Bird Genetics Phenotype Vs

Bird Genetics – Phenotype vs. Genotype and Competitive foraging

Students will work in pairs and produce two eggs, which will (hopefully) mature to produce healthy and eventually reproductive young birds. Each student will be a surrogate bird parent. The rare long-billed crested flycatcher. Surrogate parents need not actually be of opposite sexes, but one must play the role of mother (double X chromosome) and the other must play the role of father (XY chromosome). The chromosomes will be separated according to Mendel’s law of independent assortment. The genetic codes that are passed on to the babies will be recorded on the following pages. The surrogate parents must then decode the genes (genotype) inherited by their offspring to determine the phenotype traits of their baby.

Biology of the long-billed crested flycatcher This rare species is found in the high desert of southeast Idaho. Plumage may be either blue or black. Males are typically slightly larger then females. Both sexes will produce a yellow crest on their heads. Males that have a crest are able to attract a mate, while males without a crest are unable to attract a mate. Females with and without crests are able to mate. Although this species will feed on nuts and seeds, they appear to prefer Teddy Grahams, which can be found in abundance in SE Idaho. This species will cache its food cooperatively in underground bins (simulated here with coffee cans). Unfortunately, this species may cache them awfully deep. Individuals with short beaks, a recessive trait, are sometimes unable to reach to the bottom of the cache, and often die of starvation. Nature can be brutal!

Procedure

1. Choose a partner carefully. The lab must be completed on time.

2. Each partner must pick up four Popsicle sticks -- one of each color of autosome, and one sex chromosome stick. Each side of a stick represents a chromosome, and the two sides together represent a pair of homologous chromosomes.

3. For each color autosome and then for the sex chromosomes, each parent will randomly drop his or her stick on the table. The side of the stick that is up represents the allele that is passed on to the baby.

4. The alleles from each pair of homologous chromosomes will be recorded in the data sheet.

5. The decoding chart below indicates the phenotypic effect of each gene. The trait produced by each pair of alleles should be recorded in Generation One on the data chart. Remember that a CAPITAL letter is dominant over a small letter [recessive]. Each group will produce two offspring! You must do steps 3-5 twice! You will get two different results for two different offspring. Each individual should record their results in Generation One. 6. Once your offspring are produced, each parent will then take on the role of one child. Take a piece of paper and write your phenotype and corresponding genotype in large letters so the rest of the class can see, and tape it to the front of your shirt. Come to the front of the room so I can record your genotype on the graph.

7. Now it’s time to see how brutal nature can actually be. Your food has been cooperatively cached in three separate caches (simulated here with coffee cans). In order to pack on enough fat to survive migration, each bird must obtain (using only your beak!) at least 20 teddy grahams and return them to your nest site (simulated here with your paper cup). You have 5 minutes to complete this task. We will do this as a class and I will time you all, to ensure fairness. If you do not have enough food, you die. You are out of the competition. If you survive, you get a chance at reproduction. You may not steal from other people’s nest sites. You may only take food from the cache.

8. If you have the appropriate phenotype, you now have a chance to breed and produce another clutch (2 eggs). You have 30 seconds to find a mate. If you do not find a mate in that time, or all the potential mates are taken, you are unable to reproduce, and (effectively) die because you cannot pass your genes onto the next generation.

9. Those that are still in the competition get to repeat steps 2-8. This time, you will record your results in Generation Two. Upon completion, we will examine the genotypic and phenotypic composition of the population.

Questions

1. What was the phenotype of your offspring? How does genotype affect phenotype over time?

2. How did the phenotype of the population change from the first generation to the second generation?

3. How successful were your offspring? Were they able to compete in foraging? Were they able to reproduce the following spring?

4. If we did this for many generations, what might we expect our population to look like (phenotype) and be composed of genetically (genotype)? Decoding of genes

Chromosome Dominant Gene Recessive Gene

Blue autosome A. Long bill a. short bill

Red autosome B. Yellow crest b. no crest

Green autosome C. Blue body feathers c. black body feathers

X chromosome XX – female

Y chromosome XY – male

Generation 1

Genotypes Alleles in

Autosome color Mother Father Egg Sperm TRAIT - Phenotype of baby

Blue Aa Aa

Red Bb Bb

Green Cc Cc

Sex XX XY

Generation 2

Genotypes Alleles in

Autosome color Mother Father Egg Sperm TRAIT - Phenotype of baby

Sex Monitoring Phenotype and Genotype over Generations

Generation 1 Generation 2 Phenotype Total # of individuals AA Long bill Aa Long bill aa Short bill BB Yellow crest Bb Yellow crest bb No crest CC Blue body feathers Cc Blue body feathers cc Black body feathers XX Females XY Males