Unit One Review #4 KEY

The following data was collected from a representative sample of a larger population: In this population of wild hamsters there is a gene for tail length. For this gene there are two alleles "L" is dominant for "long tailed"; while "l" is recessive for "short tailed". 25 Hamsters are trapped and their DNA is taken back to the lab, after running DNA fingerprinting (Gel Electrophoresis) each hamsters genotype was determined. Use the data below to answer the rest of question #1.

Ll / ll / ll / Ll / Ll
ll / ll / ll / Ll / Ll
Ll / Ll / Ll / Ll / ll
Ll / Ll / ll / ll / Ll
ll / ll / ll / LL / Ll

1. A) 15/50 alleles are "L" = 30%

35/50 alleles are "l" = 70%

B) 13/25 hamsters are "Ll" = 52%

1/25 hamsters are "LL" = 4%

11/25 hamsters are "ll" = 44%

C) 14/25 Hamsters are Long Tailed = 56%

11/25 Hamsters are Short Tailed = 44%

2. If a Heterozygous Long-tailed hamster "Ll" mates with a Short-Tailed hamster "ll"

X / L / l
l / Ll / ll
l / Ll / ll

The Genotypic Ratio = 50% Ll : 50% ll

3. Genetic Equilibrium

4. The five conditions or requirements necessary to keep a gene pool in Genetic Equilibrium are:

·  Large Population

·  Random Mating

·  No new Mutations

·  No Differential Migration

·  Equal Viability (Fertility, Life Span etc)

5. The key things that cause gene pools to evolve are:

Natural Selection, Mutation, Genetic Drift, Differential Migration, Selective Mating, Isolation- Bottle Neck Effect

6. The Hardy Weinberg Principle states that:

That if all factors/conditions stay constant that the gene pool for a population will have the same composition from one generation to the next. Genetic Equilibrium will take place.

7. Selective Mating

8. In reality, alleles that code for favoured traits usually see an increase in their frequency.

9. If we have 25 hamsters and the allelic frequency for the gene is 0.30 (30%) “L” and 0.70 (70%) “l”. But with some differential migration this can change very quickly; imagine that 10 hamsters leave EMIGRATE (5 short and 5 long) and 10 other hamsters IMMIGRATE in (but 9 out of 10 are long-tailed). The new gene pool's allelic frequencies may now be change so that “L” goes from 30% à42% and "l" goes from 70% down to 58%.

10.  ISOLATION – “FOUNDER Effect” – Bottle Necking.

11.  Natural selection increases the frequency of the favoured allele (dominant or recessive) and it lowers the frequency of the less desirable allele (dominant or recessive)

12.  Most mutations that arise are not ADVANTAGEOUS, because over millions of years of evolution most of the best fit (advantageous) alleles have already been selected and established.

13.  Random Genetic Drift is a process that drives evolution. It occurs when allelic frequencies for a gene just change by chance, no natural selection is involved.

14.  We saw that it shifted so that the frequency of “H” went up to around 0.58 (58%) while the frequency for “h” went down to 0.42 (42%) in one generation. In a small population of three students, the frequencies changed to”H” = 0.25 and “h” 0.75 in one generation.

15.  The big three drivers of evolution are :

A) Mutation

B) Genetic Drift and

C) Natural Selection

16.  GENE POOL “A common group of genes shared by the members of a population”