Cellular Control

Question 1

Name 3 types of gene mutations

Answer 1

Substitution

Insertion

Deletion

Question 2

What do insertion and deletion lead to?

Answer 2

Frame shift

Moves the reading frame of bases changing every subsequent codon

Unless nucleotides added/deleted are multiple of 3, then no frame shift but more amino acids are added so protein is still altered

Question 3

What is substitution?

Answer 3

The changing of a single nucleotide changing the amino acid the codon codes for

However due to degenerative nature of dna, could code for same amino acid

Question 4

What are the 3 effects of gene mutations and what do they mean?

Answer 4

Beneficial
Rarely a mutation results in a new and useful characteristic in the phenotype

Harmful
Phenotype is altered in a negative way - protein is no longer synthesised or no longer functional

Neutral
The normal phenotype is produced so no effect on phenotype

Question 5

What are transcription factors?

Answer 5

Proteins in eukaryotic that bind to dna and switch on/off genes by increasing/decreasing the rate of transcription

Question 6

What is a transcription factor that increases rate of transcription

Answer 6

Activator

Question 7

What is a repressive protein?

Answer 7

A protein that binds to dna and switches genes off by decreasing the rate of transcription

Question 8

What is an example of transcription level regulation of gene expression

Answer 8

Lac operon

Question 9

What is an operon?

Answer 9

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

Question 10

What is the lac operon?

Answer 10

A group of 3 structural genes coding for enzymes

Regulatory gene near and coded for repressor protein so transcription is prevented as RNA polymerase cannot bind to promotor

Lactose changes shape of repressor protein so cannot bind

Question 11

What is post transcriptional level control of gene expression?

Answer 11

Splicing of mRNA

Editing of primary mRNA

Question 12

What is splicing?

Answer 12

Pre mRNA is modified to mature mRNA so can bind to ribosome

Cuts at specific points to remove the extrons and joining introns together

Question 13

how is mRNA edited post transcriptionally?

Answer 13

base addition, substitution and deletion resulting in proteins with different functions

Question 14

how are genes regulated post translationally?

Answer 14

some proteins arent functional when first made so need to be activated. a molecule usually binds to the cell surface membrane causing cyclic AMP to be released inside the cell which axctivates the protein by changing its structure

Question 15

What is a homeobox gene?

Answer 15

homeotic / regulatory, (gene) ;
contains, 180 bp / homeobox, sequence ;
that codes for homeodomain (on protein) ;
(gene product) binds to DNA ;
initiates transcription / switch genes, on / off ;
control of, development / body plan ;

Question 16

what are hox genes?

Answer 16

a group of homeobox genes only present in animals, which is responsible for the correct positioning of body parts.

the order in which they appear on the chromosome is the order in which they are expressed

Question 17

what is apoptosis?

Answer 17

programmed cell death

Question 18

how to mitosis and apoptosis control the development of body form?

Answer 18

mitosis increases the number of cells leading to growth and apoptosis removes unwanted cells

cells undergoing apoptosis can release chemicals to stimulate mitosis for remodelling

Question 19

what external stimulis controls apoptosis?

Answer 19

stress, lack of nutrient availability can result in gene expression that prevents mitosis

pathogens can stimulate apoptosis

Question 20

what internal stimuli control apoptosis?

Answer 20

DNA damage detected during the cell cycle causes expression of a gene that causes the cell cycle to be paused and triggers apoptosis

Question 21

?what is mitosis and apoptosis regulated by

Answer 21

hox genes

Question 22

what does RNA polymerase do?

Answer 22

makes mRNA by transcription using a section of DNA o form one strand

Question 23

what does DNA polymerase do?

Answer 23

used in DNA replication to make 2 DNA strands before cell devision

Question 24

explain why there is very little change by mutation in homeobox genes?

Answer 24

these genes very important ;
mutation would, have big effects / alter body plan ;
many other genes would be affected / knock-on effects ;
mutation likely to be, lethal / selected against

Question 25

how does failure of the control mechanism during development lead to webbed fingers

Answer 25

hox genes do not produce transcription factor
so molecules signalling apoptosis are not produced
so apoptosis to separate fingers does not occur

Question 26

how can gene expression be regulated after transcription?

Answer 26

primary mRNA is modified

removal of introns to produce mature mRNA

alternative splicing to produce different versions of mRNA

protein must be activated by cAMP

binding of cAMP alters the shape of the protein