Chapter 6: Extranuclear Inheritance, Imprinting, and Maternal Effect Flashcards
Simple Mendelian Inheritance describes inheritance patterns that obey
The Law of Segreagtion
The Law of Independent Assortment
Genes are passed _______ from generation to generation ( except for rare mutations)
unaltered
Expression of the genes __ ____ __________ directly influence their traits
in the offspring
Extranuclear Inheritance
genes not in the nucleus
Nuclear genes
located on a chromosome in the nucleus
Extranuclear Inheritance
(AKA cytoplasmic inheritance)
traits are not inherited through genes that are in the nucleus, but are in other organelles.
The two most important examples of Extranuclear are genes in the
Mitochondria and Chloroplasts.
The genome of both mitochondria and chloroplasts is composed of a
single circular double-stranded chromosome (DNA)
Chromosomes of mitochondria and chloroplasts are found in
Nucleoids
Maternal Inheritance
Extranucelear. Mitochondrial DNA comes only from the mother. (mtDNA)
Paternal leakage
mitochondria provided through the sperm. rare
Human Mitochondrial Disease
two mechanisms:
- Transmitted from mother to offspring via the egg.
- Mutations can occur in somatic cells during aging.
Symptoms of mitochondrial disease depend on
the ratio of mutant to normal mitochondria
The endosymbiosis theory
mitochondria and chloroplasts originated from bacteria that took up residence within a primordial cell.
Chloroplast originated from
cyanobacterium
Mitochondria originated from
gram-negative nonsulfur purple bacteria
Epigenetic inheritance
modification to a gene that changes gene expression, but is not permanent over the course of generation.
Epigenetic inheritance may permanently effect
the life of an individual
epigenetic inheritance has
no change in the DNA sequence itself
__________ changes may be inherited, but may not follow Mendelian inheritance
Epigenetic
DNA and Chromosomal modifications can occur during ___________ or early ___________ ____________
Gametogenesis, embryonic development
Two examples of epigenetic inheritance
- X-chromosome inactivation
- genomic imprinting
Genomic imprinting
modification occurs to a nuclear gene that alters gene expression but is not permanent over many generations.
Expression of a gene depends on
if it is inherited from the male or female parent
Phenotypes controlled by imprinted genes have a
non-Mendelian pattern of inheritance
Monoallelic expression
offspring expresses either the maternally or paternally inherited phenotype.
Stages of Imprinting
- Establishment
- Maintenance
- Earasure and re-establishment
Establishment
of the imprint during gametogenesis
maintenance
of the imprint during embryogenesis and in the adult somatic cells
erasure and re-establishment
of the imprint in the germ cell
Genomic imprinting is permanent in the somatic cells of one animal but …
it can be altered from one gen. to another.
Genomic imprinting occurs in several species including
mammals
insects
plants
Genomic imprinting may involve
a single gene
a part of a chromosome
an entire chromosome
all chromosomes from one parent
Methylation of DNA bases is part of
genomic imprinting
Imprinting Control Regions (ICRs) are
*located near the imprinted genes
*methylated either in the oocyte or sperm but not both.
* contain transcription factor binding sites
Maternal Effect
a phenotype is determined by the mother’s genotype.
The Non-Mendelian inheritance pattern of maternal effect genes can be explained by the
Process of Oogenesis
