Module 2- Cell Division

Question 1

what takes place during G1 phase?

Answer 1

cellular components apart from chromosomes are duplicated,, cell increases in size

Question 2

what takes place during G2 phase?

Answer 2

second growth phase,, cell continues to increase in size,, energy stores increased,, duplicated DNA checked for errors

Question 3

what takes place during S phase?

Answer 3

synthesis phase,, DNA replicated in nucleus

Question 4

what takes place during prophase (mitosis)?

Answer 4

-chromosomes condense becoming shorter and fatter
-nuclear envelope disintegrates
-centrioles move to opposite poles of cell to form spindle fibres

Question 5

what takes place during metaphase (mitosis)?

Answer 5

chromosomes move to metaphase plate and attach to the spindle fibres by their centromeres

Question 6

what takes place during anaphase (mitosis)?

Answer 6

-centromere divides separating sister chromatids
-spindle fibres shorten pulling chromatids to opposite poles of the cell by their centromere

Question 7

what takes place during telophase (mitosis)?

Answer 7

-chromatids reach opposite poles
-two new sets of chromosomes assemble and nuclear envelope reforms around them
-chromosomes uncoil
-cytokinesis begins

Question 8

what takes place during cytokinesis?

Answer 8

cytoplasm divides and two cells are produced,, begins during telophase

Question 9

what is a totipotent stem cell?

Answer 9

-can differentiate into any cell including extra-embryonic tissues e.g. placenta

Question 10

what is multipotent stem cell?

Answer 10

-can only form a range of cells within a certain type of tissue

Question 11

what is a pluripotent stem cell?

Answer 11

-can form all tissue types but not whole organisms
-origin of different types of tissue within an organism

Question 12

what are the potential uses of stem cells in developmental biology?

Answer 12

-can be grown into different tissues
to test how effective new medicinal
drugs are and test for side effects/toxicity of them
-studied to see how they develop into different cell types

Question 13

what happens during crossing over?

Answer 13

chromosomes entangle at the chiasmata resulting in exchange of DNA when they break off and re join during anaphase 1

Question 14

what happens during independent assortment?

Answer 14

the position of the homologous pair on metaphase plate is random ∴ different combos of alleles face poles leading to genetic variation

Question 15

how is a erythrocyte specialized for its function?

Answer 15

flattened biconcave shape=increases SA:V maximizing amount of oxygen being transported
no nuclei+not many organelles= more space for haemoglobin
flexible=squeeze through narrow capillaries

Question 16

how is a neutrophil specialized for its function?

Answer 16

-granular cytoplasm containing many lysosomes (containing hydrolytic enzymes) to attack pathogens
-multilobed nucleus=flexibility=can squeeze through small gaps to get to the site of infections + change shape to engulf (phagocytosis)

Question 17

how are squamous epithelial cells specialized for their function?

Answer 17

-very thin flattened shape (only one cell thick) providing short diffusion distance for gases e.g. O2 CO2 in alveoli

Question 18

how are ciliated epithelial cells specialized for their function?

Answer 18

-cells have hair like structures which move in a rhythm to waft mucus containing trapped pathogens away from lungs to the throat///to move egg in fallopian tubes to the uterus

Question 19

how are sperm cells specialized for their function?

Answer 19

-acrosome contains digestive enzymes which are released to digest the protective layers on the ovum allowing to fertilize
-flagellum tail to enable mobility to swim to egg
-lots of mitochondria to supply energy needed to swim

Question 20

how are guard cells specialized for their function?

Answer 20

-cell wall is thicker on one side causes, cell to bend / open stomata

Question 21

how are palisade cells specialized for their function?

Answer 21

-rectangular box shape so can be closely packed to form continuous layer
-thin cell walls to increase rate of diffusion of CO2
-large vacuole to maintain turgor pressure

Question 22

how are root hair cells specialized for their function?

Answer 22

root hairs increase SA of cell maximizing water+mineral uptake from soil

Question 23

what are stem cells?

Answer 23

renewing source of undifferentiated cells (unspecialized)

Question 24

what happens at prophase I?

Answer 24

same as prophase in mitosis ++++

-homologous chromosomes pair up to form bivalents
-crossing over occurs

Question 25

what happens at prophase II?

Answer 25

-chromosomes that consist of two chromatids condense and become visible again -nuclear envelope breaks down -spindle formation begins

Question 26

what happens at metaphase I?

Answer 26

same as metaphase in mitosis +++ -homologous pairs line up on the metaphase plate -independent assortment

Question 27

what happens at metaphase II?

Answer 27

-individual chromatids assemble on metaphase plate -due to crossing over the chromatids are no longer identical so independent assortment occurs again

Question 28

what happens at anaphase I?

Answer 28

-homologous chromosomes are pulled to opposite poles of the cell together -sections of DNA on sister chromatids break off+re-join resulting in exchange of DNA forming recombinant chromatids

Question 29

what happens at anaphase II?

Answer 29

same as anaphase of mitosis

Question 30

what happens at telophase I?

Answer 30

-chromatids reach opposite poles -two new sets of chromosomes assemble and nuclear envelope reforms around them -chromosomes uncoil -cytokinesis begins (same as mitosis)

Question 31

what happens at telophase II?

Answer 31

-chromatids reach opposite poles -two new sets of chromosomes assemble and nuclear envelope reforms around them -chromosomes uncoil -cytokinesis begins (same as mitosis)

Question 32

what happens in mitosis?

Answer 32

the nucleus divides

Question 33

what is the product of the cell cycle?

Answer 33

two genetically identical daughter cells

Question 34

what does the G1 checkpoint check for?

Answer 34

DNA damage, cell size, nutrients

Question 35

what does the G2 checkpoint check for?

Answer 35

correct DNA replication + DNA damage

Question 36

what does the metaphase checkpoint check for?

Answer 36

if all chromosomes are attached to spindle

Question 37

when do the checkpoints occur?

Answer 37

at the end of their phases

Question 38

what happens if the G1 checkpoint fails?

Answer 38

cell enters G0

Question 39

what happens if the G1 checkpoint is passed?

Answer 39

cell enters S phase for DNA synthesis

Question 40

what happens if the G2 checkpoint is passed?

Answer 40

mitosis begins

Question 41

what is mitosis needed for?

Answer 41

-asexual reproduction -growth and repair of tissues -production of new stem cells

Question 42

what is meiosis needed for?

Answer 42

-production of haploid cells -genetic variation by independent assortment and crossing over

Question 43

what are the potential uses of stem cells in repair of damaged tissues?

Answer 43

produce new skin for burns on the body

Question 44

what are the potential uses of stem cells for neurological?

Answer 44

stem cells can be transplanted to areas where needed in order to produce lacked cells causing the disease

Question 45

what are the ethical issues surrounding stem cell use?

Answer 45

-embryonic stem cells obtained from embryo and then discarded (debate on when life begins)

Question 46

what are homologous chromosomes?

Answer 46

matching pair of chromosomes, one inherited from each parent which have the same genes but but different alleles of the gene

Question 47

what stage does crossing over occur?

Answer 47

prophase 1

Question 48

what stage does independent assortment occur?

Answer 48

metaphase 1 and 2

Question 49

what is a tissue?

Answer 49

made up if a collection of differentiated cells that have specialized function,, each tissue is adapted for a particular function within an organism

Question 50

what is an organ?

Answer 50

collection of tissues adapted to perform a particular function within an organism

Question 51

what is an organ system?

Answer 51

multiple organs working together to carry out a major function in the body e.g. digestive system

Question 52

what are the four main types of tissue in an organism?

Answer 52

xylem, phloem, muscle, cartilage, squamous and ciliated epithelia

Question 53

what is cartilage?

Answer 53

firm flexible connective tissue

Question 54

what is the potency of a stem cell?

Answer 54

its ability to differentiate

Question 55

where and how are xylem and phloem produced?

Answer 55

produced in meritem by differentiation

Question 56

where is meristematic tissue found?

Answer 56

-wherever growth is occurring e.g. tips of roots and shoots -vascular cambium (area sandwiched between phloem and xylem)--can differentiate into the different cells present in xylem + phloem tissues

Question 57

where are erythrocytes and neutrophils both derived from?

Answer 57

bone marrow