D2 Flashcards

1
Q

Cytokinesis

A

Splitting of the cytoplasm to create two daughter cells from one parent cells (last step of cell division after mitosis)

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2
Q

Cleavage furrow

A

region of pinching @ the centre/equator of the cell that occurs in the early stages of cytokinesis, achieved using a ring of contractile proteins

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3
Q

Cell plate

A

layer of fused vesicles at the equator of a plant cell during cytokinesis, which will eventually form a new cell wall

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4
Q

sister chromatids

A

two identical copies of a chromosome attached to each other by proteins. they are created after chromosomes replicate

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5
Q

DNA condensation

A

processing of compacting DNA tightly around histones, forming nucleosomes, and then linking said nucleosomes together

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6
Q

cell cycle

A

series of events that lead up to cell division (including interphase and stages of division)

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7
Q

interphase

A

stages prior to division in which growth, DNA replication and preparation occur

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8
Q

what percentage of the cell cycle is spent in interphase

A

90%

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9
Q

cell proliferation

A

when there is a rapid increase in the number of cells i.e. rate of cellular divison exceeds rate of cell death

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10
Q

what is the name for prokaryotic cell division

A

binary fission

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11
Q

what happens in binary fission

A

circular DNA is replicated and separated

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12
Q

what type of genetic material does mitosis occur for

A

when DNA is linear and contained in the nucleus

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13
Q

How does cytokinesis differ between plant and animal cells?

A

In animals, it is quite a straightforward process. The outside of the cytoplasm pinches to form the cleavage furrow (made out of contractile rings). In plants, the cell plate forms from merging vesicles

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14
Q

Examples of cytokinesis in which the cytoplasm is not equally divided

A

Oogenesis
Budding

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15
Q

Why does oogenesis result in uneven division of the cytoplasm?

A

Cytoplasm divides unequally to create one large egg cell (with lots of organelles and cytoplasm) and three polar bodies (that have minimal cytoplasm)

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16
Q

Why does budding result in uneven division of the cytoplasm?

A

Nucleus divides evenly to form two identical nuclei but the new daughter cell only takes a small amount of the cytoplasm. This daughter cell can then grow later.

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17
Q

Structure of sister chormatids formed by DNA replication

A

two identical strands held together by a centromere and multiple cohesin looops. during mitosis, spindle fibres will attach to kinetichore proteins in order to break them apart

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18
Q

What does DNA replication form?

A

sister chromatids

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19
Q

What occurs in G1?

A

Cell grows in size and accumulates important materials (e.g. increased proteins, increased nucleotides)

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20
Q

What occurs in S phase?

A

DNA is replicated, creating sister chromatids

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21
Q

What happens in G2 phase?

A

Further cell growth, further replication of important organelles. Microtubules begin to form visible centrosomes

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22
Q

Purposes of cell proliferation

A

growth, replacement, repair

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23
Q

examples of rapid mitosis for growth in plant cells

A

Plan meristem cells rapidly divide then specialise

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24
Q

examples of rapid mitosis for growht in animal cells

A

Having grown from a zygote, an animal embryo in the late stages undergo rapid unspecialised division and then specialisatin

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25
Q

examples of cells that are frequently replaced by mitosis

A

skin cells, as layers are constantly growing the next layer of skin cells

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26
Q

when does mitosis occur for repair

A

following injury rapid cell replacement occurs

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27
Q

How does cytokinesis typically occur in an animal cell?

A

Contractile proteins (actin and myosin) migrate to form a ring within the cell. This creates a cleavage furrow, which then eventually splits the cell

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28
Q

How does cytokinesis typically occur in a plant cell?

A

A line of vesicles merge in the centre of a plant cell. Once merged, this forms a temporary cell plate.
These vesicles contain cellulose within them, which eventually become the cell wall. The two phospholipid outsides of the vesicle become the new cell membrane for the daughter cells.

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29
Q

What are the two DNA changes that occur before cell division?

A
  1. DNA replication to form sister chromatids
  2. DNA condensation into short wide chromosomes
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30
Q

Why is DNA loosely coiled normally?

A

This is the optimal state for transcription

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31
Q

Process of DNA condensation

A

The DNA is originally loose (for transcription). It is then wrapped around histones to form a nucleosome. These nucleosomes then stack and coil, forming visible chromosomes

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32
Q

Product of DNA condensation

A

Short, wide and visible chromosomes

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33
Q

What is the cell cycle

A

events that cells go through to divide

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34
Q

all stages of the cell cycle

A

G1, S, G2, prophase, metaphase, anaphase, telophase and cytokinesis
OR
interphase, mitosis, cytokinesis

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35
Q

Which part of the cell cycle do heart and brain cells always remain in?

A

G0 (not part of cell cycle!!)

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36
Q

Where does normal cellular activity occur (part of cell cycle)?

A

G0

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37
Q

What part of the cell cycle can cells exit to enter G0?

A

During G1

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38
Q

How do cells in G0 re-enter the cell cycle?

A

If signalled to engage in growth, repair or replacement

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39
Q

How quickly can white blood cells replicate?

A

Within 10 hours

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40
Q

What occurs during mitosis?

A

Division of the nucleus

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41
Q

What is the metaphase plate?

A

imaginary plate that runs along the centre of the cell (i.e. midpoint)

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42
Q

Centrosomes

A

Organelle composed of two centrioles, which form spindle fibres to attach to chromosomes

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43
Q

synonyms for centrosomes

A

microtubule organising centres (MTOCs)

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44
Q

purpose of kinetichores?

A

have microtubules attach

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45
Q

what are kinetochores?

A

protein structures that form at the centromere of each chromatid. microtubules can attach

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46
Q

what is the mitotic index?

A

calculation that quantifies the proportion of cells currently dividing i.e. no. cells in mitosis / total no. cells

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47
Q

what can a high mitotic index indicate?

A

tissue dividing too rapidly -> cancer

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48
Q

order of phases in mitosis

A

prophase, metaphase, anaphase, telophase

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49
Q

Key features of interphase

A

DNa is in its loose form called chromatin, which allows for protein synthesis. No chromosomes are visible.
During this phase, DNA replication occur.

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50
Q

What happens in prophase?

A

Nuclear membrane dissolves/migrates as vesicles
DNA condenses to become visible chromosomes
Centrosomes form and begin developing microtubules.

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51
Q

What happens in metaphase?

A

Microtubules attach to each end of the centromere (of each sister chromatid) at the kinetochore.
Motor proteins (which exist between microtubules) move the chromosome, aligning them at the centre of the cell. This alignment occurs because both ‘ends’ of chromatids are being pulled in opposite directions by motor proteins.

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52
Q

What happens in anaphase?

A

Motor proteins continue to pull apart sister chromatids. Eventually, this migration of centromeres puts enough pressure on cohesin loops to break them, separating chromatids at the centromere. Kinetochores shorten microtubules (by breaking off tubulin subunits), which pulls the chromosomes to the poles.

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52
Q

What happens in telophase?

A

Nuclear membrane reforms.
DNA decondenses into loose chromatin. Cell elongates in preparation for cytokinesis.
The pinching of the membrane begins cytokinesis

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53
Q

What is between two microtubules?

A

Motor proteins, which help pull microtubules towards opposite poles.

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53
Q

How do motor proteins interact with microtubules to move chromatids in anaphase?

A

Motor proteins (between two microtubules) ‘walk’ along, separating sister chromatids. This creates the required tension to break cohesin loops.

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54
Q

Mitosis

A

the process by which a cell replicates its chromosomes and then segregates them, producing two identical nuclei in preparation for cell division.

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55
Q

Gametes

A

specialised cell made purposefully for sexual reproduction.

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56
Q

how many chromosomes do gametes have?

A

23 (half the normal number) i.e. haploid

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57
Q

what is reduction division

A

refers to the fact that in meiosis, cell division causes genetic material to halve in its daughter cells

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58
Q

what is the product of two gametes?

A

zygote

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59
Q

homologous chromosomes

A

pair of the same chromosomes. same genes in the same positions but different alleles

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60
Q

bivalent

A

when homologous chromosomes each have sister chromatids join together, so that inner chromatids overlap at the chiasma. They break at the chiasma and swap genetic material.

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61
Q

Diploid nucleus

A

Two of each chromosome (46 total)

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62
Q

Haploid nucleus

A

One of each chromosome (23 total)

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63
Q

What type of cells are diploid?

A

all somatic cells

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64
Q

What type of cells are haploid?

A

all gametes

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65
Q

difference between meiosis I and meiosis II

A

Meiosis I: chromosomes line up in homologous pairs in metaphase.
Meiosis II: sister chromatids line up to be separated

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66
Q

Similarities between mitosis and meiosis

A

1 DNA replication occurs.
PMAT format

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67
Q

Differences between mitosis and meiosis

A

Which cells it occurs in
Number of division
What it forms
Whether chromosomes interact
Purpose

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68
Q

Product of mitosis

A

Two genetically identical diploid daughter cells, each with a full chromosome set

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69
Q

WHat cells does meiosis occur in

A

Germ cells (which become gametes)

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70
Q

What cells does mitosis occur in?

A

Somatic cells

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71
Q

Process of meiosis

A

1 DNA replication
2 divisions (i.e. 2 x PMAT)

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72
Q

Product of meiosis

A

Four genetically unique haploid daughter cells

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73
Q

Do homologous chromosomes interact in mitosis?

A

No.

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74
Q

How do homologous chromosomes interact in meiosis?

A

Homologous chromosomes join together to create bivalents and crossing over occurs

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75
Q

Purpose of meiosis

A

Sexual reproduction

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76
Q

Process by which homologous chromosomes become bivalents

A

Synpasis

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77
Q

What happens to chromosomes in DNA replication?

A

Chromosomes undergo DNA replication to form chromosomes with two sister chromatids connected by a centromere and cohesin loops. These sister chromatids have identical alleles.

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78
Q

When do homologous chromosomes first interact in meiosis?

A

Prophase I, in which they undergo synapsis to form bivalents, connected at the chiasma.

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79
Q

What is different between homologous chromosomes?

A

Alleles. However, same genes

80
Q

What cells undergo meiosis?

A

Diploid germ cells

81
Q

Stages of Meiosis I

A

Prophase I
Metaphase I
Anaphase I
Telophase I

82
Q

Stages of Meiosis II

A

Prophase II
Metaphase II
Anaphase II
Telophase II

83
Q

What occurs in Prophase I that is specific to meiosis?

A

Synapsis forms bivalents and crossing over occurs.

84
Q

What occurs in Metaphase I that is specific to meiosis?

A

Line up as homologus pairs, with random orientation of each pair on either side

85
Q

What occurs in Anaphase I that is specific to meiosis?

A

Separation of homologous chromosomes

86
Q

What is the product of meiosis I?

A

Two haploid germ cells

87
Q

What happens after Telophase I

A

Prophase II (does not re-enter interphase!)

88
Q

What part of meiosis is most similar to mitosis?

A

Meiosis II

89
Q

What happens to the nuclear membrane in Prophase II?

A

Nuclear membrane dissolves

90
Q

What happens to the nuclear membrane in Telophase I?

A

Nuclear membrane reforms

91
Q

Name of process that creates sperm cells

A

Spermatogenesis

92
Q

Name of process that creates egg cells

93
Q

Recombinant chromatids

A

Chromatids that have gone through crossing over and now contain new combinations of genetic material

94
Q

Random orientation

A

In metaphase, it is random which side each chromosome/chromatid goes on

95
Q

Non-disjunction

A

when chromosomes fail to separate, meaning that spindle fibres do not attach to one of the centromeres

96
Q

what have the spindle fibres failed to do if non-disjunction occurs?

A

Attach to centromere

97
Q

How does crossing over contribute to genetic variation?

A

Creates new combinations of alleles, which work together to create new phenotypic variation

98
Q

How does random orientation contribute to genetic variation?

A

Alters combinations of alleles that are inherited, leading to greater uniqueness between offspring and thus, greater genetic variation

99
Q

What role does meiosis play in natural selection?

A

New phenotypes can be made (via crossing over and random orientation)

100
Q

Cause of Down Syndrome

A

Trisomy 21 (due to non-disjunction of chromosome 21)

101
Q

characteristics of down syndrome

A

Developmental condition characterised by hearing, heart and vision concerns and intellectual disability

102
Q

Why does non-disjunction increase with maternal age?

A

As age increases (i.e. leave biological fertile window), it becomes less of a priority for checking spindle fibres. This causes errors to go unchecked, which contributes to increased number of gametes with errors

103
Q

What happens to the location of the chiasma with every round of meiosis?

A

Location changes

104
Q

What is crossing over?

A

Breaking and exchanging DNA between homologous chromosomes

105
Q

What is the name for chomatids that have not been affected by crossing over?

A

Parental chromatids

106
Q

Does random orientation create new alleles?

A

No, just new phenotypes

107
Q

Number one cause of miscarriage

A

Non-disjunction

108
Q

Which part of meiosis does non-disjunction most often occur in?

A

Anaphase I, due of cohesin loops

109
Q

If non-disjunction of Chromosome 21 occurs in Anaphase I, what cells will it produce?

A

2 x trisomy 21
2 x monosomy 21

110
Q

Euploidy

A

a term used in genetics to describe when an organism or cell has the correct number of chromosomes

111
Q

What happens if non-disjunction occurs in Anaphase II for Chromosome 21?

A

1 x Trisomy 21
1 x Monosomy 21
2 x euploidy

112
Q

What contributes to genetic variation?

A

Meiosis -> creates new combinations of alleles through crossing over and random orientation
Mutations -> new alleles
Sexual reproduction

113
Q

Cyclins

A

Groups of proteins that will control whether a cell will progress through the cell cycle, by binding to Cyclin-Dependent Enzymes

114
Q

Cyclin-dependent enzymes

A

Enzymes that cyclin proteins bind to (and are inactive without cyclin being bound)

115
Q

Checkpoints

A

Multiple times udring cell cycle where events will stall until certain requirements are met

116
Q

Cancer cells

A

Cells that undergo extremely rapid and uncontrolled reproduction with very little or improper differentiation

117
Q

Proto-oncogenes

A

Genes that stimulate or cause cell divison

118
Q

What is a proto-oncogene called if mutated and not functioning properly?

119
Q

Oncogene

A

Proto-oncogene mutated and not functioning properly

120
Q

Tumour suppressor genes

A

genes that code for proteins that play a role in slowing, pausing or stopping the cell cycle

121
Q

benign tumour

A

tumour contained to a single part of the body and that is not spreading

122
Q

metastasis

A

process when cells from a primary tumour break and enter the bloodstream, and cells travel via the blood to a new location + start growing a new tumour

123
Q

relationship ebtween cyclin and Cyclin-Dependent Kinases?

A

CDK enzymes rely on cyclin binding to become activated

124
Q

significance of the G0 stage

A

stage where cells do not replicate or progress through the cycle i.e. just perform normal functions

125
Q

how can a mutation of a proto-oncogene lead to tumour formation

A

mutated to promote cell division when conditions are not appropriate or in the absence of check points, which therefore overpromotes divion

126
Q

how can a mutation of a tumour suppressor gene lead to tumour formation

A

mutation compromises the ability of this gene to stop cell division in the event of DNA damage or when the cell type does not need division -> cannot stop cell division -> constant cell division

127
Q

difference between primary and secondary tumour

A

primary = first cluster of cancerous cells that form due to mutation
If the primary tumour metastasises and invades other healthy tissue, the new tumour formed is called the secondary tumour

128
Q

Are CDKs activated by the same cyclin?

A

No, CDKs are activated by cyclin specific to its phase e.g. growth, DNA checked, replication, spindle fibres, etc.

129
Q

What produces G1 cyclin?

A

cell growing

130
Q

what happens if not enough G1 cyclin is produced?

A

The cell goes into G0

131
Q

What releases G1/S cyclin?

A

DNA checks being passed

132
Q

What releases S cyclin?

A

DNA replication

133
Q

what releases M cyclin?

A

spindle fibres being checked

134
Q

how many checkpoints are there in the cell cycle?

135
Q

What happens when proto-oncogenes are expressed normally?

A

They promote/accelerate cell division

136
Q

What are the ways proto-oncogenes can be modified to form oncogenes?

A

CDK mutates to be active all the time
Gene mutates to create cyclin all the time

137
Q

When is the tumour suppressor gene most active?

A

Most active in S Phase and M spindle fibres phase

138
Q

What is the process of a secondary tumour being formed?

A

Healthy cells experience a mutation and thus; a primary tumour is formed. If no intervention occurs, these cells become vascularised at some point and thus, metasise into the bloodstream and arrive at another part of the body. The tumour cells then form a secondary tumour

139
Q

Gene regulation

A

Process of controlling timing, location and amount in which genes are expressed in an organisation

140
Q

Phenotype

A

physical trait that is the result of specific proteins that an individual has due to their gene expression

141
Q

mRNA degradation

A

use of enzymes to break up mRNA to nucleotides for recycling e.g. removing poly A tail

142
Q

exonucleases

A

enzymes that break down nucleic acids by removing individual nucleotides

143
Q

epigenesis

A

process of changing the phenotype of a cell without altering its genotype/pattern of gene expression that causes cells to change parts of their genome to become specialised

144
Q

epigenetic tags

A

chemical modifications to DNA in order to flag part of the genome to guide its regulation

145
Q

DNA methylation

A

process of adding a -CH3 methyl group to a DNA nucleotide as an epigenetic tag

146
Q

promoter

A

region ahead of coding bases that is a binding site for transcription factors which then allow RNA Polymerase to bind

147
Q

transcription factors

A

proteins that regulate transcription that can eiteher act as ‘activators’ or ‘silencers’

148
Q

enhancer region

A

having binding sites that activators can bind to, allowing DNA to form a loop,which allows activators to interact with transcription factors at promoters. this ultimately increases the rate of transcription

149
Q

what do activators bind to to initiate transcription?

A

activators bind to enhancer to promote/accelerate transcription

150
Q

what do repressors bind to to prevent transcription?

A

repressors bind to silencers

151
Q

how is the length of the poly A tail a form of gene regulation

A

longer tail = more time before enzymes break off adenosines -> more proteins are made

152
Q

what role does DNA methylation play in regulating transcription?

A

turn off expression of a gene by not allowing binding of necessary transcription factors

153
Q

Where does the majority of gene regulation occur?

A

Earlier in the process, so that energy is not wasted

154
Q

What binds to an enhancer site?

A

Activator transcription factor

155
Q

What binds to a silencer site?

A

Repressor transcription factor

156
Q

What is the effect of a repressor transcription factor binding to a silencer site?

A

Slows/stops the rate of transcription

157
Q

What is the effect of activator transcription factors binding to an enhancer site?

A

Increases rate of transcription

158
Q

What do transcription factors allow the regulations of?

A

careful regulation of amount and timing of transcription

159
Q

If mRNA is present in the cytoplasm, what will occur?

A

(generally) translation

160
Q

What is one way to regulate translate?

A

Regulate rate of mRNA degradation

161
Q

What can exonucleases do to degrade mRNA?

A

Decap the GTP cap
Deadenylation
Both of which need to occur to eventually break down mRNA

162
Q

What happens if the activity of exonluceases increases?

A

More mRNA degradation
Decreased mRNA lifespan

163
Q

What two processes must occur before exonucleases can break down mRNA?

A

Removal of GTP cap
Removal of poly A tail

164
Q

What is the most common use of DNA methylation?

A

Turn genes off

165
Q

How can DNA methylation turn genes on?

A

Binding to a silencer region

166
Q

What do methyl groups bind to?

A

Histones (to block a group of genes)
DNA (to regulate a specific genes, usually at the promoter to stop transcription factors binding)

167
Q

what is the duration of methylation?

A

usually permanent

168
Q

Two outcomes of DNA methylation

A

Cell specialisation
Cellular response to external environment

169
Q

When does DNA methylation occur first?

A

During utero and then throughout lifetime

170
Q

What happens if a methyl group binds to a promoter?

A

The transcription factor cannot bind and thus, this gene is not transcribed

171
Q

Genome

A

All the genes an organism has

172
Q

Transcriptome

A

All mRNAs a cell can produce

173
Q

What is one of the reasons the transcriptome is larger than the genome?

A

Alternate splicing, different Poly A tail lengths, etc

174
Q

Proteome

A

All proteins an organism can produce

175
Q

Why is the proteome larger than the transcriptome?

A

Modifications

176
Q

Epigenetic inheritance

A

when epigenetic tags are passed from a parent to offspring

177
Q

primordial germ cells

A

diploid cells that will go through meiosis to form gametes

178
Q

epigenetic reprogramming

A

process of removing epigenetic tags during the formation of primordial germ cells

179
Q

imprinted genes

A

genes that are silenced only in one type of gamete

180
Q

differentially methylated regions

A

genome regions with different methylation patterns across samples

181
Q

operon

A

group of several related genes that share a single promoter and thus, allows groups of genes to be turned off or on

182
Q

what role can the environment play in the formation of epigenetic tags?

A

can change gene expression to optimise coping with an external stressor

183
Q

explain specifically how air pollution has been linked to methylation

A

two chemicals (nitrous oxides and hydrocarbons) have been shown to decrease DNA methylation acorss the genome and thus, increase the expression of proteins related to the immune system, leading to issues such as asthma and allergies

184
Q

how do the differences between ligeons and tigers relate to patterns of epigenetic inheritance?

A

maternal and paternal lions imprint genes differently. male imprinting favours larger offspring by not silencing a gene that promotes growth, whilst female imprinting silences this gene and therefore does not express it.
male lion + tiger = liger
female lion + tiger = tigeon

185
Q

how have monozygotic twin studies been helpful to understand methylation?

A

despite having identical DNA sequences, idential twins have different phenotypes and therfore, indicate how methylation patterns can explain phenotypic differences

186
Q

when is the most significant time for external influence to change epigenetic inheritance?

A

during pregnancy

187
Q

How can epigenetic inheritance be intergenerational?

A

If a parent is exposed to an external stressor (esp. during pregnancy), their gametes will experience different methylation patterns. The children will then carry this pattern and it will continue

188
Q

Eukaryote example of external regulators of gene expression

A

Glucose regulates insulin production

189
Q

How does glucose regulate insulin production?

A

glucose causes the activation of a transcription factor, by binding to it. this allows the insulin gene to be expressed, meaning that insulin is made. this ultimately lowers the glucose level, causing the glucose to be removed from the transcription factor

190
Q

prokaryote examples of external regulators of gene expression

A

lactose activates the lac operon. the lactose binds to the repressor on the operator which allows RNA Polymerase to express the genes. this means that the lactose is broken down, including in the repressor

191
Q

Solvation

A

interaction between solvent and solute

192
Q

dynamic equilibrium

A

when particles are evenly spread out and net water movement is 0

193
Q

crenation

A

shrinking of a cell (usually for animal cells)

194
Q

contractile vacuole

A

adaptation in unicellular aquatic organisms to prevent swelling, as it collects water from the cytoplasm + periodically empties it into the environment

195
Q

hypertonic

A

environment with higher solute concentration than other environment

196
Q

hypotonic

A

environment with lower solute concentration than other environment

197
Q

isotonic

A

environment with same solute concentration as other environment