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PanI is a gene in cod fish that codes for an integral membrane protein called pantophysin. Two alleles of the gene, $\operatorname{PanI}{ }^{\mathrm{A}}$ and $\operatorname{PanI}{ }^{\mathrm{B}}$ , code for versions of pantophysin, that differ by four amino acids in one region of the protein. Samples of cod fish were collected from 23 locations in the north Atlantic and were tested to find the proportions of PanI ${ }^{\mathrm{A}}$ and PanI ${ }^{\mathrm{B}}$ alleles in each population. The results are shown in pie charts, numbered 1-23, on the map below. The proportions of alleles in a population are called the allele frequencies. The frequency of an allele can vary from 0.0 to 1.0 . The light grey sectors of the pie charts show the allele frequency of PanI ${ }^{\mathrm{A}}$ and the black sectors show the allele frequency of PanI ${ }^{\mathrm{B}}$ .

Figure for Question D4.1.10 (HL)—Allele frequencies question 1 — IB Biology HL

(a)

State the two populations with the highest $\operatorname{PanI}^{\mathrm{B}}$ allele frequencies.

[ 1 ]

(b)

State the population in which the allele frequencies were closest to 0.5 .

[ 1 ]

(c)

Deduce the allele frequencies of a population in which half of the cod fish had the genotype $\operatorname{PanI} \mathrm{I}^{\mathrm{A}} \operatorname{PanI} \mathrm{I}^{\mathrm{A}}$ , and half had the genotype $\operatorname{PanI} \mathrm{I}^{\mathrm{A}} \operatorname{PanI} \mathrm{I}^{\mathrm{B}}$ .

[ 1 ]

$P a n \mathrm{I}^{\mathrm{A}} 0.75$ and $P a n \mathrm{I}^{\mathrm{B}} 0.25 / 3 P a n \mathrm{I}^{\mathrm{A}}$ to $1 P a n \mathrm{I}^{\mathrm{B}}$

Both must be correct for the mark to be awarded, accept frequencies in form of ratio.

(d)

The graphs below show the latitude and the mean surface sea temperature in June of the sampling locations and the frequency of the $PanI^{A}$ allele.

State the relationship between
(i) latitude and the frequency of the $PanI^{A}$ allele. [1]
(ii) mean surface sea temperature in June and the frequency of the $PanI^{A}$ allele. [1]

$Graphs showing latitude, June mean surface sea temperature and $PanI^{A}$ allele frequency.$

Graphs showing latitude, June mean surface sea temperature and $PanI^{A}$ allele frequency.

[ 2 ]

(i) The frequency of $PanI^{A}$ is greatest at the lowest latitudes, drops rapidly at about 60–65° latitude, and is lowest at the highest latitudes.

(ii) The frequency of $PanI^{A}$ is lowest at the lowest temperatures, increases rapidly at about 8–10 °C, and is highest at the warmest temperatures.

(i)

Using the graphs, state the relationship between latitude and the frequency of the $\operatorname{PanI}^{\mathrm{A}}$ allele.

[ 1 ]

greatest/great frequencies of $\operatorname{PanI}^{\mathrm{A}}$ at lowest/low latitudes / a rapid drop in frequency at (60-65 degrees latitude) / lowest/low frequencies at highest/high latitudes

Answers which describe/imply the correct step-wise relationship should get credit. Answers stating or implying a negative correlation alone should not get credit.

(ii)

Using the graphs, state the relationship between mean surface sea temperature in June and the frequency of the $\operatorname{PanI}^{\mathrm{A}}$ allele.

[ 1 ]

lowest/low frequencies of $\operatorname{PanI}^{\mathrm{A}}$ at lowest/low temperatures / a rapid increase in frequency at ( 8-10 degrees Celsius) / highest/high frequencies at warmest/warm temperatures Answers which describe/imply the correct step-wise relationship should get credit. Answers stating or implying a negative correlation alone should not get credit.

IB Biology HL D4.1.10 Hl Allele Frequencies Topic Practice

D4.1.10 (HL)—Allele frequencies question 1

Question (a)

Question (b)

Question (c)

Question (d)

Question (i)

Question (ii)