Genetic mapping

linked genes

genes that reside on the same chromosome and do not assort independently

phenotype for y m w

mutant and yellow body, white eyes, miniature wings

phenotype for y+ w+ m+

light brown body color, red eyes, and normal wing wings

Wing size for normal and miniature wings

Normal (+) - extends about 1/3 of abdomen length past abdomen tip

Miniature - extends to tip of abdomen

meconium

Newly emerged flies of both sexes have a dark spot on the abdomen

traits of a freshly emerged fly

wrinkled wings, elongated body, and lighter pigmentation

life cycle day 1

egg, first instar, second instar, third instar l

life cycle day 5

Pupa

Life cycle day 8-11

Adults

what types of cells are Sordaria

Haploid cells formed by meiosis and undergo mitosis

ascus

Meiosis and mitosis that occurs in a sack

Order of ascospores in ascus

reflects the positions of chromosomes in meiosis

• Chromosomes that move toward the “north pole” of the spindle are closer to the top of the ascus

Perithecium

is a reproductive structure found in sordaria and job is to produce and release spores for reproduction

is 4:4 recombinant or nonrecombinant

nonrecombinant because crossing over doesn’t occur

mutation

heritable genetic change that can happen spontaneously and by induced by a mutagen

Mutagen

any environmental agent that increases the rate of mutations

Direct acting mutagen

react directly with DNA to produce base changes

Indirect-acting mutagen

are not themselves muragens, but are converted during metabolism in the liver to chmicals that are mutagens

carcinogens

agents that induce cancer in animals

frameshift mutation

insertion or deletion of one or more nucleotides and changes the reading frame of the gene

• so every codon after the mutation is read incorrectly

Base pair substitution Mutation

Only changes one base, usually less severe than frameshift,

Ames test

used to evaluate the potential of chemicals or radiation to cause mutations

deamination

removal of an amino group from a base in DNA

• Alters base-pairing rules → causes point mutations

• Base substitution (transition mutation)

intercalates

• molecules that insert between stacked dna base pairs

• Distorts the DNA helix

• Frameshift mutations