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Gene Expression Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a mutation?

A

An alteration to the DNA base sequence. Often arise during DNA replication

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2
Q

What are addition and deletion mutations?

A

Where one or more nucleotides are either inserted or deleted from the DNA sequence

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3
Q

What is a substitution mutation?

A

Where one nucleotide in the DNA sequence is replaced by another

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4
Q

What is a duplication mutation?

A

Where one or more nucleotides duplicate and repeat

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5
Q

What is an inversion mutation?

A

Where a group of nucleotides become separated from the DNA sequence then rejoin in the reverse order i.e they have flipped

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6
Q

What is a translocation mutation?

A

Where a group of nucleotides become separated from the DNA sequence and are then inserted into the DNA of a different chromosome

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7
Q

Which mutations are most likely to have a significant impact and why?

A

Insertion, deletion, duplication and translocation because they produce a frameshift meaning the entire amino acid sequence produced will be different

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8
Q

Which mutations are less likely to have a significant impact and why?

A

Substitution and inversion because they only alter one or very few triplets, the amino acid sequence might not be affected due to the degenerate nature of the genetic code

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9
Q

Is a mutation resulting in a change to the amino acid sequence always harmful?

A

No; may be neutral if the resulting change in protein has no effect on the organism

Also may be beneficial which is the basis for evolution and natural selection

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10
Q

What is a mutagenic agent?

A

Factors that increase the rate of gene mutation. Chemical mutagens such as alcohol and ionising radiation such as UV and X ray

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11
Q

What is a stem cell?

A

Undifferentiated cells that can divide indefinitely and turn into other specific cell types

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12
Q

Name and define the three types of stem cell

A

Totipotent = can develop into any cell type including the placenta and embryo

Pluripotent = can develop into any cell type excluding the placenta and embryo

Multipotent = can only develop into a few different types of cell

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13
Q

What happens to totipotent cells during embryonic development?

A

Certain parts of the DNA are selectively translated so that only some genes are switched on in order to differentiate the cell into a specific type and form the tissues that make up the foetus

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14
Q

Give a unique feature of pluripotent cells and the use of this feature

A

They can divide in unlimited numbers and can therefore be used to repair or replace damaged tissue

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15
Q

What is a unipotent cell, give an example

A

A cell that can only develop into one type of cell. This happens at the end of specialisation when the cell can only propagate its own type. An example is cardiomyocytes (heart cells)

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16
Q

Which type of stem cells are found in embryos?

A

Totipotent and pluripotent

Multipotent and unipotent are only found in mature mammals

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17
Q

Give some uses of stem cells

A

Medical therapies e.g bone marrow transplants

Drug testing on artificially grown tissues

Research e.g on embryos

18
Q

How are induced pluripotent stem cells produced?

A

From mature, fully specialised cells. The cell regains capacity to differentiate through the use of proteins, in particular transcription factors

19
Q

What is a transcription factor?

A

A protein that controls the transcription of genes so that only certain parts of the DNA are expressed

20
Q

How do transcription factors work?

A
  1. Move from the cytoplasm into nucleus
  2. Bind to promoter region upstream of target gene
  3. Makes it easier or more difficult for RNA polymerase to bind to the gene. This increases or decreases rate of transcription
21
Q

Give an example of a hormone that affects transcription and explain how it works

A
  1. Steroid hormone oestrogen diffuses through cell membrane
  2. Forms hormone receptor complex with ER a receptor in the cytoplasm
  3. Complex enters the nucleus and acts as transcription factor to facilitate binding of RNA polymerase
22
Q

What is meant by epigenetics?

A

A heritable change in gene function without change to the base sequence of DNA

23
Q

How does increased methylation of DNA affect gene transcription?

A

Involves addition of CH3 group to cytosine bases which are next to guanine. Prevents transcription factors from binding. Therefore gene transcription is suppressed

24
Q

How does decreased acetylation of histones affect gene transcription?

A

Positively - charged histones are positively charged bind to negatively charged DNA. Decreasing acetylation increases positive charge of histones.
Binding becomes too tight and prevents transcription factors from accessing the DNA. Therefore gene transcription is suppressed

25
Q

How might epigenetic changes affect humans?

A

They can cause disease, either by over activating a gene’s function or by suppressing it

26
Q

Give an application of epigenetic’s

A

Treatments of various diseases. Development of ways to reverse epigenetic changes

27
Q

Describe the process of RNA interference, including the organisms in which it occurs

A

RNA molecules act to inhibit gene expression, usually by destroying mRNA so that it cannot be translated. Occurs in eukaryotes and some prokaryotes

28
Q

Give some characteristics of benign tumours

A

Slow growth

Defined by a clear boundary due to cell adhesion molecules

Cells retain function and normal shape

Don’t spread easily

Easy to treat

29
Q

Give some characteristics of malignant tumours

A

Rapid, uncontrollable growth

Finger-like projections

Cells do not retain function and often die

Spreads quickly and easily

Difficult to treat

30
Q

Describe the role of tumour - suppressor genes

A

Code for proteins that control cell division; in particular, stopping the cell cycle when damage is detected. They are also involved in programming apoptosis i.e self destruction of the cell

31
Q

Explain how tumour suppressor genes can be involved in developing cancer

A

A mutation in the gene could code for a nonfunctional protein. Increased methylation or decreased acetylation could prevent transcription

Cells will divide uncontrollably resulting in a tumour

32
Q

Describe the role of proto-oncogenes

A

Control cell division; in particular, code for proteins that stimulate cell division

33
Q

Explain how proto-oncogenes can be involved in developing cancer

A

Mutation in the gene could turn it into permanently acitvated oncogene. Decreased methylation or increased acetylation can cause excess transcription

This results in uncontrolled cell division and formation of a tumour

34
Q

Explain how abnormal methylation of genes can cause cancer

A

Hyper-methylation of tumour - suppressor genes or oncogenes can impair their function and cause the cell to divide uncontrollably

35
Q

Explain how oestrogen can be involved in developing breast cancer

A

We already know oestrogen is an activator or RNA polymerase. Therefore in areas of high oestrogen concentration, such as adipose tissue in the breasts, cell division can become uncontrolled

36
Q

What is a genome?

A

The complete set of genetic information contained in cells of an organism

37
Q

What is genome sequencing?

A

Identifying the DNA base sequence of an individual. This allows us to determine the amino acid sequence of the polypeptides coded for by that DNA

38
Q

What is the proteome?

A

The complete set of proteins that can be produced by a cell

39
Q

Can we directly translate the genome into the proteome?

A

In simple organisms, yes. In complex organisms due to the presence of non-coding DNA and regulatory genes, it is much harder to obtain the proteome

40
Q

Give an application of sequencing the proteome in simple organisms

A

Identifying potential antigens for use in vaccine production

41
Q

Give some applications of genome sequencing

A

Comparing genomes between species to determine evolutionary relationships

Genetic matching

Personalised medicine

Synthetic biology

42
Q

How have sequencing methods changed over time?

A

Used to be a manual process, however now it has become automated. A reaction mixture is created and after the process is complete a machine reads the base sequence

Biology (20 decks)

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