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