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

▪️1.6 -cell cycle And Cell Division Flashcards

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
Are chromatids genetically identical? Are chromosomes genetically identical?
Chromatids are genetically identical | Chromosomes are not genetically identical (but are homologous)
26
What is Cytokinesis?
The division of the cytoplasm of a cell after mitosis to form 2 cells
27
Describe cytokinesis in animal cells
Cytokinesis occurs by construction of the parent cell are the equator, from the outside, inwards.
28
Describe cytokinesis in plant cells
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
29
What is the shape of a plant/animal cell?
Animal=cell becomes rounded before mitosis | Plant= no shape change
30
Are centrioles present in animal/plant cells during mitosis
Animal cell= yes | Plant cell = no
31
Where does cytokinesis occur in a plant vs animal cell?
``` Animal= Cleavage furrow Plant= Cell plate ```
32
Compare how cutokinesis occurs in plant vs animal cell
``` Animal= cleavage furrow develops from the outside inwards Plant= cell plate develops from the centre outwards ```
33
Compare the spindle in mitosis in plant and animal cells
``` Animal= degenerates at telophase Plant= remains throughout new cell wall formation ```
34
Where does mitosis occur in plant/animals?
``` Animal = epithelial, bone marrow and other sites Plants= meristems ```
35
Name 3 main significant reasons for mitosis
1) growth 2) Asexual reproduction 3) chromosome number 4) damage and disease
36
Why is mitosis vital in maintaining the chromosome number?
Mitosis producers 2 cells which have the same number of chromosomes as the parent cell, genetically identical. Gives genetic stability
37
Why is mitosis vital for growth
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
What does mitosis occurring continuously in bone marrow produce?
Red and white blood cells
39
Where does asexual reproduction occur?
Some flowering plants, unicellular organisms such as yeast and bacteria and in some insects such as greenfly
40
Is there genetic variation between individuals from asexual reproduction?
No genetic variation because they are genetically identical
41
Why is mitosis vital in asexual reproduction
Produces complete offspring that are genetically identical to the parent
42
What controlls where and when mitosis occurs/is needed? | What does this allow?
Genes | Allows for the timely replacement and repair of tissues in adults and correct development of embryos
43
What happens to cell division when the genes that control the cell cycle are damaged?
Cells may fail to divide, may divide too frequently or at the wrong time
44
What can cause genes to mutate?
Radiation, certain chemicals, and some viruses
45
What happens when uncontrollable mitosis occurs
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
What prevents rapid replication?
Tumor suppressor genes
47
What is an Oncogene?
A gene with the potential to cause cancer
48
What is a pronto-onocognes
A gene that has the possibility to cause cancer if mutated/altered but has not been changed
49
Define Meiosis
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
Describe the change in number of chromosomes in meiosis
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
Why is it important that dipoloid number halves in gametes?
If the chromosome number did not half during gamete formation, the number of chromosomes would double every generation
52
Basically what divisions happen in meiosis 1
Homologous chromosomes separate
53
Basically what divisions happen in meiosis 2
Chromatids separate
54
Name the stages of meiosis
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
Describe interphase
1)cell grows, Produces organelles DNA replicates
56
Describe the stages of prophase 1
First stage Pairing stage Last stage
57
Describe the first stage of prophase 1
The diploid cell with 2 homologous pairs of chromosomes containing both paternal and maternal homologous
58
Describe the pairing stage of prophase 1
The chromosomes pair up (pairing = synapis) forming a bivalent (2 paired homologues)
59
Describe the last stage of prophase 1
The chromosomes from the maternal and paternal homologues cross over (at the chiasmata) DNA from both parents become recombined into a new chromosome
60
Describe metaphase 1
The nuclear envelope disappears and spindle is formed. Spindle attaches to centromeres and pulls the bivalent to equator
61
Describe Anaphase 1
Spindle Fibres attach to centromeres and pull each bivalent to opposite poles causing chromatids to separate
62
Describe Telophase 1
Spindle disappears and nuclear envelope forms around each group of chromosomes In nucleus there are 2 centromeres and the nuclei is haploid
63
What happens after Telophase 1
Mitosis occurs after Telophase 1 in the forms of prophase 2 metaphase 2 Anaphase 2 and Telophase 2
64
What happens after Telophase 2
Cytokinesis
65
Describe cytokinesis
Cytoplasm divides and 4 haploid daughter cells form
66
Give reasons why meiosis is significant
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
Describe how variation is produced during meiosis
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
How many divisions In meiosis vs mitosis
``` Meiosis = 2 Mitosis = 1 ```
69
How many daughter cells produced in meiosis vs mitosis
``` Mitosis = 2 Meiosis = 4 ```
70
Is there a chiasmata in mitosis vs meiosis
``` Mitosis = absent Meiosis = present ```
71
Is there genetic crossing over in mitosis vs meiosis
``` Mitosis = none Meiosis = In prophase 1 ```
72
Produce Genetically identical/different cells in mitosis vs meiosis?
``` Mitosis = genetically identical with parent cell and each other Meiosis = genetically different ```

✅Biology AS Unit 1 (10 decks)

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