Cellular Control

Question 1

What are transcription factors?

Answer 1

Proteins that move from the cytoplasm to the nucleus

Question 2

In e.coli…

Answer 2

The protein lactase is only made when lactose is actually present

Genes are switched on to make this protein

Question 3

What are epigenetics?

Answer 3

Heritable changes in in gene function without a change to the base sequence of DNA

Question 4

What does acetylation do to the process of transcription?

Answer 4

Decreased acteylation of histone decreases transcription

Question 5

What is a lac operon?

Answer 5

A group of three genes

LacZ, lacY and lacA

Question 6

What is an operon?

Answer 6

A group of genes that are under the controlof the same regulatory centre mechanism and are expressed at the same time

Question 7

What does the respressor protein in lac operon do?

Answer 7

Prevents the transcription of the structural genes in the absence of lactose

Question 8

What are the different ways in which genes are operated?

Answer 8

Transcriptional

Post-transcriptional

Translational

Post-translational

Question 9

What is a mutation?

Answer 9

Change in the sequence of bases in DNA

Question 10

How is a change in the sequence of DNA caused?

Answer 10

Substitution, deletion or insertion of one or more nucleotides within a gene

Question 11

What is a point mutation?

Answer 11

A mutation in which only one neculeoride is affected

Question 12

What is a mutagen?

Answer 12

A mutagen is a chemical, physical or biological agent which causes mutations

Question 13

What are antioxidants also known as?

Answer 13

Anticarcinogens because of their ability to negate the effects of mutagens (such as free radicals)

Question 14

What are free radicals?

Answer 14

Oxidising agents

Question 15

Where is radial symmetry seen?

Answer 15

Diploblastic animals like jellyfish

They only have a top and a bottom (no left or right sides)

Question 15

What kind of symmetry is seen in most animals?

Answer 15

Bilateral symmetry

Question 16

Where is asymmetry seen?

Answer 16

Sponges

Question 17

What are somites?

Answer 17

Segments in the embryo

Question 18

What is an example of a beneficial mutation?

Answer 18

The ability to digest lactose

Question 19

How does chromatin remodelling affect the transcription of genes?

Answer 19

Acetylation / phosphorylation of histones makes them more nagtuve and causes them to coil less tightly (euchromatin)

This is the opposite of heterochromatin

Question 20

What is heterochromatin?

Answer 20

Tightly wound DNA causing chromosomes to be visible during cell division

Question 21

What is another way in which histones can be modified?

Answer 21

Methylation make histones more hydrophobic so they bind more rightly to each other and the DNA coils more tightly

Prevents transcription of genes

Question 22

What is lac operon?

Answer 22

Structural genes that code for three enzymes

B-galactosidase, lactose permease, transacetylase

Question 23

What is the role of cyclic AMP in transcriptional control?

Answer 23

Increase the rate of transcription to produce the required quantity of enzymes to metabolise lactose efficiently

Question 24

What does a cap (a modified nuc,emotive) help do?

Answer 24

Help stabilise mRNA and delay degradation in th cytoplasm

Aids binding of mRNA to ribosomes

Question 25

What is an example of translational control?

Answer 25

Protein kinases, enzymes that catalyse the addition of phosphate groups to proteins

Addition of a phosphate group changes the tertiary structure = changes the function of a protein

Protein kinases are important regulators of cell activity (+ are activated by secondary messenger, cAMP)

Question 26

What are examples of post-translational control?

Answer 26

• Addition of non-protein groups
• Modifying amino acids and formation of bonds e.g. disulfide bridges
• Folding / shortening of proteins
• Modification by cAMP

Question 27

What is a homeodomain

Answer 27

60 amino acids in a protein that is highly conserved in animals, fungi and plants