Elizabeth Beeson

Jessica Kraemer

Tharindhie De Silva

• There are 46 chromosomes in a normal human and 23 in the egg or sperm.

•Allele: are genes that are carried on chromosomes.

•Dominant alleles are always expressed if present.

•Recessive alleles are expressed when there is no dominant alleles expressed.

•Homozygous: Both alleles are the same for a trait.

•Heterozygous: Alleles are different for a trait.

http://teachline.ls.huji.ac.il/72155/chromosome3.jpeg

Mitosis: Is when one cell divides to make two cells that are exactly the same with 46 chromosomes.

http://genetics.gsk.com/index_flash.htm

Meiosis: When one cell copies it DNA and dived twice to form four genetically different daughter cells with 23 chromosomes.

http://www.yksd.com/DistanceEdCourses/YKSDbiology/lessons/ThirdQuarterLessons/Chapter09/9-2.html

•Nondisjunction: During cell division a pair of chromosomes does not separate.

•One daughter cell will end up with 24 chromosomes while the other has 22.

http://www.gillettechildrens.org/default.cfm/PID=1.3.18

• Most common defect to Central Nervous System

• Caused by the failure of the neural tube to close during development

• Spinal cord may protrude from the back

• Paralysis occurs in varying degrees

http://www.humanillnesses.com/Behavioral-Health-A-Br/Birth-Defects-and-Brain-Development.html

http://health.enotes.com/genetic-disorders-encyclopedia/spina-bifida

•Caused by nondisjunction of the 21st chromosome.

•If a sperm or egg with an abnormal number of chromosomes fertilize, the resulting fertilized egg will have an abnormal number of chromosomes.

•This is called trisomy 21.

Physical features

•A flatter face

• Upward slanting eyes

• A somewhat larger tongue

• Possible heart defects.

• They usually have some mental retardation.

• May have trouble learning.

•Turner syndrome is a chromosomal condition that girls and women have. Due to complete or partial absence of the second sex chromosome.

•The syndrome is named after Dr. Henry Turner, who was the first to describe its features in the 1930s.

•This occurs in about 1 in 2,000 live female births and as many as 10% of all miscarriages today.

http://www.antenataltesting.info/images/karyotypeTurners.jpg

•A normal female has two X chromosomes and males have one X and one Y.

•People with Turner Syndrome are missing all or part of one of their sex chromosomes.

•Half of girls with Turner syndrome have only one X chromosome. A third has two X chromosomes with part of one X missing

Characteristics:•Narrow, high-arched palate• Low-set ears •Low hairline •Webbed neck •Slight droop to eyes •lazy eye•Broad chest •arms that turn out slightly •Scoliosis •Flat feet •Small, narrow fingernails•toenails that turn up

http://learn.genetics.utah.edu/units/disorders/karyotype/images/turner_person.jpg

• Kleinfelter syndrome is a genetic disorder that occurs in males.

• Normal person has 46 chromosomes and the one who has this syndrome has 47 chromosomes.

• Two of the sex chromosomes are X chromosomes, and one is a Y chromosome.

• This is also called XXY syndrome.

• Mental retardation.

• Lower IQ test scores.

• Affected males look tall with long, skinny fingers and toes.

• Poorly developed secondary sexual characteristics.

• Delayed motor function, speech, and maturation development.

• X- linked disease that mainly affects boys.

• Caused by a lack of the protein dystrophin.

• Characterized by muscle weakness and progressive muscle wasting away of voluntary muscles

• Distinctive posture and movement

http://www.humanillnesses.com/original/Men-Os/Muscular-Dystrophy.html

http://www.dinf.ne.jp/doc/english/global/david/dwe002/dwe00212.htm

•Neurofibromatosis: is a genetic disorder of the nervous system. They cause growth of noncancerous tumors along nerves. It can also cause abnormalities of skin and bone.

•There are two types NF1 and NF2. They both had different levels of severity.

•The gene for NF1 is located on chromosome 17.

• The gene for NF2 is on chromosome 22.

•The abnormal gene are inherited from one parent who has the disorder or can result from a new mutation in a normal gene.

http://cc.oulu.fi/~anatwww/NF/Neurofibromatosis/plexiform.gif

Characteristics:

•Six or more tan spots on the skin

•Freckles that appear under the arms or in the groin

•Two or more benign tumors

•tumor on the eye nerve

•bowing of the legs

•People with NF1 normally have mild case and will life a normal life. There is not serious risk to their heath.

•While NF2 can also cause hearing loss, ringing in the ears, dizziness, facial numbness, balance problems and headaches.These people will have a harder time living normal lives.

http://www.sjxwl.com/pic/neurofibromatosis2.jpg