Ch 15 Flashcards
Thomas Hunt Morgan
20th century embryologist at Columbia whose evidence supported Mendelism and the chromosome
What organism did Morgan choose?
fruit fly/ Drosophila
What made the fruit fly vital to genetics?
Prolific mating
Only 4 chromosomes
eye color variant
Morgan’s system of nomenclature
Symbol of mutant is the gene symbol and superscript + for wild type
XY
male
XX
female
XO
XX for female XO for male
Ex: many insects
ZW haplodiploidy
female = fertilized and diploid, male = unfertilized and haploid (no father)
Inheritance of x-linked genes
Mothers pass an x to all offspring, 50% chance which one. Fathers pass the one x to all daughters only. For a recessive trait, female must be homozygous recessive and male must be hemizygous
What happens when an organism has more than one of a sex chromosome?
inactivation
Barr body
condensed form of an inactive x that lies along the inside of nuclear envelopes
mosaicism
half of cells will express one X and half of cells will express the other. This allows for calico cats.
Linked genes
located near each other so tend to be inherited together
Linked genes break the law of…
independent assortment
genetic recombination
production of offspring with combos of traits different from parents
parental types
match either parent phenotype
recombinants
new combos
crossing over
recombines linked genes or genes on same chromosome
genetic map
ordered list of genetic loci on chromsome
linkage map
genetic map based on recombination frequencies
map unit
1% recombination frequency
max map units
50
nondisjunction
failure of homologous chromosomes or sister chromatids to separate
aneuploidy
abnormal number of a particular chromosome
monosomic
one chromosome missing
trisomic
one chromosome extra
polyploidy
more than 2 full sets of chromosomes
4n =
tetraploidy
Polyploidy is common in plants because
it makes them larger and more robust
What is Down syndrome?
trisomic for chromosome 21
deletion
chromosomal fragment lost
duplication
chromosomal fragment copied
inversion
fragment reattached to original chromosome backwards
translocation
fragment joins non homologous chromsomes
reciprocal translocation
non homologous chromosomes switch fragments
Klinefelter
XXY, sterile males
XYY
aneuploidy that makes men typically taller
Trisomy X/Triple X
XXX, taller females who are at risk for learning disabilities
Turner Syndrome
XO, sterile female
cri du chat chromosomal alteration
specific deletion of chromosome 5
chronic myelogenous leukemia chromosomal alteration
exchange of a large part of chromosome 22 with a small part of chromosome 9 in white blood cells
the CML alteration is an example of…
translocation
Philadelphia chromosome
the new shortened chromosome 22 in CML
genomic imprinting
variation on a phenotype depending on whether the allele is inherited from the male or female parent
