6.1.1 cellular control

Question 1

gene mutation

Answer 1

change in a base sequence of DNA
randomly occur during DNA replication (S phase of interphase)

Question 2

possible consequences of gene mutations

Answer 2

• harmless
• damages/kills cells
• makes cells cancerous
• advantageous, increase genetic diversity
• passed to next generation if during meiosis

Question 3

mutagenic agents

Answer 3

increase likelihood of random mutations
e.g.
- high energy radiation like UV light
- ionising radiation like gamma or x rays
- chemicals

Question 4

substitution

Answer 4

point mutation where a base is replaced for another base

Question 5

insertion

Answer 5

adding a base to the sequence

Question 6

inversion

Answer 6

reinserting bases backwards

Question 7

deletion

Answer 7

removing a base from the sequence

Question 8

why are some substitutions silent

Answer 8

genetic code is degenerate as multiple codons code for the same amino acid so the mutation makes no difference

Question 9

silent mutation

Answer 9

no change in what base codes for

Question 10

nonsense mutation

Answer 10

base change creates a STOP codon

Question 11

missense mutation

Answer 11

codes for the wrong amino acid so a different polypeptide is made

Question 12

gene expression

Answer 12

converting the info encoded in a gene into a functional gene product

Question 13

example of a functional gene product

Answer 13

protein or RNA

Question 14

gene regulation

Answer 14

regulates gene expression
increases or decreases production of specific gene products

Question 15

transcriptional control

Answer 15

controlling gene expression by altering rate of transcription of genes

Question 16

regulatory gene

Answer 16

make products to control expression of structural genes

Question 17

structural gene

Answer 17

code for any RNA or protein product other than a regulatory factor

Question 18

what do regulatory genes make

Answer 18

transcription factors

Question 19

transcription factors

Answer 19

bind to DNA near structural genes to activate or repress genes to control rate of protein synthesis

Question 20

promoter region

Answer 20

sequence of DNA that DNA/RNA polymerase bind to

Question 21

activator

Answer 21

transcription factors that turn genes on
help RNA polymerase bind to promoter

Question 22

repressor

Answer 22

transcription factors that turn genes off
prevent RNA polymerase from binding to promoter

Question 23

where do transcription factors have to go to work

Answer 23

cytoplasm to nucleus
bind the promoter

Question 24

what the i gene

Answer 24

codes for the repressor protein for lac operon

Question 25

lacZ

Answer 25

structural gene that codes for B-galactosidase

Question 26

lacY

Answer 26

structural gene that codes for lactose permease

Question 27

B-galactosidase

Answer 27

hydrolyses lactose

Question 28

lactose permease

Answer 28

carrier protein for lactose

Question 29

why do bacterial cells want to break lactose down

Answer 29

to metabolise it and use it in respiration

Question 30

what happens when lactose is absent

Answer 30

1. waste of energy to produce enzymes as there's nothing to hydrolyse 2. repressor binds to operator region 3. this blocks RNA polymerase 4. mRNA can't be made 5. no proteins or enzymes are made

Question 31

what happens when lactose is present

Answer 31

1. lactose binds to repressors that would usually bind with the operator region of a DNA strand 2. lactose changes the conformation of the repressor protein so it can't bind to the complimentary operator region 3. RNA polymerase can bind to the operator and promoter regions 4. transcription occurs 5. mRNA is produced 6. lacZ codes for B-galactosidase which breaks down lactose and lacY codes for lactose permease which moves lactose out of cell 7. lactose can then be metabolised and used in respiration

Question 32

post-transcriptional control

Answer 32

pre-mRNA contains unnecessary introns and only exons are needed introns are cut out exons spliced together by enzymes produced mature mRNA

Question 33

post-translational control

Answer 33

1. protein hormone binds to receptor 2. activates transmembrane protein 3. G protein activated 4. adenyl cyclase enzymes activated 5. ATP converted to cAMP by adenyl cyclase 6. cAMP activates PKA 7. PKA phosphorylates proteins

Question 34

what is post-translational control used for

Answer 34

regulating gene expression

Question 35

homeodomain sequence

Answer 35

region of homeodomain protein in the gene sequence of amino acids that act as transcription factor

Question 36

homeobox gene

Answer 36

DNA sequence that codes for a protein transcription factor (homeodomain protein)

Question 37

homeobox sequence

Answer 37

180 base pairs coding for 60 amino acids

Question 38

what is the function of the homeobox sequence

Answer 38

control body development all code for transcription factors

Question 39

Hox gene

Answer 39

'master' homeobox genes found only in animals control polarity and segmentation of animal

Question 40

highly conserved

Answer 40

remained unchanged over evolutionary time

Question 41

polarity

Answer 41

organisation of an organism's head-to-tail axis

Question 42

segmentation

Answer 42

the establishment of separate distinct body parts

Question 43

colinearity

Answer 43

genes in Hox cluster are arranged in a linear sequence on the chromosome, body plan is organised in order of where they appear in body (head-to-tail)

Question 44

what happens when mutations affect homeobox genes

Answer 44

organisms are not viable

Question 45

apoptosis

Answer 45

controlled cell death

Question 46

necrosis

Answer 46

uncontrolled cell death

Question 47

stages of apoptosis

Answer 47

1. cytoskeleton hydrolysed by enzymes 2. cell membrane forms blebs 3. chromatin condenses 4. nuclear envelope breaks 5. DNA breaks into fragments 6. vesicles called apoptotic bodies form and macrophages phagocytose them

Question 48

how do homeobox genes influence apoptosis

Answer 48

- control development of body plans - all cells contain genes that code for proteins that are activators/inhibitors of apoptosis - they can be switched on or off by transcription factors