cell division Flashcards
1
Q
what is the importance of mitosis?
A
- tissue repair
- organism growth
- asexual reproduction
- development
2
Q
what is interphase?
A
- active phase
- preparation for successful division
3
Q
how many stages in interphase and what are they?
A
3
- G1
- S
- G2
4
Q
what occurs in interphase?
A
- replication (of DNA)
- nutrients
- growth
- cellular respiration
5
Q
what happens in G1?
A
- prepare for replication
- cells grow
- synthesis of proteins
6
Q
what is being checked at the end of G1 and what happens when passes/fails?
A
- nutrients
- growth
- DNA damage
pass: enter S phase
fail: G0
7
Q
what is S phase?
A
DNA replication
8
Q
what happens in G2 phase?
A
- cell finishes growing
- prepares for division
- increased ATP
9
Q
what is being checked at the end of G2 and what happens if passes/fails?
A
- cell size
- DNA replication
pass: mitosis
fail: repair DNA
10
Q
what is G0?
A
a non dividing stage
11
Q
why might a cell enter G0?
A
- ageing (enter permanent cell arrest)
- dormant (can reenter G1 later)
- diffferentiation (specialised cells can no longer divide)
12
Q
what happens in prophase?
A
- chromatin fibres coil and condense to form chromosomes
- nucleus disappears and nuclear membrane breaks down
-protein microtubules form spindle like shapes linking to the poles of the cell - spindle fibres attach to the centromere and move chromosomes to the centre of the cell
13
Q
what happens in metaphase?
A
chromosomes are moved by spindle fibres to form the metaphase plate
14
Q
what happens in anaphase?
A
- centromeres holding together the pairs of chromatids in each chromosome divide
- chromatids are separated by shortening the spindle fibre
15
Q
what happens in telophase?
A
- chromatids reach the poles and become chromosomes
- nuclear membrane forms
16
Q
what happens in telophase?
A
- chromatids reach the poles and become chromosomes
- nuclear membrane form
17
Q
what happens in cytokinesis in animals?
A
microtubules pull membrane inward until cells separate
18
Q
what happens in cytokinesis in plants?
A
- vesicles from the golgi assemble where the metaphase plate was
- vesicles fuse with eachother and forms the new cell surface membrane
19
Q
how many divisions occurs in meiosis?
A
2
20
Q
how many new cells are formed in meiosis?
A
4
21
Q
what happens in prophase I?
A
- homologous chromosomes undergo synapsis where they pair up to form bivalents
- they are held together at points called chiasmata where crossing over happens
22
Q
what happens in metaphase I?
A
- spindle fibres move towards chromosomes
- bivalents line up along metaphase plate and independent assortment occurs
23
Q
what is independent assortment?
A
maternal and paternal chromosomes in each pair position themselves independently of eachother
24
Q
what happens in anaphase I?
A
- homologous chromosomes are separate as microtubules pull chromosomes to opposite ends of the spindle
- centromere dont divide
25
what happens in telophase I?
- chromosomes arrive at opposite poles
- spindle fibres break down
- nuclear envelopes form around the two groups of chromosomes
26
what is formed at the end of the first division?
2 haploid cells
27
what happens in prophase II?
- nuclear envelope breaks down and chromosomes condense
- spindle forms at a right angle to the old one
28
what happens in metaphase II?
chromosomes line up in a single file line along the equator
29
what happens in anaphase II?
- centromeres divide and each individual chromosome is pulled to opposite poles
- this created 4 groups of chromosomes that have half the number of chromosomes compared to parents
30
what happens in telophase II?
nuclear membrane forms around each group of chromosomes
31
what is the end product of meiosis?
4 haploid cells
32
how does organisation of homologous chromosomes during metaphase I increase genetic variation?
- independent assortment causes random arrangement of maternal and paternal chromosomes
- chromosomes line up on the metaphase plate
- each bivalent is genetically different
33
pros of stem cells
- develop life saving treatments
- new organs can be made
- drug production
- treat genetic disorders
- replace damaged tissue
34
what are stem cells?
undifferentiated and unspecialised cells
35
what are totipotent cells?
- can produce any body cell
- embryonic development in mammals
- unspecialised
36
what are pluripotent cells?
- develop from totipotent cells
- used to treat disorders
- can become all tissue types
37
what are multipotent cells?
- mature animals
- develop into a limited number of cells
38
explain why a zygote would undergo mitosis rather then meiosis
- mitosis is required for the growth of the zygote
- this means genetically identical cells need to be produced
- meisosis would produce haploid cells
39
suggest why hydra reproduces asexually when conditions are favourable
- produce genetically identical offspring
- all offspring will have the same favourable adaptations
40
how can embryonic stem cells be used in research to benefit biological knowledge?
- grown into different tissue to observe the effects of different drugs
- test toxicity of new drugs
- see how they differentiate into new cells
41
why is a leaf described as an organ?
- group of different tissues working together to perform a specific function
- made of tissues like palisade mesophyll to carry out photosynthesis
42
what features of adult stem cells make them suitable for regeneration of tissues in the kidney?
- they are multipotent
- can differentiate into any cell within the kidney
43
explain the role of embryonic stem cells in the development of the embryo
they are undifferentiated and can differentiate into any type of cell
44
explain why the cells of the inner cell mass are not totipotent stem cells
they cannot form any type of cell so cannot give rise to any extra embryonic tissue
45
where are erythrocytes and neutrophils formed?
bone marrow
46
how are erythrocytes adapted for function?
- biconcave for larger sa:v ratio
- flexible to squeeze through blood vessels
- no nucleus so has more room for haemoglobin and oxygen
47
how are neutrophils adapted for function?
- many lysosomes and hydrolytic enzymes to digest waste from phagocytosis
48
how is the squamous epithelium adapted for function?
- flat and very thin for shorter diffusion distance
- fit tightly together
- rapid diffusion of oxygen and carbon dioxide in alveoli
49
how is the ciliated epithelium adapted for function?
hair like structures to waft dust, microbes and mucus out of the lungs
50
what is the process that contributes to genetic variation in metaphase 1+2?
independent assortment of chromosomes ad chromatids
51
how does prophase 1 contribute to genetic variation?
crossing over of alleles between homologous chromosomes and non sister chromatids
52
why is genetic variation in meiosis two is reliant on crossing over?
- crossing over enables exchange of genetic info between non sister chromatids
- chromatids assort randomly
53
discuss the ways in which genetic variation is produced including the role of nuclear division
- independent assortment of bivalents occurs in metaphase 1 and chromatids in metaphase 2
- crossing over of alleles in prophase 1
- these produces a variety of allele combinations
- mutations in DNA base sequences due to the faults in the check at the end of G2 phase
- random fertilisation means that gametes will be genetically different
54
how is a molecule prepared and secreted after translation?
- moved by transport vesicle from RER to golgi apparatus
- packaged, modified and moves in a secretory vesicle along the cytoskeleton to the plasma membrane
- vesicle fuses with the plasma membrane and leaves via exocytosis
55
what are two potential sources of human stem cells and for one source, describe an ethical
issue associated with the use of stem cells?
- bone marrow
- embryonic
- some people believe the embryo is killed which gives rise to a debate about whether and embryo needs to consent
56
why is transcription needed for protein synthesis?
- DNA is transcribed into mRNA
- DNA is too large to fit through nuclear pores
57
compare prophase in mitosis and meiosis
- mitosis forms chromatids and meiosis forms bivalents
- both have spindle fibres
- crossing over occurs in meiosis not mitosis
- meiosis has 2 prophases
- nuclear membrane breaks down in both
58
