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A Level Biology > Cell Cycle And Division > Flashcards

Cell Cycle And Division Flashcards

1
Q

What are the stages of the cell cycle?

A

-interphase
-prophase
-metaphase
-anaphase
-telophase
-cytokinesis

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2
Q

What are the three stages within interphase?

A

-G1 Phase
-S Phase
-G2 Phase

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3
Q

What stage is the majority of the life of the cell spent in?

A

Interphase G1

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4
Q

What happens in the G1 Phase?

A

Cells increase in size/volume and new biomass is made (proteins)

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5
Q

What happens in the S phase?

A

DNA replication by semiconservative DNA replication

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6
Q

What happens in the G2 phase?

A

So prepared for division, synthesis& & stores of ATP and new organelles synthesised

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7
Q

What is nuclear division?

A

Period when the nucleus divides into two (mitosis) or four (meiosis)

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8
Q

What is cytokinesis?

A

-division of the cytoplasm which follows nuclear division and produces two new genetically identical cells (mitosis) or four new genetically identical cells (meiosis)

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9
Q

Typically, how long does a mammalian cell take to complete a cell cycle and how much of this is interphase?

A

-takes 24 hours
-90% is interphase

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10
Q

How is genetic information carried?

A

In the form of genes

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11
Q

What is a gene?

A

A section of DNA that causes for one specific polypeptide

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12
Q

What is a chromosome?

A

An independent DNA molecule which has been super coiled into a condensed form

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13
Q

Draw an unduplicated chromosome

A
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14
Q

Draw a duplicated chromosome

A
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15
Q

How is a chromosome made?

A

-during semiconservative DNA replication, 2 genetically identical copies of the DNA molecule made
- they remained attached at a central point called the centromere
-each of the DNA copies now supercoils (using histones proteins to help them coil into eukaryotes)
-when they are still joined, the two condensed DNA molecules are called identical sister chromatids
-the whole structure is called a chromosome

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16
Q

What is the number of chromosomes possessed by an organism known as and what is it represented by?

A

-chromosome number
- represented by n

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17
Q

What is a homologous chromosome?

A

Have the same gene in the same gene Loki but have many different alleles.

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18
Q

What are diploid cells?

A

-Body cells have their chromosomes in homologous chromosomes.
-These somatic cells are called diploid cells

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19
Q

What is the number of homologous chromosomes in a diploid cell?

A

2n

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20
Q

What are haploid cells?

A

-cells with only one copy of each chromosome
-these are the gamete’s (sex cells)

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21
Q

Why is it important to have haploid cells?

A

To restore the species chromosome number when gametes fuse to make a zygote

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22
Q

Are somatic cells such as skin cells and liver cells diploid or haploid ?

A

Diploid (2n)

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23
Q

Are gametes such as sperm cells diploid or haploid?

A

Haploid (n)

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24
Q

What is mitosis used for?

A

-increasing cell numbers and growth of an organism
-Repair of damaged tissues (not cells)
-Replacement of worn out/dead cells

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25
Q

In mitosis, what types of cells are produced?

A

Two genetically identical daughter cells
These are clones
No variation occurs

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26
Q

In what types of environments do some organisms use mitosis for asexual reproduction?

A

In favourable, stable environment environments (where there is no environmental change)

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27
Q

Draw the stages of mitosis

A
28
Q

How to remember the order of mitosis

A

Pro Met Ana on the Telophone

Interphase
Prophase
Metaphase
Anaphase
Telophase

29
Q

What happens during prophase in mitosis?

A
  • The nuclear membrane starts to breakdown
  • The centrioles start to move to the poles of the cell and make spindle fibres
    -The chromosomes super coil and condensed/shorten/thicken and become visible
    -each chromosome appears as two identical sister chromatids joined at the centromere
30
Q

What is the easiest way to spot prophase during mitosis?

A

You first see the chromosomes PROperly = PROphase

31
Q

What happens during metaphase in mitosis?

A

-The centrioles complete the production of spindle fibres
-The chromosomes are attached to the spindle fibres by their centromere
-The chromosomes align down the equator of the cell

32
Q

What is the easiest way to spot metaphase during mitosis?

A

The chromosomes look like they lineup in the Middle= Metaphase

33
Q

What happens during anaphase in mitosis?

A

-The spindle fibres contract/shorten
-The centromere splits
-The identical sister chromatids are pulled to opposite poles
-making a ‘V’ shape

34
Q

What is the easiest way to spot anaphase during mitosis?

A

Chromosomes are pulled apart=anaphase

35
Q

What happens during telophase in mitosis?

A
  • A nuclear membrane starts to reform around each set of chromosomes
    -The chromatids/chromosomes unwind/coil/become longer/thinner and become invisible
36
Q

What is the easiest way to spot telophase in mitosis?

A

The chromosomes has split and clustered into Two nuclei =Telophase

37
Q
A
38
Q

What is an allele?

A

Different version of the same gene

39
Q

What is a gene?

A

Section of DNA on a chromosome coding for one or more polypeptide

40
Q

What is a chromosome?

A

Independent DNA molecule in a condensed form which contains many genes (using histones)

41
Q

What does the term sister chromatid mean?

A

One of the two strands of a replicated chromosome that are joined together by a single centromere prior to cell division

42
Q

What does the term haploid mean?

A

Cells that contain only a single copy of each chromosome (i.e gametes)

43
Q

What does the term diploid mean?

A

Cell in which the nucleus contains two set of homologous chromosomes

44
Q

What is a somatic cell?

A

A normal body cell

45
Q

What is a homologous chromosome?

A

Same genes are in the same location

46
Q

What do tumour suppressor genes do?

A

Code for proteins that slow down the cell cycle

47
Q

What do proto-onco genes do?

A

Code for proteins that speed up the cell cycle

48
Q

What happens if a mutation occurs in the tumour suppressor genes or the proto onco genes?

A
  • cell division continues uncontrolled
    -It is often rapid
    -Cells produced are abnormal
    -Tumour develops
    -If the cell spread into the surrounding tissues, this is cancer
49
Q

Give one way in which cancer can be treated

A

-Giving drugs that inhibit cell division (mitosis)
-these drugs may stop the DNA replication, spindle formation and cytokinesis

50
Q

What does binary fission in prokaryotic cell involve?

A
  • replication of the circular DNA and of plasmids
  • Division of the cytoplasm to produce two daughter cells each with a single copy of the circular DNA and a variable number of copies of plasmids
51
Q

Is binary fission a type of mitosis?

A

No

52
Q

how do viruses replicate? (7)

A

-attachment proteins on the virus attach to receptors on the cell
-The virus nucleic acid enters the cell cytoplasm
-* reverse transcriptase makes DNA from viral RNA*
-The viruses DNA is inserted into the host cells own nuclear DNA/genome
-The viral DNA is transcribed(viral mRNA) and translated into viral proteins (enzymes/attachment proteins)
-The cell replicates the viral DNA
-The genetic material and protein coats are assembled into virions
-Eventually these virions burst out of the cell, often destroying the host cell

53
Q

How do mitochondria and chloroplasts replicate?

A

Binary fission

54
Q

What is the formula for calculating mitotic index?

A
55
Q

What is the equation for calculating the length of time for each stage of mitosis?

A
56
Q

What is the calculation for dilution series?

A
57
Q

What is meiosis?

A

-A form of cell division used by diploid organisms to produce haploid gametes for sexual reproduction.
-This increases variation within the population
-It results 4 genetically different daughter cells

58
Q

Why is meiosis important?

A

-increases variation within the population
-Halves the chromosome number (ensuring each egg or sperm cell only has one copy of each chromosome) before fertilisation to restore the full chromosome number at fertilisation 2n

59
Q

What happens during meiosis 1?

A

P1 & M1- chromosome supercoil, condense (around histones) and become visible. Homologous pairs of chromosomes form a bivalent and align along the equator. Spindle fibres attached at the centreomere.
A1- spindle fibres contract and separate homologous chromosome pairs, pulling one of each pair to the opposite poles of the cell
T1-nuclear membrane forms around the separated homologous chromosomes
-Each daughter is now a haploid

60
Q

What happens during meiosis 2?

A

P2-each daughter cell only contains one chromosome from each homologous pair (haploid)
M2-chromosomes align along the equator
A2-non-chromatids are split by their centromere and pulled to opposite poles of the cell
T2- nuclear membrane reforms
-4 genetically different haploid daughter cells are produced

61
Q

What happens in crossing over?

A

-homologous chromosomes associate/bivalent is formed
-chiasma(ta) form
-Equal lengths of non-sister chromatids/alleles are exchanged
-Producing new combinations of alleles

62
Q

Show what chromosomes would look like before and after crossing over

A
63
Q

When does Independent segregation take place?

A

In metaphase one

64
Q

What is independent segregation of homologous chromosomes?

A

During metaphase one, the homologous chromosomes attatch to the spindle fibres and they pair up side-by-side and can be reshuffled in any combination

65
Q

How can you calculate the possible number of different combinations of chromosomes following meiosis without crossing over?

A
66
Q

Describe the process of crossing over and explain how it increases genetic diversity (4)

A

-Homologous chromosomes associate/bivalent is formed
- chiasma(ta) form
-Equal lengths of non-sister chromatids are exchanged
-Producing new combinations of alleles

67
Q

Contrast mitosis and meiosis

A

A Level Biology (7 decks)

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