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Chromosome Number in Human Cells


Sex Cells Body Cells



How to Detect Chromosome Number 

_____________________________ - A way of looking at the chromosomes in a fetus. Amniotic fluid is taken at 14-16 weeks.









___________________ (Chorionic Villus Sampling) – Tissue is taken from the fetal placenta, and chromosomes are analyzed.  Taken at 10 weeks. (Pricedure is same as above)


Types of Chromosomes:


_____________________________ - Numbered chromosomes, do not determine sex (chromosomes pairs, numbers 1 through 22)


_____________________________ - Chromosomes X and Y. This pair of chromosomes determines sex of an organism.


Female Sex Chromosomes = _________    Male Sex Chromosomes = _________




The _______________________ determines the sex of a child because he may contribute either an ___ OR a ___ to that child. The _____________________ may only contribute an ___.


There is a 50/ 50 chance of having either a boy or a girl each time a couple has a baby: Do the Punnett Square…





Complete Dominance

 A ____________________ gene completely masks a _____________________ gene so that the _____________________ is not seen at all in the person, even though it may be present.



Free Earlobes (_____) are dominant to attached earlobes (_____)

FF, Ff - __________________________________
Ff - __________________________________


Cross two heterozygous, free earlobed persons:





Incomplete Dominance

 A “____________________” of traits resulting in an ________________________ phenotype. NEITHER gene is totally _____________________ over the other (lack of true dominance).



Red Snapdragons (_____) are dominant to White Snapdragons (_____)


RR - ___________________________________
Rr - ____________________________________
rr - ____________________________________


Cross two PINK snapdragons:






_______________________________________ - A recessive genetic disorder in which Red Blood Cells are sickle (irregularly) shaped. This results in _______________________________ because sickled red blood cells cannot travel through capillaries as efficiently as round red blood cells. ______________ does not reach the tissues effectively when necessary.


This disease occurs primarily in ________________________________________


Normal Red Blood Cells (_____) are INCOMPLETELY DOMINANT to Sickled Red Blood Cells (_____). This means that HETEROZYGOTES  (RR’) are ___________________________________________, showing a _____________  of _______________________ This may have an advantage:






RR - ______________________________________________
RR’ - ______________________________________________


Cross 2 individuals heterozygous for The Sickle Cell Gene (RR’) X (RR’)






Blood Types in Humans


Blood Type (Phenotype) Genotype (Genes Present)


Blood type is determined by the Presence or Absence of _____ Proteins (or ______________): Protein ____ or Protein ____.


If a person has ____ Protein in his blood, he will be Type ____
If a person has ____ Protein in his blood, he will be Type ____
If a person has BOTH  ____ AND ____ Protein in his blood, he will be Type _____
If a person has NEITHER Proteins in his blood, he is designated Type ____


Predict the offspring of a cross between a Person Heterozygous for Type A (AO) and a person Heterozygous for Type B (BO):






Sex-Linked Traits  -



Traits that are carried on the X Chromosome:





_________________ have only ONE __________ for each of these trait because they only have ONE ___________________________________. They are ____________________________ for these traits.


If there is a deletion or mistake in one of these genes, the __________ will not be able to produce ______________________ necessary for these functions – they now have _____ copies of this gene! (They lost their only copy!)



Cross a Male who has normal color vision (______) with a Female who carries the gene for colorblindness (______)






Genetic Disorders – Mistakes in Chromosome Number

 During __________________, sister chromatids are supposed to   _______________________ from each other. When sister chromatids of a chromosome _____________________________________________, this results in _________ or __________ with MORE or LESS than ______ chromosomes.






Down Syndrome (Trisomy 21)

        Karyotype – _________________ or __________________

        Individuals have an ____________ chromosome # _______







Edward’s Syndrome (Trisomy 18)

        Karyotype - ________________ or _________________

        Have an ________________ chromosome # ______

        Live no longer than ___________________







Patau’s Syndrome (Trisomy 13)

        Karyotype - _______________ or __________________

        Have an ______________ chromosome # ______

        Live for approximately _________________________








Turner Syndrome

        Karyotype - ________________

        ____________ stature

        Normal _______________________

        ___________________ neck


        Characteristic __________________________________

        May have ________________ or ________________ anomalies



Klinefelter Syndrome

        Karyotype - ________________

        Develop both ______________ & ________________ secondary sex characteristics

        Extremely ___________ and ___________ with ____________ limbs

        ______________________ problems


        Poor __________________________ adjustment





Single Gene Disorders


Dyslexia – Autosomal dominant

        See/ write some letters of the alphabet or parts of words backwards


Cross a Normal Male (dd) with a Heterozygous Female, affected with dyslexia (Dd):








Achondroplasia  (Dwarfism) – Autosomal Dominant

        Small stature

        Short limbs, large head, low nasal bridge, prominent foerhead


Cross 2 persons heterozygous for Achondroplasia (Dd) X (Dd)






PKU (phenylketonuria) – Autosomal recessive

        ___________________ in the body are not broken down properly, harming ______________ cells

        Infants are screened for the disease upon birth

        PKU patients are placed on a special ___________ to help them break down _______________ properly


Cross a heterozygous individual (Pp) with an affected individual (pp)







Cystic Fibrosis – Autosomal recessive

        Individuals cannot produce a protein necessary for clearing mucus out of lungs

        Results in lung infections

        Patients die of lung infections – usually in their 20’s

        Predominant in Caucasians


Cross 2 parents, heterozygous carriers of Cystic Fibrosis (Ff) X (Ff)






Red-Green Colorblindness – Recessive, Sex-linked (on X chromosome)

        Red & Green look like shades of Gray

        Mostly occurs in ______________ because they only have ____ X chromosome, or ____ copy of the ___________.


Cross a Male normal for color vision (______) with a Female carrier of colorblindness (________)






Hemophilia – Recessive, Sex-linked (on X chromosome)

        Individuals lack the gene that make a protein to ___________________

        Many bleed to death from open wounds because they cannot clot blood

        Blood transfusions to Hemophiliacs in the 70s & 80s increased the spread of AIDS to these patients by transfusing infected blood

        Occurs mostly in ____________ because they only have ____ X chromosome


Cross a Male Hemophiliac (______) with a normal Female (______)






Genetic Counseling


 The counselor creates a ______________________, a diagram that can show how a certain trait is passed along in a family. It is used to trace a family trait and predict whether future generations will have that trait.


Test such as _________________________ test to see if the child will have the disorder.


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