genetic mutations. mutations … are changes in the genetic material can be good or bad can be on a...

Genetic Mutations

Mutations …

• are changes in the genetic material

• can be good or bad• can be on a single

gene or the whole chromosome

What is a karyotype?

• Picture of your chromosomes

• Arranged from largest to smallest

• quickly identify chromosomal changes

http://en.wikipedia.org/wiki/Image:NHGRI_human_male_karyotype.png

4 Types of Genetic Disorders

• Single gene – Change in the DNA sequence– More than 6000 known disorders– Autosomal or sex linked– 1 in 200 births– cystic fibrosis, sickle cell anemia, Marfan

syndrome, Huntington’s disease

Types of Genetic Disorders

• Multifactoral– combination of environmental factors and

mutations in multiple genes – more complicated – heart disease, high blood pressure, Alzheimer’s

disease, arthritis, diabetes, cancer, and obesity


• Chromosomal– abnormalities in chromosome structure as

missing or extra copies or gross breaks and rejoining

– Down Syndrome


• Mitochondrial– rare type of genetic disorder – caused by mutations in the non-chromosomal

DNA of mitochondria

Genetic Disorders

• On our chromosomes are a total of about 100,000 genes. Among these 100,000 genes, each person has on average 5-8 bad genes. However, these seldom have any effect at all. But sometimes there are serious errors in our genetic code and these can give us the blueprint for genetic disorder. When we have a serious genetic error, there are three primary ways that the error can be inherited (passed from generation to generation). These three patterns of inheritance are:

• Dominant genetic disorders

• Recessive genetic disorders

• Sex-linked genetic disorders

Dominant Genetic Disorders:

• In the dominant genetic disorder pattern of inheritance, one bad gene from either parent will cause the genetic disorder. Since only one bad gene causes the disorder, if either parent has the disorder the chance of the child inheriting the bad gene and developing the disorder is 50% with each conception.

Recessive Genetic Disorders:

• To develop a recessive genetic disorder both parents must contribute the same defective gene. The parents usually don't have the disorder, but are carriers for the disorder. They carry one defective gene, which is recessive, and one normal dominant gene.

Sex-linked Genetic Disorders: • These disorders occur due to errors in the 23rd pair of

chromosomes (the chromosomes responsible for gender). These genetic disorders occur only in males. Since males have an XY sex chromosome combination, they are vulnerable to defects on their X chromosome that lacks a partner gene on the Y. These disorders do not appear in females (which are XX) because if one of the X chromosomes has an affected gene, the partner X chromosome carries a normal gene. In females, the other X will compensate any defect on one X. Since males get a Y, there is no compensation. Although the female can carry a defective gene, females do not develop the disorder – they are carriers for the disorder.

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Sex-linked TraitsSex-linked Traits

• Traits (genes) located on the sex Traits (genes) located on the sex chromosomeschromosomes

• Sex chromosomes Sex chromosomes are are X and YX and Y• XXXX genotype for females genotype for females• XYXY genotype for males genotype for males• Many sex-linked traits carried on Many sex-linked traits carried on

X chromosomeX chromosomecopyright cmassengale

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Sex-linked TraitsSex-linked Traits

Sex ChromosomesSex Chromosomes

XX chromosome - female Xy chromosome - male

fruit flyeye color

Example: Example: Eye color in fruit Eye color in fruit fliesflies

copyright cmassengale

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Sex-linked Trait ProblemSex-linked Trait Problem• Example: Eye color in fruit flies• (red-eyed male) x (white-eyed female)

XRY x XrXr

• Remember: the Y chromosome in males does not carry traits.

• RR = red eyed• Rr = red eyed• rr = white eyed• XY = male• XX = female

XR

Xr Xr

Y


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Sex-linked Trait Solution:Sex-linked Trait Solution:

XR Xr

Xr Y

XR Xr

Xr Y

50% red eyed female

50% white eyed male

XR

Xr Xr

Y


Other Genetic Disorders:

• Other genetic disorders do not fall neatly into one of these three patterns. These involve having too many or too few chromosomes.

Turners Syndrome1 in 5,000 births

45 chromosomesX only #23 MonosomyNondisjunction

Turners Syndrome

96-98% do not survive to birthNo menstruationNo breast developmentNo hipsBroad shoulders and neck

Cri-Du-Chat Syndrome1 in 216,000 births

46 chromosomesXY or XX

#5 Deletion of lower arm

Cri-Du-Chat Syndrome

Moon-shaped faceHeart diseaseMentally retardedMalformed larynxNormal lifespan

Aniridia-Wilms Tumor Syndrome

1 in 50,000,000 births


#11 Deletion of upper arm

Aniridia-Wilms Tumor Syndrome

Mentally retardedGrowth retardedBlindnessTumors on kidneysShort lifespan

Thirteen Q Deletion Syndrome

1 in 500,000 births



Thirteen Q Deletion Syndrome

Mentally retardedDeformed faceNo thumbsHeart diseaseShort lifespan

Prader-Willi Syndrome1 in 5,000,000 births

46 chromosomesXY=97% XX=3%


Prader-Willi Syndrome

Small bird-like headMentally retardedRespiratory problemsObesityShort lifespan

Eighteen Q Deletion Syndrome

1 in 10,000,000 births



Eighteen Q Deletion Syndrome

Mentally retardedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan

Cat-Eye Syndrome1 in 1,000,000 births


#22 Deletion of bottom arm

Cat-Eye Syndrome

Fused fingers and toesMentally retardedSmall jawHeart problemsNormal lifespan

Four-Ring Syndrome1 in 10,000,000 births


#4 Inversion

Four-Ring Syndrome

Cleft palateClub feetTestes don’t descendShort lifespan

Down Syndrome1 in 31,000 births

46 chromosomesXY=97%

XX=3%

#14/21 Translocation

1 in 1,250 births


#21 Trisomy Nondisjunction

Down Syndrome Trisomy

Down Syndrome

Short, broad hands Stubby fingersRough skinImpotency in malesMentally retardedSmall round faceProtruding tongueShort lifespan

Patau’s Trisomy Syndrome1 in 14,000 births



Patau’s Trisomy Syndrome

Small headSmall or missing eyesHeart defectsExtra fingersAbnormal genitaliaMentally retardedCleft palateMost die a few weeks after birth

Edward’s Trisomy Syndrome

1 in 4,400 births

47 chromosomesXX=80%

XY=20%


Edward’s Trisomy Syndrome

Small headMentally retardedInternal organ abnormalities90% die before 5 months of age

Jacob’s Syndrome1 in 1,800 births

47 chromosomesXYY only


Jacob’s Syndrome

Normal physicallyNormal mentallyIncrease in testosteroneMore aggressiveNormal lifespan

?

Klinefelter Syndrome1 in 1,100 births

47 chromosomesXXY only


Klinefelter Syndrome

Scarce beardLonger fingers and armsSterileDelicate skinLow mental abilityNormal lifespan

Triple X Syndrome1 in 2,500 births

47 chromosomesXXX only

#23 TrisomyNondisjunction

Triple X Syndrome

Normally physically

Normal mentallyLearning disabilitiesTaller than averageBehavior Problems

Huntington’s

Chromosome 4 mutation

*involuntary twitching or movement*onset 40 yrs.*deterioration of the CNS that affects muscle control

Sickle-cell Anemia

Moon shaped RBC that has low hemoglobin•Shows up more often in African Americans; or whose ancestors once inhabited parts where malaria is a high risk.•Sickle-shaped cells clog capillaries so that cells cannot get oxygen and nutrition •Blood transfusions, pain killers, and drugs •Pain, strokes, jaundice.

Cystic Fibrosis

Chromosome 7 mutation

•Affects mucus, salivary and sweat glands.

•Many respiratory problems

•Thick, sticky mucus in lungs and digestive tracts.

Tay-Sachs

• No Hex A enzyme• Recessive genetic disorder most often found in

Jewish or eastern Europe origin.• Appears in children starting at 6 mo. • Child cannot metabolize a certain lipid which incases

the CNS and prevents the brain from expanding.• Fat builds up in the brain causing blindness &

paralysis• Death occurs in early childhood

Hemophilia

•Blood has less than 1% of the normal clotting factor

•Bleeds longer because blood won’t clot.

Color-blindness

• Cones in the eye do not perceive certain colors

• Most common form is reds/greens but some are brown/blue

• Seen as gray

genetic mutations. mutations … are changes in the genetic material can be good or bad can be on a...

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