Cell division and nucleotides Flashcards
(129 cards)
1
Q
What is the role of the cell cycle?
A
Makes genetically identical cells, consists of interphase, mitosis and cytokinesis.
2
Q
What happens in the interphase?
A
G1, S, G2.
3
Q
What is the G1 phase?
A
The growth phase, cells increase in size but perform normal metabolic roles, most organelles produced, cell differentiation, volume of cytoplasm increases, DNA content = 20 arbitrary units.
4
Q
What is the S phase?
A
The synthesis phase, when DNA replication occurs, DNA content = 40 arbitrary units.
5
Q
What is the G2 phase?
A
A second growth phase, preparation for mitosis, cytoskeleton breaks down, microtubules begin to reassemble into spindle fibres, DNA content = 40 arbitrary units.
6
Q
What are the four phases of mitosis?
A
Prophase, metaphase, anaphase, telophase.
7
Q
What happens during the mitotic phase?
A
DNA copies are separated.
8
Q
What happens during cytokinesis?
A
The cells divide and the nuclear membrane reforms.
9
Q
What does the G1 checkpoint check for?
A
Nutrients, growth factors, DNA damage.
10
Q
What does the S checkpoint check for?
A
DNA replicated correctly, (not a main checkpoint).
11
Q
What does the G2 checkpoint check for?
A
Cell size, DNA replication.
12
Q
What does the metaphase checkpoint check for?
A
Chromosome spindle attachment.
13
Q
What does the cell do if harmful mutations that can’t be fixed are discovered at a checkpoint?
A
Apoptosis (programmed cell death).
14
Q
What is G0?
A
The resting state.
15
Q
What is the definition of mitosis?
A
Division into two daughter cells that are genetically identical to each other and to the parent cell.
16
Q
What is the definition of meiosis?
A
Division into four unique daughter cells with half the chromosomes of the parent cell.
17
Q
What can uncontrolled and repeated cell division result in?
A
Cancerous tumours.
18
Q
What are poles of a cell?
A
Opposite ends of a cell.
19
Q
What is the equator of a cell?
A
The middle of a cell.
20
Q
What are chromosomes?
A
A structure found in the nucleus of cell containing DNA.
21
Q
What is a chromatid?
A
One of two identical halves of a chromosome.
22
Q
What is a centromere?
A
The region where two chromatids join.
23
Q
What is a telomere?
A
A region of repetitive DNA sequences at the end of a chromosome.
24
Q
What happens during prophase?
A
Nuclear envelope disintegrates, nucleolus disappears, chromosomes condense and become visible, centrioles move to opposite poles and form spindle fibres.
25
What happens during metaphase?
Chromosomes attach to spindle fibres by their centromeres and line up at the equator, one chromatid either side.
26
What happens during anaphase?
Centromere splits and chromatids move to opposite poles as spindle fibres shorten.
27
What happens during telophase?
Nuclear envelope reforms, spindle fibres break down, new cell surface membrane visible down the centre of the cell.
28
What happens during cytokinesis?
The cytoplasm divides and daughter cells are formed.
29
What are features of mitosis?
For growth, produces two genetically identical daughter nuclei with the same number of chromosomes as the parent cell, no variation.
30
What are features of meiosis?
For gamete production, produces for genetically different daughter nuclei with half the amount of chromosomes as the parent cell, causes variation.
31
What are homologous chromosomes?
A pair of chromosomes that contain genes for the same characteristics.
32
How many chromosomes do normal body cells have?
Have 46 chromosomes, are diploid meaning two copies of each chromosome, one from mum and one from dad.
33
How many chromosomes do gametes have?
Have 23 chromosomes, are haploid meaning one copy of each chromosome.
34
What happens during fertilisation?
A haploid sperm cell fuse with a haploid egg cell to form a diploid embryonic cell.
35
What happens in prophase 1?
Chromosomes condense, nuclear membrane break down, crossing over.
36
What happens in metaphase 1?
Homologous pairs line up at equator.
37
What happens in anaphase 1?
Homologous pairs are separated to opposite poles.
38
What happens in telophase 1?
Nuclear envelope may reform.
39
What happens in prophase 2?
Nuclear membrane break down.
40
What happens in metaphase 2?
Chromosomes line up at the equator.
41
What happens in anaphase 2?
Chromatids separated to opposite poles.
42
What happens in telophase 2?
Nuclear envelope reforms.
43
What is the name for crossing over?
Chiasma.
44
When does independent assortment happen in meiosis?
Metaphase 1 and 2.
45
When does independent segregation happen in meiosis?
Anaphase 2.
46
What is mitosis used for?
Growth, tissue repair, asexual reproduction.
47
Why do multicellular organisms need specialised cells to carry out functions?
They have a small surface area to volume ratio.
48
Why are zygotes not specialised?
All of its genome are able to be expressed, it can divide by mitosis, it's a stem cell.
49
How can embryonic cells differentiate?
By choosing whether to express certain genes or not so its shape, contents and proportion can change.
50
What are features of meristem tissue?
Contains stem cells, found in the roots and shoot tips (and the cambium of vascular bundles) in plants.
51
What are features of meristematic cells?
Thin cell walls, no chloroplasts, large vacuole, can divide by mitosis and differentiate into other types of cells.
52
What are stem cells?
A renewing source of undifferentiated cells.
53
Where are stem cells found?
Bone marrow of human adults, human embryos, meristem tissue in plants.
54
What are two body cells that are made from the same stem cells?
Erythrocytes (red blood cells) and neutrophils (a type of white blood cell).
55
How are erythrocytes differentiated to carry oxygen?
Lots of ribosomes early on to synthesise haemoglobin, most organelles later hydrolysed.
56
How are neutrophils differentiated to ingest invading pathogens?
Larger cells, multi-lobed nucleus.
57
How are xylem cells differentiated to transport water?
Lignin impregnates cell walls (waterproof), pits left unlignified for movement of water, all contents of cell is lost.
58
How are phloem cell differentiated to transport sucrose?
Sieve tube elements become elongated and lose most cell content, companion cells form linked to phloem by plasmidomata (holes).
59
What does pluripotent mean?
Can divide by mitosis to produce different cell types, not a whole organism (e.g. bone marrow).
60
What does totipotent mean?
Can produce any cell type and produce a whole new organism.
61
What are two examples of totipotent cells
Embryonic cells for the first couple of divisions only, plant callus to produce plantlets.
62
What are embryonic cells for the first three days?
Totipotent.
63
What are embryonic cells after day three?
Pluripotent, differentiation has happened, a blastocyst forms.
64
Where can stem cells be harvested from?
Bone marrow tissue, early embryonic stem cells, umbilical cord blood, converting somatic cells into pluripotent cells.
65
How can stem cells be used in medical research?
Grown into different tissues to test medicinal drug efficacy or side effects/toxicity, study of cell function in cases of disease.
66
How can stem cells be used in organism development research?
Grown and studied to see different cell types developing.
67
How can stem cells be used in medicine?
Repair/replace damaged cells, potential to treat neurological conditions, bone marrow transplant.
68
What is the function and location of palisade cells?
To carry out photosynthesis for energy in plants, located in palisade mesophyll of leaves.
69
What are the adaptations of palisade cells?
High chloroplast density to capture sunlight for photosynthesis, elongated shape to increase surface area.
70
What is the function and location of guard cells?
Control the size of the stomata to allow water and gases in and out of the plant, located in the leaf epidermis.
71
What are the adaptations of guard cells?
Thin outer walls that bend easily, opening the stomata, aquaporins in the cell surface membrane allow water to enter by osmosis.
72
What is the function and location of ciliated epithelial cells?
Help move particles out of the body by trapping dust and bacteria, located in airways, the uterus and fallopian tubes.
73
what are the adaptations of ciliated epithelial cells?
Thin layer of tiny moving hairs, lots of mitochondria for hair motion.
74
What is the function and location of squamous epithelial cells?
Protection against water loss or microorganisms invading underlying tissue, located in the alveoli of lungs and interior walls of blood cells and lymphatic vessels.
75
What are adaptations of squamous epithelial cells?
Thin cross-section to allow for a shorter diffusion pathway, permeable allowing for easy diffusion of gases.
76
What is the function and location of sperm cells?
To fertilise an egg cell to pass on DNA, located in testes.
77
What are the adaptations of sperm cells?
A flagella to swim towards the egg, many mitochondria to provide energy, an acrosome that releases enzymes to digest the egg membrane.
78
What is the function and location of neutrophils?
Engulfs and destroys pathogens, located in bone marrow.
79
What are the adaptations of neutrophils?
Very flexible shape that allows them to squeeze through cell junctions in the capillary wall, contain large numbers of lysosomes.
80
What is the function and location of root hair cells?
Used for water uptake and nutrient uptake as well as anchorage, located in the roots of plants.
81
What are adaptations of root hair cells?
Big projections give a large SA:V to maximise absorption of water and mineral ions, thin and permeable cell wall to minimise transport distance for absorption of water and nutrients.
82
What is the function and location of erythrocytes?
To carry oxygen throughout the body and deliver it to cells and working muscles, located in blood vessels.
83
What are adaptations of erythrocytes?
Small so can fit through narrow vessels and have a concave shape to maximise surface area to carry more oxygen.
84
What is the process of DNA replication?
DNA helicase unzips DNA molecule, free nucleotides are activated,
85
What is a nucleotide?
A monomer made from a sugar, a phosphate group and a base, that makes up a nucleic acid.
86
Where is the phosphate group joined to the sugar?
Carbon 5.
87
Where is the base joined to the sugar?
Carbon 1.
88
What are all the nitrogenous bases?
Adenine, cytosine, guanine, thymine, uracil.
89
What does DNA stand for?
Deoxyribonucleic acid.
90
What does RNA stand for?
Ribonucleic acid.
91
What are features DNA?
Deoxyribose sugar, phosphate group, ATCG bases, double helix structure, antiparallel stands.
92
What are features of RNA?
Ribose sugar, phosphate group, AUCG bases, single helix structure.
93
What are features purine bases?
Adenine and guanine, two rings, always bonds with a pyrimidine base.
94
What are features of pyrimidine bases?
Cytosine, thymine and uracil, one ring, always bonds with a purine base.
95
How many bonds hold A and T/U together?
Three hydrogen bonds.
96
How many bonds hold C and G together?
Two hydrogen bonds.
97
What are features of phosphodiester bonds?
Links adjacent nucleotides, phosphate group with two ester bonds to sugars, formed by condensation reaction, broken by hydrolysis.
98
What are phosphorylated nucleotides?
ATP and ADP, pentose ribose sugar bonded to adenine and two or three phosphate groups, inorganic phosphate, breaking of phosphate group provides small packets of energy.
99
What are features of ATP?
Adenosine triphosphate, high energy release.
100
What are features of ADP?
Adenosine diphosphate, low energy release.
101
Why is DNA replication semi conservative?
Two copies of the original DNA molecule are produced, each copy conserving one half of the original DNA molecule.
102
What does each stand of DNA act as in DNA replication?
A template strand for the new DNA molecule.
103
What does DNA Helicase do?
Causes DNA helix to unwind, hydrogen bonds between bases to break, DNA molecule to unzip.
104
What is the process of DNA replication?
DNA Helicase unzips DNA molecule, free nucleotides are activated and form hydrogen bonds between complimentary base pairs, DNA Polymerase links new nucleotides, DNA molecule winds back into double helix.
105
What does DNA Polymerase do?
Catalyses condensation reactions to form (phosphodiester) covalent bonds between the phosphate of one nucleotide and the sugar of the next to form the sugar phosphate backbone.
106
Why is DNA replication important?
Conserves the genetic information accurately, (however spontaneous mutation can occur).
107
What is a gene?
A sequence of DNA nucleotides that codes for a polypeptide.
108
What does the sequence of bases enable DNA to do?
Store information.
109
What are introns?
Regions of DNA that enable several different proteins that share some sections in common to be predicted from a single gene.
110
What two stages does protein synthesis consist of?
Transcription and translation.
111
What is transcription?
Making mRNA from DNA in the nucleus.
112
What is translation?
Using the mRNA template to make a polypeptide chain in the cytoplasm.
113
What happens to the polypeptide chain after synthesis?
It can be sent to the Golgi for modification.
114
What is the orientation and function of the sense stand of a DNA molecule?
5' - 3', codes for the protein.
115
What is the orientation and function of the antisense stand of a DNA molecule?
3' - 5', template stand.
116
What will the complimentary RNA strand be the same as in protein synthesis?
The sense strand.
117
What is the process of transcription?
DNA molecule unwinded and unzipped by helicase, free RNA nucleotides activated and pair up with complimentary bases on the template stand, RNA polymerase causes phosphodiester bonds to form between RNA nucleotides, mRNA leaves the nucleus the nuclear pore.
118
Why can RNA fit through the nuclear pore but DNA can't?
RNA is single stranded so is smaller.
119
What are features of triplet codes?
Non-overlapping so each triplet is separate code, degenerate so if the third base changes the amino acid coded for stays the same, universal so the code is the same for all organisms.
120
What does having three bases mean for the number of possible amino acids?
64 possible amino acids.
121
What are features of degenerate code?
4 bases, 64 different possible codons, one start codon, 3 stop codons.
122
Why does degenerate code have 1 start codon?
To ensure that it reads from base 1 not base 2 or 3.
123
What does degenerate code having 3 stop codons mean?
Each amino acid has more than one code.
124
What does mRNA stand for?
Messenger ribonucleic acid.
125
What does tRNA stand for?
Transfer ribonucleic acid.
126
What does rRNA stand for?
Ribosomal ribonucleic acid.
127
What are features of tRNA?
Found in the cytoplasm, have an anticodon triplet code, each one attaches to a specific amino acid depending on its anticodon.
128
What are features of rRNA?
Two subunits and rRNA in equal amounts make up ribosomes, maintain structural stability of protein synthesis sequence, catalyses reaction (peptidyl transferase).
129
What is the process of translation?
The mRNA moves to a ribosome, tRNA anticodons bind to mRNA codons, formation of peptide bonds between the amino acids.
