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A- Level Biology > C6- Cell Division > Flashcards

C6- Cell Division Flashcards

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1
Q

Karyotype

A

Number and appearance of chromosomes

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2
Q

homologous chromosomes

A

Chromosomes in a pair that have the same gene order

Slight variation results in alleles

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3
Q

Chromatid

A

two identical copies of DNA ( chromosomes) held together at the centromere

> < < is a chromatid

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4
Q

Chromosome structure

A

pair of chromatids
–> identical genetic information

Joined by a centromere

> .<

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5
Q

Chromatin

A

uncondensed DNA in a complex with histones

histones= proteins

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6
Q

Diploid Cell

A

Full set of chromosomes, one inherited form each parent

2n= 23 x ><
4n= 23 x >< ><

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7
Q

Cell cycle

general

3 stages

A

sequence of cell growth and division

interphase = Cell growth

Mitosis or meiosis = Chromosomes divide

Cytokinesis = Cytoplasm divides

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8
Q

Haploid cells

A

single set of unpaired chromosomes

n = 23x >

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9
Q

Interphase

G1

A

Growth 1

Cellular components duplicate
–> e.g ribosomes duplicate

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10
Q

Interphase

S phase

A

Synthesis

Chromosomes duplicate
–> to a pair of chromatids

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11
Q

Interphase

G2

General order

A

Growth 2

ATP levels increase

Cell checks duplicated chromosomes for error, making any needed repairs

G1, (G0), S, G2

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12
Q

Interphase

G0

A

Growth Zero

Cells leave cycle temporarily or for good
–> differentiation or specialisation

DNA Damage, cell can no longer divides
–> hits permanent arrest

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13
Q

Hayflick Limit

A

The finite number of times a cell can divide

  • Limit is reduced by cortisol ( stress hormone)
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14
Q

Telomere

A

Protects gene, slightly damaged/lost every division

Mended by telomerase, which is inhibited by cortisol

Therefore, cortisol reudces the Hayflick limit

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15
Q

PMAT

A

Prophase

Metaphase

Anaphase

Telophase

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16
Q

Functions of mitosis

A

Growth

Repair

Asexual reproduction

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17
Q

Prophase

A

Chromatin coils and condenses into visible chromosomes

nucleolus disappears

nuclear membrane breaks down

centrioles migrate to poles of the cell

spindle fibres attach to centromeres and begin to move chromosomes

nuclear envelope disappears

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18
Q

Metaphase

A

Chromosomes moved by spindle fibres to the equator of the cell

chromosomes lined up in a plane called the metaphase plate

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19
Q

Anaphase

A

The centromeres that hold the pair of chromatids together divide

chromatids are separated

spindle fibres shorten

chromatids pulled to opposite poles

V shape of chromatid caused by centromere being pulled

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20
Q

Telophase

A

Centromeres that join chromatids reach poles

Chromatids now chromosomes

nuclear envelope reforms around chromosomes

chromosomes uncoil

nucleolus formed

cytokinesis begins

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21
Q

Cytokinesis

A

The actual division of the cell into two separate cells

22
Q

Cytokinesis

Plant cells

A

Vesicles assemble where the metaphase plate was formed

vesicles fuse with each other and cell surface membrane

23
Q

Cytokinesis

Animal cells

A

Cleavage furrow forms at the middle of cell.

Cell Surface membrane pulled inwards by cytoskeleton until close enough to fuse around the middle, forming two cells

24
Q

Meiosis II

Key differences

A

P- Chromosomes ( 2 chromatids) unlike I
–> Like mitosis

M- independent assortment

A- individual chromatids

T- 4 genetically different daughter cells formed

25
Q

Meiosis II

A

independent assortment of sister chromatids

each cell divides again- 4 haploid cells formed

26
Q

Meiosis I

A

homologous chromosomes pair up to form bivalents

Crossing over ( exchange sections of genetic material, occurring at chiasmata)

Cell divides into two, homologous chromosomes separate randomly
–> maternal or paternal copy

27
Q

how is the cell cycle regulated

A

Checkpoints regulated by cell signalling proteins ensure damaged cells do not progress to next stage of cycle

Between G1 and S = Check for DNA damage

G2 and M = Check chromosome replication

Metaphase= Sister chromatids attached to centromere correctly

28
Q

What is meiosis

A

From of cell division that produces 4 genetically different haploid cells known as gametes

29
Q

Meiosis

Prophase 1

A

Similarities= chromosomes condense, nuclear envelope dissolves, nucleolus disappears, spindle formation begins

Differences= Homologous chromosomes pair up, forming bivalents
chromatids entangle and cross over

30
Q

Meiosis

Metaphase I

A

Independent assortment of homologous pairs

Maternal/ paternal chromosomes end up facing the poles

Genetic variation

31
Q

Meiosis

Anaphase I

A

Homologous chromosomes are pulled to opposite poles and chromatids stay joined together

Sections on chromatids entangle, break off and re-join, may result in exchange of DNA
–> happens on chiasmata

32
Q

Meiosis

Metaphase II

A

Different form metaphase I
–> individual chromosomes assemble on metaphase plate

independent assortment

33
Q

Meiosis

Genetic variation

A

Crossing over during Meiosis I

Independent assortment of homologous chromosomes and sister chromatids

New combination of alleles

34
Q

Chiasmata

A

Sections of DNA entangle during crossing over, break and re-join during Anaphase I

Results in exchange of DNA between bivalent chromosomes
–> genetic variation

35
Q

Organs and organ systems

A

Group of tissues/ organs working together to perform a specific function

36
Q

Specialised cells

Erythrocytes

A

RBC

Flattened biconcave shape, increases surface area to volume ratio, so RBC can transport more O2

No nucleus or mitochondria= more space for haemoglobin

Flexible- squeeze through narrow capillaries

37
Q

Specialised cells

Neutrophils

A

WBC

Multilobed nucleus= easier to squeeze through small gaps to get to infection site

Granular cytoplasm, many lysosomes that contain enzymes to attack pathogens

38
Q

Specialised cells

Sperm cells

A

Flagellum for movement

Many mitochondria to provide energy for swimming

Acrosome contains digestive enzymes to digest outer layers of ovum to penetrate for fertilisation

39
Q

Cells

Tissues

A

cells= basic unit of life

Tissues= group of differentiated cells working together to perform a specific function

40
Q

Stem cells

A

Undifferentiated cells

  • can replicate many times
  • Potential to become different types of cells
41
Q

Stem cell potency

A

Totipotent- capable of giving rise to any cell type or complete embryo

Pluripotent- capable of giving rise to any tissue type but not whole organisms

Multipotent- capable of giving rise to only a range of cell types

42
Q

Sources of animal stem cells

A

Embryonic-
early stages of embryo development- totipotent
After 7 days, changes to a blastocyst, now pluripotent

Adult- present throughout life
multi potent
found in bone marrow and umbilical chords

43
Q

sources of plant stem cells

A

Meristematic tissue
- roots/ shoots= apical meristem

Cambium= wall between phloem and xylem

44
Q

uses of stem cells

A

Drug trails- test for efficacy and toxicity

Study of developmental biology

Burn treatments

Parkinson’s

Spinal injuries

45
Q

Stem Cells

Ethics

A

Leftover IVF embryos

Religious and moral obligations
–> debate about when life begins

Embryo cannot give consent

Uses up leftover umbilical chords

46
Q

Specialised tissue

Squamous epithelium

A

Thin
–> one cell thick

Forms lining of lungs, allowing raid diffusion of oxygen into blood

47
Q

Specialised tissues

Ciliated epithelium

A

Cilia on surface move in rhythmic manner

Trachea- Sweep away mucus form the lungs

Goblet cells- secrete mucus

48
Q

Specialised tissues

Cartilage

A

Contains fibres of proteins elastin ad collagen

Prevents end of bones form rubbing and causing damage
–> connective tissue

49
Q

Specialised tissues

Muscle

A

Skeletal muscle ( muscle to bone)
Contains myofibrils- contractile proteins

50
Q

Specialised tissues

Plant epidermis

A

Adapted to cover plant surfaces

Covered by waxy cuticle
–> reduces water loss

Guard cells- control stoma opening size

A- Level Biology (5 decks)

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