Population Genetics, Pedigrees And Mendelain Inheritance Flashcards
What is population genetics?
Study of allele and genotype frequency distribution change
List the 4 evolutionary processes that influxes population genetics
Natural selection
Genetic drift
Mutation
Gene flow
Define population
Every member with a selected characteristic
Define sample
Subset of given sample which represents the population
Define locus
A specific position of a specific chromosome
Define allele
Alternative form of a gene/ DNA marker that is located at a specific locus
Define genotype
Genetic makeup of an individual at a specific gene of DNA marker
Define phenotype
Observable characteristics due to genetic makeup
List and define the 3 genotypes
Homozygote- Possesses the same alleles at a specific locus
Heterozygote- Possesses different alleles at a specific locus
Polymorphism- Multiple forms of a gene in a population
Define and explain the Hardy-Weinberg principle
If a population is in genetic equilibrium then:
1. The frequencies of the alleles will not change from one generation to the next
2. Genotype frequencies can be predicted from allele
frequencies
Give the 2 equations used to calculate allele and genotype frequency
P + Q= 1
P^2 + Q^2 + 2PQ=1
Where p= dominant allele and q= recessive allele
On what conditions is a population is genetic equilibrium?
- The population is infinitely large
- Random mating occurs
- No migration occurs
- No natural selection occurs
- No mutations arise
How can you estimate the carrier frequency of an autosomal recessive disorder?
Frequency of disease causing allele (q) is derived from the incidence (=I)
Often the incidence is known and you the allele and genotype frequencies have to be calculated
How do you use the HW equation for X-linked conditions like haemophilia?
In females the carrier incidence is 2pq
For males the frequency of q= frequency of disease
Frequency in males can be used to estimate carrier frequency
For example:
Carrier frequency is 2pq= 2 x p x 1/5000
How do you estimate allele frequency of Autosomal dominant disorders?
AD disorders are manifested in heterozygotes
Therefore People affected = 2pq + q^2
However q^2 i usually negligible, aprox 0
Therefore people affected=
Q= 1/2 x I
List some commonly used shapes on a pedigree tree
Filled shape= clinically affected
Empty shape= unaffected
Male= square
Female= circle
Dead= diagonal line through shape
Pregnant= P inside shape
Miscarriage= Triangle
TOP= Lin through triangle
List common lines seen on a pedigree tree
Generation (parents and siblings, biological)= straight line from line connecting parents to their children
Former relationship= dashed line breaking relationship line
Consanguinity= two lines connecting related individuals in a relationship
Identical twins= Line between individuals
Non- identical twins= Twins come from same descendant line of parents
How can you tell a genetic disorder is autosomal recessive?
Both sexes are affected (dot inside squares and circles)
Unaffected parents have affected offspring
Condition can ‘skip’ generations
How can you tell if a genetic disorder is autosomal dominant?
Vertical mode of transmission
Those who are carriers are affected by symptoms
Both sexes are affected
How can you tell if a disorder is sex linked (X-linked)
Only males are affected
Females are carriers only and unaffected by symptomatic
Define Mendelian genetics
The basic patterns (or laws) of inheritance that were discovered and described by Gregor Mendel
List the basic patterns discovered by Mendel
Dominance and recessiveness
Laws of segregation
Law of independent assortment
Describe the law of segregation
Offspring require one allele from each parent
For each trait there are 2 copies off each ‘unit of hereditary’
Each alternative form determines the appearance of specific characteristic
One alternative from is maternally inherited, one is paternal
Describe the law of dominance
Hybrid offspring inherit the dominant phenotype
