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7/29/2019 Chapter 11-3.ppt
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Chapter 11.3
Chromosomes and Human
Heredity
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Karyotype Studies
A Karyotype is an array ofchromosomes created byphotographing themetaphase chromosomes
from one cell, cutting outthe individualchromosomes from thephotograph and liningthem up in order from
largest to smallest,pairing the appropriatehomologouschromosomes. ...
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Karyotype Studies
Notice on this
Karyotype there are 3
copies of the 21st set
of chromosomes This results in downs
syndrome (trisomy
21)
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Nondisjunction at M1
Nondisjunction at M2
Non-disjunction occurs when chromosomes inthe developing gamete (sex cell) fail to separateduring one of the divisions of meiosis. The resultis a sperm or egg cell with either an additionalchromosome, or one that lacks onechromosome. When this sex cell combines withone from the opposite sex, the resulting fetus willhave cells with an extra, or one chromosome
that is lacking. Generally, such fetus' will notdevelop properly and we would say that theresulting baby would have a birth defect.
http://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20I.htmhttp://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20II.htmhttp://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20II.htmhttp://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20I.htm7/29/2019 Chapter 11-3.ppt
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Animation of Non-
Disjunction
http://www.sumanasinc.com/webcontent/animations/content/mistakesmeiosis/mistakesmeiosis.swfhttp://www.sumanasinc.com/webcontent/animations/content/mistakesmeiosis/mistakesmeiosis.swfhttp://www.sumanasinc.com/webcontent/animations/content/mistakesmeiosis/mistakesmeiosis.swfhttp://www.sumanasinc.com/webcontent/animations/content/mistakesmeiosis/mistakesmeiosis.swfhttp://www.sumanasinc.com/webcontent/animations/content/mistakesmeiosis/mistakesmeiosis.swf7/29/2019 Chapter 11-3.ppt
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Changes in Numbers of Sex
Chromosomes
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Turners Syndrome (0X)
Turner syndrome is agenetic disorder thataffects a girl'sdevelopment. Thecause is a missing orincomplete Xchromosome. Girlswho have it are short,
and their ovaries don'twork properly. Mostare infertile.
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XXX female
Triple X syndrome is a
form of chromosomal
variation characterized by
the presence of an extra
X chromosome in eachcell of a human female.
Usually these woman are
undiagnosed and function
normally
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XXY maleKlinefelters Syndrome
Chromosomal defectin males in whichthere is an extra Xchromosome;manifestations mayincludeunderdevelopedtestes, physical
feminization, sterility,and mentalretardation.
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XYY Male
Most often, this chromosomal change causes nounusual physical features or medical problems.
XYY boys and men are usually taller than
average and several centimeters taller than theirparents and siblings
XYY males have normal sexual developmentand usually have normal fertility. XYY males
may be taller, tend to be wiry-built, and tend tohave severe acne. Minor birth defects -- likepectus, crooked eye, and minor outturning of theelbows, are possible in XYY's.
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OY Chromosome
A person with only one Y chromosome
(45,Y) could not survive or be born alive.
The X chromosome has important genes
on it that would be completely missing insuch a person.
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Fetal Testing - amniocentesis
A sample of amniotic
fluid can be withdrawn
and analyzed (fluid
contains fetal cells). It
is useful for
Diagnosing sex linked
disorders
Chromosomal defects
Sex can also be
determined
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Fetal Testing Chorionic villus
sampling
Tissue is taken from
membrane surrounding
the fetus. Can test for:
(1) Chromosomal
abnormalities.
(2) Some inherited
disorders. Dominant,
Recessive and X-linked
patterns of inheritance.
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Fetal Testing Fetal Blood
sampling A fetal blood sample may betaken to:
diagnose genetic orchromosome abnormalities.
check for and treat severe fetalanemia or other blood problemssuch as Rh disease.
check for fetal oxygen levels.
check for fetal infection.
give certain medications to thefetus.
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Extra Review
REVIEW: Nondisjunction can be caused by_____ .
Answer: Failure of the chromosomes toseparate during meiosis
REVIEW: A gamete affected bynondisjunction would have _____ .a. a change from the normal chromosome
numberb. one extra or one missing chromosomec. the potential for a genetic disorderd. all of the above
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More questions
Amniocentesis involves sampling
Fetal cells in amniotic fluid
The condition occurring when an organism
has a 2n + 1 chromosome composition isknown as
Trisomy
The sex chromosome composition of a
person with Turner syndrome is XO
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Assessment
1. Sex of individual and whether the
proper number of chromosomes are there
2. In homologous pairs from largest to
smallest.
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3.
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4.
Males only receive on X and one Y so
missing sections could contain vital genes
. With females having 2 XX deletion in one
X could be made up for by the other
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Further study
Really interesting information on human
genetics
http://www.thetech.org/genetics/asklist.phphttp://www.thetech.org/genetics/asklist.php