Basic concepts of formal genetics

Question 1

What are monogenic traits also known as?

Answer 1

Mendelian traits

Named after Gregor Mendel, who studied these traits in garden peas.

Question 2

What principle states that sexually reproducing organisms possess genes that occur in pairs?

Answer 2

Principle of segregation

This principle indicates that only one member of the gene pair is transmitted to the offspring.

Question 3

What does the principle of independent assortment state?

Answer 3

Genes at different loci are transmitted independently

The transmission of an allele from one locus does not affect the transmission of alleles from another locus.

Question 4

What is the definition of phenotype?

Answer 4

What is actually observed physically or clinically

Phenotypes do not uniquely correspond to genotypes.

Question 5

Give an example of a condition where the recessive homozygote is affected.

Answer 5

Cystic fibrosis

This is an autosomal recessive condition.

Question 6

What is the key cause of morbidity and mortality in cystic fibrosis patients?

Answer 6

Pulmonary disease

Characterized by chronic bronchial infection and airway obstruction.

Question 7

What is the prevalence of cystic fibrosis among European-American newborns?

Answer 7

Approximately 1 in 2000 to 1 in 4000

Prevalence varies among different ethnic groups.

Question 8

What gene is mutated in cystic fibrosis?

Answer 8

CFTR

CFTR encodes the cystic fibrosis transmembrane conductance regulator.

Question 9

What is the most common mutation associated with cystic fibrosis?

Answer 9

F508del

This mutation accounts for nearly 70% of all CF mutations.

Question 10

What kind of diet can prevent severe mental impairment in babies with PKU?

Answer 10

Low-phenylalanine diet

Initiating this diet within 1 month after birth can avoid damage to the brain.

Question 11

What does a pedigree illustrate in medical genetics?

Answer 11

Relationships among family members and affected status for genetic diseases

It denotes the proband, the first diagnosed person in the pedigree.

Question 12

What are first-degree relatives?

Answer 12

Those related at the parent-offspring or sibling level

Examples include parents and siblings.

Question 13

Fill in the blank: The principle of _______ states that genes remain intact and distinct.

Answer 13

segregation

Question 14

True or False: Genotypes uniquely correspond to phenotypes.

Answer 14

False

Different genotypes can result in the same phenotype.

Question 15

What percentage of males with cystic fibrosis are sterile due to absence or obstruction of the vas deferens?

Answer 15

More than 95%

This is one of the complications associated with CF.

Question 16

What are second-degree relatives?

Answer 16

Those related by one additional generational step

Examples include grandparents and grandchildren.

Question 17

What is the role of CFTR in cystic fibrosis?

Answer 17

Regulates sodium and chloride ion transport across epithelial cell membranes

Defects lead to thick secretions in various organs.

Question 18

What is the estimated median survival time for cystic fibrosis patients in the United States?

Answer 18

Nearly 40 years

Survival rates have improved due to better treatment options.

Question 19

What is the effect of environmental factors on phenotype?

Answer 19

Can profoundly alter the phenotype

This includes genetic environments and external conditions.

Question 20

What is the relationship between genotype and pancreatic function in cystic fibrosis?

Answer 20

Generally a good correlation

However, there is more variability in the relationship with pulmonary function.

Question 21

Fill in the blank: The _______ is the first person in whom the disease is diagnosed in the pedigree.

Answer 21

proband

Question 22

What are the classes of mutations in the CFTR gene?

Answer 22

Class I to VI

Each class has different effects on the CFTR protein and its function.