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AS Biology > 1.6 - The Cell Cycle and Cell Division > Flashcards

1.6 - The Cell Cycle and Cell Division Flashcards

1
Q

What are chromosomes made of?

A

DNA and the protein histone

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2
Q

When are chromosomes visible?

A

When chromatin condenses prior to cell division

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3
Q

What do chromosomes replicate to become?

A

They replicate to become chromatids, joined by a centromere

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4
Q

What is the haploid number?

A

The number of chromosomes in a complete set

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5
Q

What are homologous pairs?

A

When organisms receive 1 chromosome from each parent

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6
Q

What is the ploidy level?

A

The number of complete sets in an organism

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7
Q

How many complete chromosome sets are in a haploid level?

A

1, example being human gametes

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8
Q

How many complete chromosome sets are in a diploid level?

A

2,example human body cells

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9
Q

How many complete chromosome sets are in a triploid level?

A

3, example a banana

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10
Q

What is the definition of mitosis?

A

A type of cell division in which 2 daughter cells have the same number of chromosomes and are genetically identical with each other and the parent cell
It is a continuous process

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11
Q

What are the 3 broad stages of mitosis?

A

Interphase (synthesis and growth)
Mitosis (formation of 2 nuclei)
Cytokinesis (division of the cytoplasm)

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12
Q

What are the 4 stages of interphase?

A

G1 - growth
S - DNA synthesis
G2 - growth and prep for mitosis
M- beginning of prophase
Longest phase of the cell cycle with much metabolic activity

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13
Q

Name all the phases of mitosis.

A

Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

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14
Q

What is prophase?

A
  • The chromosomes condense
  • Centrioles are present in animal cells, moving to opposite ends of the cell
  • Protein microtubules form, radiating from each centriole, making the spindle
  • nuclear envelope disintergrates and the nucleolus disappears
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15
Q

What is metaphase?

A

Chromosomes attach to the spindle fibres at their centromeres and align along the equator

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16
Q

What is anaphase?

A
  • very rapid stage
  • the centromere seperates and the spindle fibres shorten, pulling the now separated chromatids to the poles, centromere first
17
Q

What is telophase?

A
  • final stage of mitosis
  • chromatids can be referred back to as chromosomes
  • chromosomes uncoil and lengthen
  • the spindle fibres break down
  • nuclear envelope reforms
  • nucleolus reappears
18
Q

What is cytokinesis?

A
  • division of the cytoplasm to make 2 cells
  • animal cells : constriction around the equator from the outside
  • plant cells: cell plate forms across the equator and extends to form a new cell wall
19
Q

How does cancer occur?

A
  • proto-oncogenes control the cell cycle by acting as a break, preventing the cell from repeating continually (tumor supressing genes)
  • if these genes become damaged, a tumour can form, forming onco-genes
  • some genes have the potential to cause cancer if mutated or infected with a virus
20
Q

What is an oncogene?

A

A gene with the potential to cause cancer

21
Q

What is a proto-oncogene?

A

A gene that currently does not have the ability to cause cancer, unless mutated

22
Q

What is the definition of meiosis?

A

A 2 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

23
Q

What happens in prophase 1? (meiosis)

A
  • Paternal and maternal chromosomes come together in pairs, the pairing of chromosomes is called synapsis and each homologous pair is a bivalent
  • The chromosomes coil up and condense to become shorter and thicker, visible as 2 chromatids, a spindle forms
  • the chromatids wrap around eachother and then partially repel eachother but remain joined at points called chiasmata
  • at the chiasmata, a segment of DNA may be exchanged, this swapping is called crossing over and is a form of genetic variation
  • this genetic recombination produces a mixture of new alleles
  • the nuclear envelope disintergrates and nucleolus disappears
24
Q

What is metaphase 1? (meiosis)

A
  • Pairs of homologous chromosomes arrange themselves at the equator of the spindle
  • Independant assortment occurs, which is the random arrangement of chromosomes along the equator
25
Q

What is anaphase 1? (meiosis)

A
  • The chromosomes in each bivalent separate and as the spindles shorten, one of each is pulled to one pole and the other to the opposite
  • Each pole only receives 1 of each homologous pair of chromosomes and because of their random assortment at metaphase, there is a random assortment
26
Q

What is telophase 1? (meiosis)

A
  • in some species the nuclear envelope reforms and the haploid group of chromosomes and the chromosomes condense and become invisible
  • many species keep chromosomes in a condensed form
27
Q

What is cytokinesis 1? (meiosis)

A

Division of the cytoplasm occurs making 2 haploid cells

28
Q

What is prophase II (meiosis)

A

The centrioles separate and organise a new spindle at right angles to avoid the old spindle

29
Q

What is metaphase II (meiosis)

A

The chromosomes line up along its equator, with each chromosome attached to a spindle fibre by its centromere
Independant assortment occurs because the chromosomes can face either pole

30
Q

What is anaphase II? (meiosis)

A

The centromeres divide and the spindle fibres shorten, pulling the chromatids to different poles

31
Q

What is telophase II? (meiosis)

A

At the poles, the chromatids lengthen and no longer can be distinguished in the microscope. The spindle disintergrates and the nuclear envelope and nucleoli reforms

32
Q

What is cytokinesis II? (meiosis)

A

Produces 4 haploid cells from the division of the cytoplasm

33
Q

What is significant about meiosis?

A
  • the number of chromosomes remain constant from one generation to the next
  • creates genetic variation (crossing over and independant assortment)
  • helps keep species adaptable in changing environments

AS Biology (11 decks)

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