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✅Biology AS Unit 1 > ▪️1.6 -cell cycle And Cell Division > Flashcards

▪️1.6 -cell cycle And Cell Division Flashcards

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1
Q

What are chromosomes made out of?

A

Made of DNA and a protein called histone

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2
Q

What are genes?

A

Sections along a DNA molecule inside a chromosome

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3
Q

When do chromosomes become visible?

A

When chromatin condenses prior to cell division after each DNA molecule has replicated and made an exact copy of itself

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4
Q

What are chromatids?

A

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

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5
Q

What is a centromere

A

Specialised region of a chromosome where two chromatids join and to which the microtubules of the spindle attach at cell division

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6
Q

Describe the DNA in a centromere

A

Has a short repeated sequence of DNA, maintains chromosome structure but doesn’t carry genetic information

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7
Q

How many chromosomes are in a normal human body cell?

A

46

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8
Q

Define haploid

A

Having a complete set of chromosomes (n, 23 chromosomes (e.g gametes)

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9
Q

Define Diploid

A

Having 2 complete sets of chromosomes (2n, 46 chromosomes)

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10
Q

What is the ploidy level

A

Number of complete sets of chromosomes in an organism

E.g haploid, diploid, Triploid

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11
Q

What are polyploid organisms?

A

Organisms with more than 2 complete sets of chromosomes

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12
Q

Define chromosomes in homologous pairs

A

Identical in shape, size, and carry the same gene loci, with genes for the same characteristics
1 chromosome of each pair comes from each parent

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13
Q

What are alleles

A

2 versions of the same gene e.g green eyes and brown eyes

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14
Q

Define mitosis

A

A type of cell division where the 2 daughters cells have the same number of chromosomes and are genetically identical with each other and the parent cell

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15
Q

Name the stages in mitosis:

A 
Interphase 
Propane 
Metaphase 
Anaphase 
Telophase
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16
Q

Describe what happens in interphase

A

The cell grows, produces organelles and replicated its DNA

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17
Q

Describe what happens during prophase

A

1) chromosomes condense and become visible
2) Each chromosome consists of 2 chromatids
3) Centriole divides and begin to migrate to poles laying down spindle

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18
Q

What happens at the end of prophase?

A

The nuclear membrane breaks down

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19
Q

What happens during metaphase

A

1) centrioles are at poles
2) Spindle is fully formed
3) chromosomes pulled by spindle line up along the equator

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20
Q

Describe what happens during anaphase

A
  • Centrosomes divide
  • Chromatids separate forming individual chromosomes
  • chromosome pulled by spindle (as the spindle fibres shorten) to poles of the cell
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21
Q

Describe the process of telophase

A
  • chromosomes arrive at the poles of the cell
  • Nuclear membrane reforms
  • chromosomes uncoil and lengthen
  • cell may begin to divide
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22
Q

Why is interphase describes as a metabolically active process?

A

Because proteins such as histones and enzymes are synthesised which requires ATP

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23
Q

What is the S phase

A

A phase of interphase where the DNA is replicated, s stands for synthesis

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24
Q

What percentage of the cell cycle is interphase?

A

90%

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25
Q

Are chromatids genetically identical?

Are chromosomes genetically identical?

A

Chromatids are genetically identical

Chromosomes are not genetically identical (but are homologous)

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26
Q

What is Cytokinesis?

A

The division of the cytoplasm of a cell after mitosis to form 2 cells

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27
Q

Describe cytokinesis in animal cells

A

Cytokinesis occurs by construction of the parent cell are the equator, from the outside, inwards.

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28
Q

Describe cytokinesis in plant cells

A

Droplets of the cell wall material (cell plate) form across the equator of the parent cell from the centre outwards and they extend and join to form a new cell wall

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29
Q

What is the shape of a plant/animal cell?

A

Animal=cell becomes rounded before mitosis

Plant= no shape change

30
Q

Are centrioles present in animal/plant cells during mitosis

A

Animal cell= yes

Plant cell = no

31
Q

Where does cytokinesis occur in a plant vs animal cell?

A 
Animal= Cleavage furrow 
Plant= Cell plate
32
Q

Compare how cutokinesis occurs in plant vs animal cell

A 
Animal= cleavage furrow develops from the outside inwards 
Plant= cell plate develops from the centre outwards
33
Q

Compare the spindle in mitosis in plant and animal cells

A 
Animal= degenerates at telophase
Plant= remains throughout new cell wall formation
34
Q

Where does mitosis occur in plant/animals?

A 
Animal = epithelial, bone marrow and other sites 
Plants= meristems
35
Q

Name 3 main significant reasons for mitosis

A

1) growth
2) Asexual reproduction
3) chromosome number
4) damage and disease

36
Q

Why is mitosis vital in maintaining the chromosome number?

A

Mitosis producers 2 cells which have the same number of chromosomes as the parent cell, genetically identical.
Gives genetic stability

37
Q

Why is mitosis vital for growth

A

Produces new cells to grow, repair and replace dead cells

In mammals some tissues are constantly worn away e.g skin therefore identical cells replace them by mitosis

38
Q

What does mitosis occurring continuously in bone marrow produce?

A

Red and white blood cells

39
Q

Where does asexual reproduction occur?

A

Some flowering plants, unicellular organisms such as yeast and bacteria and in some insects such as greenfly

40
Q

Is there genetic variation between individuals from asexual reproduction?

A

No genetic variation because they are genetically identical

41
Q

Why is mitosis vital in asexual reproduction

A

Produces complete offspring that are genetically identical to the parent

42
Q

What controlls where and when mitosis occurs/is needed?

What does this allow?

A

Genes

Allows for the timely replacement and repair of tissues in adults and correct development of embryos

43
Q

What happens to cell division when the genes that control the cell cycle are damaged?

A

Cells may fail to divide, may divide too frequently or at the wrong time

44
Q

What can cause genes to mutate?

A

Radiation, certain chemicals, and some viruses

45
Q

What happens when uncontrollable mitosis occurs

A

Tumors form which causes cancers e.g if in the bone marrow immature blood cells accumulate that spill our into general blood circulation as bone cancers (leukaemia)

46
Q

What prevents rapid replication?

A

Tumor suppressor genes

47
Q

What is an Oncogene?

A

A gene with the potential to cause cancer

48
Q

What is a pronto-onocognes

A

A gene that has the possibility to cause cancer if mutated/altered but has not been changed

49
Q

Define Meiosis

A

A two stage cell division in sexually reproducing organisms that produces 4 genetically distinct daughter cells each with half the number of chromosomes of the parent cell (haploid)

50
Q

Describe the change in number of chromosomes in meiosis

A

The diploid number is halved to haploid.
When 2 haploid gametes dude at fertilisation the zygote that is formed has 2 complete sets of chromosomes, 1 from each gamete, restoring diploid condition

51
Q

Why is it important that dipoloid number halves in gametes?

A

If the chromosome number did not half during gamete formation, the number of chromosomes would double every generation

52
Q

Basically what divisions happen in meiosis 1

A

Homologous chromosomes separate

53
Q

Basically what divisions happen in meiosis 2

A

Chromatids separate

54
Q

Name the stages of meiosis

A

1) interphase
2) prophase 1
3) metaphase 1
4) Anaphase 1
5) Telophase 1
6) Prophase 2
7) Metaphase 2
8) Anaphase 2
9) Telophase 2
10) Cytokinesis

55
Q

Describe interphase

A

1)cell grows,
Produces organelles
DNA replicates

56
Q

Describe the stages of prophase 1

A

First stage
Pairing stage
Last stage

57
Q

Describe the first stage of prophase 1

A

The diploid cell with 2 homologous pairs of chromosomes containing both paternal and maternal homologous

58
Q

Describe the pairing stage of prophase 1

A

The chromosomes pair up (pairing = synapis) forming a bivalent (2 paired homologues)

59
Q

Describe the last stage of prophase 1

A

The chromosomes from the maternal and paternal homologues cross over (at the chiasmata)
DNA from both parents become recombined into a new chromosome

60
Q

Describe metaphase 1

A

The nuclear envelope disappears and spindle is formed. Spindle attaches to centromeres and pulls the bivalent to equator

61
Q

Describe Anaphase 1

A

Spindle Fibres attach to centromeres and pull each bivalent to opposite poles causing chromatids to separate

62
Q

Describe Telophase 1

A

Spindle disappears and nuclear envelope forms around each group of chromosomes
In nucleus there are 2 centromeres and the nuclei is haploid

63
Q

What happens after Telophase 1

A

Mitosis occurs after Telophase 1 in the forms of prophase 2 metaphase 2 Anaphase 2 and Telophase 2

64
Q

What happens after Telophase 2

A

Cytokinesis

65
Q

Describe cytokinesis

A

Cytoplasm divides and 4 haploid daughter cells form

66
Q

Give reasons why meiosis is significant

A
  1. Meiosis keeps the chromosome number constant from one generation to the next
  2. Generates genetic variation in the gametes and therefore the zygotes they produce
67
Q

Describe how variation is produced during meiosis

A

A) crossing over during prophase 1
B) in Metaphase 1 the daughter cells contain different combinations of maternal and paternal chromosomes
C) in Metaphase 2 the daughter cells have different combinations of chromatids

68
Q

How many divisions In meiosis vs mitosis

A 
Meiosis = 2
Mitosis = 1
69
Q

How many daughter cells produced in meiosis vs mitosis

A 
Mitosis = 2
Meiosis = 4
70
Q

Is there a chiasmata in mitosis vs meiosis

A 
Mitosis = absent 
Meiosis = present
71
Q

Is there genetic crossing over in mitosis vs meiosis

A 
Mitosis = none 
Meiosis = In prophase 1
72
Q

Produce Genetically identical/different cells in mitosis vs meiosis?

A 
Mitosis = genetically identical with parent cell and each other 
Meiosis = genetically different

✅Biology AS Unit 1 (10 decks)

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