2.1.6 Cell division, cell diversity and cellular organisation COMPLETE

Question 1

Structure of a chromosome

Answer 1

• Tips are the Telomere
• Centre held together by a centromere
• Protein is wound around histones

Question 2

The cell cycle order

Answer 2

1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase
   Proper meteors always telephone

Question 3

Interphase

Mitosis

Answer 3

DNA is uncoiled and not visible
DNA replication occurs
Cell size increases so more cytoplasm, organelles and chloroplast

Question 4

Prophase

Mitosis

Answer 4

Chromosomes becomes visible as they shorten and thicken.
Centrioles move towards the opposite poles
Microtubules develop
Nuclear envelope breakdown

Question 5

Metaphase

Mitosis

Answer 5

Chromosomes line up at the equator
centrioles reach the two poles
Spindle fibres attach to the centromeres and pulls to arrange them

Question 6

Anaphase

Mitosis

Answer 6

Chromatids pull apart to opposite ends of the cell
The centromeres divide and spindle fibres contract and shorten to pull them apart
Centromere leads

Question 7

Telophase

Mitosis

Answer 7

Nuclear envelope reforms around chromosomes as the chromatids have now reached the poles.
The nucleus reappears and the chromosomes uncoil to form chromatin

Question 8

Cytokinesis

Answer 8

Cytoplasm divides into two each containing a full set of chromosomes
ANIMALS: Furrows a cleavage by starting at the edge
PLANT: Forms a cell plate and starts from the middle

Question 9

Importance of Mitosis

Answer 9

• Asexual reproduction
• Growth of multicellular organisms
• Repair to replace damaged cells
• Replace the blood cells broken down in the liver

Question 10

Purpose of Checkpoints

Answer 10

• Prevent uncontrolled division
• Detect and repair damage to DNA
• Ensure cycle doesn’t reverse
• DNA only copied once

Question 11

G2 Checkpoint

Answer 11

Checks cell size, DNA replication and that theres no damage

Question 12

G1 Checkpoint

Answer 12

Checks cell size, Nutrients, Growth factors, DNA damage

Question 13

G0 Checkpoint

Answer 13

Resting phase where cells leave permanently or temporarily
Cell differentiation to specialise them
Check for DNA damage
Lymphocytes can start dividing again and re enter cycle

Question 14

Mitosis in Plants

Answer 14

Takes place in the meristem regions, just behind the root tips and shoot tips, the cambium and in the buds.
No centrioles present just the cell plate

Question 15

Mitosis in Yeast Cells

Answer 15

Known as Budding
The nucleus divides by mitosis and the cell swells on one side creating an uneven distribution of cytoplasm.
The cell wall forms and so do two genetically identical cells

Question 16

Mitosis in Prokaryote Cells

Answer 16

Known as binary fission
The cell grows to its limit then DNA begins to replicate
The two loops of DNA are pulled to opposite ends of the cell
This divides into two cells and a new wall forms

Question 17

Stem Cells

Answer 17

Undifferentiated Cells that can differentiate into specialised ones

Question 18

Totipotent Cell

Answer 18

Has the potential to develop into any type of cell found in the human body

Question 19

Pluripotent Cell

Answer 19

Stem cells that develop the 3 primary germ layers

Question 20

Multipotent cells

Answer 20

Thy can develop into more than one cell type, limited to adult stem cells and cord blood cells

Question 21

Sources of animal stem cells

Answer 21

Embryonic Stem Cells

Adult Stem Cells

Question 22

Uses of Stem Cells

Answer 22

• Cellular Medicines such as diabetes treatment
• To understand how our bodies work
• Test drug efficiency
• Therapies to replace damaged cells

Question 23

Differentiation

Answer 23

Cells become specialised to perform a particular function.

Question 24

Erythrocytes

Answer 24

Produced in the bone marrow
Only contain haemoglobin
Have a biconcave disk shape

Question 25

Neutrophils

Answer 25

Destroy bacteria and other foreign materials by phagocytosis. Produced in bone marrow Contain lots of lysosomes

Question 26

Squamous Epithelial Cells

Answer 26

Thin flat cells that lie inside blood vessels to reduce friction

Question 27

Ciliated Epithelium Cells

Answer 27

Column Shaped with lots of cilia and mitochondria | Found in the trachea, bronchi, bronchioles

Question 28

Sperm Cells

Answer 28

Small long thin shape with a flagellum containing microtubules for movement Mitochondria for energy Acrosome on the tip specialised to breakdown the outside of an egg.

Question 29

Palisade Cells

Answer 29

Long thin walls | Contains lots chloroplasts for photosynthesis

Question 30

Root hair cells

Answer 30

Hair line projection with thin cell walls Found near the tips of roots Increases the SA Aids the absorption of water and minerals

Question 31

Guard Cells

Answer 31

Contain chloroplasts and open during the day to let CO2 into the leaves

Question 32

DEFINITION- Tissues

Answer 32

Collection of Cells specialised to work together to perform a particular function

Question 33

DEFINITION- Organs

Answer 33

Collection of tissues working together to perform a particular function

Question 34

DEFINITION- Organ System

Answer 34

Organs working together to perform a life function

Question 35

Examples of Tissues

Answer 35

Cartilage Muscle Xylem Phloem

Question 36

Leaf Structure

Answer 36

- Cuticle - Upper Epidermis - Palisade Mesophyll layer - Spongy Mesophyll Layer - Stroma - Guard Cells - Vascular bundle

Question 37

Prophase I Early | Meiosis

Answer 37

Chromosomes condense, supercoil and become visible The nucleus disappears and the envelope breakdown Centrioles migrate to the poles and form spindle fibres

Question 38

Prophase I Late | Meiosis

Answer 38

Homologous chromosome pairs form bivalent pairs | Recombination occurs and chromosomes are crossed over at points called the chiasmata

Question 39

Metaphase I | Meiosis

Answer 39

The bivalents randomly line up at the equator Independent Assortment takes place Spindle fibres attach onto the centromeres

Question 40

Anaphase I | Meiosis

Answer 40

The homologous chromosomes are pulled apart by spindle fibres. The chiasmata are pulled apart as they separate Centromeres do not divide

Question 41

Telophase I | Meiosis

Answer 41

In animal cells the nuclear envelope reforms | Cytokinesis may occur and the cell might split

Question 42

Prophase II | Meiosis

Answer 42

Chromosomes re condense, each consisting of two nucleotides Nuclear envelope goes Centrioles replicate and spindle fibres develop perpendicular to the last ones

Question 43

Metaphase II | Meiosis

Answer 43

Chromosomes randomly line up at the equator and theres independent assortment of the chromatids Spindle fibres attach to the centromere

Question 44

Anaphase II | Meiosis

Answer 44

Chromosomes are pulled apart by spindle fibres Centromere divides to allow chromosome to split Pulled to the poles

Question 45

Telophase II | Meiosis

Answer 45

Chromatids reach the poles and re condenses | The nuclear envelope reforms forming a separate nuclei

Question 46

Cytokinesis | Meiosis

Answer 46

Cytoplasm splits forming four non identical daughter cells with half of each parent cell 1 diploid -> 1 Haploid

Question 47

Causes of Variation

Answer 47

Crossing Over Independent Assortment Random Fertilisation Mutation

Question 48

Crossing over

Answer 48

Occurs in prophase 1 | Alleles are switched at the chiasmata producing q different combination for each chromatid

Question 49

Independent Assortment

Answer 49

Metaphase 1 Bivalents randomly line up so paternal and maternal are jumbled. This means a combination of both chromosomes could be in the gamete produced, Metaphase 2 Chromatids orientate randomly so after crossing over they're not identical

Question 50

Random Fertilisation

Answer 50

Any one of the 300 million of the genetically different sperm could fertilise the egg

Question 51

Mutation

Answer 51

During Interphase when DNA is replicated, mutation may occur