Genetics I and II Flashcards
Mendel’s first law
The principle of segregation, meaning two members of a gene pair segregate from each other in the formation of gametes> Half of the gametes carry one allele and the other half carry the other allele.
Mendel’s second law
The principle of independent assortment meaning genes for different traits assort independently of one another in the formation of gametes.
What is a compound heterozygote?
A genotype in which two different mutant alleles of the same gene are present rather than one mutant and one normal
What is hemizygosity?
A male that has an abnormal alleles for a gene located on the X-chromosome and there is not other copy of the gene
In pedigrees, what does kindred mean?
Extended family depicted in pedigrees
What is a pro band?
The member through whom a family with a genetic disorder is first brought to the attention of a geneticist
What is the consultand?
The person who brings the family to the attention of the geneticist
Who is the first degree of a pedigree?
Parents and sibs of offspring and proband
Who is the second degree of a pedigree?
Grandparents and grandchildren, uncles and aunts, nephew and nieces and half sibs
Who is the third degree of a pedigree?
First cousins
Most recessive disorders are due to ________
Loss of function
What is penetrance?
Percentage of people with a predispositioning genotype who are actually affected, at least to some degree; can be age dependent
What is expressivity?
Severity of expression of the phenotypes among individuals with the same disease causing genotypes.
There are three types of heterogeneity, what are they?
Allelic heterogeneity, Locus heterogeneity, and phenotypic heterogeneity
Genome mutations produce _________ and are the most common mutations in humans
Chromosomal aneuploidy
Chromosomal mutations are usually ___________
Not compatible with life
Gene mutations can be caused by two mechanisms, _________ or ____________
- Errors introduced during the normal process of DNA replication 2. Mutation arising from a failure to repair DNA
Dynamic mutations such as Huntington disease or fragile X syndrome involve ___________
Amplification of trinucleotide repeats sequence
The longer oocytes remain in meiosis I, the greater the chance for _________ to occur when the cells finally complete meiosis.
Nondisjunction error
_______________ are common in sperm
Point mutations that usually cause missense mutations
Huntington’s disease is a _____________ of paternal order
Trinucleotide repeat disorder
In _________, there are massive expands in the CGG repeat region and nearly always occurs during female gametogensis
Fragile X
Genetic Polymorphism occurs when a variant is so common that it is found in ___________
1% of chromosomes
Alleles with frequencies less than 1% are called _________
Rare Variants
The Hardy-Weinberg Law is a relationship for calculating ________ from __________
Genotype frequencies from allele frequencies
For x-linked genes, there are only two possible _______ but three ___________
Male genotypes; famale genotypes
Assumptions of HW equilibrium (3)
- Population in large 2. Mating is random 3. Allele frequencies are not changing over time
Non-random mating could be due to three factors. What are they?
- Stratification 2. Assortative mating 3. Consanguinity
_________ occurs in small populations
Genetic drift
Most deleterious recessive alleles are hidden in heterozygotes and ____________
Not subject to selection
What is the founder effect?
When a small subpopulation breaks off from a larger population and may not have the same genetic frequencies as the parent group.
For both hemophilia A and B, the level of _____ and _____ activity predict the clinical severity.
Factor VIII and IX
Point mutations and the common F8 inversions almost always arise in male meiosis and therefore, mother carriers get it from a new mutation from their _________
Father
