Cell Divison

Question 1

what are the phases of the cell cycle

Answer 1

interphase, M phase and cytokinesis

Question 2

describe the processes occuring in interphase

Answer 2

G1 phase- cell grows and new organelles and proteins are made
G1 checkpoint- cell checks chemicals needed for replication are present and check for any DNA damage
S phase- cell replicates its DNA ready to divide
G2 phase- cell keeps growing and proteins needed for cell division are made
G2 checkpoint- cell undergoes apoptosis if DNA has been damaged but if not cell undergoes mitosis

Question 3

what is the structure of chromosomes in mitosis

Answer 3

chromosomes made up of two strands joined by a centromere, separate strands are called chromatids, called sister chromatids if two strands on the same chromosome

Question 4

what are the four stages of mitosis

Answer 4

prophase, metaphase, anaphase, telophase

Question 5

describe what happens during prophase

Answer 5

chromosomes condense, centrioles move to opposite end of cell forming the spindle, nuclear enveloped breaks down

Question 6

describe what happens during metaphase

Answer 6

chromosomes line up in the middle of the cell and become attached to spindle by centromere

Question 7

describe what happens during anaphase

Answer 7

centromeres divide, separating each pair of sister chromatids, spindles contract and pull chromatids to opposite ends of the cell

Question 8

describe what happens during telophase

Answer 8

chromatids reach opposite poles on the spindle, uncoil and become long and thin, called chromosomes again, nuclear envelope forms around each new group of chromosomes, two nuclei present

Question 9

describe what happens during cytokinesis

Answer 9

cytoplasm divides, cleavage furrow forms, two daughter cells produced which are genetically identical to each other

Question 10

why is mitosis necessary for organisms

Answer 10

allows growth and repair, some organisms reproduce asexually

Question 11

what are zygotes

Answer 11

two gametes joined together through fertilisation

Question 12

what is a diploid cell

Answer 12

cell containing two of each chromosome (one from mum and one from dad)

Question 13

what are pairs of matching chromosomes called

Answer 13

homologous chromosomes

Question 14

what type of cells are haploid cells

Answer 14

gametes (only one copy of each chromosome)

Question 15

what is meiosis

Answer 15

type of cell division that occurs in reproductive organs to produce gametes, produce genetically different cells because each new cell ends up with a different combination of chromosomes

Question 16

what occurs during prophase 1 of meiosis

Answer 16

chromosomes condense, homologous chromosomes pair up, crossing over occurs, centrioles move to opposite ends of the cell forming spindle fibre, nuclear envelope breaks down

Question 17

what occurs during metaphase 1 of meiosis

Answer 17

homologous pairs line up across the centre of the cell and attach to spindle fibres by their centromeres

Question 18

what occurs during anaphase 1 of meiosis

Answer 18

spindles contract, pulling pairs apart so one chromosome goes to each end of the cell

Question 19

what occurs during telophase 1 of meiosis

Answer 19

nuclear envelope forms around each group of chromosomes, cytokinesis occurs and two haploid cells are produced

Question 20

what occurs during meiosis 2

Answer 20

same as meiosis 1 but with half the number of chromosomes, in anaphase 2 sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosome, four haploid cells are produced

Question 21

how does crossing over cause genetic variation

Answer 21

during prophase 1 homologous pairs of chromosomes pair up, chromatids twist around each other and bits of the chromatid switch over, causing a different combination of alleles but same genes

Question 22

how does independent assortment cause genetic variation

Answer 22

when homologous pairs are lined up in metaphase 1 and then separated in anaphase 1 its completely random which chromosome from each pair end up in which daughter cell

Question 23

what are stem cells

Answer 23

unspecialised cells which can develop into any type of cell

Question 24

what type of disease could be treated with stem cells

Answer 24

type 1 diabetes, alzeiheimers, parkinson’s and heart disease

Question 25

how are erythrocytes specialised

Answer 25

biconcave shape provides large surface area for gas exchange, no nucleus so more room for haemoglobin

Question 26

how are neutrophils specialised

Answer 26

flexible shape allowing them to engulf foreign particles, many lysosomes containing digestive enzymes to breakdown pathogens

Question 27

epithelial cells

Answer 27

ciliated epithelia have cilia to beat particles awa, others have microvilli which increase surface area squamous epithelia are very thin to allow efficient diffusion of gases

Question 28

how are sperm cells specialised

Answer 28

have a flagellum so they can swim to the egg, lots of mitochondria to provide energy to swim, acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg

Question 29

how are palisade mesophyll cells specialised

Answer 29

contain many chloroplasts, walls are thin so CO2 can diffuse easily into the cell

Question 30

how are root hair cells specialised

Answer 30

have a large surface area, permeable cell wall, cytoplasm contains lots of mitochondria for active transport

Question 31

how are guard cells specialised

Answer 31

in light take up water to become turgid, their thin outer walls and thickened inner walls forced them to bend outwards opening the stomata

Question 32

define the term tissue

Answer 32

group of cells that are specialised to work together to carry out a particular function

Question 33

how is squamous epithelial tissue specialised and where it is found

Answer 33

thin exchange surface for diffusion, found in many places including alveoli in the lungs

Question 34

where is ciliated epithelium found

Answer 34

found on surfaces where things need to be used like the trachea where cilia wave mucus along

Question 35

what are the three types of muscle tissue and what is its basic structure

Answer 35

bundles of elongated cells called muscle fibres smooth, cardiac and skeletal

Question 36

describe cartilage

Answer 36

type of connection time tissue, formed when cells called chrondoblasts secrete extracellular matrix

Question 37

describe the role and basic structure of xylem tissue

Answer 37

transports water and supports the plant, contains hollow xylem vessels made up of which are dead

Question 38

describe the structure and role of phloem tissue

Answer 38

transports sugar around the plant, arranged in tubes made up of sieve cells and companion cells and some ordinary plant cells

Question 39

define the term organ

Answer 39

a group of different tissues that work together to perform a particular function

Question 40

give two examples of organs, one for plants and one for animals

Answer 40

lungs and leaf

Question 41

erythrocytes and and neutrophils are derived from stem cells from where

Answer 41

bone marrow

Question 42

xylem and phloem are produced from stem cells found where

Answer 42

meristems