Genetics Chapter 6 Flashcards
Extranuclear Inheritance
Traits are inherited through genes that are not in the nucleus, but are in other organelles
Ex: mitochondria and chloroplast
Maternal Inheritance
A form of inheritance wherein the traits of the offspring are maternal in origin due to the expression of extranuclear DNA present in the ovum during fertilization (Inherited from mother)
Pigmentation of a flower solely depends on the MOTHER’S PHENOTYPE
Parental pigmentation has NO EFFECT on the phenotype
Mitochondria provided through the sperm
Maternal Effect Inheritance
Only the genotype of the mother controls phenotype of offspring and is based on oogenesis
Genotype of father has no effect
Genotype of offspring has no effect
Controlled by nuclear genes
Phenomenon is due to the donation of gene products that the mother provides to her developing eggs
Explained by a process of oogenesis
Maturing animal oocytes are surrounded by maternal cells that provide them with nutrients
These nurse cells are diploid, whereas the oocyte becomes haploid
Chloroplast genomes
found in nucleoids
Circular chromosomes
The nucleoid may contain many copies of the one chromosome
There may also be multiple nucleoids
The main function of chloroplasts is photosynthesis
The genetic material in chloroplasts is cpDNA
Chloroplast Inheritance
Has maternal inheritance
The organelles are inherited only through the egg cytoplasm
Sperm do not transmit chloroplasts however, there are exceptions to this rule
Gymnosperms have paternal inheritance
Some angiosperms have biparental inheritance
Mitochondria genomes
The main function of mitochondria is oxidative phosphorylation to produce ATP
Single circular chromosome
Contained within the nucleoid
The genetic material in mitochondria is referred to as mtDNA
Mitochondrial inheritance mechanism depends on species
Human mitochondrial diseases and two mechanisms of mitochondrial disease
1.Transmitted from mother to offspring via the egg
Follow a strict maternal inheritance pattern
2. Mutations can occur in somatic cells during aging
Mitochondria are especially susceptible to DNA damage from free radicals
Typically, chronic degenerative disorders affecting cells that need high levels of ATP (Nerve and muscle cells)
Methylenetetrahydrofolate reductase (MTHFR)
Endosymbiosis theory
Mitochondria and chloroplasts originated from bacteria that took up residence within a primordial eukaryotic cell
Chloroplasts originated from cyanobacteria
Mitochondria originated from Gram-negative nonsulfur purple bacteria
Endosymbiosis theory is supported by several observations
Organelles have circular chromosomes (like bacteria)
Organelle genes are more similar to bacterial genes than to those found within the nucleus
During the evolution of mitochondria and chloroplasts, most genes have been lost or transferred to the nucleus
MZT: maternal to zygotic transition
Maternal effect genes important in early embryogenesis
Regulated by a protein in the oocyte or mRNA
Example - cell division, cleavage pattern, body axis
Accumulation of maternal proteins before fertilization allows development to proceed very quickly after fertilization
Concordance
degree to which a disease is inherited, should be higher in identical twins
Locus heterogeneity
when mutations in different genes cause the same disease
Autosomal recessive disease
cystic fibrosis
Autosomal dominant disease
huntington’s disease
X-linked recessive disease
hemophilia (problems with blood clotting
“the royal disease”
X-linked Dominant disease
vitamin D deficiency with rickets
Inheritance patterns that arise from maternal effect break which rule of Mendelian inheritance?
the law where expression of genes in the offspring directly influences their traits
Which statements are true for genes that follow a Mendelian inheritance pattern?
The genes are passed unaltered from generation to generation.
The genes obey the law of segregation.
The genes assort independently.
Expression of genes in the offspring directly influences their traits.
Inheritance patterns that arise from epigenetic inheritance break which rule of Mendelian inheritance?
the law in which genes are passed unaltered from generation to generation
Which statements regarding the nucleoid structure of chloroplasts are true?
The genome consists of double-stranded DNA.
There may be more than one nucleoid per organelle.
There may be more than one chromosome in the nucleoid.
The genome is circular.
Inheritance patterns that arise because genetic material is not located in the cell nucleus break which rule of Mendelian inheritance?
the law of segregation
Which of these statements are true for chloroplast genes and proteins?
A typical chloroplast genome is about 100,000 to 200,000 bp in length.
Many chloroplast proteins are encoded by nuclear genes.
The type of inheritance that occurs because extranuclear genes are inherited through the cytoplasm of an egg is called
maternal
The mitochondrial DNA encodes ______ polypeptides that are important for oxidative phosphorylation, and these are ______ of the proteins involved in that process.
13
some
Two kinds of gametes are made such that the distribution of cytoplasmic organelles is unequal in the two gamete types, and organelles are often inherited from one parent, in ——- species.
heterogamous
