CHAPTER 27 – HUMAN GENETICS 

Chromosome Number in Human Cells

How to Detect Chromosome Number 

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

 Procedure:

___________________ (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.

EXAMPLE:

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).

EXAMPLE:

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

RR - ___________________________________
Rr - ____________________________________
rr - ____________________________________

Cross two PINK snapdragons:

EXAMPLE:

_______________________________________ - 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’ - ______________________________________________
R’R’_______________________________________________

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

Blood Types in Humans

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 # _______

·        Symptoms:

Edward’s Syndrome (Trisomy 18)

·        Karyotype - ________________ or _________________

·        Have an ________________ chromosome # ______

·        Live no longer than ___________________

·        Symptoms:

Patau’s Syndrome (Trisomy 13)

·        Karyotype - _______________ or __________________

·        Have an ______________ chromosome # ______

·        Live for approximately _________________________

·        Symptoms:

Turner Syndrome

·        Karyotype - ________________

·        ____________ stature

·        Normal _______________________

·        ___________________ neck

·        Infertile

·        Characteristic __________________________________

·        May have ________________ or ________________ anomalies

Klinefelter Syndrome

·        Karyotype - ________________

·        Develop both ______________ & ________________ secondary sex characteristics

·        Extremely ___________ and ___________ with ____________ limbs

·        ______________________ problems

·        Infertile

·        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.