27.3 genetic disorders errors in the chromosome number genetic disorders and sex chromosomes genetic...
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27.3 Genetic Disorders
•Errors in the chromosome number•Genetic Disorders and sex chromosomes•Genetic Disorders and autosomes•Genetic Counseling
Errors in Chromosome Numbers
• Less than 46 chromosomes
• OR
• More than 46 chromosomes
• Due to mistakes in meiosis
• Anaphase, chromosomes do not get pulled appart
Errors due to Meiosis
*Normal *Normal *Too many *Too few
4 Possible Gametes
Sperm or Egg
Trisomy
• Inheriting three copies of a chromosome instead of two
• Too many
• 47 chromosomes
Down syndrome
• Outwardly slanted eyes • Exaggerated fold of skin
on the inside of the eye • Flat ears set low on the
head • Flattened face • Small teeth • Relatively short arms and
legs.
Edward syndrome • Defects of the kidneys,
ureters, heart, lungs and diaphragm.
• Cleft lip or cleft palate. • Small skull
(microcephaly). • Malformations of the
hands and feet • Neural tube defect, where
the spinal cord, meninges and blood vessels protrude through a gap in the vertebrae
• Malformations of the sex organs
Patau syndrome
• Small skull (microcephaly). • An abnormal opening in the skull. • Malformations of part of the brain. • Structural defects of the eyes. • Cleft lip or cleft palate. • Additional toes or fingers • Congenital heart disorders, such as
ventricular septal defect. • Neural tube defect, where the spinal
cord, meninges and blood vessels protrude through a gap in the vertebrae
• Malformations of the sex organs.
Monosomy
• Inherit one copy of a chromosome instead of two
• Too few
• 45 chromosomes
Monosomy Disorders
• Turner Syndrome
Turner Syndrome
• condition in females (XX)• Due to an absent X-chromosome• short stature• sexual underdevelopment• physical abnormalities
Types of Chromosomes
1. Autosome: a non-sex chromosomes pairs 1 -22 on a karyotype
2. Sex chromosomes: the XX or XY pair 23 on a karyotype
Genetic Disorders
Carried by Sex Chromosomes:
• Hemophilia
Carried by Autosomes
• Dyslexia
• PKU
Hemophilia
• Disorder
• Blood can not form clots
• Found on recessive gene
Dyslexia
• A learning disorder
• Can not see or write letters and or words
• Appear backwards
• Dominant gene
PKU
• Body lacks the enzyme necessary to metabolize phenylalanine to tyrosine.
• Causes brain damage and progressive mental retardation
Genetic Counseling
• Provide information and support to families who have members with birth defects or genetic disorders
• Or
• to families at risk for a variety of inherited conditions.
Counselors
• They identify families at risk, investigate the problem present in the family, interpret information about the disorder, analyze inheritance patterns and risks of recurrence, and review available options with the family.
Pedigree
• a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships.
• Determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases.
Pedigree
• A series of symbols are used to represent different aspects of a pedigree.
Pedigree
Dominant traits:
• Never skips a generation
• Two affected individuals can give rise to unaffected individuals
Recessive traits:
• may skip a generation
• two unaffected individuals can give rise to affected individuals
I
II
III
IV
Marriage Line
Children line
Siblings