Warmup!

In your lab notebook, answer these questions in complete sentences.

What is a genotype?

What is a phenotype?

Genotype or Phenotype?

Genotype or Phenotype?

RR

Genotype or Phenotype?

DdRr

Genotype or Phenotype?

WHY FRUIT FLIES ARE SO AMAZING

An Intro to One of the Most Important Organism in Genetics

History(second to E. coli)

Meet Drosophila melanogaster

Drosophila is a Model Organism

Breeds quickly Easy to take care of Can be handled easily Shows clear phenotypes

What for?

By pairing males and females of selected phenotypes, genotypes can be determined.

Genes can be mapped!

Studied with fruit flies

Thomas Hunt Morgan described 61 mutations in his 1925 book, The Genetics of Drosophila.

48,981 articles about fruit flies, since 1905

Genetics, biochemistry, cell biology, developmental biology, evolutionary biology, ecology, zoology, toxicology, neuroscience

Source: Michan et al. (2010)

Increased Understanding of Ourselves

Alzheimer’s disease, drug effects, metabolism, radiation effects

Most mutations produce weaknesses as observed in the lab, in such ways as body morphology, shortened life span, sterility, or death.

Homeobox: master control genes that control the body plan; humans and flies have a similar code for determining front and back, up and down

Homologs

Some Drosophila genes have homologs (corresponding genes with similar structure and fuctions), in other animals, even vertebrates.

Some vertebrate genes when introduced into flies, do the job of the homologous fly gene.

It seems that there are more similarities among organisms than there are differences: universality.

Terms to Know

Wild type: the phenotypes typical of wild flies in the Northeastern U.S.

Mutant: any fly that isn’t wild type Mutation: a difference in the allele of wild

type

Drosophila Chromosomes:

4 homologous pairs of chromosomes: 2 pairs of large autosomes (non-sex

chromosomes) 1 pair of very small autosomes 1 pair of sex chromosomes. Females normally

have two X chromosomes; males have one X and one tiny Y chromosome.

A New Way to Write Genotypes

+ = wild type v = vestigial

+/+ would be homozygous wild type v/v would be homozygous vestigial +/v would be heterozygous

Meiosis

Practice distinguishing male and female

Crossing Flies

Now we can set up a cross. We'll start with wingless flies. Apterous (ap) is a recessive trait that results in flies with no wings. We will start by crossing a wingless female fly with a wild type male:

ap/ap x +/+

Terms for Crosses

P = parental generation, the parent flies we mate in the cross.F1 = the first generation of offspringF2 = the second generation. There can be an F3, F4, etc.Progeny = offspring, the children of the parents.

Testing Genetic Hypotheses

Predicting Genotypes and Phenotypes

P: ap / ap x + / +

How do we determine what the progeny will be?