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Biology > Unit 6 - Gene Expression > Flashcards

Unit 6 - Gene Expression Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Describe how a mutation can create a non-functional protein?

A

-A change in a DNA base sequence
-Changes the amino acid sequence of the protein
-Changes the position of the hydrogen, ionic and disulphide bonding
-Changes tertiary structure
-Changes its function or making it non-functional

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2
Q

When are mutations most likely to occur?

A

Spontaneous mutations can occur randomly during DNA replication which takes place during interphase.

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3
Q

Name 2 mutagens which increase the rate of mutation?

A

1) High energy radiation (UV radiation, X-rays, gamma rays)
2) Chemicals (asbestos, tobacco tar, benzene, free radicals)

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4
Q

Define a substitution mutation?

A

When one base is changed for a different base.

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5
Q

Definition of an addition mutation?

A

When one or more bases is inserted into the DNA base sequence. Causes a frame shift.

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6
Q

Definition of a deletion mutation?

A

When one or more bases is removed from the DNA base sequence. Causes a frame shift.

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7
Q

Definition of an inverse mutation?

A

A sequence of bases become separated from the DNA sequence and re-join at the same position but in the inverse order. Not a frame shift.

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8
Q

Definition of a duplication mutation?

A

One or more bases are repeated. Causes a frame shift.

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9
Q

Definition of a translocation mutation?

A

A section of DNA from one chromosome breaks off and attaches to another chromosome. Sometimes pieces from 2 different chromosomes will exchange places with each other.

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10
Q

What are the 3 types of substitution mutations?

A

1) Mis-sense mutation-one base
2) silent mutation
3) nonsense - stop

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11
Q

What effect on the polypeptide does a mid-sense mutation-one base have?

A

New amino acid has been coded for. If amino acid is involved with hydrogen bonding the tertiary structure will change. If not involved with bonding it may not change the tertiary structure.

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12
Q

What effect on the polypeptide does a silent mutation have?

A

No effect as the same amino acid is still being coded for as it is degenerate.

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13
Q

What effect on the polypeptide does a nonsense have?

A

It stops the polypeptide chain/no more translation. Polypeptide is shorter as is released earlier.

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14
Q

How does a cell differentiate and become specialised?

A

Specific genes are expressed (transcribed + translated) for the specific proteins the cells need (‘switched on’). All other genes are not expressed (‘switched off’).

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15
Q

Definition of stem cells?

A

-Are undifferentiated/unspecialised cells
-Can keep dividing
-Can differentiate into specialised cells

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16
Q

Definition of a totipotent stem cells and when they are present?

A

Totipotent cells can divide and differentiate into any type of body cell. Found in early embryonic stem cells (up to 4 days).

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17
Q

Definition of a pluripotent stem cell and when they are present?

A

Pluripotent cells can divide and differentiate into most cell types. These cells are found in the (later) embryo.

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18
Q

Definition of a multipotent stem cell and when these cells are present?

A

Multipotent cells can divide and differentiate into a limited number of cell types. These cells are found in mature mammals (after birth).

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19
Q

Definition of an unipotent stem cell and when these cells are present?

A

Unipotent cells can divide and differentiate into only one cell type. Example=cardiomyocytes (heart muscles).

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20
Q

How can stem cells be used in the treatment of disease?

A

Stem cells can be transplanted to divide and differentiate into the cell type required.

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21
Q

How can you treat leukemia with stem cells?

A

-Stem cells from bone marrow are used to treat leukemia (white blood cells cancer).
-Bone marrow is used from a close relative to reduce chance of rejection
-The stem cells continuously divide and differentiate to produce healthy white blood cells, giving a long term treatment.

22
Q

What are adult stem cells?

A

From the same individual/close relative. Produce multipotent stem cells.

23
Q

What are embryonic stem cells?

A

Produce pluripotent stem cells.

24
Q

What are advantages of adult stem cells?

A

-No ethical issues.
-Less chance of rejection (same/similar DNA).

25
Q

What are disadvantages of adult stem cells?

A

-Can be rejected by the body.
-Multipotent so can only divide into a limited number of cell types.
-Difficult to isolate.
-If you don’t have any direct family willing to donate.

26
Q

What are advantages of embryonic stem cells?

A

-Pluripotent stem cells so can divide and differentiate into most types of body cells.
-Easy to isolate, use embryos from IVF.

27
Q

What are disadvantages of embryonic stem cells?

A

-Lots of ethical concerns
-High chance of rejection

28
Q

Uses of induced pluripotent stem cells - iPS cells?

A

-Normal cells are removed from a patient and factors added to make the cell pluripotent.
-The iPS cell then divides and differentiates into the desired cell type.
-The specialised cells are transplanted back into the patient.

29
Q

What are the advantages of iPS cells?

A

-No ethical issues as using own cells
-Can differentiate into any cell type
-Less chance of rejection
-Can divide indefinitely

30
Q

How to use in vitro cell culture for plant cell differentiation and tissue culture?

A

Cells in a mature plant are all totipotent. Basically any specialised plant cell can differentiate into a different specialised cell given the right conditions.
-By adding certain growth factors and given the right conditions, plant cells can develop into a whole new organism or plant organ and will be a clone.
-Within plant tissue culture totipotent plant cells are grown in sterile conditions to produce a callus - a mass of undifferentiated plant cells.
-The callus is placed in a growth medium and subjected to specific conditions.
-Under these condition the callus differentiate into specific plant tissues or tiny planters which grow into whole plants.

31
Q

Explain how transcription factors control transcription?

A

1) Transcription factors are proteins
2) They move from the cytoplasm to the nucleus
3) They bind a promoter (specific base sequence) of a gene
4) This stimulates RNA polymerase
5) Gene is transcribed and produces mRNA

32
Q

What are the 2 types of transcription factor?

A

1) Activators - activate transcription by binding a promoter and causing RNA polymerase to bind
2) Repressors - inhibit transcription by binding the promoter and preventing RNA polymerase binding.

33
Q

How does oestrogen act as a transcription factor?

A

1) Oestrogen is a lipid so crossed the phospholipid bilayer by diffusion
2) Oestrogen binds to a complementary protein receptor in the cytoplasm
3) Receptor-oestrogen complex is a transcription factor. It binds to a promoter.
4) This stimulates RNA polymerase to transcribe the gene and produce mRNA.

34
Q

How does oestrogen and cancer link?

A

Increases oestrogen concentrations can increase the risk of breast cancer.
-Oestrogen can cause breast cells to divide more
-More likely that mutations occur when DNA replicates
-Faster division of cancerous cells will produce tumours more quickly.

35
Q

What does RNA interference RNAi do?

A

It prevents mRNA being translated into a protein.

36
Q

Steps of RNA interference?

A

1) Small interfering RNA (siRNA) has a specific complementary base sequence to the target mRNA
2) The siRNA binds to a protein (RISC) which acts as an enzyme
3) One of the siRNA strands is removed to make it single stranded
4) The siRNA now binds to mRNA molecules by complementary base pairing
5) The mRNA is destroyed
6) The mRNA can no longer be used in translation and is broken down by enzymes.

37
Q

miRNA vs siRNA?

A

MicroRNA (miRNA) can also be used to target and destroy mRNA.
miRNA is not fully complementary and not specific to one mRNA and therefore targets more than one type of mRNA (unlike siRNA which targets one).

38
Q

What is cancer caused by?

A

It is caused by mutations in the genes which control mitosis. This leads to uncontrolled cell division, forming a mass of cells called a tumour.

39
Q

What are malignant tumours?

A

They are cancerous. Cells can break off and spread to other parts of the body, forming a tumour elsewhere which is called metastasis.

40
Q

What are benign tumours?

A

They are not cancerous. Cells do not spread to other parts of the body. Not metastasis.

41
Q

What are tumour suppressor genes?

A

They code for proteins which prevent cell division.

42
Q

What happens when there is a mutation in a tumour suppressor gene?

A

Mutations in tumour suppressor genes stop the formation of proteins which prevent mitosis. This leads to uncontrolled cell division.

43
Q

What are proto-oncogenes?

A

They code for proteins which stimulate cell division.

44
Q

What happens when there is a mutation in a proto-oncogene?

A

Mutations of proto-oncogenes to oncogenes, forms more proteins which cause cell division. This leads to uncontrolled cell division.

45
Q

Define epigenetics?

A

Heritable changes in gene function without changes to the DNA base sequence.

46
Q

What is methylation of DNA?

A

-Methyl groups (CH3) are added to DNA
-Transcription factors cannot bind to the promoter
-RNA polymerase is not activated
-Gene is not transcribed (and translated)

47
Q

What is acetylation of histone proteins?

A

-The addition of acetyl groups to histone proteins make chromatin less condensed
-Transcription factors can bind the promoter
-RNA polymerase is activated
-Transcription does occur

48
Q

What would happen if the acetyl groups were removed from the histone proteins?

A

There would be less acetylation. Therefore more condensed chromosomes. Transcription factors cannot bind the promoter, RNA polymerase is not activated, no transcription.

49
Q

The effect of the environment of epigenetics?

A

The environment can cause increased or decreased methylation of DNA and acetylation of histone proteins and therefore effect gene expression. Therefore offspring can “inherit” environmental effect from their parents. The gametes need to be methylated/acetylated for the offspring to inherit them.

50
Q

Which type of gene can lead to tumour formation when methylated?

A

Tumour suppressor genes. Methylation leads to no transcription therefore inhibiting the tumour suppressor gene from slowing down cell division.

51
Q

Which type of gene can lead to tumour formation when it is less methylated?

A

Oncogene. Less methylation leads to transcription. Protein gets over expressed therefore uncontrolled cell division.

Biology (21 decks)

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