Principles of Genetic Inheritance Flashcards
Chromosomes common in both genders
Autosomes
This disease is a mitochondrial disease that affects many body systems, particularly brain and nervous system, and muscles.
– Stroke and dementia – Lactic acidosis
Mitochondrial encephalomyopathy, lactic acidosis, and
stroke-like episodes (MELAS)
Example of X-linked Recessive Disease.
Duchenne Muscular Dysterophy
Turner Syndrome Characteristics
45, XO karyotype
Female (no Y)
Short stature
Ovarian hypofunction/premature Ovarian failure- require hormone therapy
Most are infertile
~30% webbed neck
Low hairline on neck
CV defects (coarctation of aorta, bicuspid aortic valve)
Normal intelligence
Is pyloric stenosis more common in men or women?
Men, they need less risk genes.
Children born of affected males are less likely to get it as well.
Probabilty rules
Multiply individual probabilities for “and”
Add for “or”
When environmental factors cause variation
in the trait, the term ______ is used
Multifactorial
Process by which monosomy and trisomy occur.
Non-Disjunction
Meiosis reduces the total number of chromosomes by ___ producing ____ number of haploid gametes
1/2, 4
Order and nomenclature is divided into how many sections
Arm P / Q
Region 2 / 1
Band 1,2,2 / 1,2,3,4
Subbands 321,21,54321 / 3,123,1234.123
Describe the structure of mitochondrial DNA
16,569 bp, double stranded, circular
The frequency at which a gene manifest itself is called _____.
penetrance
Klinefelter Syndrom Characteristics
– Some with no/limited symptoms
– Varying degrees of cognitive, social,behavioral, learning difficulties
– Primary hypogonadism (low T)
– Small and/or undescended testes
– Gynecomastia
– Tall stature
– Infertility
– Can be mosaic
– Variability in X numbers can increase
symptoms (48, XXXY; 49, XXXXY)
47, XXY
Name the phases in order for mitosis
Interphase
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Phase of Mitosis at which one copy of each chromosome (chromatid) and 1/2 of cytoplasm/organelles are distributed between the two daughter cells
Cell Division
Law of Independent assortment in Mendelian Genetics
Genes are inherited independently of one another
What is Trisomy 21?
Downs syndrom (47, XX + 21)
Most common trisomy
Inreased risk with maternal age
Can also occur due to translocation 46, CU
Multifactoral diseases that due not show a phenotypic bell curve have an underlying ________. In order for disease to become present they must pass the _________.
Liability distribution
Threshold of liability
X-Linked Dominant Disease
Very rare; No carriers
Hyophosphatemia
Low phosphorus in blood due to defective reabsorption of phosphate in kidney due
Deficient absorption of calcium in intestine causing sofenting of bone (Rickets)
Vitamin D metabolism abnormal
Short stature
How are genomic imprints passed down?
They’re not!
Epigenetic imprints remain throughout the lifespan of somatic cells.
In germ cells, epigentic imprints are reset at each generation.
Normal number of chromosomes
Euploid
Paternal deletion of region of chromosome 15
Prader Willie Syndrome
Short stature, hypotonia, small
hands/feet, obesity, mild to moderate
intellectual disability
What makes multifactoral inheretance recurrent risk more likely?
Environmental factors
More then one family member affected
Expression is more severe
Less commonly affect proband is more likely to pass on
More related the parents = Higher chance
Disease example given for Reduced penetrance
Retinoblastoma
autosomal dominant inheritance
Phenotype occurs in 90% of individuals inheriting gene
Name the stages of meiosis in order
One round of DNA replication
two rounds of nuclear division
Prophase I => Metaphase I => Anaphase I => Telophase I => Metaphase II => Anaphase II
Disease example of Locus Heterogeneity.
OSTEOGENESIS IMPERFECTA
Brittle-bone disease – Mutations in collagen genes (two loci: chromosome 7 and 17), either mutation exhibits the same phenotype
Hardy Weinberg Principles
p2= AA
q2=aa
2pq= Aa
p + q = 1
Condition in which cells from a patient have different genotypes. List three examples of disease.
Mosaicism
Downs Syndrome
Klinefelter Syndrome
Turner Syndrome
What is the Down’s Syndrome Karyotype?
Some 46XX, some 47XX, +21
What is Trisomy 18?
47, XX +18; Edwards Syndrome
– Abnormal development
– Most perinatal death within 1 year (10% of
live births survive to 10 y.0.)
Law of segregation in Mendelian Genetics
Each gamete recieves one copy of a gene (an allele).
In meiosis, ______ can produce new combinations of genes.
Homologous recombination
What is the choice of an X chromosone to be active at random called
Lyonization or X-activation
What is it called when the same genotype has multiple phenotype.
Pleiotropy
Example: PKU
Plane a gene locates on a chromatid
Loci
What aspects contribute to genetic variability among homologous chromosomes made during meiosis?
Mutations of sequence
(Cross-over exchange) Homologous recombinations
Random segregation of homologs
Example given of autosomal recessive disease
Tyrosinase-Negative Albinism
_____ undergo mitosis, but divide asymmetrically, resulting in one stem cell, and one daughter cell
Stem Cells
What is the Klinefelter Syndrome Karyotype?
some 46XY, some 47XXY
Why is the mutation rate higher with Mitochondrial DNA? By what amount?
Higher by 10X
Lacks DNA repair mechanisms
Damage from free oxygen radicals released during oxidative phosphoryalation.
Consaquinous matings
Matings between relatives
Studies show mortality rates among offspring generated by cousins is up 9%
What is the Turner Syndrome Karyotype?
some 46XX, some 45XO
What is Leber’s hereditary optic neuropathy (LHON)?
Mitochondrial disorder
• Typically early teens or 20’s
Degeneration of retinal ganglion cells
Acute or subacute loss of central vision
Presence of a complete extra set of chromosomes in a cell
Polyploidy, often seen in plants
What is Trisomy 13?
47, XX +13; Patau Syndrome
– Severe developmental abnormalities
– Most perinatal death within 1 week (13% of live births survice to 10 y.o.)
Genomic imprinting works through what method
Through methylation of 5’ region of gene and chromatin condensation
At least 100 human genes are known to be imprinted
Traits that are thought to be caused by a combined effect of multiple genes are called ______.
Polygenic
Combination of non-disjunction and genomic imprinting
Uniparental Disomy
If two chromosomes are
inherited from the same parent
(Uniparental Disomy), they
will have parent-specific
imprinting
This results in no gene product
Phase of Mitosis at which chromosome duplication occurs
Interphase
Deletion of a region of Maternal chromosome 15
Angelman Syndrome
Severe intellectual disability, seizures,
ataxic gait
Example of multifactoral inherited disease
Pyloric Stenosis
Muscular hypertrophy between stomach and
duodenum – leading to vomiting and obstruction
What is the term related to the range of phenotypes that vary between indivuals with a specific genotype?
What is a disease example
Variable expressitivity
Neurofibromatosis = tumor-like growths called neurofibromas, spots differ in size shape and position.
Single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci.
Locus Heterogeneity
Cells with a missing or addition individual chromosome
Monosomy, trisomy
Polygenic and multifactorial genes follow what type of distribution.
A bell curve.
