Lab 5. Overview Instructor collects lab.4 write up and

checks pre-labs. in lab notebook Discussion of graded plant species

richness write up. Basic Genetics Overview. Microevolutionary Processes Overview. Evolution simulation Complete and turn in in-class exercise Simulation discussion & questions

(discuss graphs & exercise due in Lab 6) C-fern and Arabidopsis culturing exercise

Genetics Overview Genes (DNA) in cells direct cell activities. Most cells have TWO copies of every kind of

gene. One copy from each parent. (DIPLOID) Sperm or egg have ONE copy of every kind of

gene. (HAPLOID)

The same gene can have different forms (Alleles, abbreviated e.g., B or b).

Dominant alleles affect the physical characteristics in any individuals with the allele. (capital, B)

Recessive alleles affect the physical characteristics ONLY in individuals with 2 copies of the allele. (lowercase, b)

Individual w/ same 2 alleles = homozygote. (e.g., bb or BB)

Individual w/ 2 diff. alleles = heterozygote. (e.g., Bb)

Genetics Overview

Genotype & Allele FrequenciesGenotype Frequency – Answers “What

proportion (percent) of individuals in this population has this genotype”?

e.g., The frequency of Aa in the pop. is 0.25 .

– See Appendix in lab manual.

Allele Frequency – Answers “What proportion (percent) of all alleles in this population is this specific allele”? e.g., The frequency of a in the pop. is 0.5 .

– See Appendix in lab manual.

Allele Frequency

12 beetles (individuals)2 alleles per beetle = 24 alleles

17 green alleles7 tan alleles

17 24 = 0.708 = green allele frequency

7 24 = 0.292 = tan allele frequency

Microevolutionary Processes Mutation = new random genetic variation (new

alleles). Change in the DNA (in a sex cell).

Genetic Drift = change in the genotype or allele freq. of a (small) pop. due to chance.

Natural Selection = differential reproduction (survival) if individuals due to the effect of particular genotypes in an environment.

Gene Flow = change in genotype or allele freq. in a population due to movement of individuals or gametes between populations

Non-Random MatingInbreeding = increases homozygosity in pop.Outbreeding = increases heterozygosity in pop.

Microevolutionary Processes

Over time… mutation increases variation (makes new

alleles). genetic drift and natural selection usually

decrease variation (lose alleles/fixation). gene flow and non-random mating

usually redistribute variation (maintaining or decrease).

Simulation Reminders Remember you are a hermaphrodite in this

simulation. (Lucky you.)

You and a partner create two offspring,

you both “die,” and

then you both become the two offspring (1 each).

You will always have only one genotype.

Don’t be a lazy mate. Move around to mate randomly.

You only need to flip the coin to determine which allele to give if you are heterozygous.

Figure. Hypothetical graphical example of the allele frequency of allele A in a population over 1000 generations.

[A graph example for review after simulation data are tallied.]

Reminders for the Lab READ the instructions () in the manual For culturing Ceratopteris spores be certain

to maintain a sterile work environment. Fungal spore contamination can be a problem.

Be careful with the Bunsen burners and open flames. Do not set yourself on fire.

Do not roast the spreaders in the flame.

Do not put a hot spreader into the alcohol beaker.

Spread samples on the medium, not on the lid.