’s the order of the cell cycle of mitosis?

A

G1, (G0), S, G2, mitosis, cytokenesis

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2
Q

What are the 3 stages of interphase?

A

G1, S G2

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3
Q

In general what occurs in interphase?

A

DNA is replicated and checked for errors in the nucleus
Protein synthesis occurs in the cyctolplasm
Mitochondria grow and divide, increasing in number in the cytoplasm
Chloroplasts grow and divide in plant cyctoplasm
Normal cell metabolic processes eg. respiration

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4
Q

What specifically occurs in G1?

A

The first growth phase:
Proteins from which organelles are synthesised replicate
Organelles replicate
Cell increases in size

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5
Q

What specifically occurs in S phase?

A

Synthesis phase, DNA is replicated in the nucleus

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6
Q

What specifically occurs in G2 phase?

A

Second growth phase:
Cell continues to grow in size
Energy stores increased
Duplicated DNA checked for errors

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7
Q

What is the mitotic phase?

A

Period of cell division involves 2 phases

Mitosis- the nucleus divides
Cytokinesis- the cytoplasm divides and 2 cells are produced

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8
Q

What is the G0 phase?

A

Name of the phase when the cell leaves the cycle, either temporarily or permanently

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9
Q

Why might a cell go into G0 phase?

A

Differentiation- A cell that becomes specialised to carry out a particular function, can no longer divide but must just carry out it’s function

DNA of cell might be damaged, so can no longer divide

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10
Q

Why is it important to control the cell cycle?

A

So only divides when grown to correct size, the replicated DNA is error free, and chromosomes are in correct positions for mitosis

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11
Q

What is a checkpoint?

A

Are the control mechanisms of the cell cycle, they check if that at the end of the phase if it’s been completed correctly

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12
Q

What occurs at G1 checkpoint?

A 
Occurs at the end pf G1 phase, checks for:
Cell size
Nutrients
Growth factors
DNA damage

If factors not satisfied, goes into G0 phase

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13
Q

What occurs at G2 checkpoint?

A

End of G2 phase, checks for cell size, DNA replication and DNA damage

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14
Q

What occurs at spindle assembly checkpoint (metaphase checkpoint)?

A

Located in metaphase, checks for chromosome attachment to spindle

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15
Q

What is a chromosome?

A

A linear DNA molecule. wrapped around histone proteins, found in the nucleus. Chromosomes become visible in prophase

(So after replication it’s the whole X shape)

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16
Q

What is a chromatid?

A

A replicated chromosome, appears as 2 identical strands in the early stages of cell division. Each strand is a chromatid (1/4 of the X shape)

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17
Q

What are sister chromatids?

A

A sister chromatid refers to either of the two identical copies (chromatids) formed by the replication of a single chromosome, with both copies joined together by a common centromere. In other words, a sister chromatid may also be said to be ‘one-half’ of the duplicated chromosome

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18
Q

Mitosis definition?

A

a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth

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19
Q

Centromere definition?

A

The region of a chromosome where 2 sister chromatids are joined together, and where the spindle fibres attach during cell division

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20
Q

Centriole definition?

A

An organelle from which spindle fibres develop during cell division in animal cells

21
Q

What’s a homologous pair?

A

pair of chromosomes containing a maternal and paternal chromatid joined to together at the centromere. The have the exact same gene - although may have different alleles of these genes

(so 2 x’s)

22
Q

4 Stages of mitosis in order?

A

Prophase, metaphase, anaphase and telophase

23
Q

What occurs in Prophase?

A

Chromatin fibres ( complex made up of DNA and RNA and proteins), begin to coil and condense to form visible chromosomes.

Nucleolus disappears, nuclear membrane begins to break down

Protein microtubules form spindle shaped structures linking the poles of the cell. Required to move chromosomes into right position before division

In animals and some plants centrioles go to opposite poles of the cell.

Spindle fibres attach to specific areas on the centromers and start to move the chromsomes to the centre of the cell

By the end of prophase the nuclear envelope has disappeared.

24
Q

What occurs in metaphase?

A

Chromosomes are moved by the spindle fibres to form a plane in the centre of the cell called the metaphase plate, and then held in posistion

25
Q

What occurs in anaphase?

A

The centromers holding together the pairs of chromatids in each chromosome divide, the chromatids are separated and pulled to opposite poles of the cells by the shortening spindle fibres.

26
Q

What occurs in telophase?

A

The chromatids have reached the poles and are now called chromosomes.

The 2 new sets of chromosome assemble at each pole, and the nuclear envelope forms around them.

Chromosomes start to uncoil, and the nucleolus is formed.

Cytokenesis begins

27
Q

What’s cytokinesis?

A

The actual division of the cell into 2 new cells

28
Q

Describe cytokinesis in animal cells?

A

Cleavage furrow forms around the middle of the cell

The cell surface membrane is pulled inwards by the cytoskeleton until it is close enough to fuse around the middle forming 2 new cells

29
Q

Explain cytokinesis in plant cells?

A

They have cell walls so it’s not possible for cleavage furrow to be formed.

Vesicles from the Golgi apparatus begin to form where the metaphase plate was, the vesicles then fuse with each other and the cell surface membrane dividing the cell into 2

New sections of the cell wall then form along the new sections of the membrane

30
Q

Apperance of chromosomes the number of chromosomes and quantity of DNA in different phases?

A

Interphase G1- single strand chromosome, 46, X

Interphase G2- Full X shape, 46, 2X

Prophase Full X shape but now condensed, 46, 2X

Late telophase Single strand chromosome, 46, X

31
Q

How to calculate mitotic index?

A

(Cells in mitosis / total number of cells) x 100

32
Q

Purpose of mitotic division?

A

cell reproduction, regeneration and growth

33
Q

What’s a homologous chromosomes?

A

A homologous pair is a pair of chromosomes containing a maternal and paternal chromatid joined to together at the centromere. The have the exact same gene - although may have different alleles of these genes (so 2 x’s)

34
Q

What’s a diploid cell?

A

Contains 2 complete sets of chromosomes, one from each parent

35
Q

What’s a haploid cell?

A

Has half the amount of chromosomes of a normal cell

36
Q

What’s a haploid cell?

A

Has half the amount of chromosomes of a normal cell

37
Q

Gamete definition?

A

a mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

38
Q

Zygote definition?

A

a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

39
Q

Meiosis definition?

A

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

40
Q

How does meiosis create variation?

A

During fertilisation, 1 gamete from each parent combines to form a zygote. Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote

41
Q

Stages of meiosis?

A

Meiosis 1:

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1

Meiosis 2:

Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
(the same as mitosis)
42
Q

What occurs in prophase 1?

A

Chromosomes condense

Homologous chromosomes each consisting of 2 sister chromatids pair up in a process called synapsis to form bivalents

Arms of chromatids become entangled, and segments of chromosome can be exchanged in a process called crossing over

43
Q

What occurs in metaphase 1?

A

Bivalents become attached to spindle and are randomly arranged along the spindle

44
Q

What occurs in anaaphase 1?

A

The homologous chromosomes are separated

The centromers are pulled by the spindle fibres towards opposite poles.

The reduction of the number of chromosomes is achieved by this separation

45
Q

What occurs in telophase 1?

A

Does not always occur

Mostly the chromatids begin to uncoil, and a nuclear envelope forms around each group of chromosomes

The cytoplasum divides by constriction

No replication of DNA inbetween telophase 1 and prophase 2

46
Q

What does bivalent mean?

A

A pair of homologous chromosomes

47
Q

Chiasma definition?

A

The point where crossing over occurs in metaphase 1

48
Q

What is recombinant chromatids?

A

Crossing over occurs between two non-sister chromatids at prophase I of meiosis and these chromatids having exchanged genetic material are the recombinant chromatids.

49
Q

What is random independent assortment

A

formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes

Biology A level (19 decks)

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