Genetics Flashcards
Acrocentric
Chromosomes in which the centromere lies close to one end and ends up producing one long and one short arm
Autosome
Any chromosome that is not a sex or mitochondrial chromosome there are 22 pairs
Chromatid
One of two strands held together by the centromere that make up the chromosome during cell division
Chromatin
Genetic DNA coiled and supercoiled in association with histone proteins
Concordance
Occurrence of the same trait in both members of a pair of twins
Mendelian
Single gene mutation
Inherited in recognizable patterns
Polygenic
Multi factorial conditions where generic mutations involve more than one gene and non generic factor interact in ways that are always not good
Chromosomal aberrations
Includes both structural defects and deviations from the normal number
Single gene defects
Can be autosomal dominant; autosomal recessive; x linked dominant; x linked recessive
Autosomal dominant inheritance
Every affected individual has at least one affected parent
Equal male to female distribution
Affected person marries a normal person has equal number of affected and normal children
-But if the the genes expression is minimal may not be seen clinically
-Persons without apparent abnormalities can pass the gene to children who may develop all characteristics of a particular inherited disorder (lack of penetrance)
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X linked inheritance
In autosomal dominant
only appears in one sex usually males
pleiotrophy-
In autosomal dominant
many forms and single gene can produce many anomalies
Homozygous dominant genotype
In autosomal dominant
Occurs in children of parents who are heterozygous or homozygous for same dominant gene
Parents with same autosomal dominant abnormalities can produce offspring with severe abnormalities
Autosomal recessive inheritance
Single gene affected
If an affected person is born to normal parents then both were heterozygous 1/4 offspring will be affected, 1/4 normal 1/2 heterozygous
If affected person marries normal person all offspring will be normal heterozygous
Male and female distribution equal
X linked dominant inheritance
Affected males transmit trait to all daughters but not sons
Affected heterozygous males transmits disease to 1/2 children regardless of sex
Affected homozygote male transit trait to all children
X linked recessive inheritance
Nearly all males affected
Trait transmitted by heterozygous mom when phenotype is normal
Affected males do not transmit to sons
All daughter of affected males will be carriers
All genes expressed on the X chromosome are expressed
Codominant inheritance
Ability to detect either or both of two alleles in an individual
A trait or disease can be dominant or recessive
Mutifactoral inheritance
Variations within populations results from genes and environmental factors together
Many common congenital anomalies are familial but do not fit a pattern of Mendelian inheritance
Affected person have a predisposition but results are also due to environmental factors
Examples- neural tube defects, congenital anomalies of the heart, epilepsy, megacolon, cleft lip
Autosomal recessive disorders
PKU
Tay sachs
Glucose storage disease
CF
Autosomal dominant disease
Osteogenesis imperfects
Familial cholesterolemia
X linked disease
MPS
Mitochondrial DNA abnormalities
Maternal inheritance as mitochondria is passed via ova
All offspring are affected but if she had a son his kids are not affected
Examples- chronic progressive external opthalmoplegia, kearns sayre syndrome, pearsons syndrome, lebers hereditary optic neuropathy
Malignant genetics
Passing of oncogenes
Normal on everyone but remain inactive
Active in predisposed individuals
Retinoblastoma, familial polyposis, neuroblastoma
Downs more likely to get leukemia
BRCA, Wilms tumor, xeroderma pigmentosum, lung cancer
