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Biology > Cellular control > Flashcards

Cellular control Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What varies between genes and why

A

Structure and function as not all genes in a cell are expressed (selectively switched on or off).

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2
Q

Why do cells show a different gene expression

A

Different proteins are made that modify the cell and determine structure and processes

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3
Q

What level can gene expression be controlled

A

The transcriptional, post-transcriptional and post-translational level

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4
Q

Transcription factors control gene expression at what level

A

Transcriptional level

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5
Q

How can gene expression be controlled

A

By altering the rate of transcription of genes

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6
Q

What are transcription factors

A

Proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription

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7
Q

What are activators

A

Factors that increase the rate of transcription

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8
Q

What are repressors

A

Factors that decrease the rate of transcription

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9
Q

What does the shape of a transcription factor determine

A

Whether it can bind to DNA or not and can be altered by the binding of some molecules

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10
Q

In Eukaryotes where do transcription factors bind to specific DNA sites

A

Near the start of their target genes - the genes they control the expression of

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11
Q

In Prokaryotes where do transcription factors bind to specific DNA sites

A

Binding to operons

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12
Q

What is an operon

A

A section of DNA that contains a cluster of structural genes, that are transcribed together as well as control elements and sometimes a regulatory gene

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13
Q

What do structural genes code for

A

Useful proteins such as enzymes

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14
Q

What do regulatory genes code for

A

An activator or repressor

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15
Q

What do control elements include

A

A promoter and an operator

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16
Q

What is a promoter

A

A DNA sequence located before the structural genes that RNA polymerase binds to

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17
Q

What is an operator

A

A DNA sequence that transcription factors bind to

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18
Q

Process of the Lac operon in E.coli when lactose is not present

A

1) The regulatory gene (lacl) produces the lac repressor, which is a transcription factor that binds to the operator site when there is no lactose present.
2) This blocks transcription because RNA polymerase can’t bind to the promoter

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19
Q

Process of the Lac operon in E.coli when lactose is present

A

Lactose binds to the repressor, changing its shape so it can no longer bind to the operator site. RNA polymerase can now begin transcription of the structural genes

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20
Q

What is the lac operon and what is involved

A

1) E coli respires glucose or lactose if no glucose is available
2) The genes that produce the enzymes needed to respire lactose are found on an operon called the lac operon
3) The structural genes lacZ, lacY and lacA produce proteins (beta-galactosidase and lactose permease) to help digest lactose

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21
Q

What level is mRNA edited

A

Post-transcriptional level

22
Q

What are introns

A

In eukaryotic DNA sections that don’t code for amino acids

23
Q

What are exons

A

Sections of DNA that do code for an amino acid.

24
Q

During transcription what is copied into mRNA

A

Both introns and exons

25
Q

What are mRNA strands containing introns and exons

A

Primary mRNA transcripts (pre mRNA)

26
Q

How and where are introns removed from primary mRNA

A

Splicing - introns are removed and exons joined forming mature mRNA strands taking place in the nucleus

27
Q

What is protein activation controlled by

A

Molecules such as hormones or sugars

28
Q

What is cAMP

A

Cyclic AMP - a secondary messenger relaying the message from the control molecule

29
Q

How can cAMP activate a protein

A

Molecules bind to cell membranes triggering the production of cAMP inside the cell. It then activates proteins inside the cell by altering their 3D structure. This can change the active site making it more or less active.

30
Q

How does cAMP activate protein kinase A (PKA)

A

1) PKA is an enzyme made of four subunits
2) When cAMP isn’t bound, the four units are bound together and are inactive
3) When cAMP binds, it causes a change in the enzyme’s 3D structure, releasing the active subunits - PKA is now active

31
Q

What is a body plan

A

The general structure of an organism that are arranged in a particular way

32
Q

What controls the development of a body plan

A

Proteins as they help to set up the basic body plan so everything is in the right place

33
Q

What are the proteins that control body plan coded by

A

Hox genes

34
Q

How can you tell if body plan development is controlled in a similar way from species to species

A

Similar hox genes are found

35
Q

What are homeobox sequences

A

They are highly conserved (changed very little from evolution) and code for a part of the protein called the homeodomain. This binds to specific sites on DNA enabling the protein to work as a transcription factor. This happens at the start of developmental genes, activating or repressing transcription altering the production of proteins involved in the development of the body plan.

36
Q

What is apoptosis

A

Programmed cell death

37
Q

Once apoptosis is triggered how is the cell broken down

A

1) Enzymes inside the cell break down important cell components such as proteins in the cytoplasm and DNA in the nucleus
2) As the cell’s contents are broken down it begins to shrink and breaks up into fragments
3) The cell fragments are engulfed by phagocytes and digested

38
Q

How does apoptosis and mitosis/differentiation work together

A

Mitosis and differentiation create the bulk of body parts and then apoptosis refines he parts removing unwanted structures

39
Q

What is an internal stimulus

A

Factors located inside the body that are detected and cause a response such as DNA damage

40
Q

What is an external stimulus

A

Changes to conditions outside of the body, or in general, information from outside the body that our senses detect such as stress from lack of nutrient availability

41
Q

What does an internal stimuli mean for genes

A

Expression of the genes which causes the cycle to be paused and can trigger apoptosis

42
Q

What does an external stimuli mean for genes

A

It could result in gene expression that prevents cells from undergoing mitosis. This can also lead to apoptosis being trigged.

43
Q

What is substitution

A

One or more bases are swapped for another

44
Q

What is deletion

A

One or more bases are removed

45
Q

What is insertion

A

One or more bases are added

46
Q

What is duplication

A

Sections get duplicated on a chromosome

47
Q

What is translocation

A

A section of one chromosome breaks off and joins another non-homologous chromosome

48
Q

What is inversion

A

A section of chromosome breaks off, is reversed and then joins back onto the chromosome

49
Q

What is a mutation

A

A change to the base sequence of DNA

50
Q

What are neutral mutations

A

The base of a triplet changes but the amino acid dose not change as some amino acids are coded for by more than one triplet.

The mutation could code for a different amino acid that is chemically similar so functions the same

The mutated triplet codes for an amino acid not involved with the proteins function

51
Q

What is a beneficial mutation

A

They have advantages on an organism such as increasing chance of survival such as enzymes working in antibiotics on a larger range of bacteria

52
Q

What is a harmful mutation

A

They have disadvantageous effects on an organism such as decreasing their survival chances. An example is cystic fibrosis is a result of a deletion of three bases producing excess mucus

Biology (20 decks)

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