2.1.6 cell division and cellular organisation

Question 1

what is the cell cycle

Answer 1

the process that all body cells in multicellular organisms use to grow and divide

Question 2

how many chromosomes do humans have in each cell

Answer 2

46 chromosomes, 23 pairs

Question 3

what is interphase

Answer 3

the stage of cell growth before division
the cell carries out normal functions but also prepares to divide. the cells DNA is unravelled and replicated. organelles are replicated and ATP content is increased.
split into G1, S and G2

Question 4

what is M phase

Answer 4

the period of cell division

Question 5

what is the G1 (gap phase 1) stage

Answer 5

cell grows and new organelles and proteins are made

Question 6

what does the G1 checkpoint check for

Answer 6

checks that all the chemicals needed for replication are present and any damage to the DNA

Question 7

what is the G2 stage

Answer 7

cell keeps growing and proteins are needed for cell division are made

Question 8

what does the G2 checkpoint check for

Answer 8

checks whether the replicated DNA has no damage

Question 9

what is the S stage (synthesis)

Answer 9

cell replicates its DNA ready to divide my mitosis

Question 10

what is the structure of a chromosome in mitosis

Answer 10

2 sister chromatids joined in the centre by a centromere. there is 2 because it has been replicated

Question 11

what is mitosis

Answer 11

needed for the growth of multicellular organisms and a method of asexual reproduction. it produces two identical daughter cells

Question 12

what happens in prophase (mitosis)

Answer 12

the chromosomes condense. centrioles move to opposite ends of the cell forming a network of protein fibres called a spindle. the nuclear envelope breaks down

Question 13

what happens in metaphase (mitosis)

Answer 13

the chromosomes (each with two chromatids) line up along the equator and are attached to the spindle fibres by the centromere.

Question 14

what happens in the metaphase checkpoint

Answer 14

cell checks that all chromosomes are attached to the spindle

Question 15

what happens in anaphase (mitosis)

Answer 15

the centromeres divide separating the sister chromatids. the spindles contract pulling the chromatids to opposite ends of the cell

Question 16

what happens in telophase (mitosis)

Answer 16

the chromatids reach the opposite ends of the cells. they uncoil and become less condensed again. they are chromosomes again.
the nuclear envelope forms around them so there is two nuclei.

Question 17

what is cytokinesis

Answer 17

the cytoplasm and cell membrane divides to form two separate cells

Question 18

what is sexual reproduction

Answer 18

two gametes join together at fertilisation to for a zygote which develops into a new organism

Question 19

what is an advantage of sexual reproduction

Answer 19

it produces genetically different offspring

Question 20

what is a gamete

Answer 20

have half the number of chromosomes than a normal cell

Question 21

what is meiosis

Answer 21

meiosis is the formation of gametes in sexual reproduction

Question 22

what is a homologous pair

Answer 22

a pair of chromosomes, one from the father one from the mother. the chromosomes that make up each pair are the same size and have the same genes although they may be different versions of these genes

Question 23

what happens in meiosis I

Answer 23

it is the reduction division it halves the number of chromosomes. two haploid daughter cells are formed.

Question 24

what happens in prophase I

Answer 24

chromosomes condense. the chromosomes arrange themselves into homologous pairs and crossing over occurs. nuclear envelope breaks down and centrioles move to opposite ends of the cell to form the spindle.

Question 25

what happens in metaphase I

Answer 25

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

Question 26

what happens in anaphase I

Answer 26

the spindles contract separating the homologous pairs, one chromosome goes to each end of the cell

Question 27

what happens in telophase I

Answer 27

nuclear envelope reforms forming 2 nuclei. two haploid daughter cells are produced.

Question 28

what happens in meiosis II

Answer 28

4 haploid daughter cells are made from 2 haploid daughter cells

Question 29

what is the difference between anaphase 1 and anaphase II

Answer 29

in anaphase II the sister chromatids are separated and in anaphase I the homologous pairs are separated

Question 30

what is crossing over

Answer 30

homologous pairs of chromosomes come together to pair up. the chromatids twist around each other and parts of the chromatids swap over. they contain the same genes but have a different combination of alleles.

Question 31

when does crossing over occur

Answer 31

prophase I

Question 32

what is independent assortment

Answer 32

when homologous pairs line up in metaphase I and are pulled apart in anaphase II it is completely random which pair ends up in each daughter cell. so the gametes are all different combinations of maternal and paternal chromosomes this leads to genetic variation

Question 33

what are stem cells

Answer 33

unspecialised cells that can develop into different specialised cells

Question 34

what is the difference between adult and embryonic stem cells

Answer 34

adult stem cells can only differentiate into a limited range of cells, embryonic can differentiate into all specialised cells

Question 35

what can stem cells in the bone marrow differentiate into

Answer 35

they can differentiate into blood cells to replace worn out ones. this includes erythrocytes and neutrophils

Question 36

what can stem cells in vascular cambium meristem differentiate into

Answer 36

they can differentiate into xylem vessels and phloem sieve tubes

Question 37

how may we use stem cells in the treatment of Alzheimer's

Answer 37

we could use stem cells to regrow healthy nerve cells after they die in people with Alzheimer's

Question 38

how may we use stem cells in the treatment of Parkinson's

Answer 38

transplanted stem cells could regenerate dopamine producing cells that are lost in patients with Parkinson's

Question 39

how are erythrocytes specialised for their function

Answer 39

erythrocytes carry oxygen in the blood. they have a biconcave shape which provides a large surface area for gas exchange. they have no nucleus so there is more room for haemoglobin.

Question 40

how are neutrophils specialised for their function

Answer 40

neutrophils defend the body against disease. they are flexible due to their multilobed nucleus which allows them to engulf pathogens. they also have many lysosomes to break down the engulfed pathogens.

Question 41

how are epithelial cells specialised for their function

Answer 41

epithelial cells cover the surface of organs. the cells are connected by interlinking cell membranes. ciliated epithelium has cilia which beat to move particles away squamous epithelium is very thin to allow efficient diffusion

Question 42

how are sperm cells specialised for their function

Answer 42

have flagellum so they can swim to the egg to fertilise it. they have lots of mitochondria to provide the energy to move. the acrosome contains digestive enzymes to penetrate the eggs surface

Question 43

how are palisade cells specialised for their function

Answer 43

palisade mesophyll cells do most of the photosynthesis. they contain many chloroplasts so thy can absorb sunlight. the walls are thin so CO2 can diffuse in easily

Question 44

how are root hair cells specialised for their function

Answer 44

root hair cells absorb water and mineral ions from the soil. they have a large surface area and thin permeable cell wall for efficient diffusion. they also have lots of mitochondria to provide energy for active transport

Question 45

how are guard cells specialised for their function

Answer 45

they surround a stoma which is a pore in the leaf used for gas exchange. in light they take up water and become turgid. this bends them outwards opening the stomata which allows gas to diffuse in for photosynthesis.

Question 46

what is a tissue

Answer 46

a group of similar cells working together to preform a specific function

Question 47

what is an organ

Answer 47

a group of tissues working together to preform a specific function

Question 48

what is an organ system

Answer 48

a group of organs working together to preform a specific function