Cellular Control

?
Why do the functions and structures of cells differ?
Despite carrying the same genes, different cells will have different expressed genes.
1 of 30
What are transcription factors?
Proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription. Their shape determines whether or not they can bind to the DNA.
2 of 30
What are the 2 types of transcription factors, and what do they do?
Activators (start transcription) and repressors (stop transcription)
3 of 30
Where do transcription factors bind to in eukaryotes and prokaryotes?
Eukaryotes - specific DNA sites near the start of their target genes; Prokaryotes - the factors bind to operons.
4 of 30
What is an operon?
A section of DNA that contains a cluster of structural genes (that are transcribed together), control elements, and sometimes a regulatory genes.
5 of 30
What are structural genes?
Genes that code for useful proteins e.g. enzymes.
6 of 30
What are the control elements?
A promoter (DNA sequence located before structural genes that RNA polymerase binds to), and an operator (DNA sequence that factors bind to).
7 of 30
What are regulatory genes?
Genes that code for activators and repressors
8 of 30
What is E.Coli?
A bacterium that respires glucose, but can use lactose in the absence of glucose.
9 of 30
What is the lac operon?
The section of DNA that codes for the enzymes needed to respire glucose.
10 of 30
What are the 3 structural genes found on the lac operon, and what is the function of the proteins they produce?
They are lacZ, lacY and lacA. The proteins they produce help bacteria digest lactose (using beta-galactosidase and lactose permease).
11 of 30
Lac Operon - What happens when lactose is not present?
1. Regulatory gene lacI produces the lac repressor which binds to the operator site. 2. Transcription is blocked as RNA polymerase cannot bind to the promoter.
12 of 30
Lac Operon - What happens when lactose is present?
1. Lactose binds to the lac repressor and changes its shape. 2. The repressor can no longer bind to the operator site so moves off. 3. RNA polymerase can now begin transcription of the structural genes.
13 of 30
What are introns and exons?
Introns - sections of DNA that don't code for amino acids. Exons - the rest of the DNA that does code for amino acids.
14 of 30
How is gene expression controlled at a post-transcriptional level?
Primary transcripts (mRNA strands containing introns and exons) are edited to remove the introns by a process called splicing. The exons are then joined together to form mature mRNA strands. The mature mRNA then leaves the nucleus to be translated.
15 of 30
How is gene expression controlled at a post-translational level?
Molecules that control protein activation work by binding to cell membranes and triggering the production of cAMP. This activates proteins inside the cell by altering their 3D structure (e.g. enzyme active site can be altered).
16 of 30
What is a body plan?
The general structure of an organism.
17 of 30
What are Hox genes?
Genes that code for proteins which control body plan development.
18 of 30
What are homeobox sequences?
Regions on Hox genes which are highly conserved (these sequences have changed very little during the evolution of the organisms).
19 of 30
How do Hox genes control development?
Homeobox sequences code for a part of the protein called the homeodomain, which binds to sites on DNA enabling the protein to work as a transcription factor. The proteins bind to DNA and activate or repress transcription.
20 of 30
What is apoptosis?
A highly controlled process where cells die and break down as part of normal development.
21 of 30
What are the steps of apoptosis?
1. Enzymes inside the cell break down cell components. 2. The cell begins to shrink and fragment. 3. Phagocytes engulf and digest the cell fragments.
22 of 30
What roles do mitosis and apoptosis play in development?
Mitosis and differentiation create the bulk of body parts and apoptosis refines the body parts by removing unwanted structures. Genes that control mitosis are switched on and off in appropriate cells so the correct body plan develops.
23 of 30
What is a mutation?
Any change to the base sequence of DNA.
24 of 30
What are the types of mutation?
Substitution (one/more bases are swapped for another base), deletion (one/more bases are removed) and insertion (one/more bases are added).
25 of 30
What effect could mutations have?
As the order of bases determines the order and type of amino acids, completely different proteins could be made as the primary structure of the protein could change.
26 of 30
What is frameshift mutation?
When an insertion or deletion changes the way the rest of the base sequence is read. The earlier the frameshift mutation, the greater the effect it will have on the protein.
27 of 30
What is the effect of a neutral mutation?
The protein function is not affected as amino acids not changed/changed amino acid is similar chemically/mutated triplet code not involved with protein function.
28 of 30
What can be the effects of a beneficial mutation?
Increased chance of survival as the organism now has an advantage. Natural selection ensures this mutation is passed onto future generations.
29 of 30
What can be the effects of a harmful mutation?
Decreased chance of survival as the organism now has a disadvantage. Can also affect protein production which could lead to genetic disorders.
30 of 30

Other cards in this set

Card 2

Front

What are transcription factors?

Back

Proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription. Their shape determines whether or not they can bind to the DNA.

Card 3

Front

What are the 2 types of transcription factors, and what do they do?

Back

Preview of the front of card 3

Card 4

Front

Where do transcription factors bind to in eukaryotes and prokaryotes?

Back

Preview of the front of card 4

Card 5

Front

What is an operon?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all DNA, genetics and evolution resources »