Lec 14-3 Flashcards
Sex can regulate
Autosomal gene
expression
genes located in cytoplasm
Characteristics regulated by maternal genotypes
Sex-influenced characteristics
Traits regulated by autosomal genes and mendelian inheritance
but
trait is more readily expressed in one sex
In other words
Sex influenced traits have higher penetrance in one sex
Goat beards
Autosomal but more strongly expressed in males
Sex-limited characteristics
Traits that are regulated by autosomal genes and only expressed in one sex
Example of sex-limited characteristics
Cock feathering for domestic chickens
hh cock feather is only in males
Male-limited precocious puberty
Males undergoing puberty at a very early age
example of a sex-limited characteristic
Sex-limited characteristics can be
Inherited from either parent but only expressed in one sex
Nuclear genes
Regulate characteristics
Humans have about 20k genes
Mitochondrial genes
Can regulate important characteristics
Only 37 genes in humans
Mendelian genetics (principles of segregation and assortment) are based on the assumption that
genes are located on chromosomes in the nucleus
Traits that are encoded in mitochondrial genome exhibit
Cytoplasmic inheritance
Cytoplasmically inherited traits are present in both
Males and females
Only passed from mothers to children
Reciprocal crosses give different results when cytoplasmic genes are used
Cytoplasmically determined traits display extensive
phenotypic
variation
Cytoplasmic inheritance
Four-o clocks
Flowering plants that display cytoplasmic inheritance
Some strains have branches that are
different across the plant.
- some branches all green
- some branches all white
- some branches are variegated
(mottled pattern)
green leaves have only wild-type
White have only mutant
variated have both
Mitochondrial diseases
Number of rare human diseases involve cytoplasmic inheritance
These diseases are the result of mutations in mitochondrial DNA
LHON
People with this have rapid loss of vision in early adulthood
Mitochondrial disease
Arthur Boycott
Tried to study snail chirality using mendelian principles of heredity
Found that right handed snail was dominant, but this was not due to the genotype of the individual rather than the individual’s mother
Arthur Boycott found
The genetic maternal effect
Genetic maternal effect
Phenotype is determined by the genotype of the mother
is NOT cytoplasmic inheritance
Genomic imprinting
Differential expression of genetic material depending on whether it is inherited from the male or female
Igf2 (insulin-like growth factor) example
progeny receive Igf2 from both parents
maternal is silenced, thus progeny can have only one copy which can lead to low fetal size and growth
Genomic imprinting involves
Methylation of the DNA/genes (addition of methyl CH3 group)
Genomic imprinting is a type of
epigenetics- some traits are determined by modifications to DNA or chromatin (like DNA methylation)
