cellular control

Question 1

Programmed cell death is known as ……………………………………. . Firstly, the fine network of protein filaments and microtubules known as the ……………………………………. , which gives structure to the cell, is broken down and digested by ……………………………………… .

Answer 1

apoptosis
cytoskeleton
enzymes/ liposomes

Question 2

after the liposomes have digested the cytoskeleton, changes start to occur on the plasma membrane.

Answer 2

the cell surface membrane forms small bulges called blebs. the cells break into membrane bound fragments that are removed by a process known a phagocytosis so that toxic substances are not released into the neighbouring tissues.

Question 3

However, mutation in a gene called p53 can prevent programmed cell death. When this occurs, the rate at which somatic cells are produced by the process of ……………………………………………… becomes greater than the rate at which cells die, resulting in the formation of a mass of cells known as a
……………………………………….. .

Answer 3

mitosis
tumor

Question 4

state what is meant by homeobox genes

Answer 4

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 5

why are homeobox genes highly conserved

Answer 5

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

ie having no arms would make you more susceptible to predation and harder for reproductive success.

Question 6

outline what happens in anaphase one and anaphase 2 (that is different)

Answer 6

A1 - chromosomes pull to opposite ends
A2 - sister chromatids pull to opposite ends

Question 7

Explain why meiosis needs to have twice as many stages as mitosis

Answer 7

halves the number of chromosomes (diploid 2n to haploid n)
to separate homologous chromosomes and sister chromatids

Question 8

outline the function of PCR

Answer 8

to amplify DNA
at many different lengths

Question 9

outline the function of electrophoresis

Answer 9

separate out pieces of DNA
to read base sequences

Question 10

outline the uses of restriction enzymes

Answer 10

to cut DNA into smaller fragments
to cut vectors

Question 11

Suggest why a genome has to be fragmented before sequencing

Answer 11

genome is too big, takes too long to sequence
accuracy is better as less errors

Question 12

Use your knowledge of the effects of polyploidy in bread wheat to suggest one way in which the fruit of a hexaploid (6n) blueberry might differ in appearance from that of a diploid (2n) blueberry.

Answer 12

bigger, plumper

Question 13

How does the phylogenetic approach to classifying species differ from the biological species concept?

Answer 13

phylogenetic involves evolutionary relationships which can be explored using fossils and assexual reproduction
whereas the biological species concept involves inbreeding to give fertile offspring so doesn’t apply to asexually reproducing organisms or extinct species

Question 14

Describe how genes Z and Y are switched on in bacteria that are moved to a nutrient medium
that contains lactose.

Answer 14

lactose binds to the repressor protein
changing the shape of the repressor protein
removes it/ stops it binding to the protein
RNA polymerase binds to the promoter
x and y are transcribed

Question 15

Suggest why yogurt is a suitable food for lactose-intolerant people

Answer 15

lactose has been digested by bacteria into glucose and galactose and undergone anaerobic respiration forming lactic acid

Question 16

What is an operon

Answer 16

A cluster of genes under the control of a promoter.