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LAB Meiosis and Human Traits
Name:
Polygenic Traits, Karyotypes, Create a Kid Simulation
Polygenic Human Traits ............................................................................................................................................... 2
TASK 1: EYE COLOR DETERMINATION ................................................................................................................. 2
TASK 2: SKIN COLOR DETERMINATION ................................................................................................................ 3
Karyotypes..................................................................................................................................................................... 4
DISORDERS AND ABNORMAL KARYOTYES ......................................................................................................... 5
TASK 3: ANALYZING KARYOTYPES ....................................................................................................................... 7
Create a Kid Simulation ................................................................................................................................................ 8
TASK 4: YOUR FACIAL HUMAN TRAITS ................................................................................................................. 8
TASK 5: CREATE A KID SIMULATION ................................................................................................................... 10
TASK 6: THE CHILD’S FACIAL TRAITS ................................................................................................................. 10
General Biology
1
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
Polygenic Human Traits
Polygenic traits are coded by several pairs of alleles passed by mother and father. This results in a greater
variability of observable outcomes or phenotypes. These traits are also called “quantitative”, because the
phenotype is the result of how many dominant alleles are present. Hair color, eye color, skin color, and height are
examples of polygenic traits. We will consider here the traits eye color and skin color (modified from Wu, Biology
101 Lab manual from Fullerton College)
TASK 1: EYE COLOR DETERMINATION
Eye color is known to have a polygenic inheritance pattern, possibly governed by 3 or more genes. There are also
6 different described eye colors. Basically, dark is dominant at each of the 3 genes, and the assumption here is
that your eye color genotype is composed of 6 alleles having an additive effect, where the more dominant alleles
(uppercases) you have out of the six the darker your eyes are
EYE COLOR
# OF DOMINANT ALLELES
Light blue
0
Blue
1
Blue-green
2
Hazel
3
Light brown
4
Brown
5
Dark brown / black
6
Procedure
A. Determine your genotype for eye color based on your phenotype. Make as many heterozygous genotypes as
possible if you have less than 4 dominant alleles
Example: if you eye color is hazel, then your genotype has to be Aa, Bb, Cc
B. Flip a coin for every gene (A,B,C) using heads for dominant and tails for recessive alleles to simulate
independent assortment in meiosis 1 and determine which allele you would pass to your child during
fertilization.
Example: if your genotype for the first letter is Aa, and you get “Tails”, your allele would be “a”
C. Get the information for eye color from lab partner and combine the alleles for each pair (fertilization) to see
what eye color your child would have
Your
phenotype
Genotype genes
Head or tail?
Your alleles in
sex cell
Child’s
genotype
Child’s
phenotype
A
B
…... …….
C
Partner’s
phenotype
Genotype genes
Head or tail?
Partner’s allele
in sex cell
…… …….
………………..
Eye color!
…… …….
A
B
C
General Biology
2
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
1) Give 3 different genotypes that would produce eyes with light brown color
…………………………...
…………………………….
……………………………
2) What possible phenotypes for eye color in the offspring would NOT be possible if the two parents have
hazel and blue eyes respectively?
………………………………………………………………………………………………………………………………….
3) What event of meiosis that takes place in anaphase 1 are you simulating by flipping head or tail to get
the allele you are going to pass to the offspring?
………………………………………………………………………………………………………………………………….
4) What event of meiosis that happens in metaphase 1 are you also simulating when considering that
every time you flip the coin the result you get is random and independent from the other flips?
………………………………………………………………………………………………………………………………….
TASK 2: SKIN COLOR DETERMINATION
Skin color is determined by at least four genes. As for eye color, the allele for skin pigmentation is dominant
(uppercase) and the more dominant alleles that you have the darker your skin color is. The assumption here is that
your skin color genotype is composed of 8 alleles having an additive effect, where the more dominant alleles
(uppercases) you have out of the eight the darker your skin is.
SKIN COLOR
# OF DOMINANT ALLELES
Melon
0
Almond
1
Fawn (light yellowish tan color)
2
Toast (light brown)
3
Cinnamon (brown)
4
Gingerbread (mid brown)
5
Mahogany (dark brown)
6
Chestnut (very dark brown)
7
Ebony (brown/black)
8
5) What is the darkest skin color a baby could have if both parents have toast skin color? Explain
………………………………………………………………………………………………………………………………….
6) What parents’ genotypes would allow this couple to have a baby with almond color skin?
………………………………………………………………………………………………………………………………….
7) If the genotypes for both parents are AABbccdd, what skin colors are NOT possible in the baby?
………………………………………………………………………………………………………………………………….
General Biology
3
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
Procedure
A. Determine your genotype for skin color based on your phenotype. Determine your genotype for eye color based
on your phenotype. Make as many heterozygous genotypes as possible if you have less than 4 dominant
alleles
Example: if you skin color is cinnamon, then your genotype has to be Dd, Ee, Ff, Gg
B. Flip a coin for every gene (D, E, F, G) using heads for dominant and tails for recessive alleles to simulate
independent assortment in meiosis 1 and determine which allele you would pass to your child during
fertilization.
Example: if your genotype for the first letter is Dd, and you get “Tails”, your allele would be “d”
C. Get the information for skin color from lab partner and combine the alleles for each pair (fertilization) to see
what skin color your child would have
D. Get the information for skin color from lab partner and combine the alleles for each pair (fertilization) to see
what skin color your child would have
Your
phenotype
Genotype genes
Head or tail?
Your alleles in
sex cell
Child’s
genotype
Child’s
phenotype
D
E
Partner’s
phenotype
F
…… …….
G
…… …….
Genotype genes
Head or tail?
Partner’s allele
in sex cell
D
…… …….
…… …….
E
F
G
Karyotypes
A karyotype (from the greek karyon = nucleus) is a “picture” of all the chromosomes inside the nucleus of an
eukaryotic organism during cell division. A karyotype allows seeing the number and appearance of all the
chromosomes. We know already that eukaryotic organisms are mostly diploid (2N) in their somatic cells, which
means there are two copies of each chromosome called homologous chromosomes, one passed down by the
mother and one by the father during sexual reproduction.
A karyotype analysis allows pairing up homologous chromosomes by analyzing their length, the position of
the centromeres, the banding pattern, and any differences between the sex chromosomes X and Y. A normal
karyotype for humans has 46 chromosomes: 44 autosomes (chromosomes not connected with sex determination)
plus XX for a female or XY for a male. Any abnormal karyotype is the result of non-disjunction during meiosis in
either the father or the mother that resulted in an abnormal sex cell with either 22 or 24 chromosomes (instead of
23). Non-disjunction happens either during anaphase 1 or anaphase 2 of meiosis. If these sex cells are later
used during sexual reproduction the baby would have either 45 or 47 chromosomes.
General Biology
4
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
DISORDERS AND ABNORMAL KARYOTYES
Missing (part of) 5: CRI-DU-CHAT: Also known as 5p- syndrome and cat cry syndrome - is a rare genetic
condition that is caused by the partial deletion (a missing piece) of genetic material on the small arm of
chromosome 5. The cause of this rare chromosomal deletion is unknown. The clinical symptoms of cri du chat
syndrome usually include a high-pitched cat-like cry, mental retardation, delayed development, distinctive facial
features, small head size (microcephaly), widely-spaced eyes (hypertelorism), low birth weight and weak muscle
tone (hypotonia) in infancy. The cat-like cry typical becomes less apparent with time. Most individuals who have cri
du chat syndrome have difficulty with language. Half of children learn sufficient verbal skills to communicate.
(http://www.genome.gov/19517558)
Extra 13: PATAU SYNDROME is a syndrome in which some or all of the cells of the body contain extra genetic
material from chromosome 13. The extra genetic material from chromosome 13 disrupts the normal course of
development, causing multiple and complex organ defects. Patau syndrome affects somewhere between 1 in
10,000 and 1 in 21,700 live births (http://en.wikipedia.org/wiki/Patau_Syndrome)
Extra 18: EDWARDS SYNDROME is a genetic disorder caused by the presence of all or part of an extra 18th
chromosome. It is the second most common autosomal trisomy, after Down's syndrome. Edwards syndrome
occurs in around one in 6,000 live births and around 80 percent of those affected are female. The majority of
General Biology
5
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
fetuses with the syndrome die before birth. The incidence increases as the mother's age increases. The syndrome
has a very low rate of survival, resulting from heart abnormalities, kidney malformations, and other internal organ
disorders (http://en.wikipedia.org/wiki/Edwards_Syndrome)
Extra 21: DOWN SYNDROME is a chromosomal condition related to an extra chromosome 21 (trisomy). It affects
1 in 800 to 1 in 1000 live born infants. People who have Down syndrome have learning difficulties, mental
retardation, a characteristic facial appearance, and poor muscle tone (hypotonia) in infancy. Individuals with Down
syndrome also have an increased risk for having heart defects, digestive problems such as gastroesophageal
reflux or celiac disease, and hearing loss. Some people who have Down syndrome have low activity of the thyroid
gland (hypothyroidism) - an organ in the lower neck that produces hormones (http://www.genome.gov/19517824)
Extra Y: JACOBS SYNDROME: XYY syndrome is characterized by an extra copy of the Y chromosome in each
of a male's cells. Although males with this condition may be taller than average, this chromosomal change typically
causes no unusual physical features. Most males with 47,XYY syndrome have normal sexual development and
are able to father children. 47,XYY syndrome is associated with an increased risk of learning disabilities and
delayed development of speech and language skills. Delayed development of motor skills (such as sitting and
walking), weak muscle tone (hypotonia), hand tremors or other involuntary movements (motor tics), and behavioral
and emotional difficulties are also possible. These characteristics vary widely among affected boys and men. A
small percentage of males with 47,XYY syndrome are diagnosed with autistic spectrum disorders, which are
developmental conditions that affect communication and social interaction.( http://ghr.nlm.nih.gov/condition/47xyysyndrome)
Extra X (male): KLINEFELTER SYNDROME XXY s a condition that occurs in men as a result of an extra X
chromosome; the most common symptom is infertility. Klinefelter syndrome is found in about 1 out of every 5001,000 newborn males. Women who have pregnancies after age 35 have a slightly increased chance of having a
boy with this syndrome. Males who have Klinefelter syndrome may have the following symptoms: small, firm
testes, a small penis, sparse pubic, armpit and facial hair, enlarged breasts (called gynecomastia), tall stature, and
abnormal body proportions (long legs, short trunk) (http://www.genome.gov/19519068)
Missing X (female): TURNER SYNDROME X0 is a chromosomal condition that alters development in females as
a result of having only one X chromosome. Women with this condition tend to be shorter than average and are
usually unable to conceive a child (infertile) because of an absence of ovarian function. Other features of this
condition that can vary among women who have Turner syndrome include: extra skin on the neck (webbed neck),
puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, heart defects and kidney
problems. This condition occurs in about 1 in 2,500 female births worldwide, but is much more common among
pregnancies that do not survive to term (miscarriages and stillbirths). (http://www.genome.gov/19519119).
Extra X (female): TRIPLE X SYNDROME Unlike most other chromosomal conditions (such as Down syndrome),
there is usually no distinguishable difference to the naked eye between women with triple X and the rest of the
female population. Symptoms may include tall stature; small head (microcephaly); vertical skinfolds that may cover
the inner corners of the eyes (epicanthal folds); speech and language; learning disabilities, such as dyslexia; or
weak muscle tone.[2] The symptoms vary from person to person, with some women being more affected than
others. There are seldom any observable physical anomalies in Triple X females, other than being taller than
average (http://en.wikipedia.org/wiki/Triple_X_syndrome)
General Biology
6
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
TASK 3: ANALYZING KARYOTYPES
Procedure
A. Pick any of the available incomplete unorganized karyotype (notice each one has a letter)
B. Using the space provided in the next page, cut and glue the chromosomes in order to organize all
chromosomes in pairs according to their number
C. Determine the chromosomal abnormality of the baby based on the information provided before, use the picture
of the normal male karyotype as reference
General Biology
7
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
8) What is the letter of your karyotype? ……………………………………………………………………………..
9) How many total chromosomes are in this karyotype? ………………………………………………………….
10) What is the name of this syndrome? ..............................................................................................................
11) Describe the specific chromosomal abnormality of this karyotype (what is missing or what is extra)
.…..……. ………………………………………………………………………………………..………………………………..
12) What are the consequences of this syndrome?
.…..……. ………………………………………………………………………………………..………………………………..
.…..……. ………………………………………………………………………………………..………………………………..
.…..……. ………………………………………………………………………………………..………………………………..
.…..……. ………………………………………………………………………………………..………………………………..
13) What is the gender of this baby? ……………………………………………………………………………………..
Create a Kid Simulation
We will examine some easily seen human traits or characteristics that give each person their uniqueness.
We will then pair up and see what type of children we might have, assuming that were to “reproduce”.
TASK 4: YOUR FACIAL HUMAN TRAITS
According to Mendel genetics, genes come in two “versions”: the dominant and the recessive one. When
and individual is a mixed of both versions (called “alleles”), the dominant allele masks the presence of the
recessive one and the observable characteristic (called phenotype) is the dominant one. However, genes not
always show the dominant/recessive behavior. One different alleles’ interaction appears when there are two
versions or alleles of the same gene and three possible genotypes, but there is no real dominance of one allele
over the other. In this case, called incomplete dominance, a third phenotype shows when the individual is
heterozygous (hybrid). For example, hair type can be curly, wavy, or straight. There are three phenotypes but only
two alleles for that gene (C or c). Individuals having the alleles CC will have curly hair, individuals having the
alleles Cc will have a wavy hair, and individuals having the alleles cc will have straight hair.
Procedure
A. Work in pairs and use the following information to fill in the data table below with the genotypes of both
students.
B. Notice that some of these traits exhibit complete dominance (Mendelian situation, where there is one dominant
and one recessive form of the gene) and some show incomplete dominance (where a third possible phenotype
appears if the individual is heterozygous). Select in the table the right the genetic situation for each trait
(DOMINANCE / INCOMPLETE DOMINANCE)
C. If you show the dominant condition for any of these traits, then assume you are heterozygous for that trait.
(e.g. if you are tongue rolling assume you have Rr in your genes). If the trait shows incomplete dominance,
write the genotype you know you have
General Biology
8
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
GENOTYPE
STUDENT 1
TRAIT
GENOTYPE
STUDENT 2
1-Hair type: Naturally curly (CC), wavy (Cc), or straight (cc)
2-Widow’s peak: Forehead hairline forms a point (widow’s peak) in the center. Present
(Ww), absent (ww)
3-Eyebrows: Bushy (Bb) or fine (bb)
4-Color of the eyebrows: Darker (HH), lighter (hh), or same (Hh) than the hair color
5-Eyelashes: Long (Ll) or short (ll)
6-Eye color: Non-blue eyes (Ee) is dominant over blue (ee). Note that we are really oversimplifying this because eye color is determined by several genes, at least 8, and is
termed a quantitative trait
7-Freckles: Present (Ff) or absent (ff)
8-Earlobes: Free or unattached earlobes (Uu) and attached earlobes (uu)
9-Dimples: Present (Dd) and absent (dd)…
10-Tongue rolling: This is the ability to roll the tongue into a U-shape, quite an adaptive
trait eh? Imagine impressing a potential partner with this ability! Rolling (Rr) and Nonrolling (rr)
14) Based on the information given on the following page, which TRAITS show DOMINANT/ RECESSIVE
interaction? (CIRCLE ALL THAT APPLY)
Hair
type
Widow’s
peak
Eyebrows
Eyebrows
color
Eyelashes
Eye
color
Freckles
Earlobes
Dimples
Tongue
rolling
15) Which TRAITS show INCOMPLETE DOMINANCE interaction? (CIRCLE ALL THAT APPLY)
Hair
type
Widow’s
peak
Eyebrows
Eyebrows
color
Eyelashes
Eye
color
Freckles
Earlobes
Dimples
Tongue
rolling
16) Is the number of possible genotypes different between Mendel (dominant/recessive) and Incomplete
Dominance? YES / NO
17) Is the number of possible phenotypes different between Mendel (dominant/recessive) and Incomplete
Dominance? YES / NO
18) Explain your previous answer
.…..……. ………………………………………………………………………………………..………………………………..
….……. …………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………..
General Biology
9
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
TASK 5: CREATE A KID SIMULATION
PROCEDURE
I. For each parent’s genotype (example= Dd) flip a coin to represent the random assortment during metaphase
of meiosis 1 and the posterior segregation of mother and father chromosomes during anaphase 1, which
ultimately decide which allele is being passed to the baby. You will have to flip a coin 10 times for all 10 trais
then
II. Flip a coin one more time in order to decide the gender of the baby!
III. Use the table provided in the following page to represent the alleles each “parent” is contributing to the baby
IV. In the same table, combine the alleles and determine the baby’s genotype
V. Knowing the genotype and the type of genetic interactions, obtain the phenotype for each trait
TRAIT
Mother’s Father’s
alelle
allele
Child’s
GENOTYPE
Child’s PHENOTYPE
1- HAIR TYPE
2- WIDOW’S PEAK
3- EYEBROWS
4- COLOR OF THE EYEBROWS
5- EYELASHES
6- EYE COLOR
7- FRECKLES
8- EARLOBES
9- DIMPLES
10- TONGUE ROLLING
VI. Record the sex of the child and name him/her!
Father’s name: ………………………………………
Mother’s name ………………………………………
Child’s name: ………………………………………
Sex: ………………………………………………….
19) In the previous procedure, what is the flipping of the coin simulating to be during meiosis?
…………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………..
20) Which parent determines the sex of each child? ……………………………..…………………………………
TASK 6: THE CHILD’S FACIAL TRAITS
21) Make a drawing of the child’s face in the space provided, each parent has to make his/her own
representation of the child’s face
General Biology
10
Instructor: Jose Bava, Ph.D
LAB Meiosis and Human Traits
Name:
Child’s face according to you! (print your name)……………………………………..………………………. …………..
General Biology
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Instructor: Jose Bava, Ph.D