Biology Test Ii - Human Genetic Disorders

Front 1

Recessive inherited disorders (cause)

Back 1

Phenotype is caused by the inheritance of two recessive alleles

Front 2

Recessive inherited disorders must have...

Back 2

homozygous recessive alleles
- allele codes for malfunctional protein or no protein at all

Front 3

Recessive inherited disorders (examples)

Back 3

I. Cystic Fibrosis
- Lethal
- Disease of mucus secreting glands
II. Tay Sacks
- Lethal
- Lacks enzyme which metabolizes lipids in the brain
III. Sickle Cell anemia
- single amino acid substitution
- red blood cells deform in shape
IV. Albinism

Front 4

Dominantly inherited disorders are... (result)

Back 4

expressed even if only one allele is affected

Front 5

Dominantly inherited disorders (example)

Back 5

Huntington's disease
- degenerative disease of the nervous system
- onset of disease at 40-50 years old

Front 6

Sex is determined by... (chromosomes)

Back 6

sex chromosomes, X and Y

Front 7

Each gamete has one... (chromosome)

Back 7

sex chromosome

Front 8

Chances of producing a male or female

Back 8

50/50

Front 9

Males receive their X chromosome from...

Back 9

their mothers

Front 10

Females receive their X chromosomes from...

Back 10

each parent

Front 11

Female have... (number of X chromosomes)

Back 11

two X chromosomes
- alleles can be either homozygous or heterozygous

Front 12

Recessive allele (in females, what happens?)

Back 12

The trait is only expressed if she is homozygous
e.g. X(G) X(g) -> carrier
X(g) X(g) -> expresses the trait

Front 13

Recessive allele (in males, what happens?)

Back 13

The trait is expressed
e.g. X(g) Y -> expressed

Front 14

Autosomal recessive (define)

Back 14

The trait is on one of the 44 autosomes

Front 15

Sex linked recessive (define)

Back 15

They are found on one of the two sex chromosomes, the X

Front 16

Fathers pass their X genes to...

Back 16

all their daughters only

Front 17

Mothers pass their X genes to...

Back 17

both sons and daughters

Front 18

Recessive sex linked disorders are predominantly...

Back 18

male

Front 19

Sex linked disorders (examples)

Back 19

I. Colour blindness
II. Hemophilia
- lacks one of many clotting factors
- gene is found on the X chromosome
- similar inheritance pattern as for colour blindness
III. Duchenne Dystrophy

Front 20

X-inactivation (define)

Back 20

In females, only one X-chromosome is active
- Embryonic cells inactivate one of the two X chromosomes
- Condenses into a dense object: barr body (genes are inactive)

Front 21

Process of X-inactivation

Back 21

Lyon hypothesis
- Inactivation occurs randomly in embryonic cells
- Patches of tissue have only one active X-chromosome