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A- Level Biology > C6- Cell Division > Flashcards

C6- Cell Division Flashcards

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
Meiosis II
independent assortment of sister chromatids each cell divides again- 4 haploid cells formed
26
Meiosis I
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
how is the cell cycle regulated
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
What is meiosis
From of cell division that produces 4 genetically different haploid cells known as gametes
29
Meiosis Prophase 1
Similarities= chromosomes condense, nuclear envelope dissolves, nucleolus disappears, spindle formation begins Differences= Homologous chromosomes pair up, forming bivalents chromatids entangle and cross over
30
Meiosis Metaphase I
Independent assortment of homologous pairs Maternal/ paternal chromosomes end up facing the poles Genetic variation
31
Meiosis Anaphase I
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
Meiosis Metaphase II
Different form metaphase I --> individual chromosomes assemble on metaphase plate independent assortment
33
Meiosis Genetic variation
Crossing over during Meiosis I Independent assortment of homologous chromosomes and sister chromatids New combination of alleles
34
Chiasmata
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
Organs and organ systems
Group of tissues/ organs working together to perform a specific function
36
Specialised cells Erythrocytes
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
Specialised cells Neutrophils
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
Specialised cells Sperm cells
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
Cells Tissues
cells= basic unit of life Tissues= group of differentiated cells working together to perform a specific function
40
Stem cells
Undifferentiated cells - can replicate many times - Potential to become different types of cells
41
Stem cell potency
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
Sources of animal stem cells
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
sources of plant stem cells
Meristematic tissue - roots/ shoots= apical meristem Cambium= wall between phloem and xylem
44
uses of stem cells
Drug trails- test for efficacy and toxicity Study of developmental biology Burn treatments Parkinson's Spinal injuries
45
Stem Cells Ethics
Leftover IVF embryos Religious and moral obligations --> debate about when life begins Embryo cannot give consent Uses up leftover umbilical chords
46
Specialised tissue Squamous epithelium
Thin --> one cell thick Forms lining of lungs, allowing raid diffusion of oxygen into blood
47
Specialised tissues Ciliated epithelium
Cilia on surface move in rhythmic manner Trachea- Sweep away mucus form the lungs Goblet cells- secrete mucus
48
Specialised tissues Cartilage
Contains fibres of proteins elastin ad collagen Prevents end of bones form rubbing and causing damage --> connective tissue
49
Specialised tissues Muscle
Skeletal muscle ( muscle to bone) Contains myofibrils- contractile proteins
50
Specialised tissues Plant epidermis
Adapted to cover plant surfaces Covered by waxy cuticle --> reduces water loss Guard cells- control stoma opening size

A- Level Biology (10 decks)

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