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21 Cards in this Set

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  • Back
Recessive inherited disorders (cause)
Phenotype is caused by the inheritance of two recessive alleles
Recessive inherited disorders must have...
homozygous recessive alleles
- allele codes for malfunctional protein or no protein at all
Recessive inherited disorders (examples)
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
Dominantly inherited disorders are... (result)
expressed even if only one allele is affected
Dominantly inherited disorders (example)
Huntington's disease
- degenerative disease of the nervous system
- onset of disease at 40-50 years old
Sex is determined by... (chromosomes)
sex chromosomes, X and Y
Each gamete has one... (chromosome)
sex chromosome
Chances of producing a male or female
50/50
Males receive their X chromosome from...
their mothers
Females receive their X chromosomes from...
each parent
Female have... (number of X chromosomes)
two X chromosomes
- alleles can be either homozygous or heterozygous
Recessive allele (in females, what happens?)
The trait is only expressed if she is homozygous
e.g. X(G) X(g) -> carrier
X(g) X(g) -> expresses the trait
Recessive allele (in males, what happens?)
The trait is expressed
e.g. X(g) Y -> expressed
Autosomal recessive (define)
The trait is on one of the 44 autosomes
Sex linked recessive (define)
They are found on one of the two sex chromosomes, the X
Fathers pass their X genes to...
all their daughters only
Mothers pass their X genes to...
both sons and daughters
Recessive sex linked disorders are predominantly...
male
Sex linked disorders (examples)
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
X-inactivation (define)
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)
Process of X-inactivation
Lyon hypothesis
- Inactivation occurs randomly in embryonic cells
- Patches of tissue have only one active X-chromosome