Cellular Control

Question 1

Types of gene expression control

Answer 1

Transcriptional, post-transcriptional, translational and post-translational

Question 2

Operon

Answer 2

Section of dna that contains a cluster of structural genes that are transcribed together, under a regulatory control system.

Question 3

Reason for existence of lac operon

Answer 3

Allows E. coli to respire lactose when it is present but not produce the enzymes required when it isn’t

Question 4

Sequence of lac operon

Answer 4

Regulator gene
Promoter gene
Operator gene
Structural genes (lac Z, lac Y and lac A)

Question 5

Structural gene

Answer 5

One which actually codes for proteins that are then used

Question 6

Specific genes in lac operon

Answer 6

B-galactosidase, lactose permease and transacetylase

Question 7

Role of regulator gene

Answer 7

Codes for repressor protein which then binds to operator region or lactose

Question 8

Lac operon when lactose is not present

Answer 8

Repressor gene codes for repressor protein which then binds to the operator region. RNA polymerase then can not access the promoter region so doesn’t bind and no structural genes are transcribed.

Question 9

Lac operon in the presence of lactose

Answer 9

Repressor gene codes for the repressor protein. Lactose then binds to the repressor protein (essentially acting as a competitive inhibitor) changing its shape so it doesn’t bind to the operator region. RNA polymerase is then free to bind to the promoter region and transcribes the structural genes. These are translated into the enzymes which allow lactose to be used as a respiratory substrate.

Question 10

Transcription factors

Answer 10

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

Question 11

Methylation

Answer 11

Addition of a CH3 group causing histones to become more hydrophobic and so bound tightly

Question 12

Acetylation

Answer 12

Charge of histones change so they become less tightly bound

Question 13

Histone modification

Answer 13

Methylation or acetylation changing the structure of the histones and so ability of the DNA to be transcribed

Question 14

Heterochromatin

Answer 14

DNA is tightly bound around histones and cannot be physically accessed by RNA polymerase for transcription. Particularly during mitosis or meiosis where chromosomes become visible

Question 15

Euchromatin

Answer 15

DNA is loosely wound around histones so the genes are available for transcription

Question 16

RNA processing

Answer 16

Part of post-transcriptional control adding a modified nucleotide ‘cap’ to the 5’ end and a poly A tail to the 3’ end

Question 17

RNA splicing

Answer 17

Removal of non coding introns to produce functional DNA

Question 18

Examples of post translational control

Answer 18

Addition of non-protein groups
Modicficatoon of amino acids
Folding or shortening of the protein
Modification by c AMP

Question 19

Post translational activation by cAMP

Answer 19

Bind to proteins altering their 3D structure eg then changing the shape of their active site

Question 20

Example of modification by cAMP

Answer 20

Four units of protein kinase A bound together
cAMP binds changing the 3D structure so the subunits are released
PKA is activates

Question 21

Homeotic genes

Answer 21

Genes regulating where anatomical structures will develop

Question 22

Hox genes

Answer 22

Specific genes which control body plans in animals plants and fungi

Question 23

Homeobox sequence

Answer 23

A region of the Hox gene 180 based pairs long, so coding for a 60 amino acids protein called the homeodomaibn.

Question 24

Role of homeodomain protein

Answer 24

Binds to specific sites on DNA acting as a transcription factor for developmental genes

Question 25

Apoptosis

Answer 25

Programmed cell death

Question 26

Sequence of events in apoptosis

Answer 26

Signals trigger cell to die
Cells shrink as cytoskeleton breaks down
DNA, proteins and organelles are degraded by enzymes
Blebs containing digested contents form on the cell surface membrane
Blebs are engulfed by phagocytes

Question 27

Use of apoptosis in development

Answer 27

Some cells triggered to die in order to create accuracy eg trimming and shaping hands and feet

Question 28

Stimuli for apoptosis

Answer 28

Internal such as DNA damage detected

External such as stress caused by lack of nutrients so that cells can not undergo mitosis

Question 29

Mutation

Answer 29

Permanent change in the sequence of nucleotide bases that can be induced or spontaneous

Question 30

Types of mutation

Answer 30

Substitution
Deletion
Insertion

Question 31

Point mutation

Answer 31

Insertion, substitution or deletion of a single nucleotide

Question 32

Silent mutation

Answer 32

Mutation occurring in non coding region

Question 33

Nonsense mutation

Answer 33

Change of amino acid to a STOP codon meaning protein is cut short

Question 34

Missense mutation

Answer 34

Change in order of nucleotides which causes a change in amino acid sequence

Question 35

Frame shift

Answer 35

Insertion and deletion of nucleotide causes a movement in the reading frame as codons are no longer read in sequence

Question 36

3 types of mutagen

Answer 36

Physical, biological and chemical

Question 37

Physical mutagens

Answer 37

Ionising radiation

Question 38

Biological mutagens

Answer 38

Viruses

Question 39

Chemical mutagens

Answer 39

Base analoguse
Deaminating agents
Alkylating agents

Question 40

Chromosome mutation

Answer 40

Mutation affecting the whole chromosome

Question 41

4 types of chromosome mutation

Answer 41

Deletion
Duplication
Translocation
Inversion

Question 42

Beneficial mutation

Answer 42

One which confers evolutionary advantage on carrier eg antibiotic resistance in bacteria

Question 43

Neutral mutation

Answer 43

Neither advantageous or disadvantageous

Question 44

Harmful mutation

Answer 44

Characteristic produced causes disadvantage to the organism eg genetic disease