Genetic Alterations Flashcards
X-linked dominant
- Described a dominant trait or disorder caused by a mutation in a gene on the X chromosome
- Both males and females express the phenotype, although, although males affected tend to have a more severe phenotype
- Only one affected X chromosome is required to cause the disease
Examples of X-linked dominant disease
- Fragile X syndrome
What is the probability pf transmitting an X-linked dominant gene mutation through the mother (female)?
- 50% probability for each child regardless of gender
- 50% affected and 50% unaffected
What is the probability pf transmitting an X-linked dominant gene mutation through the father (male)?
- 50% are affected (ALL FEMALES)
- 50% are unaffected (ALL MALES)
X-linked dominant gene mutation from an affected male to his offspring VS
X-linked dominant gene mutation from an affected female to her offspring
- Affected male to his offspring: All of his daughters and none of his sons will inherit the mutation
- Affected female to her offspring: Each child, regardless of gender, has a 50% chance of inheriting this mutation
X-linked recessive
- A mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males who are hemizygous for the gene mutation (i.e., they only have one X chromosome) and in females who are homozygous for the gene mutation (i.e., they have a copy of the gene mutation on each of their two X chromosomes)
- Males only require one mutated X chromosome (since they only have one X chromosome, to begin with) in order to cause the disease
- Phenotype expressed in males only
- Affected males are always related to each other through females. MALE –> TO MALE TRANSMISSION DOES NOT OCCUR
- Females are less likely to have an x-linked recessive disorder because they have two X chromosomes
- If females do inherit it, it will most likely be less severe
Examples of X-linked recessive disorders
- Hemophilia
- Fabry disease
Autosomal Dominant
- Describes a trait/disorder in which the phenotype is expressed in those who have inherited only one copy of a particular gene mutation (heterozygotes)
- Specifically refers to a gene on one of the 22 pairs of autosomes (non-sex chromosomes)
- Only one copy of the abnormal gene
- Not sex linked
What is the chance of passing on an autosomal dominant disorder from parent to offspring?
- Each offspring has a 50% chance of inheriting it
- Son and daughters of an affected parent are equally likely to inherit and transmit the disorder
Examples of autosomal dominant disorders
- Huntington disease
- Marfan syndrome
Autosomal Recessive
- Describes a trait/disorder requiring the presence of two copies of a gene mutation at a particular locus in order to express the observable phenotype
- Refers to genes on one of the 22 pairs of autosomes (non-sex chromosomes)
-
Needs two copies of the mutation for an offspring to exhibit the phenotype
- Generally seen in a single generation of a family
- Each offspring has a 25% chance of inheriting it
Examples of autosomal recessive disorders
- Cystic fibrosis
- Sickle cell disease
What is the probability of transmitting an autosomal recessive gene mutation to an offspring if one parent carries the mutation?
- 50% are carriers
- 50% are non-carriers
- NO ONE SHOWS!
What is the probability of transmitting an autosomal recessive gene mutation to an offspring if both parents carry the mutation?
- 25% are noncarriers and 50% are carriers } (unaffected)
- 25% are homozygotes for the mutation (affected)
What is the probability of transmitting an autosomal recessive gene mutation to an offspring if one parent is affected and one parent is a carrier of the mutation?
- 50% are carriers (unaffected)
- 50% are homozygotes for the mutation (affected)
Identify 7 disorders/diseases with a strong familial history
- CAD
- Stroke
- HTN
- Cancer
- Diabetes
- Pulmonary conditions
- Mental Illness
What increases an individual’s genetic susceptibility to developing CAD?
- Two or more closed relatives with CAD
- Female relatives with CAD
- Presence of related disorders such as diabetes in a close relative
- Presence of multiple established/emerging risk factors in close family members
- Early-onset of CAD ( <55 for men, <65 for women)
What two common genetic variants or single-nucleotide polymorphisms (SNPs) were consistently associated with total stroke (all types) and ischemic stroke in white individuals?
- Located on chromosome 12p13 near the gene NINj2, which encode ninjurin 2
What is GINA and how is it related to genetic discrimination?
- Stands for Genetic Information Non-Discrimination Act
- A federal law passed in 2008
- Prohibits discrimination in employment and health insurance coverage based on genetics
- Prohibits insurance companies from requesting/requiring genetic information of an individual or their family, or using genetic information for decisions regarding coverage, rates, or preexisting conditions
What is one thing GINA does not do?
- It does not extend to:
- Life insurance
- Disability insurance
- Long0term care insurance
What does a patient need to be aware of before they order a genetic test?
- Patients need to be aware that they need to have purchased forms of insurance (life, disability, long-term care) prior to genetic testing
Mutations in BRCA 1 and BRCA 2 genes are associated with what?
- Hereditary breast and ovarian cancer
When BRCA 1 and BRCA 2 genes are functioning normally, what do they act as?
- They both act as tumor suppressor genes
