Some isotopes, however, decay slowly, and several of these are used as geologic clocks. Dating rocks by these radioactive timekeepers is simple in theory, but the laboratory procedures are complex. <span>All methods rely on the fact that certain elements (particularly uranium and potassium) contain a number of different isotopes whose half-life is exactly known and therefore the relative concentrations of these isotopes within a rock or mineral can measure the age.</span>
Answer: 4 Guanines
Explanation: Following Chargaff's ratio that describes the ration of purines to pyrimidines as 1:1, if there are 23 purines, it follows that there should be 23 pyrimidines; 15 Thymines should therefore be hydrogen bonded to 15 Adenines by complementary base pairing.
We are then left with 8 nucleotides composed of guanines and cytosines in complementary base pairs. This means that half that number (4) should be guanines and the rest cytosines.
Going down A-D
Going across is 1-4
A 4
B 3
C 1
D 2
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Answer:
1/8
Explanation:
An individual must have all three dominant alleles to be red, in homozygosis or heterozygosis (R_E_D_).
<u>The parental cross was:</u>
RREEDD x rreedd
F1: RrEeDd
<u>The test cross</u> is between the RrEeDd indiviudals and homozygous recessive rreedd.
The genes assort independently, so we can use Mendel's law of segregation to predict separately for each gene the proportion of the offspring that will have the dominant alleles.
<h3><u>Rr x rr</u></h3>
1/2 Rr
1/2 rr
<h3><u>Ee x ee</u></h3>
1/2 Ee
1/2 ee
<h3><u>Dd x dd</u></h3>
1/2 Dd
1/2 dd
Genes are independent, so the probability of having a R_E_D_ offpsring is calculated by multiplying the individual probabilities of having a dominant allele for each gene:
1/2 (Rr) × 1/2 (Ee) × 1/2 (Dd)= 1/8
