cellular control

Question 1

the proteins that control the development are coded for by genes called…

Answer 1

hox genes

Question 2

how many hox genes are needed to code for the anterior and posterior body plan?

Answer 2

two

Question 3

what are the regions called in hox genes

Answer 3

homeobox sequences

Question 4

homeobox sequences are ‘highly conserved’, what does this mean?

Answer 4

sequences change very little during the evolution of different organisms that possess these homeobox sequences.

Question 5

homeobox sequences code for a part of a protein called…

Answer 5

homeodomain

Question 6

how does homeodomain control the development of the body plan?

Answer 6

homeodomain binds to specific sites on DNA, enabling the protein to work as a transcription factor.

It can bind to DNA at the start of developmental genes, either activating or repressing transcription - so in this way, it alters the production of proteins involved in the development of body plan.

Question 7

what is apoptosis

Answer 7

programmed cell death

Question 8

once apoptosis is triggered, how is the cell broken down? (3 step process)

Answer 8

1. enzymes in cell break down proteins and DNA
2. it begins to shrink and break into fragments
3. cell fragments are engulfed by pathogen and digested.

Question 9

by what two processes creates the bulk of body parts which is refined by apoptosis, by removing unwanted structures?

Answer 9

mitosis and differentiation

Question 10

how to genes control apoptosis and mitosis?

Answer 10

genes can be switched on and off in cells which means some cells die, or are reproduced in order to create correct body plan.

Question 11

describe an example of how external stimuli can regulate gene expression/apoptosis

Answer 11

Stress/lack of nutrient/attack of pathogen - can trigger gene expression that prevents cells from undergoing mitosis.

Question 12

describe an example of how internal stimuli can regulate gene expression/apoptosis

Answer 12

DNA damage - if detected in cell cycle, this can result in expression of genes which cause cycle to be paused, and trigger apoptosis.

Question 13

substitution

Answer 13

one or more bases are swapped for another

Question 14

deletion

Answer 14

one or more bases are removed

Question 15

insertion

Answer 15

one or more bases are added

Question 16

describe how a mutation can alter the coding of proteins

Answer 16

primary structure of protein can be altered by mutation which can change tertiary structure of protein so can’t function e.g. active site in enzyme may not be complimentary so substrate can’t bind.

Question 17

describe an example of how mutations can have a neutral effect

Answer 17

mutation may change a base in a triplet, but the amino acid that the triplet codes for doesn’t change because amino acids are coded for by more than one triplet.

Question 18

describe how mutations can have a beneficial effect

Answer 18

it can increase chance of survival - enzymes break down certain antibiotics, mutations in the genes that code for these enzymes can make them work on wider range of antibiotics to combat antibiotic resistance.

Question 19

describe the harmful effects of mutations e.g. cystic fibrosis

Answer 19

decrease chance of survival - CF caused by deletion of 3 bases in the gene that codes for CFTR protein, this mutation causes protein to fold incorrectly, so it’s broken down. This can lead to excess mucus which affects lungs of CF sufferers.

Question 20

if mutation occurs at the start of gene…

Answer 20

RNA polymerase can’t bind and start transcription, so protein coded for by gene won’t be made.