Genetic Diseases

Question 1

Single gene mutation

Answer 1

mutation in sequence or nucleotide chain

Question 2

allele

Answer 2

different DNA sequences

Question 3

Homozygote

Answer 3

an individual with matching alleles at the same loci on both chromosomes

Question 4

heterozygote

Answer 4

When the paired alleles have different alleles at the same locus

Question 5

locus

Answer 5

Specific site on a chromosome at which the allele is located

Question 6

Dominant Allele

Answer 6

need only be present in one copy to be expressed in heterozygotes

Question 7

Recessive Alleles

Answer 7

Need to be present in two copies to be expressed

Question 8

Autosomal dominant inheritance

Answer 8

• Only needs one gene mutation to be dominant
• 50% of children with one affected parent are affected with the disease ex: Aa-Aa-aa-aa
• NO skipped generations
• Homozygous individuals (AA) have a more severe condition of disease…. 25% of children will get ‘AA’ when both parents carry the gene

Question 9

Autosomal dominant inheritance examples

Answer 9

• Marfan syndrome; collagen protein results in elastic protein
• Huntingtons disease; trinucleotide disorder, brain shrinks due to neuron loss

Question 10

Autosomal Recessive Inheritance

Answer 10

• Person needs 2 copies to express auto. recess.
• Disease cluster among siblings, not parents
• Males and females equally affected
• Consanguinity increase risk (incest)

Question 11

Autosomal Recessive Inheritance Examples

Answer 11

-Cystic Fibrosis; Thick mucus plugs organs in the body

-Sickle Cell Anemia; Single base pair mutation in hemoglobin
(changes shape of RBC making it sickle, cell lyses and breaks)

Question 12

X Linked recessive inheritance

Answer 12

• X and Y genes affected
• Women; X inactivation mutes the affected X

–No male-male transmission bc males give a Y

• Males more affected since they don’t have X inactivation (female needs a mom carrier and father with disease to have present)
• Skipped generations are common bc of carriers and x inactivation

Question 13

X Linked recessive inheritance Examples

Answer 13

• Hemophilia A; clotting factor deficiency

- Duchenne Muscular Dystrophy; mutation of protein found in skeletal muscle (loss of muscle tissue)

Question 14

Chromosomal disorder prevalence

Answer 14

• Abnormalities seen in 1/150 live births
• 50% of miscarriages have major abnormality
• 95% of conceptions w/ abnormalities and spontaneously aborted

Question 15

Types of chromosome disorders

Answer 15

-POLYPLOIDY (more than 2 copies of chromosome in 1 cell)
>triploidy; 69 chromosomes
>tetraploidy; 92 chromosomes

-AUTOSOMAL ANEUPLOIDY
>monosomies (lethal) full duplicate set of chromo.
>trisomes

-SEX CHROMOSOME ANEUPLOIDY 
>klinefelter synd
>turner synd
>XXX synd
>XYY synd

Question 16

Down Syndrome (trisomy 21)

Answer 16

• 3 copies of the 21st autosome instead of 2
• chromosomal nondisjunction responsible for most cases (occurs in egg during ovulation)
• maternal age pronounced after 35
• Prenatal diagnosis requires anmicentesis or chronic villus sampling

Question 17

Down Syndrome Clinical Features

Answer 17

• Developmsental delays
• distinct facial features
• congenital heart defects (hole in heart or misplaced arteries)
• increased risk of leukemia
• premature aging