chapter 6 (Part 3)

Question 1

Nondisjunction

Answer 1

Incorrect separation of chromosomes as germ cells divide during either meiosis I or meiosis II

Question 2

what does nondisjunction lead to?

Answer 2

aneuploidy (abnormal chromosome number) in gametes and zygotes

Question 3

Down syndrome (Trisomy-21)

Answer 3

These individuals have delayed development and mental impairment

Question 4

XXX (Trisomy X)

Answer 4

Female. Taller than average, long legs, wide-set eyes, delayed speech, learning disabilities, problems with fine motor skills. May have problems with fertility.

Question 5

X0 (Turner Syndrome)

Answer 5

Female. Short stature, wide neck, heart problems, sex organs don’t mature, usually infertile

Question 6

XXY (Klinefelter Syndrome)

Answer 6

Male. Severity varies. Smaller than normal testicles → reduced testosterone, lower muscle mass, reduced body hair, breast development. Usually infertile.

Question 7

XYY

Answer 7

normal male

Question 8

T/F - mutations that occur in the DNA of germ cells cannot be passed onto future generations

Answer 8

False

Question 9

a carrier

Answer 9

person who is heterozygous for a recessive trait but does not exhibit the traits

Question 10

Sickle-cell anemia

Answer 10

an autosomal recessive disease where the hemoglobin gene is mutated, causing abnormal red
blood cell formation and reduced capacity to carry oxygen

Question 11

Tay Sachs

Answer 11

an autosomal recessive disease caused by the absence of an enzyme that breaks down fatty substances in
the brain and spinal cord

Question 12

a mutated HEXA gene results in the absence of…

Answer 12

lysosomal enzyme

Question 13

tay sachs typically leads to death before…

Answer 13

adolesence

Question 14

Cystic fibrosis

Answer 14

an autosomal recessive disease where the gene that codes for a chloride channel is mutated

Question 15

Cystic fibrosis results in…

Answer 15

thick, sticky mucus in the respiratory,
digestive and reproductive systems, as well as increased salt in sweat.

Question 16

Huntington’s disease

Answer 16

an autosomal dominant disease where CAG nucleotide repeats are inserted into a gene on chromosome 4.

Question 17

Huntington’s disease results in…

Answer 17

• Basal ganglia associated with coordinated movements
• HD patients exhibit ‘chorea’ and ‘ballistic movements’
• Movement, cognitive (thinking), and psychiatric effects

Question 18

Hemophilia

Answer 18

a recessive X-linked disease that affects a gene involved in blood clotting. A lack of any of the blood
clotting factors can lead to an inability to stop bleeding

Question 19

Duchenne muscular dystrophy

Answer 19

a recessive X-linked disease that involves an important muscle protein, called dystrophin, that holds myofibrils together

Question 20

without the proper function of dystrophin…

Answer 20

muscles degenerate