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OCR A-level Biology Module 2: Foundations in Biology > Cell Divisions, Diversities and Differentiation > Flashcards

Cell Divisions, Diversities and Differentiation Flashcards

A *slight* deeper insight into what cells really do in their lives!

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1
Q

What is mitosis?

A
  • Type of nuclear division that produces 2 genetically identical daughter cells to each other and parent
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2
Q

What is Chomatin?

A
  • This is the complex of nucleic acids and histone protiens, being DNA unravelled state!
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3
Q

What are Chomosomes?

A
  • the condensed structure of the DNA double helix!
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4
Q

What are Chromatids?

A
  • These are structures of copied chromosomes during the preparation of cell division
  • The “divided and duplicated” form of the chomosomes….
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5
Q

What are Centromeres?

AND LOOK HERE RN!!!!!

A
  • This is the center of chromosomes where the spindle fibres will attach during metaphase!
    *

!!!!NUMBER OF CENTROMERES = NUMBER OF CHROMOSOMES!!!!

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6
Q

What are sister chromatids?

A

These are the 2 copies of the cell’s original chromosomes!

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7
Q

How can there be an increase in number of chromatids, but same number of chromosomes

AHEM!!!!!!!!!!!

A
  • Thes is due to the centromere-counting rule, where we count chromosomes in this manner!

ALWAYS THE CASE, SO NEVER FORGET!

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8
Q

What are homologous chromosomes?

A
  • These are the MATCHING PAIRS OF CHROMOSOMES, each from the correspondonding parent cell! (sperm+egg)
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9
Q

What is the acronym for remembering the Cell Cycle Stages????

A

I-PMAT-C!!!!!

gotta know them in order………..!

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10
Q

What takes place during Interphase?

A
  1. DNA Replication
  2. Cell growth in size
  3. Organelle duplication
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11
Q

How can we split up the massive Interphase stage into its sub-processes???

AND EXPLAIN EACH OF ‘EM!

A
  1. The G1 Stage: main Organelle Replication and increase in Cell Size
  2. The S Stage: just DNA Replication!
  3. The G2 Stage: Stimulating protien production to allow Chromosome Condensation for mitosis stage………..
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12
Q

What takes place during each of the Cell Cycles’s checkpoints?

A
  1. G1 Checkpoint: Checking for DNA damages and correct cell sizes
  2. G2 Checkpoint: Checking for errors in DNA Replication, before moving to mitosis
  3. Metaphase Checkpoint: Checking forf even distribution of chromosomes during division!
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13
Q

What is the ledgdendary G0 Stage?

A
  • This is where Senescent Cells (oldy cells with max division no.50) chill, with no more mitosis!
  • This is also where cells are before apoptosis takes place!

cell differentiation and neurones may also forever be in this stage!

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14
Q

What protiens are actually involved with the cell cycle checkpoints??

A
  1. POSITIVE REGULATORS: CDK + Cycline > the protiens that INITIATE THE FOLLOWING STAGES OF CELL CYCLE!
  2. NEGATIVE REGULATORS: P53 Supressor Protiens > the protiens that HALT THE CELL CYCLE AND BRINGS THE G0 Stage!
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15
Q

What happens in each of the mitosis stages in the Cell Cycle?

remember I-PMAT-C………………

A
  1. Prophase: Chromosome Condensation, where nueclear membrane will break down
  2. Metaphase: Chromatids attach to the spindle fibres of centriolesvia the centromeres, where Chromosomes will line at the equator!
  3. Anaphase: Chromosomes are pulled away towards opposite poles via spindle fibres
  4. Telophase: 2 fresh new nuclear envelopes will form around dublicated chromatids
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16
Q

What happens during the cytokenises stages in the Cell Cycle?

A
  1. Cytoplasme will divide, forming 2 new GENETICALLY IDENTICAL DAUGHTER CELLS,
  2. (being identical to the parent cell ofc………..)
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17
Q

What special about the way the Cell Cycle works?

A
  • ITS A CYCLE!
  • This means that it can loop around at any given moment, and can be found in whatever stage it may appear to be in!!!NEVER FORGET THIS!
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18
Q

Why are cell-cycle checkpoints needed during division?

A
  1. To ensure that DNA is only duplicated once
  2. To ensure the cycle is never reversed
  3. To prevent uncontrollable division
  4. To detect and repair any damages to DNA
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19
Q

What is the purpose of mitosis?

be sure to check ittttttttttt……

A
  1. asexual reproduction
  2. Organism growth
  3. Tissue repair

in PLANTS, ANIMALS AND FUNGI!!!!!!

20
Q

What is the difference between a gene pool and a genome?

A
  1. Gene Pool: This is all the genetic information within an entire population
  2. Genome: Refers to all the geneitc information within an individual only
21
Q

What is cell differentiation?

A
  • The process in which stem cells become specialised to become specialised cells, specific to their function
22
Q

How are erythrocytes specialised to carry out its function?

A
  1. Biconcave shape = larger SA/V ratio, faster rate of oxygen diffusion into the cell
  2. Very Flexible Cytoskeleton = this will allow shape changing to twist and turn inside narrow capilleries
  3. Very Few Organelles (no nucleus) = More space available for oxygen to bind to haemaglobin
23
Q

How are neutrophils specialised to carry out its function?

A
  1. Attraction via Chemotaxix = able to attract to sites of toxins via pathogens, to be able to engulf and digest them
  2. Large Cell Size = easily able to *engulf and digest most pathogens *efficiently
24
Q

How are sperm specialised to carry out its function?

A

1.Streamlined Shape = Allows the sperm to move very easily, towards the egg cells
2.Many Mitochondria = Provides energy from ATP to allow sperm to activly swim to egg, for fertilisation

25
Q

How are ciliated epithilium specialised to carry out its function?

A

1. Have cilia (hair-like structures) = beats in a coordinated way to shift material along the surface of the epithelium tissue
1. Goblet cells secrete mucus = helps to trap dust, dirt and microorganisms - preventing them from entering vital organs where they may cause infection

26
Q

How are squamous epithilium specialised to carry out its function

A
  1. Squamous epithelium consists of a single layer of flattened cells on a basement membrane
  2. **The layer of cells forms a thin cross-section **= reduces the distance that substances have to move to pass through (it shortens the diffusion pathway)
  3. It is permeable= for the easy diffusion of gases
27
Q

How are root hair cells specialised to carry out its function?

A
  1. Root hair to increase surface area = the rate of water uptake by osmosis is greater
  2. Shorter diffusion distance = water can move through easily and at a faster rate
  3. Permanent vacuole contains cell more concentrated than soil water = maintaining a water potential gradient
  4. Mitochondria for active transport of mineral ions
    Remember that chloroplasts are not found in these cells – there’s no light for photosynthesis underground!
28
Q

What are Somaic Cells?

A

THESE ARE BODY CELLS!

29
Q

What makes meiosis not so much as a cycle as mitosis?

A
  1. MITOSIS = Any somatic cell can undergo this process, for Growth, Repair and Asexuall Reproduction
  2. MEIOSIS = Only germ cells can undergo meiosis to form gammete cells
  3. Hence, a gammete will ALWAYS STAY a gammete (until old age or unused……. :D)

germ cells = special cells that undergo meiosis and will give rise to sperms or eggs

30
Q

What makes a germ cell different to gammete cells?

A

Germ = full set of chromosomes (46), undergoing meiosis to CREATE the gammete cells
Gammete = half set of chromosomes (23), the meiosis PRODUCT of germ cells

31
Q

What are the 4 main differences of meiosis and mitosis?

A
  • MITOSIS =Somatic cells only, Growth+Repair+Asexuall, Diploid Cells, 2 Genetically Identical cells
  • MEIOSIS =Germ cells producing gammetes, Key player in genetic diversity, 4 genetically unique daughter cells, Hapliod Cells
32
Q

What makes Meiosis significant in Life?

A
  1. This will increase the genetic variation of a population!!
  2. Increases the chance of survival when environment changes, as some individuals will be better adapted than others, due to slight differing characteristics
  3. Mantains the correct chromosome number in an organism, halving number in gammete cells (for fusion)
33
Q

What are the stages of Meiosis 1??

A
  1. Prophase 1: Chromosome Condensation, where chromosomes will link via chiasmata, causing a bivalent pair, exchanging alleles
  2. Metaphase 1 : Chromosomes attach to the spindle fibres of centriolesvia the centromeres, where Chromosomes will line at the equator!
  3. Anaphase 1 : Chromosomes are pulled away towards opposite poles via spindle fibres, breaking chiasmata
  4. Telophase 1 : 2 fresh new nuclear envelopes will form around dublicated Chromatids
34
Q

What are the stages of Meiosis 2??

A
  1. Prophase 2: Chromosome Condensation, where nuclear membrane breaks down again.
  2. Metaphase 2 : Chromosomes attach to the spindle fibres of centriolesvia the centromeres, where Chromosomes will line at the equator!
  3. Anaphase 2 : Centromeres of each chromosomes divides, where now chromatids at pulled..
  4. Telophase 2 : 2 fresh new nuclear envelopes will form around dublicated Chromatids, now becoming chromosomes, becoming chromatin state when unravelled!
35
Q

What takes place after Meiosis 2?

A
  • CYTOKENISIS OCCURS!!!

Here, 4 hapliod, genetically unique cells are produced….

36
Q

What are Homologous Chromosomes?

A
  • These are mathcing pairs of chromosomes containing the exact same genes at the same loci
  • HOWEVER, they may also have different alleles for the same genes, as different alleles may be inheritied from differnt parents…..

loci = place

37
Q

What is Indpendant Assortment?

A
  • This is when homologous chromosomes are RANDOMLY separated to opposite poles of cell, during meiosis, at Anaphase 1 and 2
  • Leads to RANDOM DISTRIBUTION of maternal and paternal chromosomes
38
Q

What is crossing over?

VIP CHECKING LOCATION!!!!!!!!!!!!!!

A
  • This is the point of exchanges of genetic information with homologous chromosome pairs.

POINT OF EXCHANGE = CHIASMATA!!!!!!!!!!!!!!

39
Q

What are the 3 main factors of Genetic Variation in meiosis?

A
  1. Crossing over of Chromosomes at Prophase 1 = shuffles alleles randomly
  2. Independant Assortment at Anaphase 1 and 2 = random paternal+maternal genetic distribution
  3. Randomised Gammete Fusion at Fertilisation = random chance of specific alleles carried by both cells to join…..
40
Q

What is a stem cell?

A
  • Undifferentiated cells continually dividing by mitosis having the ability to differnetiate into any cell type!
41
Q

What is independant assortment?

A

This is homogolus chromosome pairs arranged randomly upon lining at cell equator during MEIOSIS

42
Q

How does a stem cell differentiate?

A
  • This occurs when certian genes becomes switched on or off
  • This will mean certain genes will be expressed in the cell
  • Leading to different organelle proportions, cellular shape, and cell contents!
43
Q

What are the different types of Stem Cells?

A
  1. Pluripotent = Stem cells differentiating into any cell type EXCEPT PLACENTA CELL STYPES
  2. Multipotent = Stem cells differentiating into LIMITED CELL TYPES
  3. Totipotent = ANY SPECIALISED CELL
  4. Unipotent = ONE TYPE OF CELL (e.g. skin, muscle….)
44
Q

Where can stem cell be found in humans?

A
  • Bone marrow = Multipotent stem cells
  • Embryonic = Totipotent (at early stages!)
  • Umbilical Cord = Multipotent
45
Q

How else can we get stem cells….?

A

INDUCED STEM CELLS!
* This is where we take somatic, unipotent cells and transcription proteins to switch genes on and off into a state of pluripotency!
* Genes swicthed of for differentiation will need to be switched BACK ON! to return to undifferentiated state….

OCR A-level Biology Module 2: Foundations in Biology (6 decks)

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