Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Biology > 2.6 - Cell division > Flashcards

2.6 - Cell division Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is the cell cycle and what are it’s stages?

A

The sequence of events that take place in a cell resulting in the division of the cell and the formation of two genetically identical daughter cells
Stages:
- interphase
- mitosis
- cytokinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens during interphase

A

The long period of growth and normal cell working inbetween cell division
Stages:
G1
- first growth phase
- cell synthesises proteins for replication and synthesis or organelles
- organelles replicate, cell grows (doubles in size)
S
- synthesis
- DNA replicated in nucleus
- chromosomes becomes 2 chromatids fused at the centromere
G2
- second growth phase
- cell continues to grow in size
- energy stores increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the checkpoints in interphase

A

Checkpoints check for errors. if there are errors, the cell enters G0, a resting phase to either repair or enter a permanent stage of cell arrest
G1 checkpoint:
- between G1 and S
- checks for sell size, nutrients, growth factors, DNA damage
G2 checkpoint:
- before mitosis
- checks for cell size, DNA damage, DNA replication
Metaphase/spindle assembly checkpoint:
- in mitosis (metaphase)
- checks chromosomes are attached to spindle fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the purpose of mitosis

A

Ensures both daughter cells produced are genetically identical (will have an exact copy of the DNA present in the parent cell)
For use in:
- growth
- cell replacement/ tissue repair
- asexual reproduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the stages of mitoses

A
  1. Prophase
  2. metaphase
  3. anaphase
  4. telophase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens during prophase

A
  • chromatin fibres condense into visible chromosomes
  • nucleolus disappears, nuclear envelope breaks down
  • protein microtubules form spindle fibres, linking the poles of the cell
    (animal cells)
  • 2 centrioles migrate to opposite sides of the cell
  • spindle fibres attach to the centromeres and start to move the chromosomes to the centre of the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens during metaphase?

A
  • the chromosomes are moved by the spindle fibres to form a plane in the centre of the cell (the cell equator) called the metaphase plate
  • the chromosomes are held into position
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens during anaphase

A
  • centromeres holding together the pairs of chromatids in each chromosome divide
  • chromatids are separated and pulled to opposite poles of the cell by the shortening/contracting spindle fibres
  • from the resistance of being pulled through the cytosol, the chromatids look like Vs
  • spindle fibres break down
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens during telophase

A
  • the two new sets of chromosomes assemble at each pole (one chromatid is now one chromosome)
  • the chromosomes decondense, becoming invisible again
  • new nuclear enveloped form around each set of chromosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Outline cytokinesis in animal cells

A
  • a cleavage furrow forms around the middle of the cell
  • the cytoskeleton pull the cell-surface membrane inwards until it is close enough to fuse around the middle
  • the fuse around the middle breaks, forming two identical daughter cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Outline cytokinesis in plant cells. Why can’t plant cells form a cleavage furrow?

A

Plant cells have rigid cell wall so a cleavage furrow cannot form.
- vesicles from Golgi apparatus line up across the middle, assembling where the metaphase plate was
- vesicles fuse with each other and the cell surface membrane, dividing the cell into two
- new sections of cell wall form along the new sections of membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is the cell cycle regulated through checkpoints?

A

The passing of a checkpoint is brought about by kinases
= enzymes that catalyse phosphorylation of the checkpoint proteins. This changes their structure, activating them at certain point in the cycle.
Checkpoint proteins = cyclins
forms cyclin-dependent kinase (CDK) complex
- ensures a cell enters different phases of the cycle at appropriate times

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is meiosis

A

A form of cell division that produces 4 genetically different haploid cells known as gametes (sex cells)
These cells have half the number of chromosomes found in the diploid parent cell. This is why meiosis is known as reduction division

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Zygote

A

A fertilised egg. Is the fusion of two gametes, so contains the standard number of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Homologous chromosomes

A

Two pieces of DNA within a diploid organism which carry the same genes, one from each parental source. Each chromosome in a homologous pair has the same genes at the same loci

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Alleles

A

Different versions of the same gene. The different alleles of the same gene will have the same locus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the stages of meiosis

A
  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I
  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telophase II
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Prophase I`

A
  • Same as mitosis. Chromosomes condense, nuclear envelope disintegrates, nucleolus disappears, spindle formation begins
  • difference is that homologous chromosomes pair up, forming bivalents. Chromosomes entangle, creating crossing over
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Metaphase I

A
  • same as mitosis except the homologous pairs of chromosomes assemble along the metaphase plate instead of the individual chromosomes
  • orientation of each homologous pair on the metaphase plate is random, so the maternal and paternal chromosomes can end up facing each pole
  • called independent assortment, resulting in genetic variation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Anaphase I

A
  • different from mitosis as the homologous chromosomes are pulled to opposite poles, so the chromatids stay joined to each other
  • sections of DNA on sister chromatids that became entangled during crossing over in prophase I break off and rejoin, sometimes resulting in an exchange of DNA. The points at which the chromatids break off and rejoin are called chiasmata
  • forms recombinant chromatids, resulting in a new combination of alleles. Genetic variation arises and the sister chromatids are no longer identical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Telophase I

A
  • the same as telophase in mitosis
  • chromosomes assemble at each pole, the nuclear membrane reforms and the chromosomes uncoil
  • cell undergoes cytokinesis and the reduction of chromosome number from diploid to haploid is complete
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Prophase II

A
  • chromosome which still consist of two chromatids condense and become visible
  • nuclear membrane breaks down and spindle fibre formation begins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Metaphase II

A
  • the individual chromosomes assemble on the metaphase plate, as in mitosis
  • chromatids are no longer identical due to crossing over, so there is independent assortment and more genetic variation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Anaphase II

A
  • results in the chromatids of the individual chromosomes being pulled to opposite poles after division of the centromeres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Telophase II

A
  • chromatids assemble at the poles, uncoil and form chromatin again
  • nuclear membrane reforms and nucleolus becomes visible
  • forms 4 genetically different haploid daughter cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Specialised cell

A

a cell that is adapted to a particular function e.g. a muscle cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Tissue

A

A group of specialised differentiated cells with the same function e.g. muscular tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Organ

A

A group of different tissues working together
e.g. heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Organ system

A

A group of organs working to carry out a function
e.g. circulatory system

30
Q

Organism

A

A living thing made up of several organ systems
e.g. human

31
Q

rythrocytes

A
  • specialised animal cell; red blood cell
  • flattened biconcave shape increases surface area to volume ratio
  • in mammals they have no nuclei, increasing space for haemoglobin, which carries oxygen
  • flexible, so they are able to squeeze through narrow capillaries
32
Q

Neutrophils

A
  • specialised animal cell; type of white blood cell
  • play an essential role in the immune system
  • multi-lobed nucleus makes it easier for them to squeeze through small gaps to get to the site of infection
  • granular cytoplasm = contains lots of lysosomes that contain enzymes to attack pathogens
33
Q

Sperm cells

A
  • specialised animal cell; male gametes
  • have a tail/flagellum, so are capable of movement to get to the ovum
  • contain many mitochondria to supply the energy needed to swim
  • acrosome on the head of the sperm contains digestive enzymes
  • digestive enzymes released to digest the protective layers around the ovum to allow the sperm to penetrate (leading to fertilisation)
34
Q

Palisade cell

A
  • specialised plant cell present in the mesophyll
  • contains large amounts or chloroplasts to absorb light and carry out photosynthesis
  • rectangular box shaped cells means that they can be closely packed to form a continuous layer
  • thin cell walls increases the rate of diffusion of carbon dioxide
  • large vacuole maintains turgor pressure
  • chloroplasts can move within cytoplasm so can absorb more light
35
Q

Root hair cells

A
  • specialised plant cell present at the surfaces of roots near growing tips
  • long extensions called root hairs increases the cell surface area
  • maximises uptake of water and minerals from the soil
36
Q

Guard cells

A
  • specialised plant cells
  • pairs on the surface of leaves form small openings called stomata
  • necessary for carbon dioxide to enter plants for photosynthesis
  • cell wall is thicker on one side of the plant, so the cell does not change shape symmetrically as its volume changes
  • when guard cells lose water and become less swollen, they change shape and the stomata closes. This prevents further water loss from the plant
37
Q

Four main categories of tissues in animals

A
  • nervous tissue, adapted to support the transmission of electrical impulses
  • epithelial tissue, adapted to cover internal and external body surfaces
  • muscle tissue, adapted to contrast
  • connective tissue, adapted to hold other tissues together or as a transport medium
38
Q

Squamous epithelium

A
  • specialised animal tissue that forms lining of the lungs
  • made up of specialised squamous epithelial cells
  • very thin as one cell thick, short diffusion distance so oxygen can rapidly diffuse into the blood
39
Q

Ciliated epithelium

A
  • specialised animal tissue that lines trachea
  • made up of ciliated epithelial cells and goblet cells
  • cells have cilia that move in a rhythmic manner to sweep mucus away from the lungs
  • goblet cells release mucus to trap unwanted particles
  • stops bacteria from reaching lungs
40
Q

Cartilage

A
  • specialised animal connective tissue
  • contains fibres of the proteins elastin and collagen, making it firm and flexible
  • made of chondrocyte cells embedded in an extracellular matrix
  • prevents bones from rubbing together and causing damage
41
Q

Muscle

A
  • specialised animal muscle tissue
  • needs to contract in order to move bones
  • skeletal muscle fibres contain myofibrils (dark pink bands) which contain contractile proteins
42
Q

Different types of tissues in plants

A
  • epidermis tissue, adapted to cover plant surfaces
  • vascular tissue, adapted for transporting water and nutrients
43
Q

Epidermis

A
  • specialised plant tissue
  • single layer of closely packed cells
  • covered by a waxy, waterproof cuticle to reduce water loss
  • stomata present in epidermis allows carbon dioxide, oxygen and water vapour in and out the cell
44
Q

Xylem tissue

A
  • vascular tissue responsible for transport of water and minerals throughout plants
  • made of vessel elements = elongated dead cells
  • strengthened and waterproofed with lignin = provides structural support
45
Q

Phloem tissue

A
  • vascular tissue responsible for the transport of organic nutrients (e.g. sucrose)
    from leaves and stems where it is made to all parts of the plant where it is needed
  • composed of columns of sieve tube cells separated by perforated walls called sieve plates
46
Q

Function of digestive system

A
  • takes in food
  • breaks down large insoluble molecules into small soluble ones
  • absorbs nutrients into the blood
  • retains water needed by the body
  • removes any undigested material from the body
47
Q

Function of cardiovascular system

A
  • moves blood around the body to provide an effective transport system for the substances it carries
48
Q

Function of gaseous exchange system

A
  • brings air into the body so oxygen can be extracted for respiration and carbon dioxide can be expelled
49
Q

Animal examples of organ systems

A
  • digestive system
  • cardiovascular system
  • gaseous exchange system
50
Q

Stem cells

A

Undifferentiated cells that can continually divide to create more stem cells and differentiate to produce specialised cells

51
Q

Potency

A

A stem cell’s ability to differentiate into different cell types

52
Q

Totipotent

A

can differentiate into all forms of differentiated and undifferentiated cells. Totipotent cells can also differentiate into extra-embryonic tissue such as the placenta and embryo

53
Q

Pluripotent

A

Can form all tissue types by not an embryo or the placenta

54
Q

Multipotent

A

Can only form a range of cells within a certain type of tissue e.g. blood stem cells can differentiate into red or white blood cells

55
Q

Where are totipotent stem cells found?

A

Animals - a zygote and the 16 cells from its first few miotic divisions
Plants - meristematic tissue in root and shoot tips

56
Q

Where are pluripotent stem cells found in animals?

A

embryos (mass of cells called a blastocyst)

57
Q

How does meiosis create genetic variation

A
  • crossing over during meiosis I
  • independent assortment of homologous chromosomes and sister chromatids
    Results in new combinations of alleles
58
Q

How do cells become specialised

A

Some genes are expressed while others are silenced due to cell differentiation mediated by transcription factors. Cells produce proteins that determine their structure and function

59
Q

What is a transcription factor

A

A protein that controls the transcription of genes so that only certain parts of the DNA are expressed e.g. in order to specialise

60
Q

How do transcription factors work

A
  • move from cytoplasm into nucleus
  • bind to promoter region upstream of target gene
  • makes it easier of more difficult for RNA polymerase to bind to gene. This increases or decreases the rate of transcription
61
Q

Unipotent

A

can only develop into one type of cell

62
Q

Uses of stem cells now

A
  • treatment of burns, stem cells grown on biodegradable meshes can produce new skin instead of making skin grafts
  • drug trials, potential new drugs can be tested on stem cell cultures before testing on humans
  • developmental biology, can study the changes that occur as multicellular organisms grow from a single cell and why things go wrong
63
Q

Where are multipotent stem cells found in animals?

A

Tissue/adult stem cells found in certain places such as bone marrow

64
Q

How do the specialised cells in blood form

A

From multipotent cells in the bone marrow:
- erythrocytes cannot undergo mitosis as they have n nucleus, and only have a short lifespan of 120 days so need to be replaced constantly
- neutrophils only have a lifespan of 6 hours

65
Q

Potential uses of stem cells

A
  • replacing damaged muscle tissue in the heart from heart disease/attacks
  • type 1 diabetes, replacing insulin producing cells in the pancreas
  • Parkinson’s disease, replace dopamine producing cells
  • Alzheimer’s disease, replace destroyed brain cells
  • macular degeneration, use of stem cells to treat degenerative blindness
  • birth defects, reversing birth defects
  • spinal injuries, stem cell implantation into the spinal chord restoring some movement
66
Q

Ethics of stem cells

A
  • removal of stem cells from an embryo often results in the destruction of an embryo
  • moral and religious objections to the use of embryos (life begins at conception)
67
Q

Therapeutic cloning

A

Creating a zygote clone of someone to get pluripotent stem cells for treatment, then destroying the embryo

68
Q

Induced pluripotent cells (iPs cells)

A

can use protein transcription to turn on the genes of any adult cell to turn it into a stem cell. Overcomes any ethical issues

69
Q

Risks, benefits and drawbacks of using adult stem cells

A

Benefits:
- no ethical issues
- if taken from person being treated, no risk of rejection
Drawbacks:
- difficult to identify and remove from tissue
- can only produce limited range of stem cells
Risks:
- risk of rejection if the stem cells are taken from another person

70
Q

Risks, benefits and drawbacks of using embryonic stem cells

A

Benefits:
- easier to remove from tissue
- can produce wider range of specialised cells
- clone zygotes may not be rejected
Drawbacks:
- ethical issues with destroying embryos to get stem cells
Risks:
- differentiated cells may be rejected in treatment as they come from a different person

71
Q

Sources of plant stem cells

A
  • meristematic tissue (meristem), wherever growth is occurring in plants
  • meristematic tissue sandwiched between the phloem and xylem (vascular cambium). These stem cells differentiate into the cells present in xylem and phloem tissues

A-level Biology (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions