Aqa a-level biology 7402 - paper 2 - unofficial mark scheme 13th June 2019

0.36= q^2 or recessive
q= 0.6

P must be 0.4 so p^2 = 0.16 ( number of homozygous dominant)

Therefore, 2pq =
0.64 - 0.16 = 0.48

48 percent WAS the answer can’t see how 0.46 was right unless some one can explain otherwise

Could be right I was thinking that too but then before the DNA winds into a helix the bases arent paired so I was thinking they may be talking about if the bases were placed side by side the actual length of the whole dna since theres 2 strands, and the first bit mentioned kilobases which is each singular bases and the DNA consists of double strands so maybe might have wanted you to notice it otherwise I doubt they wouldve said 10 base pairs instead of just 10 bases but who knows

No but it gave u the total number of bases not base pairs so u had to divide by two

How does the myelin seath being damaged effect rhythms of the heart tho. Wording on this question is gonna be awful in the mark scheme

How does the myelin seath being damaged effect rhythms of the heart tho. Wording on this question is gonna be awful in the mark scheme

What was the reason for the lid on the Petri dish? I put so Iaa doesn’t evaporate and contaminate the other dishes/ would alter its concerntration therefore conc not controlled but wasn’t sure

I got 48 percent

It gave you the total number of length of bases not just total number of bases present did it not ?

Slower rate of impulse transmission so delay between stimulus detected by receptors in the carotid artery and muscle contraction as neurones cannot carry out saltatory conduction so transmission from medulla to SAN slower - therefore heart muscle tissue contracts after a delay (irregular)

Yes you had to divide the total number of kilo bases by two to get the number of base pairs

How does the myelin seath being damaged effect rhythms of the heart tho. Wording on this question is gonna be awful in the mark scheme

I put so it wouldn't evaporate so IAA conc the same in each dish

I also got 48%. I think the question told you the percentage of Grey body was 64%. That percentage included GG or Gg.
I did 1-0.64 = 0.36 - So 36% must be black body, gg.
Square root of 0.36 = 0.6.
1 - 0.6 = 0.4 ( Since 1 = p + q )
The question asked for heterozygous - 2*p*q
2 * 0.6 * 0.4 = 0.48 = 48%

No but it gave u the total number of bases not base pairs so u had to divide by two

0.64 is dominant homozygous and hetrozygous (if you have 1 dominant allele, it will still be expressed) so:
p^2+2pq=0.64.
q^2= 0.36 (1-0.64)
q= 0.6 (sqrt 0.36)
p= 0.4 (1-0.6)
2pq = 2*0.4*0.6= 0.48
=48%

Base pairs are horizontal to each other not above/below so you did not have to divide by two as the base pairs did not affect length

Myelinated neurones don’t do saltatory conduction?

Anyone get 1.62 micrometres for the length of the glucagon dna question? It said 10 base pairs so its 20 bases which is what I did, let me know

0.608 for Rf Value
177...something kJ for the bottom part of q1/2
48% for Hardy Weinberg

Ah was so confused some people put about bacteria but idk how that would affect it evaporation seemed like the only logical thing