Human body cells contain 46 chromosomes. The first 22 pairs are called autosomes, and they contain numerous genes that affect the traits of the individual. The last pair, number 23, are the sex chromosomes. The sex chromosomes determine gender (i.e., either male or female), but there are other genes on this pair of chromosomes as well. Males sex chromosomes are XY, while female sex chromosomes are XX . The gametes in a human (either egg cells or sperm cells) contain only 23 chromosomes. Fertilization, the fusion of an egg and a sperm, restores the total of 46 chromosomes in a human zygote. Non-gamete cells are called somatic cells, and they have all 46 chromosomes in them. 1. Your sex chromosomes: XX Just as in Mendel's pea plant experiments, genes in humans can be dominant or recessive, and the results of "crosses" can be predicted using Punnett squares. A phenotype is the physical expression of a gene (made up of a pair of alleles). The genotype is the actual genetic makeup of the allele pair. An individual having two identical alleles for a gene is said to be homozygous. There can be homozygous dominant or homozygous recessive combinations. Dominant traits are represented by capital letters; recessive by lower case letters. An individual having non-identical alleles for a gene is said to be heterozygous. Note that the phenotype of a heterozygous individual is determined by the dominant gene. Dominant alleles tend to cover up the presence of any recessive alleles. In a case of alleles that show simple dominance / recessiveness, it is not possible to know if an individual who possesses a dominant trait has the homozygous dominant or the hatarnzunniic nanntune haced an nhanntuns tha onlv nne wo knnwe for rertain is the Accessibility: Investigate Example: What phenotypes and genotypes could one expect from a cross between two pea plants, one true-breeding for yellow seeds and the other true-breeding for green seeds? Yellow seeds are dominant to green. Complete the Punnett square below. Y The true-breeding The true- breeding green seed plant yellow seed plant can only contribute can only contribute a recessive allele. a dominant allele. Many human traits are controlled by a single pair of alleles and through simple dominant and recessive rules. Example: Tongue rolling - If you can roll your tongue lengthwise, you have the trait controlled by the dominant allele. Let " R " represent the dominant allele in your genotype and r represent the recessive allele. If you have the dominant phenotype, how do you know if you are homozygous dominant or heterozygous. That depends upon knowing if one of your parents couldn't roll their tongue. For example, my Dad cannot roll his tongue but I can. So, my genotype is Rr for this trait. If you do know know about your parents, then you have to put both possible genotypes for yourself, i.e. RR or Rr . 2. What is your phenotype (roller or non-roller)? 3. What is your genotype? A. If you and your parents can both ro.

1. Human body cells contain 46 chromosomes. The first 22 pairs are called autosomes, and they
contain numerous genes that affect the traits of the individual. The last pair, number 23, are the
sex chromosomes. The sex chromosomes determine gender (i.e., either male or female), but there
are other genes on this pair of chromosomes as well. Males sex chromosomes are XY, while
female sex chromosomes are XX . The gametes in a human (either egg cells or sperm cells)
contain only 23 chromosomes. Fertilization, the fusion of an egg and a sperm, restores the total
of 46 chromosomes in a human zygote. Non-gamete cells are called somatic cells, and they have
all 46 chromosomes in them. 1. Your sex chromosomes: XX Just as in Mendel's pea plant
experiments, genes in humans can be dominant or recessive, and the results of "crosses" can be
predicted using Punnett squares. A phenotype is the physical expression of a gene (made up of a
pair of alleles). The genotype is the actual genetic makeup of the allele pair. An individual
having two identical alleles for a gene is said to be homozygous. There can be homozygous
dominant or homozygous recessive combinations. Dominant traits are represented by capital
letters; recessive by lower case letters. An individual having non-identical alleles for a gene is
said to be heterozygous. Note that the phenotype of a heterozygous individual is determined by
the dominant gene. Dominant alleles tend to cover up the presence of any recessive alleles. In a
case of alleles that show simple dominance / recessiveness, it is not possible to know if an
individual who possesses a dominant trait has the homozygous dominant or the hatarnzunniic
nanntune haced an nhanntuns tha onlv nne wo knnwe for rertain is the Accessibility: Investigate
Example: What phenotypes and genotypes could one expect from a cross between two pea
plants, one true-breeding for yellow seeds and the other true-breeding for green seeds? Yellow
seeds are dominant to green. Complete the Punnett square below. Y The true-breeding The true-
breeding green seed plant yellow seed plant can only contribute can only contribute a recessive
allele. a dominant allele. Many human traits are controlled by a single pair of alleles and through
simple dominant and recessive rules. Example: Tongue rolling - If you can roll your tongue
lengthwise, you have the trait controlled by the dominant allele. Let " R " represent the dominant
allele in your genotype and r represent the recessive allele. If you have the dominant phenotype,
how do you know if you are homozygous dominant or heterozygous. That depends upon
knowing if one of your parents couldn't roll their tongue. For example, my Dad cannot roll his
tongue but I can. So, my genotype is Rr for this trait. If you do know know about your parents,
then you have to put both possible genotypes for yourself, i.e. RR or Rr . 2. What is your
phenotype (roller or non-roller)? 3. What is your genotype? A. If you and your parents can both
roll your tongues but your sister cannot, what is the genotype of your parents? Support your
answer using Punnett square below. Support your ancwer using Punnett square bectow Ear lobes
Aticchind earlobes come straight out borizontally from the shill, and freo earlobes hang down on
the ear, boneath the point of antachmont to the skull Let F" represent the dominant allele in your
genctype. Attached earlobes are homorygous rocessive. Farsightedness Farsightediess (wten you
need geasses to read cp cose) is caused by a dominant allele, and "norrnar" sight is recessave:
Lek 'S' represent the allele for farsightedeness: Nearsightedness: Nearsightedness (wher you reed
glusses for better distance viscon) is caused by a complotely different gone than farsighifedhess.
Herey "nocmar" sight it the dominant allebo. Lot "ne" ropecrseat the alile for nearsightednerss.
Widow's peak if you hure a poerted contour of the harine on your forehead you havet a 'widew's
poak" (think Eddie Munster from the TV stion). The trait is caused by a dominant allele,
represented WF The lack of a wibow's peak is controlled by the rocossevo allole (w) Taste.
Certain chemicals can only be tactad if you hares a paricular genotype An. example is
pheny,thiocartarnide (PTC). which has an unpieasandy bitter taste to people who thavo the

2. dominant allole (T). If you are unable fo taste thrs chomical. you are hamozygours recessive
Clasped hands: When you clasp your hands together in your lap, you consistentiy put either the
lett thuenb on top, of the right. This is not the same as being right: of Welthanded. The tecessive
trat is if the rigt thamb is clisped on top. Use "L* to represent the dominant alele: Hitchhiker's
thumb: Sciontifically known as "distal hypereatensibily of the thumb," hitchhiker's thumb is an
sutosomal tocessive trat (h) in which placing the hand in a "thumbs-up" position results in an
angle of nearly 90 " Mid-digital hair. The presence of hair on the back of the midde sogment of
at loast one finger is a dominant trat (My. The absenee of hat on the madole segment of all
fingers is at recessive trat (m). A single par of alcues does not cause the trait, se you mey have
mid-digutai fair on some lingars bul not olhers: Cleft chin: Soine peogle tiave a peominent
dimple cr crease in the front of the chun, called a cleft chin, others do not. Uise "C' to indicabe
the presence of a cleff chin which is docrinant to a smooth chin Piamented ifis: Melanin is a dark
trown piomant found in the sken and is akio the Pigmented iris: Melanin is a dark beown
pigment found in the skin, and is also the substance that produces the eye colars specified by the
genes. The arnount and placement (front or back of the iris) of the melarin prodeses the different
eye colors that wo see. Our gones lelt enzyrnes how maxh melanin to deposit in the itis and in
which part to place it. When melanin is deposited in the front of the itis, eye color ranging from
green to brown results (P) dependent upon the ameant of pigment deposited. When melanin is
deposited in the back layer only, blue eyes result (p) Toe length: In some people, the big toe is
longer than the second loe (b), while other poopla have the big toe shorter than the second toe
(B) For each of the trats shown, delerinine and record your phenohpe in Table 1 Eared on your
phenotypo, doternine your genolype. Be sure lo ket at possiblites. The study of inheritance
patterns in organisme fhat diles in two traits is called ar dihybrid cross. Mondet conduchod
ditiytorid crossens to detormine if difterent traits of pea plants, such as flower color and seed
shape, were inheritod indopendently or fogether. We now know that the traits are inhented
independently (with the erception of linked genes) because members of an allele pair separafe
from one ancther during gamefe formation. This is known as Mendel's law of independent
assortment A cross of two individuats, boiti of which are heterouygous for the two fraits being
studied. wotild look like this RrYy x Rryy Each individual is capable of producing gaeneles that
centain eather the dominant or recessive anlile for shape (R of t ) and the dornirart or recessiwe
alkle for color (Y or y ) The oflogeing probatiilies for thes cross ane - ar16 having both dominant
parental phenotypes (rourd soed shape, yellow seed color) - 316 having one dominant parental
phoinotype and cone recessive fround seed shape, green seed color) - 316 having the other
dominarit parental phenctype and the other tecossivu fwrikiled seed shape, yellow seed color) -
1/16 having both tocessive parental phonohypes (arinkled seed shape, green seed color) This
93:3.1 ratio is comence far ditytud crossia involvang non-iriad genes. Carry out the following
ditydrid cross Be sure to show your work in the 4 to Punnett square prondod B. Two indriduaks
who are doubly breterocygous for Widows poak and earlobe trats (WwFi) marry and have
childen What the chance is that theit chikien will hare both altached earobes AND ne widow's
peak? Exercise 3: Codominance Some gone obeles mathitit codominance instoat of one gene
aldele (the recessive allibie) being thddoun by the expression of ancther gene alles (tre dominant
alelo), both alleles. aie expressed at the same time. Blood groups ano an eniniple of codominance
of alleles in tumans. Blood groups Thece are toer man blood types in humans O, A., B, and AB.
These blood groups vary in the carbobydate moleciles (arbyons) that are andached to the suetace
of the red blood oels (Racs) these mabe co par of the surtace inceptor proteins (glycoproteins) on
RBCS. If yoa tave the A alten, you produce the A antigen on your tod bood cell (Type A blood)

3. if you have the B alobe you prodsee the B antigen (type B. blood) If you have the A allole and
the B altale, you wit prodyen both (thas you wil have type AB blood) it you hove nohhor the A
nor B s sthas you cary nwo O alehes and will not produce edtor A or B antigen, fesuling in bee 0
blood Biood alwavs hm antbodies in & thst nead aperot the carbohydrates that ere not notraly
present ( 0 . people with blood groes A hare the A carbetydras on ther REC: "meninggiobulin"
which is whe antededes really are? This is completey diflerent from the Fh factof, which is emer
positive or negatiwe. Usually, chiddren have the same Rh tactor as their mother. 4. Alood typo.
Phenotype? Einotype? Example. A woman with type 0 blood maeres a man with type Adi blood
Which blood groups are possible for the children? A and B in in in in C. Assumo that you are
blood grous B, your mother is blood group O. and your spouse is blood group A (ganiotype 14)
Which blood grouss are possiche for the children? Use the Punnet square to seppoit your arewer
C. Assumn that you are blood groug A. your mother is tlocd grocp 0 , and your spouro is biood
atous. A ioenatvoe 1 ( 1/ ). Which blood croups are possible for fie childen? Liso the Purine?
square to sagport your answer D. Bsood types can be used to prove that a inale is not the tather
of a child, but cannot be used alone to prove that he is the taitiri (mush mare ganetic data is
needed) Which of the following thales maght be Mo tather in the following silustrons: Mother
qroup A , child grocip B, Male it 1 groip 0, Make = 2 group AS? Use the Punnott square to
support your answer.