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What are chromosomes?What are chromosomes?
Humans have 23 Humans have 23 pairs of pairs of chromosomes, with chromosomes, with one chromosome one chromosome from each parent. from each parent. The chromosomes The chromosomes are coiled up DNA. are coiled up DNA. Under normal Under normal conditions all of the conditions all of the chromosomes are chromosomes are inherited in tact. inherited in tact.
This is a normal karyotype of
human chromosomes. A karyotype is a picture of chromosomes lined up to look
at and compare.
Chromosomal DisordersChromosomal Disorders Chromosomal deletionChromosomal deletion: when cells go through : when cells go through
meiosis, portions of the chromosome are lost.meiosis, portions of the chromosome are lost. Chromosomal inversionChromosomal inversion: when cells go : when cells go
through meiosis, parts of the chromosome through meiosis, parts of the chromosome are flipped.are flipped.
Chromosomal translocationChromosomal translocation: when cells go : when cells go through meiosis, parts of the chromosomes through meiosis, parts of the chromosomes stick together and switch.stick together and switch.
Chromosomal non-disjunctionChromosomal non-disjunction: when cells go : when cells go through meiosis the chromosomes don’t through meiosis the chromosomes don’t separate correctly and either too many or not separate correctly and either too many or not enough are passed on.enough are passed on.
Single Chromosome DisordersSingle Chromosome Disorders
1.Deletion
• Genetic material is missing
2. Duplication
• Genetic material is present twice
3. Inversion
• Genetic material is “flipped”
Two Chromosome DisordersTwo Chromosome Disorders((Both types are called “translocation”)Both types are called “translocation”)
Insertion
• Genetic material is added from another chromosome
Translocation
• Material is swapped with another chromosome
Turners SyndromeTurners Syndrome1 in 5,000 births
45 chromosomes X only
#23 MonosomyNondisjunction
96-98% do not survive to birthNo menstruationNo breast developmentNarrow hipsBroad shoulders and neck
Cri-Du-Chat SyndromeCri-Du-Chat Syndrome 1 in 216,000 births
46 chromosomes
#5 Deletion of lower arm
Symptoms:
Moon-shaped
face
Heart disease
Mentally
retarded
Malformed
larynx
Normal lifespan
Aniridia-Wilms Tumor Aniridia-Wilms Tumor SyndromeSyndrome
1 in 50,000,000 births
46 chromosomes
XY or XX
#11 Deletion of upper
arm
Symptoms:
Mentally retarded
Growth retarded
Blindness
Tumors on kidneys
Short lifespan
Thirteen Q Deletion SyndromeThirteen Q Deletion Syndrome
1 in 500,000 births
46 chromosomes
XY or XX
#13 Deletion of lower arm
Mentally retardedDeformed faceNo thumbsHeart diseaseShort lifespan
Prader-Willi SyndromePrader-Willi Syndrome1 in 5,000,000 births
46 chromosomesXY=97% XX=3%
#15 Deletion of lower arm
Small bird-like head
Mentally retarded
Respiratory problems
Obesity
Short lifespan
Eighteen Q Deletion SyndromeEighteen Q Deletion Syndrome
1 in 10,000,000 births
46 chromosomes
XY or XX
#18 Deletion of lower arm
Mentally retardedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan
Burkitt LymphomaBurkitt Lymphoma
Translocation of the Myc gene on chromosome 8
Normal Myc genes control cell growth and division
•Translocated Myc genes don’t function properly
•Leads to cancer of the lymph nodes
Down Syndrome: Trisomy
Down Syndrome
1 in 1,250 births
47 chromosomesXY or XX
#21 Trisomy Nondisjunction
1 in 31,000 births
46 chromosomesXY=97%
XX=3%
#14/21 Translocation
Down SyndromeDown SyndromeShort, broad hands Stubby fingersRough skinImpotency in malesMentally retardedSmall round faceProtruding tongueShort lifespan
Klinefelter SyndromeKlinefelter Syndrome1 in 1,100 births
47 chromosomesXXY only
#23 Trisomy Nondisjunction
Scarce beard
Longer fingers and arms
Sterile
Delicate skin
Low mental ability
Normal lifespan
Tay-SachsTay-Sachs incidence rate of incidence rate of
infantile Tay-Sachs= infantile Tay-Sachs= • Ashkenazi Jewish Ashkenazi Jewish
groups, French groups, French Canadian & Cajun: Canadian & Cajun: 1 in 30 are carriers1 in 30 are carriers
• other groups: 1 in other groups: 1 in 300 are carriers300 are carriers
accumulation of lipids on accumulation of lipids on brainbrain
brain malfunction; death by brain malfunction; death by age 5age 5
Sex-linked: X chromosomeSex-linked: X chromosome Duchenne Muscular Duchenne Muscular
DystrophyDystrophy 1 boy in every 3,0001 boy in every 3,000 progressive progressive
weakening of weakening of muscles and loss of muscles and loss of coordinationcoordination
more common in more common in malesmales
Cystic FibrosisCystic Fibrosis
1/31 is carrier in U.S.1/31 is carrier in U.S. Single gene mutationSingle gene mutation mucus in lungs, mucus in lungs,
pancreas, digestive pancreas, digestive tract and other organstract and other organs
most common lethal most common lethal genetic disease in genetic disease in U.S.U.S.
heterozygote heterozygote may be may be resistant to resistant to typhoid fevertyphoid fever