Chapter 5 - Non-Mendelian Inheritance Flashcards
What are four patterns of inheritance that deviate from the Mendelian pattern?
- Maternal effect; 2. Epigenetic inheritance; 3. Extranuclear inheritance; 4. Linkage
In this deviation from Mendelian genetics, the genotype of offspring does not directly govern the phenotype
Maternal effect
In this deviation from Mendelian genetics, genes are modified during gametogenesis or early embryonic development
Epigenetic inheritance
This deviation from Mendelian inheritance involves genes in organelles other than the nucleus (i.e. in mitochondria or chloroplasts)
Extranuclear inheritance
In this deviation from Mendelian inheritance, two or more genes are close to each other on the same chromosome
Linkage
The maternal effect on genes is due to the accumulation of these that the mother provides to her developing eggs
Gene products
This scientist first discovered the maternal effect in the 1920s
A. E. Boycott
What organism was A. E. Boycott studying when he discovered the maternal effect?
Water snail (Limnaea peregra)
What physical feature of water snails was A. E. Boycott studying when he discovered the maternal effect on genes?
Shell and internal organ coiling orientation
The maternal effect can be explained by this process
Oogenesis
In the maternal effect, maturing animal oocytes are surrounded by these that provide them with nutrients
Maternal cells (nurse cells)
Are maternal/nurse cells diploid or haploid?
Diploid
This type of inheritance refers to a pattern in which a modification occurs to a nuclear gene or chromosome that alters gene expression
Epigenetic inheritance
Is epigenetic inheritance expression changed over the course of many generations?
No
Is epigenetic inheritance reversible?
Yes
Does epigenetic inheritance change the DNA sequence?
No
The purpose of this is to offset differences in the number of active sex chromosomes
Dosage compensation
In 1949, these two scientists identified the Barr body, a highly condensed structure in the interphase nuclei of somatic cells in female cats but not in male cats
Murray Barr and Ewart Bertram
In 1960, this scientist correctly proposed that the Barr body is a highly condensed chromosome
Susumu Ohno
In 1961, this scientist proposed that dosage compensation in mammals occurs by the inactivation of a single X chromosome in females
Mary Lyon
This is another term for dosage compensation in mammals
Lyon hypothesis
This is the mechanism for dosage compensation in mammals
X-chromosome inactivation
Is X-chromosome inactivation passed along to all future somatic cells?
Yes
When inactivated X-chromosomes are replicated during cell division, do both copies remain compacted and inactive?
Yes
In 1963, these three scientists tested the Lyon hypothesis at the cellular level
Ronald Davidson, Harold Nitowsky and Barton Childs
How many X-chromosomes do mammalian cells allow to remain active?
1
Additional X-chromosomes are converted to these in mammalian cells
Barr bodies
How many Barr bodies does a cell with XXX have?
2
How many Barr bodies does a cell with X0 have?
0
What is the sex chromosome composition of a female with Turner syndrome?
X0
What is the sex chromosome composition of a female with Triple X syndrome?
XXX
What is the sex chromosome composition of a male with Klinefelter syndrome?
XXY
How many Barr bodies does a cell with XXY have?
1
Is the genetic control of X-chromosome inactivation entirely understood at the molecular interval?
No
This short region on the X chromosome plays a critical role in X-chromosome inactivation
X-inactivation center (Xic)
What are three functions of the Xic region during X-chromosome inactivation?
Nucleation, spreading, and maintenance of X-chromosome inactivation
This is the term for genes on the inactivated X-chromosome that are expressed in somatic cells of adult female mammals
Pseudoautosomal genes
How many X-linked genes in humans may escape full inactivation?
Up to 1/4
This is a phenomenon in which a segment of DNA is marked and the effect is maintained throughout the life of the organism inheriting the marked DNA
Genomic imprinting
This is the term for the genetic expression of offspring to express either the maternally-inherited or paternally-inherited allele in genomic imprinting
Monoallelic expression
Can offspring express both the maternal and paternal marked genes from genomic imprinting?
No
What are the three stages of genomic imprinting at the cellular level?
- Establishment of imprint during gametogensis; 2. Maintenance of imprint during embryogenesis and in adult somatic cells; 3. Erasure and reestablishment of imprint in germ cells
At the molecular level, the imprinting of several genes is known to involve this region, located near the imprinted gene
Imprinting control region (ICR)
Can the imprinting control region (ICR) be methylated in both the oocyte and the sperm?
No
The imprinting control region (ICR) contains these for one or more transcription factors that regulate the imprinted gene
Binding sites
For most genes, this causes inhibition of transcription
Methylation
This genomic imprinting syndrome is characterized by reduced motor function, obesity and small hands and feet
Prader-Willi syndrome (PWS)
Both Prader-Willi syndrome and Angelman syndrome involve a deletion in this chromosome
Chromosome 15
If a chromosome 15 deletion is inherited from the father, does it lead to Prader-Willi syndrome or to Angelman syndrome?
Prader-Willi syndrome
If a chromosome 15 deletion is inherited from the mother, does it lead to Prader-Willi or Angelman syndrome?
Angelman syndrome
Angelman syndrome results from the lack of expression this gene
UBE3A
Does Prader-Willi syndrome result from the lack of expression of only one gene?
No
This refers to inheritance patterns involving genetic material outside the nucleus
Extranuclear inheritance
What is another term for extranuclear inheritance?
Cytoplasmic inheritance
These two organelles are sources of genetic material in extranuclear inheritance
Mitochondria and chloroplasts
The genetic material of mitochondria and chloroplasts is located in this region
Nucleoid
How many chromosomes do mitochondria/chloroplasts have?
1
Can a mitochondrion/chloroplast contain several copies of its chromosome?
Yes
Can a mitochondrion/chloroplast contain only one nucleoid?
No
Which organelle tends to have more nucleoids, mitochondria or chloroplasts?
Chloroplasts
Do organelle genomes vary greatly among different species?
Yes
Mitochondrial genomes are fairly small in this group of organisms
Animals
Mitochondrial genomes are intermediate size in these two groups of organisms
Fungi and protists
Mitochondrial genomes are fairly large in this group of organisms
Plants
What is the main function of mitochondria?
Oxidative phosphorylation
Oxidative phosphorylation is a process used to generate this molecule
Adenosine triphosphate (ATP)
This molecule is the energy source that drives cellular reactions
ATP
This element is consumed during ATP synthesis
Oxygen
The human mitochondrial DNA consists of how many base pairs?
17,000
Are most mitochondrial proteins encoded by genes in the nucleus or in the mitochondria?
Nucleus
What is the main function of chloroplasts?
Photosynthesis
How many base pairs are in the chloroplast DNA of the tobacco plant?
156,000
This scientist discovered that pigmentation in Mirabilis jalapa (the four o’clock plant) shows a non-Mendelian pattern of inheritance
Carl Correns
Carl Correns discovered that four o’clock plants show this pattern of inheritance
Maternal inheritance
Is maternal inheritance the same as maternal effect?
No
In the four o’clock plant, maternal inheritance occurs because chloroplasts are only transmitted through this
Egg cytoplasm
A four o’clock plant that has inherited both white and green chloroplasts will display this phenotype
Variegated phenotype
This type of species produces two kinds of gametes (a large female gamete and a small male gamete)
Heterogamous
In heterogamous species, organelles are typically inherited from which parent?
Mother
In heterogamous species with maternal inheritance, is it impossible for paternal mitochondria to be passed through sperm?
No
What are two ways for human mitochondrial diseases to occur?
- Transfer from mother to offspring via egg cytoplasm; 2. Mitochondrial mutations in somatic cells
Human mitochondrial diseases strictly follow this type of inheritance
Maternal inheritance
Mitochondrial mutations may occur in these cells
Somatic cells
Do mitochondrial mutations reduce with age?
No
Are mitochondria very susceptible to DNA damage?
Yes
High oxygen consumption leads to these
Free radicals
Does mitochondrial DNA have extensive repair abilities?
No
How many mitochondrial diseases have been identified?
Over 200
Mitochondrial diseases are typically chronically degenerative and affect these two types of cells
Nerve and muscle cells
This mitochondrial disease results from a mutation in one of several mitochondrial genes that encode respiratory chain proteins, and tends to affect males more than females
Leber hereditary optic neuropathy
This mitochondrial disease results from a mutation in the ATPase6 gene that encodes a subunit of the mitochondrial ATP-synthetase, which is required for ATP synthesis
Neurogenic muscle weakness
These two mitochondrial diseases result from a mutation in a gene that encodes a tRNA for leucine
Mitochondrial myopathy and maternal myopathy/cardiomyopathy
This is an important factor in mitochondrial disease
Heteroplasmy
This is when cells contain a mixed population of mitochondria - some carrying disease-causing mutations while others do not
Heteroplasmy
When cells divide, do all cells receive the same ratio of mutant to normal mitochondria?
No
Due to heteroplasmy, disease may occur when this reaches a threshold value
Ratio of mutant to normal mitochondria
This theory describes the evolutionary origin of mitochondria and chloroplasts
Endosymbiosis theory
What is the endosymbiosis theory?
Organelles (mitochondria and chloroplasts) originated when bacteria took up residence within a primordial eukaryotic cell
According to endosymbiosis theory, what did chloroplasts originate as?
Cyanobacteria
According to endosymbiosis theory, what did mitochondria originate as?
Gram-negative nonsulfur purple bacteria
What are two observations that support the endosymbiotic theory?
- Organelles have circular chromosomes; 2. Organelle genes are more similar to bacterial genes than to nuclear genes
What advantage did endosymbiotic chloroplasts give to eukaryotic cells?
Ability to photosynthesize
What advantage did endosymbiotic mitochondria give to eukaryotic cells?
More ATP synthesis
How did cyanobacteria/purple bacteria benefit from becoming endosymbiotes?
Eukaryotic cell provided stable environment/nutrient supply
