GENETICS 2

Who first observed lampbrush chromosomes?

• a) Balbiani

• b) Painter

• c) Flemming

• d) Morgan

Polytene chromosomes are found in:

• a) Salamander oocytes

• b) Drosophila salivary glands

• c) Human somatic cells

• d) Barr bodies

Which stage of meiosis shows lampbrush chromosomes?

• a) Pachytene

• b) Diplotene

• c) Zygotene

• d) Anaphase

True or False

• Heterochromatin is transcriptionally active.

• TRUE

• FALSE

Incomplete linkage produces recombinants

• TRUE

• FALSE

Polytene chromosomes show puffing due to RNA synthesis.

• TRUE

• FALSE

Crossing over occurs during prophase I.

• TRUE

• FALSE

A Drosophila geneticist observes the following offspring from a three-point test cross:

• Parental: 400, 390

• Single crossovers (A-B): 60, 55

• Single crossovers (B-C): 50, 45

• Double crossovers: 5, 5
  Tasks:

• Determine the gene order.

• Calculate recombination frequencies.

• Compute coefficient of coincidence and interference.

Two linked genes show 5% recombination frequency. If you perform a test cross, what proportion of offspring will be recombinant? Why?

A geneticist finds that two traits in maize always co-segregate with a frequency of 99%. What does this imply about linkage? Suggest an experiment to confirm.