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A-LEVEL BIOLOGY > Cell Division > Flashcards

Cell Division Flashcards

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1
Q

What are spindle fibres?(1)

A

Protein microtubules

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2
Q

What is the significance of mitosis? (3)

A

-asexual reproduction
-growth of multicellular organisms
-repair of tissues

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3
Q

What occurs in prophase? (5)

A

-chromosomes condense
-sister chromatids are joined by the centromere
-the two centrosomes move to opposite poles
-the spindle fibres begin to emerge from centrosomes
-the nuclear envelope breaks down into small vesicles

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4
Q

What occurs in telophase? (3)

A

-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelopes begin to reform around both sets of chromosomes
-the spindle fibres break down

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5
Q

What occurs in anaphase? (3)

A

-the sister chromatids separate at the centromere (divides in two)
-spindle fibres begin to shorten
-the separate sister chromatids are pulled to opposite poles of the cell by the spindle fibres

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6
Q

What occurs in metaphase? (5)

A

-centrosomes reach opposite poles
-spindle fibres continue to emerge from the centrosomes
-the chromosomes line up along the spindle equator (or metaphase plate) so they are equidistant to the two centrosome poles
-spindle fibres reach the chromosomes and attach to the centromeres
-each sister chromatid is attached to a spindle fibre that originates at opposite poles.

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7
Q

What features of chromosomes are important for cell division? (5)

A

-the shape of a chromosome is characteristic
-chromosomes occur in homologous pairs
-not all homologous chromosomes have the same alleles
-different species have a fixed number of chromosomes
-chromosomes are copied prior to division so appear double

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8
Q

How are karograms used? (1)

A

Are used by genetic counsellors to check for abnormalities in an individual’s chromosomes (such as Down’s syndrome)

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9
Q

What is a karogram? (1)

A

Arranging an individuals chromosomes in descending order of size and numbering them.

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10
Q

What is a heterozygous? (1)

A

A diploid organism that does not have two of the same alleles for a particular gene.

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11
Q

What is an autosome? (1)

A

Any chromosome in a cell that is not a sex chromosome.

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12
Q

What is a karyotype? (1)

A

The number and shape of a chromosome in a somatic cell.

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13
Q

What is a locus? (1)

A

The position of a particular gene of a specific chromosome.

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14
Q

What is a homozygous? (1)

A

A diploid cell that have the same alleles for a particular gene.

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15
Q

What is a diploid? (1)

A

A cell that contains 2 copies of each chromosome.

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16
Q

What is an allele? (1)

A

One of two or more different forms of the same gene.

17
Q

What is a centromere? (1)

A

A narrow region occupying a specific position on each chromosome this is the only site at which spindle fibres can attach during mitosis.

18
Q

What is asexual reproduction? (1)

A

The formation of an organism without the fusion of gametes.

19
Q

What is a somatic cell? (1)

A

A cell in an organisms that is not a germ cell or undifferentiated cell.

20
Q

What are homologous chromosomes? (2)

A

A pair of chromosomes in a diploid cell that have the same size and shape and carry the same genes in the same order.

21
Q

What are the main stages of cell division? (3)

A

Interphase
Mitosis
Cytokinesis

22
Q

In the G2 phase; what is checked for? (2)

A

Cell size
DNA replication

23
Q

What is the mitotic index? (1)

A

How many cells going through a specific phase divided by the number of cells in total.

24
Q

What is the difference between plant cells and animal cells in terms of cell division? (1)

A

Plant cells do not have spindle fibres.

25
Q

How do cells divide in prokaryotes? (1)

A

Via binary fission

26
Q

How do cells divide in eukaryotes? (1)

A

Via the cell cycle

27
Q

What are the divisions in mitosis called? (1)

A

Mitotic divisions

28
Q

What is meiosis? (1)

A

The production of 4 genetically different haploid gametes.

29
Q

What is s-phase? (1)

A

When the cell gets big enough the DNA replicates.

30
Q

In the G1 phase; what is checked for? (4)

A

Cell size
Cell growth
Nutrients
DNA damage

31
Q

What are the phases of mitosis? (4)

A

-prophase
-metaphase
-anaphase
-telophase

32
Q

What is mitosis? (1)

A

The production of 2 diploid genetically identical cells

33
Q

What are the chromosomes of a human divided into? (2)

A

Autosomes
Sex chromosomes

34
Q

How are chromosomes divided in humans? (2)

A

22 autosomes
1 sex chromosomes

35
Q

What sex chromosomes do females have? (1)

A

XX

36
Q

What sex chromosomes do males have? (1)

A

XY

37
Q

What are stem cells? (1)

A

Are unspecialised/undifferentiated cells that can divide.

38
Q

What are histones? (1)

A

Proteins that DNA wraps around (protects genetic information)

39
Q

How many chromosomes do humans have? (1)

A

23 pairs of chromosomes.

A-LEVEL BIOLOGY (46 decks)

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