Genetics Part II Flashcards
___ - location/position of gene on chromosome
locus
____ - different base pair sequences for a particular gene (versions for the same gene)
allele
____ - 2+ common alleles within a population
Polymorphic allele
____ - maternal & paternal allele are the same
homozygous
____ - maternal & paternal allele are different
heterozygous
What are the 4 components to formal/Mendelian genetics?
- Single gene
- Law of Segregation (RY together in one cell and ry in the other)
- Law of Independent Assortment (rY together in one cell, Ry in the other)
- Law of Dominance
What is the difference between genotype and phenotype?
Genotype - DNA sequence(s) for a given locus
Phenotype - Gene + environment
- Observable characteristics: appearance, development, behavior, biochemical/physiological
_____ - % of individuals with genotype that exhibit the expected phenotype
penetrance
____ - extent of phenotype variation
Expressivity
How many copies of an allele do you need for dominant phenotype expression?
1
How many copies of an allele do you need for recessive phenotype expression?
2
What is codominance? Give an example.
both alleles expressed (I.e., ABO blood groups - 1 A allele and 1 B allele = both A & B expressed (AB blood type))
____ - phenotypically normal individual who has a disease causing recessive allele in their genome
carrier
Who will be affected from autosomal dominant transmission?
Heterozygous affected (Dd) => 50% children affected
What is the difference between autosomal dominant and autosomal recessive transmission? How are they similar?
Autosomal dominant - no skipping generations; heterozygous affected parent (Dd) = 50% children affected
Autosomal recessive - can skip generations (2 carrier parents (Dd) = 25% children affected); consanguinity (descending from same ancestor)
Number of affected females = number of affected males (generally)
What does “autosomal dominant” mean?
individuals with at least 1 dominant allele are affected
What does “autosomal recessive” mean”?
individuals with recessive allele are affected
Who is affected from autosomal recessive transmission?
homozygous affected (dd) - 25% of children affected (dd) from 2 carrier parents (Dd)
Who are the carriers for autosomal recessive transmission?
heterozygous carriers (Dd)
____ - 2+ genotypes in one individual
Genetic mosaicism
____ - the fusion of more than one fertilized zygote in the early stages of embryonic development
Chimerism
What kind of cells are involved with genetic mosaicism?
germline (sperm and egg)
____ - gene that affects sex determination
SRY
Which sex chromosome is SRY a gene of?
Y chromosome
What sex will an individual be if SRY is on the X chromosome? Is this a type of syndrome? If so, which one?
Male; Klinefelter (47, XX+Y)
What sex will an individual be if SRY is on the Y chromosome? Is this a type of syndrome? If so, which one?
Male; normal
What sex will an individual be if no SRY is found on the Y chromosome? Is this a type of syndrome? If so, which one?
Female; Turner syndrome (XY?)
What sex will an individual be if no SRY is found on the X chromosome? Is this a type of disorder? If so, which one/
Female; normal
What are Barr bodies?
inactive X-chromosome in a cell with more than one X chromosome
In X-linked recessive transmission, number of males affected ___ than number of females affected
>
Who is affected in X-linked recessive transmission?
male with recessive allele (XhY)
If an affected father and a normal homozygous dominant mother have children, which ones will be affected or made carrriers?
100% carrier females; 0% affected males (because X is coming from the mother and not the affected father)
If an x-recessive affected father and a normal homozygous dominant mother have children, which ones will be affected or made carriers?
100% carrier females; 0% affected males (because X chromosome is coming from the mother and not the affected father)
If a carrier mother and a non-affected x-recessive father have children, which ones will be affected or made carriers?
50% carrier female; 50% affected males
What are 2 sex-influenced traits?
- Male pattern baldness
- Breast cancer
What are the 2 sex-limited traits?
- uterus, ovaries
- prostate, testicles
List and define the 3 principles of multifactorial inheritance.
- Polygenic traits - effects of multiple genes cause the variations in traits (more difficult to predict phenotype)
- Multifactorial traits - genetic, environmental, and lifestyle factors cause variations in traits
- Quantitative traits - are measured on a continuous numeric scale (follow a normal bell curve for distribution)
What causes an increase in polygenic recurrence risk?
- If more than one family member is affected
- If the expression of the disease in the proband (the first individual identified with the disease) is more severe
- If the proband is of the less commonly affected sex
Why would recurrence risk for a disease decrease?
decreases rapidly in remotely related individuals
identical twins
monozygotic
fraternal twins
dizygotic
_____ - if one twin has a characteristic, the probability that an individual pair of individuals will both have the characteristic
Concordance
