Chapter 15: Chromosomal Basis of Inheritance Flashcards
Morgan’s explanation for incomplete linkage
Cross over of homologous chromosomes
genomic imprinting
when certain genes are silenced depending on which parent they came from
may result from adding a CH3 to cysteine nucleotides
duplication
1 of 4 types of chromosome alterations
when a chromosomal segment gets duplicated
Centimorgan
the distance between genes
represents 1% recombination frequency
the farther apart they are, the more likely there will be a cross over between them
aka map unit
Wild type
The ‘normal’ phenotype for a trait
exp. red eye flies
Aneuploidy
When an offspring has an abnormal number of a particular chromosome because of mitotic nondisjunction.
exp. trisomy 21, Turner’s syndrome
4 types of chromosome alterations
- deletion
- duplication
- inversion
- translocation
Mutant
The alternative prototype to the wild type
exp. white eyed flies
Expression of recessive x-linked genes (likelihood)
More likely in XY offspring because they don’t have another X to cancel out the first X
exp. color blindness and hemophilia
Incomplete linkage
The idea that genes can be linked even if some recombinant phenotypes are observed
Barr body
what female mammals’ second X chromosome shrivels up into as it inactivates
inversion
1 of 4 types of chromosome alterations
when a segment of a chromosome gets reversed
Miscarriage
can occur in the event of dramatic errors/large scale chromosomal changes
exps. chromosome number or structure
Linked genes
Genes on the same chromosome that tend to be inherited together
Recombined type
when an offspring has new combinations of traits
aka recombinants
Mitotic Nondisjunction
when pairs of homologous sister chromatids do not separate properly
X Inactivation
when female mammals’ second X chromosome inactivates, and condenses into a barr body
Results in mosaic expression of whatever heterozygous genes are located her X
Linkage map
genetic map of a chromosome based on recombination frequencies
deletion
1 of 4 types of chromosome alterations
when a chromosomal segments gets deleted. bad news bears.
Map units
the distance between genes
represents 1% recombination frequency
the farther apart they are, the more likely there will be a cross over between them
aka centimorgan
Parental type
when an offspring’s phenotype matches on of their parients’
Pure breed/true breed
Homozygous
translocation
1 of 4 types of chromosome alterations
when a segment of a chromosome gets moved to a non homologous chromosome
Sex linked genes
Gene located on a sex chromosome (i.e. X-linked gene and Y-linked gene)
Have unique patterns (like expressing traits unrelated to sex; different from independent assortment)
