Gene Expression (20) Flashcards by Beatrix Badger

What is a gene mutation?

Permanent changes in DNA sequence making up a gene

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What happens when a mutation occurs in body cells?

Disrupt normal functions eg. Cell division which can lead to cancer

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What happens when a mutation occurs in gametes?

Can be inherited by offspring whereas body cell mutations cannot

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Causes of mutation

Arise naturally but at low frequency. This can increase when exposed to mutagens eg. Ionising radiation or chemical mutagens.

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What does mutations provide?

Genetic diversity but are often detrimental

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What is a substitution mutation?

One DNA base replaced by another within a gene

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What is an inversion mutation?

DNA attaches and reattaches at an opposite direction

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What is a duplication mutation?

One or more DNA base sequences repeating altering reading frame (can cause a frame shift)

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What is a translocation mutation?

One chromosomes DNA switch to another chromosome which can interfere with gene expression and lead to cancer.

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List the 4 types of stem cell

Totipotent
Pluripotent
Multipotent
Unipotent

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What can totipotent cells do?

Differentiate into any cell type

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What can pluripotent cells do?

Differentiate into most cell types

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What can multipotent cells do?

Differentiate into a few types of cell

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What can unipotent cells do?

Differentiate into only one type of cell

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Describe embryonic stem cells

First few divisions stem cells are totipotent after 7ish days they become pluripotent

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Describe adult stem cells

Multipotent or unipotent
Bone marrow replace worn out red blood cells and white blood cells

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Describe plant stem cells

Meristem tissue
Pluripotent
Differentiate into xylem and phloem

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What are induced pluripotent cells produced from?

Adult unipotent stem cells that are genetically altered.
Switching genes to induce expression of genes and transcription factors

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Advantages of induced pluripotent cells

Self renew indefinitely
Differentiate into a range of cells
Avoid ethics
Unlimited source

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How are stem cells used in research and medicine

Can be used to test new drugs
Study development of an organism
Identifying causes of disorders
Stem cells have potential to treat certain disorders eg. Parkinson’s and altzimers (nerve cells)

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What are transcription factors and what happens when a gene switched off?

Proteins that bind to specific DNA sequence to initiate transcription of genes into mRNA

When a gene switched off transcription factors cannot bind to DNA which prevents transcription and synthesis of polypeptides.

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Give an example of the hormonal control of transcription?

Oestrogen

Describe the mechanism of hormonal control of transcription (5)

Steroid hormone diffuse through cell membrane

Hormone bind to receptors one transcription factors

Binding changes shape of transcription factors (activates)

Activated transcription factor enters nucleus and binds to specific DNA sequence.

Binding stimulates transcription of gene located at sequence

What is an epigenome?

Layer of chemical tags that cover DNA histone complex

What are epigenetics?

Heritable chemical modifications to DNA or histones (do not change DNA itself)

List 3 step process of how epigenetics control gene expression

Epigenetics added or removed which can change shape of DNA hisotne complex Changes may either compact gene or make genes more accessible Allows cells to control which gene active or not

List the two methods of epigenetics

Decreased histone acetylation Increased DNA methylation

What happens in decreased histone acetylation

Enzymatic removal of acetyl group from histone Increased histone positive charge Condenses chromatin Silences genes by binding of proteins for transcription

Explain increased DNA methylation

Add methyl group to DNA Increased hydrophobic interactions Tightens DNA Condensed chromatin Silences genes by binding of proteins for transcription

Explain the inheritance of epigenetic changes

Epigenetic patterns can be inherited Most epigenetic tags erased in early development Eg. Drought induced epigentic changes in plants Eg. Gastational diabetes

Explain epigenetic defects and disease in cancer

In danger involves silencing tumour suppressor genes or activating oncogenes

What happens in DNA hypomethylating agents

Counteracting the silencing of genes

List the 5 steps in RNA interference of gene expression

Enzymes cut double stranded RNA into small interfering RNA (SIRNA) SIRNA joins with enzymes SIRNA guides enzymes to specific sections of MRNA (SIRNA pairs with complementary MRNA) MRNA cut into parts MRNA no longer translated (RNA inhibits gene expression by destroying MRNA)

Describe the difference between benign tumours and malignant tumours (7)

B- slow growth M- multiply quickly B- look normal M- abnormal DNA rich appearance B- retain functions M- loose functions B- binding molecules M- no binding molecules B- encased M- spread into surroundings B- not life threatening M- highly dangerous B- treated with surgery M- surgery, chemo, radiotherapy

What are primary tumours

Original abnormal

What are secondary tumours

Primary tumours which spread to other regions of the body

tumour suppressor gene role and what happens when mutatated

Regulate cell division, repair DNA and initiate apoptosis Mutations can deactivate these and lead to cancer

Role of proto-oncogenes and what happens when mutated

Stimulate cell division when growth factors bind to cell receptors activating DNA replication Promote excessive DNA replication/ cell division Once mutated known as ONCAGENES

What is HypERmethylation and HypOmethylation?

HYPER- more methylation HYPO- less methylation

List the process of abnormal methylation in cancer (4)

HypERmethylation of tumour suppressor genes prevents them being active Stops productions of proteins normally inhibit cell division cells divide unchecked Hypomthylation of proto-oncagenes lead to activation Activation promotes excessive cell division and tumour growth

How does oestrogen stimulate breast division

By activating genes that control transcription

How can increased oestrogen levels over time lead to breast cancer

Can encourage replication of already cancerous genes or oestrogen may directly cause mutations on DNA of breast cells

What is bioinformatics

Involves developing software, computers and mathematical models to analyse biological data eg. Genes

What is genomics

Applies DNA sequencing and computational biology to study genomes

What os computational biology

Models biological systems

What is genomics

Study of genomes

What is proteomics

Examines complete set of proteins including structure and function

What underscores the complexity of genotype phenotype relationship

Number of unique proteins exceed number of genes

What is DNA barcoding

Comparing DNA sequence of unidentified organism to a database

What does comparing genomes do

Find similarities between new DNA sequences and those in database Classification of new species Fast and afordable Estimate evolutionary divergence times.

What is the advantage of studying health and disease through genome analysis

Able to identify patterns in DNA and disease risk

What are SNPs role in analysis

Single base variations in gene one can be identified (Single nucleotide polymorphisms)

Explain whole genome shotgun sequencing

DNA cut into fragments DNA fragments sequenced DNA fragments aligned to determine whole DNA sequence