Principles Of Genetic Inheritance Flashcards
What is the region at the end of a chromosome that is meant for stability
Telomere
Contrast Metacentric vs submetacentric vs acrocentric chromosomes
Metacentric- have a centromere in the center such that both arms are the same length
Submetecentric- has a centromere in the center such that one arm (p) is slightly shorter than the other (q)
Acrocentric- has a chromosome severely off set from the center such that there is one really short p arm and one really long q arm
_____ is a x-inactivation in which one X chromosome is in activated. It happens early in development and the inactivated X is called a Barr body
Lyonization
_____ is a condition in which cells from a patient have different genotypes and karyotypes because the different cells in the body have different arrangement or numbers of chromosomes
Mosaicism
Stem cells undergo mitosis, but divide asymmetrically, resulting in one _____ cell and one _______ cell
One stem cell, and one daughter cell
What is the big difference between mitosis and meiosis cell division
Mitosis results in 2 identical daughter cells that are diploid
Meiosis results in 4 non identical daughter cells that are haploid
What is responsible for producing new combination of genes in meiosis
Homologous recombination
Are homologous chromosomes identical
NO
_____ changes the sequence of alleles that are passed from generation to generation.
Mutations
T/F De novo mutations are solely hereditary
False
They can be hereditary or somatic
In meiosis there is one round of DNA replication and two rounds of nuclear division. The first separation is of _____ and the second separation is _______
- Homologs
- Sister chromatids
**Meiosis reduces the genetic material
What are two ways meiosis creates diversity
- Random segregation of homologs
2. Homologous recombination
Cells with a normal number of chromosomes (haploid gametes or diploid somatic cells) are called what
Euploid cells
_____ is the presence of a complete set of extra chromosomes in a cell (often seen in plants)
Polyploidy cells
____ are cells with missing or additional individual chromosomes (monosomy, trisomy)
Aneuploidy cells
45, XO karotype
-females with short stature, ovarian hypofunction, premature ovarian failure, infertile, CV defects, low hairline on neck, webbed neck, normal intelligence
Turners Syndrome
47, XXY karotype
- limited symptoms
- varying degree of cognitive/social/behavioral difficulties,
- primary hypogondaism
- small testes
- gyneomastia (male breasts)
- tall stature
- infertile
- can have a variable number of extra chromosomes
Klienfelter syndrome
47, XX +21
- most common
- increased risk of nondysjunction with maternal age
- can also occur due to translocation 46, XX (14:21) (q10;10)+21
- can be mosaic
Down Syndrome
47, XX +13
-severe developmental abnormalities
-most perinatal death within 1 week
(13% live births live to 10 y.o.)
Patau Syndrome
47, XX +18
-abnormal development
-most perinatal death within 1 year
(10% of live births survive to 10 y.o.)
Edwards Syndrome
Explain Robertsonian Translocation
A robertsonian translocation is when two acrocentric chromosomes q arms combine to make “one”chromosome with the essential genes of two chromosomes. They can possibly pass on a robertsonian translocation and a normal chromosome and the child will result with an extra chromosome (trisomy)
What are the acrocentric chromosomes
13, 14, 15, 21, 22
What is genomic imprints
Imprinting is essentially gene silencing through methylation of the 5’ region of a gene or chromatin condensation
When do epigenetic imprints reset for somatic and germ cells?
Somatic cell epigenetics last a lifetime
Germ cells are reset during meiosis, when imprints are erased and new ones are set
What two diseases are a result of genomic imprinting (silencing of one parental chromosome)
Prayer-willi
And
Angelmans syndrome
What are diseases caused by nondisjunction
Klienfelter Down syndrome Patau syndrome Edwards syndrome Turner syndrome
Deletion of a region on chromosome 15 of the parental chromosome causes ____
Prader-Willi syndrome
-causes short stature, hypotonia, small hands/feet, obesity, mild - moderate intellectual disability
Deletion of region of chromosome 15 of the maternal chromosome causes ______
Angelmans Syndrome
-severe intellectual disability, seizures, ataxic gait
What is related to both non-disjunction and genomic imprinting? Two chromosomes are inherited from the same parent and they have parent-specific imprinting meaning only two chromosomes are expressed but they are both from the same parent
Uniparental disomy
Can cause both Prader Willi and angelmans because only one parent is expressing chromosome 15
Law of segregation vs law of independent assortment
Segregation says you can either be tall or short (1 dominant gene for that trait)
IA- says you can be tall and wrinkly or tall and non wrinkly (different genes for different phenotypes are independently assorted )
What is an example of someone with a distinct genotype on exhibiting one single phenotype
Cystic fibrosis
What is an example of individuals with the same genotype having multiple different phenotypes (pleiotropy)
PKU
What is pleiotropy
When one gene influences two or more seemingly unrelated phenotypic traits
What is the first diagnosed person in a pedigree called
Proband (propositus):
Denoted by an arrow in a pedigree
Percent chance of autosomal dominant and recessive, and x linked recessive and x linked dominant appearing in a generation?
Dominant- 50% - postaxial polydactlyl
Recessive- 25% -albinism
X-linked recessive - duchenne muscular dystrophy
X linked -dominant (non carriers) - hypophosphatemia [causes rickets]
What is consanguinity
First cousin mating
The frequency a gene manifests itself is _____
Penetrance
If someone with a mutation and do not develop the features of the disorder then the diseases is said to have ____
Reduced penetrance
-ex: retinoblastoma (autosomal dominant with 90% P)
___ is the range of phenotypes that can vary between individuals with a specific genotype
Variable expressivity
Ex: neurofibromatosis
-neurofibromas cause spots that range in size and color and number
A single disorder, trait, or pattern of traits caused by mutation in genes at different chromosomal loci/genes.
Same phenotype from mutation on two different genes
Locus heterogeneity
-ex:
Osteogenesis imperfecta
*brittle bones and mutations in collagen genes (c 7 and 17)
When would you use the multiplication rule or addition rule of probability
Multiplication:
-probability of a given outcome in multiple trials
Ex: probability of having 3 girls
1/2 x 1/2 x 1/2 = 1/8
Addition:
-probability of either one or another outcome
Ex: probability of having 3 girls or three boys ?
1/8 + 1/8 = 2/8 = 1/4
You can used Hardy Weinberg principle when you are given the incidence of a disease and you want to find population frequency or allele frequency
P + q = 1
what has its own circular DNA
- contains no introns
- inherited solely by mother
- mutation rate is 10x that of nDNA bc lack of DNA repair mechanisms and damage from free radicals released during OxPhos
Mitochondrial DNA (mtDNA)
- encodes rRNA and tRNA and 13 polypeptides used in OxPhos
- transcription takes place in the mitochondria independent of the nucleus
Mitochondrial inheritance
*passed through the mother
**IF mother is mutated/infected then every child gets infected/mutated mitochondria
*but the degree of mutation is different for each infected individual therefore some may lead to mitochondrial disease and some may not (this is because mitochondria are distributed unequally)
Traits in which variations are thought to be caused by combined effect s of multiple genes
Polygenic
When environmental factors cause variation in the trait the term _______ is used
Multifactorial
Multifactorial inheritance follows what pattern?
If they do not follow the normal pattern then there is an underlying _____
Follow a bell shaped distribution in populations
-underlying liability distribution. Some may have a threshold of liability where the disease is either present or absent.
***A result of polygenic traits. (Simultaneous influence of multiple genetic and environment factors)
What type of inheritance is exhibited by muscular hypertrophy?
Multifactorial inheritance
*men need less risk genes vs females
(The least affected sex has a higher risk threshold and transmits the condition more often to the more affected sex)
Explain the Recurrence Risks of multifactorial inheritance
**varies more greatly than single-gene diseases bc it is population based
- the recurrence risk is higher if more than one family member is affected
- if the expression is severe in the proband, the reccurence risk is higher
- the recurrence risk if higher if the proband is the less affected sex
- the recurrence risk for the disease usually decreases rapidly in more remotely related relatives
