Inheritance Patterns Flashcards
Shape of males in pedigree drawing
Square
Shape of females in pedigree drawing
Circle
In a pedigree drawing, what do partners have between them?
Partners have a line between them
In a pedigree drawing, what do siblings have above them
Siblings have a line above them
In a pedigree drawing, who are shaded?
People who are affected are shaded
In a pedigree drawing, who have dots inside?
Carriers have dots inside
In a pedigree drawing, what do double lines mean?
Are a consanguineous couple(Same blood)
What does SB on a pedigree drawing mean?
Still born baby
What does the diamond symbol in a pedigree drawing represent?
Means unknown sex
What do small triangle symbols in a pedigree drawing represent?
Spontaneous abortion
What does a triangle with a line going through it represent?
Represents therapeutic abortion
What represents identical twins, non-identical twins?
Identical twins have diagonal lines and a line between them
Non identical twins have only diagonal lines
What does a diamond with the letter P inside represent?
Represents someone who is pregnant of a child with an unknown sex
What symbol represents no offspring?
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In what form are autosomal dominant inheritance?
Clearly in heterozygous form
How many generations are affected by autosomal dominant inheritance?
Multiple generations are affected by autosomal dominant inheritance
What will most individuals with autosomal dominant inheritance have?
Most will have an affected parent
What is the risk to offspring for autosomal dominant inheritance?
50% risk to offspring
Characteristics of autosomal dominant inheritance
- Most individuals have an affected parent
- Males and females are equally likely to inherit
- An affected individuals siblings/children whom aren’t affected, do not carry the mutation and cannot pass it on to their offspring
FEATURES OF AUTOSOMAL DOMINANT INHERITANCE
What is penetrance and incomplete penetrance?
Penetrance is the percentage of individuals who carry the mutation and develop symptoms of the disorder
-Many dominant disorders show age dependent penetrance
Incomplete penetrance is when you have the genotype, but not phenotypically expressed
FEATURES OF AUTOSOMAL DOMINANT INHERITANCE
What is variable expressivity?
Variation in several symptoms of disorders between individuals with the same mutation
FEATURES OF AUTOSOMAL DOMINANT INHERITANCE
What varies between autosomal dominant disorders?
De novo mutation rate varies considerably between autosomal disorder conditions
FEATURES OF AUTOSOMAL DOMINANT INHERITANCE
What is somatic mosaicism?
It is when new mutation arises in early stages of embryogenesis
-Present in only some tissue/cells
FEATURES OF AUTOSOMAL DOMINANT INHERITANCE
What is germ line mosaicism?
It is when new mutations arise during oogenesis or spermatogenesis
-Mutation present in variable proportion of gametes and can be transmitted to offspring
FEATURES OF AUTOSOMAL DOMINANT INHERITANCE
What is anticipation?
Worsening of disease severity in successive generations
-Characteristically occurs in triplet repeat disorders
In what form is autosomal recessive inheritance?
Clearly in homozygous form
Who aren’t affected by autosomal recessive inheritance?
Carriers aren’t affected
What sexes are affected by autosomal recessive inheritance?
Both sexes affected
How many generations are affected by autosomal recessive inheritance?
Usually one generation affected
What may be a factor of autosomal recessive inheritance?
May be consanguinity
What are compound heterozygotes?
-2 mutations in the same gene however these mutations are different
What is a homozygote?
-2 mutations in the same gene however these mutations are identical
What are the features of autosomal recessive inheritance?
- Trait often found in clusters of siblings
- All offspring of affected person are obligate carriers
Chromosomes in men and women
Men-XY
Women-XX
What are the affects on BOTH genders of X-linked inheritance?(Recessive)
- Women are carriers and are unaffected
- No male to male transmission
What are the affects on BOTH genders of X-linked inheritance?(Dominant)
- Women are affected
- Males are more severely affected
What type of genes are never passed from father to son?
X-linked genes never passed from father to son
In X-linked recessive inheritance, who are the obligate carriers?
All daughters of affected males are obligate carriers
In X-linked recessive inheritance, what do children of carrier females have a chance of inheriting mutant alleles?
Children of carrier females have a 50% chance of inheriting mutant alleles
What is skewed X-inactivation in X-linked recessive inheritance?
Normally the majority of genes on one of a women’s X chromosome are inactivated
Who are manifesting carriers?
Some women who have symptoms in x-linked recessive conditions?
Y linked inheritance
Always and only passed through fathers to sons
What is a mutation?
Change in genetic material
What do a pathogenic mutation result in?
Results in an alteration of the function of the gene product and can cause disease
What is a silent mutation?
A base change has no change in the amino acid
