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Foundation Year MBChB > Cell Cycle, Cellular Ageing and Cell Death, Regulation of Gene Expression > Flashcards

Cell Cycle, Cellular Ageing and Cell Death, Regulation of Gene Expression Flashcards

1
Q

What is a purpose of DNA?

A

Dictates cells’ structure and function

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2
Q

What are a major source of mutations?

A

Errors in copying DNA during DNA replication

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3
Q

Why do cells progress through the cell cycle?

A

To undergo mitosis

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4
Q

What are the names of controlled and uncontrolled cell death?

A

Apoptosis: controlled cell death
Necrosis: uncontrolled cell death

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5
Q

What are the definitions of the following terms?
Gene
Allele
Exon
Intron
Genotype
Phenotype
Mutation

A

Gene: functional region of DNA that codes for a sequence of RNA
Allele: individual variant of a gene
Exon: portions of a gene product that are removed via RNA splicing
Intron: portions of a gene product that are retained following RNA splicing
Genotype: the genes (and alleles of them) in a cell/organism
Phenotype: physical features of an organism as of its genotype
Mutation: changes in the genetic sequence (order of base nucleotides)

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6
Q

How can RNA be derived from DNA?

A

Transcription

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7
Q

What are the multiple forms of RNA and their function/role?

A

Messenger RNA (mRNA): translated to produce polypeptides
Transfer RNA (tRNA): involved with translation
Ribosomal RNA (rRNA): major part of ribosomes
Short interfering and micro RNA (siRNA and miRNA): inhibit translation of complementary mRNA

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8
Q

How do miRNA and siRNA inhibit translation?

A

Bind to complementary mRNA and prevent the ribosome from binding and allowing translation to occur
Marks mRNA for degradation, therefore there is no protein synthesised

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9
Q

What is the function of miRNA and siRNA?

A

To not allow too much mRNA to be present, so as to have no extremes
Reduces likelihood of mutations

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10
Q

What is all gene expression due to?

A

Dictating factors such as methylation, acetylation and transcription factors

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11
Q

What is fine tuning?

A

Nuanced activity

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12
Q

Why may a cell have cell-signalling?

A

To prevent the translation of unnecessary proteins (hence miRNA and siRNA) as cell has multiple things in multiple directions

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13
Q

What is the meaning of “one gene, one protein”?

A

One gene codes for one protein and determines its function

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14
Q

Why is there controversy regarding “one gene, one protein”?

A

Not strictly true as multiple proteins may come from one gene as not all triplets read for the gene
Splicing causes certain exons to be lost or kept e.g., antibodies

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15
Q

What is a codon?

A

3 base sequences
Read in sets of three

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16
Q

What are mutations?

A

One source of genetic variation

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17
Q

Do mutations require a response to occur?

A

No, they occur randomly

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18
Q

What happens in a substitution mutation?

A

One base is replaced with another

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19
Q

What are the different types of substitution mutations?

A

Silent: new code for same amino acid, so the protein remains the same
Missense: new code changes the amino acid
Nonsense: new code is a STOP codon and stops the protein from being produced

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20
Q

Are the effects of missense substitution mutations alarming?

A

Effects are dependent on the role of the amino acid
E.g., a linking amino acid will not change as much

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21
Q

When will a missense substitution mutation have an alarming effect?

A

If an amino acid responsible for the protein’s structure is changed

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22
Q

What is a frameshift mutation?

A

The triplet code is disrupted, so all amino acids after the mutation change

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23
Q

What are the different types of frameshift mutations?

A

Addition: a new base is added, shifting the rest forward relative to the reading frame
Deletion: a base is removed, pulling the rest back relative to the reading frame

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24
Q

Why are frameshift mutations problematic?

A

If a set of 3 nucleotides (new codon) starts a nucleotide after the frameshift mutation, then the amino acids will change

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25
How can frameshift mutations have little to no effect on a protein?
Frameshift mutations may: Occur at the ends of genes Occur in introns Occur outside of genes
26
What two groups can cells be divided into?
Somatic and germline
27
Is there a single genome of the whole body?
No, each cell has its own DNA
28
Which type of cells are defined as germline cells?
Gametes- cells that have genes that can be passed on
29
What are the products of gametes?
A person's "normal" DNA
30
What are germline mutations?
Mutations and genetic variation in germline cells- these mutations/genetic variations can be passed through families
31
What happens if there is a mutation in an embryo as of the germline cells that produced it?
The resulting embryo will have that germline mutation throughout all its cells
32
What are somatic cells?
Any cell in an organism apart from the reproductive (germline) cells
33
What happens if there is a mutation in a somatic cell?
Then only the mutated cell will be effected and this mutation won't be passed on
34
Can somatic mutations be inherited?
No
35
What are the effects of embryonic mutations?
All the cells (including somatic cells) are effected
36
How can a mutation spread from an affected somatic cell?
The mutation will be passed onto the cells it divides into
37
How does cancer develop?
From a series of mutations and changes in a stomatic cell
38
How can a germline mutation affect a zygote's somatic cells?
All the cells will have the mutations, as the zygote has the mutation Zygote continues to divide into foetus
39
What can germline mutations cause?
Genetic disorders, as it is the change of DNA over time Can also predispose affected individuals to other conditions such as cancer
40
What is an example of a germline mutation?
Mutation in the BRCA-1 gene or BRCA-2 gene can lead to breast cancer
41
Why do cells divide?
Growth: from fertilised egg cell to adult, or for subsequential growth, e.g., muscles Maintenance: replace dead/injured cells
42
How can cells divide?
By mitosis, however gametes are (partially) produced by meiosis
43
Which cells don't generally divide?
Adult cells, like neurones, as they are fully matured
44
Why do some cells divide then stop?
They will only divide when triggered, such as when a tissue is damaged or a cell dies
45
What are some examples of cells that continuously proliferate (replicate) and why do they do this?
Hair follicles and red blood cells, as to replace things that have broken down
46
Why is proliferation important regarding embryogenesis?
Early development is characterised by the embryonic cells' rapid proliferation These cells then differentiate When the cells differentiate, the rate of proliferation usually decreases
47
What other process is proliferation important in?
Maintenance of adult tissue homeostasis: Matured cells lose the ability to proliferate, however there are some cells that proliferate but only when triggered e.g., replacing damaged cells
48
What affects proliferation?
Environmental conditions: pH, nutrients, temperature and oxygen Interactions with other cells and signaling molecules Intracellular signaling
49
What is true about all body cells?
They can broadly be divided into germline and somatic cells
50
Why does a germline cell require both mitosis and meiosis?
Meiosis ensures that the DNA is halved Mitosis is to produce the cells that precede the germline production E.g., spermatogonia need to undergo mitosis to enable spermatozoa to keep being produced
51
Why can somatic cells not be passed onto the offspring?
They don't produce gametes
52
What is the cell cycle?
When a cell divides via a series of stages
53
What are the stages of the cell cycle?
G1 S phase G2 M phase (G0- resting phase)
54
What are the sub-stages of the M phase?
Prophase Prometaphase Metaphase Anaphase Telophase
55
What is are the purposes of the G1 and G2 phases?
They are gap/growth phases and also incorporate checkpoints to see if the cell is capable of being replicated
56
What roles do the G1 and G2 phases have?
G1: Preparation for DNA synthesis (S phase), replication G2: Preparation for cell division (M phase), doubles in size
57
What would happen if damage to the DNA is detected in the dividing cells?
The cell will not progress through the cell cycle until the DNA damage has been fixed If the damage cannot be fixed, then the cell will undergo apoptosis
58
What occurs during S phase?
DNA replication: DNA helicase separates DNA strands by breaking hydrogen bonds between them DNA polymerase catalyses the addition polymerisation of the DNA nucleotides
59
How do the new nucleotides form the new DNA strands?
New nucleotides are added to the 3’ (“3 prime”) end of the new strand. New nucleotides are attached via their 5’ (“5 prime”) end Leading strand is made continuously, following helicase Lagging strand is made in fragments in the opposite direction to helicase action, then combined by DNA ligase
60
Where does DNA polymerisation occur?
The length of the chromosome
61
How is the cell cycle controlled?
Checkpoints
62
How are checkpoints useful?
Allow for processes (like mitosis) to occur in fixed time intervals
63
What influences the checkpoints?
Cell cycle events and the external environment
64
How is DNA presented in the S-phase?
As two identical chromatids
65
What occurs in the S-phase?
Chromosomes undergo replication New DNA is synthesised- therefore a duplicate chromosome is formed Chromosome is only visible during division After replication, each chromosome is composed of two identical chromatids, and chromatids are joined together at the centromere
66
What is the purpose of the M-phase?
How the cell physically divides to produce two genetically identical daughter cells
67
What is the main process that occurs in the M-phase?
Mitosis- due to the cell's nucleus dividing
68
What are the stages of mitosis that the cell's nucleus undergoes?
Prophase Prometaphase Metaphase Anaphase Telophase
69
What occurs during cytokinesis?
The cell's cytoplasm divides to form the two separate daughter cells
70
What occurs to the DNA and nucleus during prophase?
The chromosomes condense and are visible and threadlike Nuclear membrane and nucleoli disappear
71
What occurs outside the nucleus during prophase?
Mitotic spindle begins to form Mitotic spindle contains centrosomes and microtubules forming aster (star shape) Centrosomes move away from each other
72
What occurs during prometaphase?
Nuclear envelope fragments Microtubules attach to the chromatids at the kinetochores Other microtubules interact connecting from different poles
73
What occurs during metaphase?
Centrosomes are now at opposite poles of the cell Chromosomes are lined up on the metaphase plate All chromosomes are attached to each of the poles
74
What occurs during anaphase?
Connection between the chromatids at the centromere is cleaved Each chromatid is now a daughter chromosome Chromosomes are pulled to opposite poles as cell elongates
75
What indicates that anaphase is over?
When the chromosome reaches the poles
76
What occurs during telophase and cytokinesis?
Two daughter nuclei form Nuclear envelope forms, nucleolus appear and cytoplasm divides
77
What happens to the DNA during telophase and cytokinesis?
Chromosomes become less dense, and so less visible
78
What else occurs during telophase and cytokinesis?
Contractile rings from- contain actin, myosin, and various other proteins and structures Cytoplasm divides into two Creates two genetically identical (diploid) daughter cells
79
Is cytokinesis apart of mitosis?
No, as cytokinesis refers to the division of the cell's cytoplasm. Mitosis is the division of the cell's nucleus
80
What occurs during the M-phase?
Two cells, each with the same number of chromosomes as the original cell Cell moves into G1- start of interphase
81
What is the importance of the process of meiosis?
Necessary for the function and production of gametes
82
What is a key difference between mitosis and meiosis?
The gametes (sperm and egg cells) that are produced are haploid, and so have one chromosome from each pair. However, mitosis produces diploid cells
83
How is meiosis a form of genetic variation?
Fusion with different gamete for mixing of gene combinations Each gamete having a different combination of the parent's genes Recombination, resulting in new chromosomes
84
What is the key principle of meiosis?
DNA is replicated once but the cell divides twice
85
What occurs during meiosis l?
Homologous (paired) chromosomes are separated from each other but remain intact (sister chromatids are still attached to each other)
86
What occurs during meiosis ll?
Sister chromatids on each chromosome are separated into the new cells
87
Are there any similarities and/or differences between mitosis and meiosis?
Yes, the processes involved are very similar apart from the processes occurring twice in meiosis
88
What are some other key differences between mitosis and meiosis?
Prophase l: Crossing over between chromatids of paired chromosomes occurs, increasing genetic variation Metaphase l: Homologous chromosomes are attached to opposite poles of the cell. Independent assortment means each division results in a different combination of chromosomes in each cell Anaphase l: One chromosome of each pair is pulled to each end without breaking the centromeres
89
What happens at the end of meiosis l?
There are two cells with unpaired chromosomes consisting of two sister chromatids joined together (unlike mitosis, which results in two cells with paired chromosomes and single chromatids)
90
What occurs during meiosis ll?
Follows similarly to mitosis: Centromeres are broken during anaphase, which results in the sister chromatids separating from one another to go into the new cells
91
What are the two main forms of cell death, and how can they be described?
Apoptosis: Controlled process Necrosis: Uncontrolled process
92
What occurs during apoptosis?
A cell will "self-destruct" if triggered by events such as DNA damage Self-destructs in a controlled manner, and makes its components available for other cells to use
93
What occurs during necrosis?
A cell cannot self-destruct in a controlled manner, as it is too heavily damaged, and so falls apart in a disordered manner
94
How can the events of apoptosis be described simply?
The cell is triggered to undergo apoptosis and so begins to shrink (webbing splits) The cell breaks into apoptotic cell bodies, called plebs
95
How can the events of necrosis be described simply?
The cell is too damaged to undergo apoptosis and so begins to swell and undergoes necrosis Leakage of the cell content occurs as the cell membrane is ruptured

Foundation Year MBChB (28 decks)

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