Non Mendelian inheritance Flashcards
__________ cannot be predicted using genotype and mendel’s laws
- gene expression/inactivation patterns
- maternal effect
- extranuclear inheritance
phenotypes
many genes ______ follow mendelian inheritance patterns
dont
- involves nuclear genes, nDNA
- genotype of mother determines phenotype of offspring
- genotype of father has no effect on phenotype of offspring
maternal effect
info is being transferred from mother to offspring.
in what form is this info stored and transmitted?
maternal effect hypothesis
DNA, RNA, or proteins?
first example of maternal effect (____)
by _________ ________
-true breeding stains of spiraling
-sinistral left-handed ___________ -dextral right-handed ___________
1920s
arthur boycott
uncommon
common
expectation of reciprocal cross experiment…
if phenotype ratios different, maybe X-linked
but observed ratios dont follow x-linkage
F1: 1:1 righty:lefty
F2: all snails righty
F3: righty:lefty
forgoing ahead with F1 and F2 crosses
maternal nurse cell gene expression affects early embryogenesis
mechanism of maternal inheritance
early _________ ________ affected by nurse cell gene products
cleavage plane
maternal effect genes important in the
development of many species
modification occurs to alter gene expression
- gene or chromosome
- not permanent over generations
ex: gene is inactivated for lifetime of individual, but in offspring, gene can be activated
epigenetic inheritance
epigenetic and dosage compensation:
- offsets differences in the number of ____ __________
- end results: males and females exhibit similar levels of _____ __________ for a particular locus
- offspring don’t _______ gene expression level
sex chromosomes
gene expression
inherit
who discover dosage compensation .. year?
Herman Muller 1932
Herman Muller discovered difference in
expression of eye color btween sexes
dosage compensation in diff. animals:
_______ ________- XX: inactivate 1X chromosome
_______ _________- XX: inactivate paternally inherited X chromosome
______ _______- XY: double expression of genes on X chromosome
__________(C. elegans)- XX: cut expression of both X chromosomes by 1/2
placental mammals
marsupial mammals
fruit flies
nematodes
- X chromosomes are randomly inactivated
- inactivated X chromosome becomes Barr body
- coat color is X-linked
Lyon Hypothesis: inactivation of X chromosome in female mammals.
Mechanism of X inactivation in mammals:
X-inactivation center (XiC)
- located on __ ___________
-expression results in compaction of x chromosome into _______ ___
-XiC are _________
-if XiC are inactivated via mutation, both X chromosome are ________
lethal condition in female embryos
x chromosome
barr body
counted
expressed
_______ gene controls bar body formation
-produces RNA that coats the X chromosome
RNA interacts with _________ that compact the chromosome
Xist
proteins
______ gene helps prevent inactivation
-expressed by activated X chromosome
Tsix
- x chromosome controlling element
- affects inactivation of x chromosome
- mechanism not well understood
Xce region
phases of X inactivation:
____________- x inactivation centers (Xics) are counted
____________- Xist is activated
___________- barr bodies maintained through mitotic cell divisions
initiation
spreading
maintenance
- occurs prior to fertilization
- DNA is marked (mark is inherited, involved in identification of maternally and paternally inherited DNA, only one of the two alleles is expressed)
- determines whether offspring express maternal of paternal inherited allele.
genomic imprinting
genomic imprinting of mouse growth factor igf2
-only __________ inherited allele is expressed
paternally
cellular level of imprinting during gametogenesis
establishment
