Dapo Adegbile Nevin Varghese Victor Veras
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Transcript of Dapo Adegbile Nevin Varghese Victor Veras
1-28-10Period 2
Polydactyly is a condition in which a person has more than five fingers per hand or five toes per foot.
Polydactyly occurs in the womb; instead of developing only one thumb and four fingers an extra finger is added
Usually the hand is formed in the womb and when it is being split it is made into 4 fingers, 1 thumb. However sometimes an extra split occurs and abnormal number of fingers is produced
It is a autosomal dominate characteristic
The cause of the disorder is usually found on chromosome 13.
However for some cases it is not known
There is another gene or chromosome that the mutation could happen in that could cause polydactyly
Mode of Inheritance
Polydactyly is autosomal dominant. Autosomal dominant means that an
offspring can get this disease by having it passed down from just one parent.
Polydactyly occurs because of genetic disorders or errors in fetal development.
Polydactyly can also be a symptom for another disease.
Ex. – Bardet-Biedl syndrome Ex. – Bloom’s syndrome Ex. – Jeune’s thoracic dystrophy syndrome
What are Alleles? A person has two alleles per geneYou get one of the two alleles in a gene from your
father and the other from your motherRecessive alleles are represented by the letter of
the characteristic in lower-case formDominant alleles are represented by the letter of
the characteristic in capital R – Dominant r – Recessive
The dominant alleles and the recessive alleles both represent two different possible characteristics.
The “characteristic” will be dominant if the gene has one dominant allele or two dominant alleles
The “characteristic” will be recessive if the gene has two recessive genes only
GG Gr
Gr gg
Gg
G
g
Ww Ww
Ww Ww
w w
W
W
Heterozygous
Homozygous
hh hh
hh hh
hh
h
h
GG Gg
Gg gg
G g
G
g
• Ratio1GG 2Gg 1gg
• Percentage 25% -GG 50% - Gg 25% - gg
• 75% chance of getting Polydactyly
• 25% chance of not getting Polydactyly
GG Gg
Gg gg
G g
G
g
GG – two dominant allelesGg – one dominant allele and one recessive allelegg – two recessive alleles
• PhenotypeGG = Recieve polydactylyGg = Receive polydactylygg = Normal amount of fingers
• GenotypeGG = Homozygous dominantGg = Heterozygous dominantgg = Homozygous recessive
•Top – Father•Left – Mother
GG Gg
Gg gg
G g
G
g
• Phenotype- Ratios- 3 for polydactyly : 1 for
normal- Percentage – 75% chance of
polydactyly 25% chance of
normal # of f fingers
• Genotype - Ratios- 1 GG : 2 Gg : 1 gg - Percentages- 25% GG : 50%
Gg : 25%gg
G g
G
g
•GenotypeRatio – 1 GG;
2 Gg; 1ggPercentage – 75% chance
receive disease25% chance of not getting disease
• Phenotype
Ratio – 3 with Polydactyly; 1 without Polydactyly
Percentage – 75% of getting Polydactyly
GG Gg
Gg gg
Female – circleMale – Square
All green – homozygous recessive gene, person doesn’t have the disease, person has 2 healthy alleles
Half green, half black (or star) – heterozygous gene, person has the disease because you only one dominant gene with the disease to get it
All black homozygous dominant. Has the disease.
Student PracticeKey –• circle – female• square – male• shaded in (black) – two dominant alleles• not shaded (red) – two recessive alleles• half shaded – one dominant and one recessive allele
• If two parents are homozygous dominant, how likely If two parents are homozygous dominant, how likely would it be for a child not have the disease?would it be for a child not have the disease?
• If one parent is homozygous dominant but another is If one parent is homozygous dominant but another is homozygous recessive, is it possible for one of the homozygous recessive, is it possible for one of the children not to obtain the disease?children not to obtain the disease?
• If one parent were heterozygous dominant and If one parent were heterozygous dominant and homozygous recessive, how likely is it for a child to homozygous recessive, how likely is it for a child to get the disease?get the disease?
Questions????????
•0% child would wind up homozygous dominant0% child would wind up homozygous dominant
•Each of the children will wind up Each of the children will wind up heterozygous dominantheterozygous dominant
50%