practice paper 2

Question 1

what occurs at prophase 1

Answer 1

crossing over of non-sister chromatids

Question 2

how could the failure of hox genes lead to deformity such as hands fused

Answer 2

-hox gene does not produce the transcription factor
-molecules signalling apoptosis are not produced
-apoptosis does not occur

Question 3

how could gene expression be regulated after transcription

Answer 3

• primary mRNA is modified
  -removal of introns to produce mature mRNA
  -alternative splicing can produce different versions of mRNA
  -protein must be activated by cAMP
  -binding of cAMP alters shape of protein

Question 4

how may bioinformatics be useful in determining whether a newly sequenced allele can cause a genetic disease

Answer 4

-base sequence of normal allele is know and alternatives held in data base
-computational analysis allows rapid comparison of sequences with newly synthesised allele
-amino acid sequence/ protein structures also held in place

Question 5

explain why only selected sections of non coding dna are used when profiling a human

Answer 5

-in most people the genome is very simmilar/ most genes are the same
-using coding sequences would not provide unique profiles
-parts of non-coding DNA contains variable numbers of STRs (short tandem repeats)/ repeating sequences

Question 6

how can a serial dilution estimate population size

Answer 6

multiply the result from the agar plate by the dilution factor

Question 7

why can swelling or discomfort occur

Answer 7

-excess tissue fluid being drained to lymph vessels
-pathogens in tissue fluid enter lymph fluid
-transported across lymph system to lymph nodes
-activity of phagocytes
-causes swelling of lymph nodes

Question 8

what can be used to release dna in bananas

Answer 8

detergent
works as an emulsifier/ attracting phospholipid molecules to water molecules
-it will break down the plasma/ nuclear membrane

Question 9

suggests the ways that use of embryonic stem cells can aid biological knowledge

Answer 9

-to test how effective medicine and drugs are
-test for side effects
-study to see development in new cell types
-cell function can be studied to find out what can be made to make it fail to work properly in certain diseases

Question 10

changes in stem cells to form rbcs

Answer 10

-synthesise hamoglobin
-remove/ digest organelles involved in protein synthesis