Post on 31-Dec-2015
Human ChromosomesHuman Chromosomes
Autosomes – 44 Autosomes – 44 chromosomes that chromosomes that everyone has no everyone has no matter what sex they matter what sex they areare
Sex chromosomes – 2 Sex chromosomes – 2 chromosomes that chromosomes that determine sexdetermine sex
Females = XX, Males = Females = XX, Males = XYXY
How is sex determined?How is sex determined?
Eggs = 22 autosomes, 1 sex chromosome (X)Eggs = 22 autosomes, 1 sex chromosome (X) Sperm = 22 autosomes, 1 sex chromosome Sperm = 22 autosomes, 1 sex chromosome
(X or Y)(X or Y)
Simple Dominant/Recessive Simple Dominant/Recessive TraitsTraits
Many human genes are inherited as Many human genes are inherited as dominant or recessive traits just like dominant or recessive traits just like the traits Mendel studied in peasthe traits Mendel studied in peas
Ear lobes provide an example of this:Ear lobes provide an example of this:
Attached ear lobes are inherited as a recessive trait.
Unattached ear lobes are inherited as a dominant trait.
Simple Dominant/Recessive Simple Dominant/Recessive TraitsTraits
Having a bent little finger is a Having a bent little finger is a dominant traitdominant trait
Dominant/Recessive Human Dominant/Recessive Human TraitsTraits
AlbinismAlbinism – Absence of pigment from Absence of pigment from
the skin, eyes and hairthe skin, eyes and hair– Albinism is a recessive Albinism is a recessive
trait.trait. Brown teeth Brown teeth
– Teeth have a brown color Teeth have a brown color that is not the result of that is not the result of poor oral hygiene or poor oral hygiene or antibiotics taken as a childantibiotics taken as a child
– White teeth are dominant.White teeth are dominant.
Dominant/Recessive Human Dominant/Recessive Human TraitsTraits
Cleft chin Cleft chin – A noticeable indentation A noticeable indentation
at the center of the chinat the center of the chin– Having a cleft chin is Having a cleft chin is
dominant to a smooth dominant to a smooth chinchin
Double-jointed Double-jointed thumbs thumbs – This is commonly called a This is commonly called a
hitchhiker's thumb hitchhiker's thumb – The thumb can bend back The thumb can bend back
at almost 90 degrees.at almost 90 degrees.– Hitchhiker's thumb is a Hitchhiker's thumb is a
recessive traitrecessive trait
Dominant/Recessive Human Dominant/Recessive Human TraitsTraits
Hand folding Hand folding – When the hands are folded either the left or When the hands are folded either the left or
right thumb will be on top right thumb will be on top – Left thumb on top is dominant.Left thumb on top is dominant.
Mid-digital hair Mid-digital hair – Hair growing from the middle section of each Hair growing from the middle section of each
fingerfinger– Hair presence is dominantHair presence is dominant
PTC tasting PTC tasting – Phenylthiocarbamide (PTC) is a chemical that Phenylthiocarbamide (PTC) is a chemical that
cannot be tasted by some individuals. cannot be tasted by some individuals. – Tasting is dominant to the inability to taste PTC.Tasting is dominant to the inability to taste PTC.
Dominant/Recessive Human Dominant/Recessive Human TraitsTraits
Tongue rolling Tongue rolling – Ability to form a tube Ability to form a tube
with your tonguewith your tongue– Rolling is dominantRolling is dominant
Widow's peak Widow's peak – A sharp point in the A sharp point in the
hairline that points hairline that points toward the nosetoward the nose
– Having a widow's Having a widow's peak is dominant to peak is dominant to a smooth hairlinea smooth hairline
Specific Human TraitsSpecific Human Traits Dimples Dimples
– Round indentations in the cheeks Round indentations in the cheeks when smiling, not lines or cleftswhen smiling, not lines or clefts
Freckles Freckles – Small patches of darker Small patches of darker
pigmented skin on various parts pigmented skin on various parts of the bodyof the body
– These may be present on both These may be present on both dark and light skinned dark and light skinned individuals.individuals.
Hair whorling Hair whorling – These may be referred to as These may be referred to as
cowlicks. cowlicks. – Areas in which hair grows from Areas in which hair grows from
your scalp in a whorl instead of in your scalp in a whorl instead of in a given direction.a given direction.
Specific Human TraitsSpecific Human Traits
Myopia Myopia – Short sightedness, the Short sightedness, the
inability to see far off objects inability to see far off objects without correction by glasses without correction by glasses or contactsor contacts
Polydactyly Polydactyly – Having more than five digits Having more than five digits
on each hand and foot.on each hand and foot.
Specific Human TraitsSpecific Human Traits
S-methyl S-methyl thioester smeller thioester smeller – S-methyl thioesters are S-methyl thioesters are
produced in the urine after produced in the urine after consumption of asparagus. consumption of asparagus. Some individuals cannot smell Some individuals cannot smell this substance. If you smell a this substance. If you smell a strong odor on urination after strong odor on urination after eating at least 5 asparagus eating at least 5 asparagus spears, you are an S-methyl spears, you are an S-methyl thioester smeller.thioester smeller.
White forelock White forelock – A white patch of hair at the A white patch of hair at the
front of the scalp.front of the scalp.
Multiple AllelesMultiple Alleles Determined by more than Determined by more than
one geneone gene Example: eye color Example: eye color
Eye color is determined by Eye color is determined by two genestwo genes– one controls texture of the iris one controls texture of the iris
which refracts light to make which refracts light to make blue. blue.
– A second determines relative A second determines relative abundance of melanin. abundance of melanin.
– When a small amount of When a small amount of melanin is present, green eyes melanin is present, green eyes result while brown and black result while brown and black eyes result from relatively eyes result from relatively increasing amounts of melaninincreasing amounts of melanin
Multiple AllelesMultiple Alleles Hair color is determined Hair color is determined
by more than one geneby more than one gene Thus hair color appears Thus hair color appears
to vary on an almost to vary on an almost continuous scale from continuous scale from black to brown to blond black to brown to blond to redto red
The brown and black The brown and black pigment is melaninpigment is melanin
The red pigment is an The red pigment is an iron containing iron containing moleculemolecule