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AQA A Level Biology > 8-20 Gene expression > Flashcards

8-20 Gene expression Flashcards

1
Q

What is an addition mutation?

A

When extra bases are inserted into the sequence
Causes a frameshift to the right

The whole sequence is affected
If three bases are added, there will not be a frameshift

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2
Q

What is a duplication mutation?

A

One or more bases are repeated, frameshift to the right

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3
Q

What is an inversion mutation?

A

Where a group of bases become separated from the DNA sequence and rejoin at the same position but back to front (inverse order)
Affects the amino acid sequence

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4
Q

What is a translocation mutation?

A

Where a group of bases becomes separated from the DNA of one chromosome and become inserted into the DNA sequence of a different chromosome
This leads to an abnormal phenotype

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5
Q

What are the causes of mutations?

A

Some are spontaneous with no outside interference
High energy ionising radiation e.g. xrays and UV

Chemicals e.g. nitrogen dioxide which alters DNA structure

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6
Q

What are totipotent cells?

A

Cells which can become any type of cell

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7
Q

What are stem cells?

A

Cells which retain the ability to differentiate into other cells

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8
Q

Which type of cells can redifferentiate?

A

Plant cells which allows them to develop once again into another completely different cell

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9
Q

What are pluripotent cells?

A

Cells found in embryos which can differentiate into almost anything

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10
Q

What are multipotent cells?

A

Cells found in adults which can differentiate into a limited number of specialised cells

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11
Q

What are unipotent cells?

A

Cells which can only differentiate into a single cell

They’re derived from multipotent cells and are made into adult tissue

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12
Q

What is epigenetics?

A

The study of markers on DNA

This allows us to understand what switches on genes

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13
Q

What is the epigenome?

A

All of the epigenetic markers in a cell or organism

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14
Q

What happens if a gene is not expressed?

A

No protein is made

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15
Q

What is chromatin?

A

The DNA molecule wrapped around histones

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16
Q

What determines whether the genes are expressed?

A

The interaction between DNA molecules and histones

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17
Q

What does the epigenome determine?

A

The shape of the DNA - histone complex

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18
Q

What is epigenetic silencing?

A

A tightly packed arrangement of the DNA-histone complex which makes a gene inactive

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19
Q

What is the addition of methyl groups called?

A

Methylation

20
Q

What is the addition of acetyl groups called?

A

Acetylation

21
Q

How do you express an addition or removal of methyl of acetyl groups?

A 
Hyper- = more
Hypo- = less
22
Q

What are the environmental factors which affect the epigenome?

A

Stress and diet affect the epigenome which affects whether genes are expressed or not

23
Q

What is the process of methylation?

A

Methyl group attaches to cytosine
This prevents the binding of transcriptional factors to the DNA

This attracts proteins to the gene which removes acetyl groups from the histones
Histones become more positively charged
DNA is negative
Association is stronger
This makes DNA become more tightly wrapped around the histone
This stops transcription because it is too tightly wound to reach the DNA

24
Q

What does decreased acetylation cause?

A

A more condensed DNA histone complex
Chromatin: heterochromatin

No access for transcriptional factors
The gene becomes inactive

25
Q

What is cancer?

A

Uncontrolled cell division

26
Q

Which genes are responsible for controlling the rate of cell division?

A

Oncogenes and tumour-suppressor genes

27
Q

Where do oncogenes come from?

A

They normally derive from proto-oncogenes

28
Q

What is the purpose of proto-oncogenes?

A

They normally code for proteins that regulate cell growth by providing protein signals that cause cell division or by regulating cell apoptosis (cell death)

29
Q

What types of proteins does proto-oncogene involvement occur in?

A

All kinds

30
Q

How is a proto-oncogene turned into an oncogene?

A

A mutation

31
Q

What is the role of tumour-suppressor genes?

A

They produce proteins that slow down cell division

32
Q

What occurs when a mutation occurs in a tumour-suppressor gene?

A

It stops proteins that slow down division from being formed

This is called silenced

33
Q

What genes are affected by epigenetics?

A

Tumour-suppressor genes

34
Q

Which hormone falls after menopause?

A

Oestrogen

35
Q

How are Oestrogen and breast cancer linked?

A

By positive feedback
In breast tissue, fat cells produce more Oestrogen

Breast cancer tumours produce more Oestrogen

36
Q

What is the process of Oestrogen affecting DNA synthesis?

A

Oestrogen diffuses across the cell membrane (lipid soluble)
Oestrogen binds to a complimentary transcriptional factor

The transcriptional factor is caused to change shape
The DNA binding site can now bind to DNA (activated)
Transcriptional factor moves through a nuclear pore to bind to DNA bases
This stimulates the transcription of a gene

37
Q

What is the genome?

A

All the genetic material in an organism or cell

38
Q

What is the proteome?

A

All the proteins in an organism or cell

39
Q

What is the genome project process called?

A

Whole-genome shotgun sequencing

40
Q

What are the three steps of whole-genome shotgun sequencing?

A

Digestion: completed manually
Align: a computer aligns the fragments of DNA

Sequence: computer step, the computer is able to determine the base sequences

41
Q

Is all the DNA from genome projects from the same person?

A

It can be from multiple people in a population

42
Q

What are genome projects designed to do?

A

To determine the prevalence of the genome

43
Q

What are the fragments in genome sequencing aligned according to?

A

Commonly occurring base sequences

44
Q

How is the frequency of bases measured?

A

The computer looks at the overlap using an algorithm

45
Q

What does it suggest if there are overlapping fragments in every part of the sample?

A

It is something that every human has

46
Q

What is the SNP?

A

Single nucleotide polymorphisms

Where a one base mutation occurs frequently in the population

AQA A Level Biology (19 decks)

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