Download Human Traits Lab

Bellwork: Tues. Jan. 10, 2017
1. Dominant trait: “masks” or covers up recessive traits.
B = brown eyes b= blue eyes Bb = Brown eyes
2. Recessive trait: will only appear without dominants.
bb = blue eyes
3. Dominant traits: capitalized ( B, T, F…)
Recessive traits: lower case ( b, t, f…)
4. Genotype:_______________________ of an
organism.
5. Phenotype:_______________________ of an
organism.
6. Homozygous: ___________________________
7. Heterozygous: ___________________________
8. Allele: ____________________________
____________________________________
Dimples are dominant
Human Traits Lab
Cleft chin is dominant
Wet ear wax is dominant…
I have the recessive “dry”
ear wax
Dimples are dominant
Human Traits Lab
Cleft chin is dominant
Wet ear wax is dominant…
I have the recessive “dry”
ear wax
Crash course biology
• https://www.youtube.com/watch?v=CBezq1fF
UEA
• https://www.youtube.com/watch?v=9SdCoNp
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What is dominant? What is recessive?
• A trait that is considered “dominant” masks
recessive traits. In other words, it “dominates”
the recessive.
• A recessive trait requires no dominant traits to
be present. These recessive traits will only
appear without dominants.
• Dominant traits are capitalized (IE: A, X, F, etc)
• Recessive traits are lower case (IE: a, x, f, etc)
…So having dimples, and a
Dimples are dominant
yet rare because
the dimple gene
version is rare…
the same goes for
cleft chin…
cleft chin is rare because
the versions of these genes
are rare. And as long as there
is no advantage or disadvantage
to having dimples, then the
relative amounts of people with
dimples won't change over time
in a stable population.
So dominant does not mean more common 
Dominant just means that form of the trait will
“win out” over the recessive form.
But… if the form of the gene is advantageous to a population, more
Individuals with than form will survive to pass on that gene to their
offspring. So for some other genes it seems like almost everyone
has that dominant trait….
•
•
•
•
Tasters in class:
Non-tasters in class:
Total:
Percent tasters:
Accidental Taster in 1931
Chemist Arthur Fox sat at his DuPont Company
lab bench, mixing a powdered chemical.
Accidentally a bit of the powder blew into the
air.
Fox and another scientist got some of the
chemical into their mouths. Dr. Fox's
colleague exclaimed how bitter the powder
tasted. Fox was surprised -- he had been
much closer to the chemical, but he tasted
nothing at all.
Both men tasted the chemical again. To Fox it
was still tasteless, but his co-worker insisted it
was very bitter. Fox handed out crystals of the
chemical, which were not poisonous, to his
friends, family members and fellow scientists
and asked them if they tasted anything.
Some people, like Fox, tasted nothing; others
found the chemical somewhat bitter or
intensely bitter.
What was going on?
Since then, the chemical phenylthiocarbamide
(PTC) has been used to detect genetic variation in
tasting abilities. Studies soon after the incident in
Fox's lab showed that there is a genetic
component that influences how PTC tastes!
Scientists found that people were much more
likely to find PTC bitter if other members of their
family also found it bitter.
The evidence was so strong for a genetic
link that PTC tasting ability was used as
evidence in paternity tests before DNA
tests were available!
•
•
•
•
•
About 70% of people can taste PTC
Dominant/recessive trait in humans…
taste = dominant allele “T” for the gene
Cannot taste = recessive allele “t”.
But since you get an “allele” (gene) from each
parent… if you can taste the PTC you COULD be
either TT or Tt
• If you cannot taste the PTC then you are tt…
• If you listen and “get” this concept NOW the
weeks after break will be a lot easier AND you
can compare traits with relatives during break.
TT or Tt
taste
tt
can’t taste
•
http://www.telegraph.co.uk/science/evolution/6019200/Scientists-discover-thatNeanderthals-hated-Brussel-sprouts.html
Some Terms:
• Phenotype: physical appearance/
WHAT the trait “causes”.
• YOU CAN OBSERVE phenotypic traits: Eye
color, hair color height, nose shape eye
shape…:
• In this lab, you will determine some of your
own phenotypic traits and figure out some of
your possible genotype(s) for these traits.
• You only need one copy of a dominant gene in order to see
a dominant phenotypic trait, but you need two copies of a
recessive gene in order to see a recessive phenotypic trait.
• A dominant phenotypic trait is represented capitol letter
 like B for brown eyes
• A recessive phenotypic trait is represented lower case letter
 like b for blue (or light color) eyes
BB =
Bb =
bb =
You must have two recessives to “exhibit” (show) the
recessive trait
• Your Genotype (gene make-up) “letters” can be:
• homozygous dominant: BB, (phenotype: brown)
or
• homozygous recessive: bb , (phenotype: blue)
or
• Heterozygous Bb (phenotype: brown)
• …write the capital letter first
• Incomplete dominance is a
special case when the
heterozygous (BIG LETTER, little
letter – Bb) phenotype “mixes” (or
is intermediate), and not
DOMINATED by dominant gene.
Snapdragon flowers are an
example of this: , homozygous
dominant flowers are red
homozygous recessive flowers are
white, and heterozygous flowers
are pink.
• http://learn.genetics.utah.edu/content/begin/
traits/
• http://www.thetech.org/genetics/ask.php?id=188
Hairline: A widow’s peak (W) hairline comes to a
point in the center of the forehead. It is dominant
trait (genotype can be WW or Ww) to having a
straight hairline (w) has to be ww).
Eye shape: Almond-shaped eyes are dominant (A) to
round-shaped eyes (aa).
round shaped eyes (a)
(notice the white
visible under the iris)
almond shaped eyes (A)
• Eyelash length: Long eyelashes are dominant
(E) to short eyelashes (e).
Short eyelashes (e)
ee
long eyelashes (E) so EE or Ee
Tongue-rolling: The ability to roll the tongue is
dominant (C) to the inability to roll the tongue (c).
Can roll tongue (C) so CC or Cc
Can’t roll tongue (c) cc
Thumb: The hitchhiker’s thumb (thumb tip bends
backward more than 30 degrees) is dominant (B)
to a straight thumb (b).
Straight thumb (mine) (b) I’m bb
Hitchhiker’s thumb (B) so… BB or Bb
• Lip Thickness: Thick lips are dominant (L) to
thin lips (l).
Thick lips (L) so… LL or Ll
Thin lips (l) have to be ll
• Hair Texture: Curly hair is incompletely
dominant (HH) to straight hair (SS). Those
who have wavy hair are intermediate (HS).
Curly Hair HH
Wavy Hair HS
Straight Hair SS
• Inter-eye Distance: Close-set eyes are
incompletely dominant (DD) to eyes set far
apart (FF). Medium-set eyes are DF.
Close set eyes:
DD
Wide set eyes FF
Lip Protrusion: Protruding lips are incompletely
dominant (PP) to nonprotruding lips (NN). Slightly
protruding lips are intermediate (PN).
Protruding lips PP
slightly protruding lips PN
nonprotruding lips NN
Bellwork: Wed. Jan. 11, 2016
In seals, the gene for whisker length is controlled by 1 gene.
The dominant allele (W) = long whiskers
the recessive allele (w) = short whiskers.
If a homozygous dominant male seal and homozygous
recessive female seal mate, what is the probability that their
pups will have long whiskers? Draw a Punnett Square &
show the cross:
______ X ______ and show the:
genotypic ratio:______:______
phenotypic ratio:_____:______
Check only one:
Trait
Hairline
W
w
Eye Shape
A
a
Eyelash Length
E
e
Tongue Dexterity
C
c
Thumb
B
b
Lip Thickness
L
l
Hair Texture
H / S
Inter-Eye Distance
D / F
Lip Protrusion
P / N
Your
Possible
Phenotype Genotype(s)
Dominant
Recessive
Intermediate
Hairline: A widow’s peak (W) hairline comes to a point in the center of the forehead. It
is dominant trait (genotype can be WW or Ww) to having a straight hairline (w) has
to be ww).
Eye shape: Almond-shaped eyes are dominant (A) to round-shaped eyes (aa).
Eyelash length: Long eyelashes are dominant (E) to short eyelashes (e).
Tongue-rolling: The ability to roll the tongue is dominant (C) to the inability to roll the
tongue (c).
Thumb: The hitchhiker’s thumb (thumb tip bends backward more than 30 degrees) is
dominant (B) to a straight thumb (b).
Lip Thickness: Thick lips are dominant (L) to thin lips (l).
Hair Texture: Curly hair is incompletely dominant (HH) to straight hair (SS). Those
who have wavy hair are intermediate (HS).
Inter-eye Distance: Close-set eyes are incompletely dominant (DD) to eyes set far
apart (FF). Medium-set eyes are DF.
Lip Protrusion: Protruding lips are incompletely dominant (PP) to nonprotruding lips
(NN). Slightly protruding lips are intermediate (PN).
Trait
Hairline
(widow’s/straight)
Eye Shape
Almond/round
Eyelash Length
Long/short
Tongue Dexterity
Roll/not roll
Thumb
Lip Thickness
Hair Texture
Inter-Eye
Distance
Lip Protrusion
Check only one:
Your
Phenotype
Possible
Genotype(s)
Dominant Recessive Intermediate
Answer the questions and turn in
1. Which traits do you have that are dominant? (list them)
2. Which traits do you have that are recessive? (list them)
3. Which of your traits are incompletely dominant (mixed)?
4. Which of your traits do you share with one or more of your
classmates?
5. What determines your traits (i.e., how do you acquire them)?
6. Which traits are more common (dominant or recessive)? Why?
Smooth
Constricted
Axial
Terminal
https://www.youtube.com/watch?v=mnSkz8s-b44
• https://www.youtube.com/watch?v=pk0CHH7
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