2Haploid cell
only one member of each chromosome pair
3Somatic cells
all other cells
46 chromosomes (23 pairs)
4Diploid cells
one donated by father and mother to each chromosome pair
5Homologous (autosomes)
22 of 23 pairs are identical in male and female
6Karyotype
order of display of chromosomes
7Why do genetic testing?
uncover possible abnormalities
predict certain traits (normal and abnormal
assess risks/ benefits
8Chromosome Aberrations?
leading cause of mental retardation (MR) an miscarriage
9Euploid
normal number of chromosomes = 46
10Polyploidy
more than diploid number = over 46
liver, bronchial, and epithelial tissues
11Triploidy
zygote has three copies instead of two
incompatible with postnatal survival
12Tetraploidy
euploidy cells have 92 chromosomes
incompatible with postnatal survival
13Aneuploid
does not contain 23 chromosomes
14Trisomy
three copies of one chromosome
15Monosomy
one copy of chromosome
16What is aneuploidy?
nondisjunction
failure of chromatid separation
autosomal = down syndrome; risk increases with age
1 in 500 males; 1 in 900 females
17What is the patho of down syndrome?
trisomy 21 (96%)
risk increases with maternal age
risk for Alzheimer's disease
18What is the patho of turner's syndrome?
monosomy 45, X
underdeveloped sex organs
short in stature
female genitalia
thick neck -- webbed neck
ovaries are underdeveloped
wide set nipples
thickened legs
19What is the patho of Klinefelter Syndrome?
47, XXY
karyotype
small testes - underdeveloped
excessive breast tissue
limbs are very long
20Deletions
broken chromosomes, one chromosome is there and one is missing
21Duplications
two of something, less serious than deletions
22Inversions
piece of genetic material gets flipped around
23Translocations
should be on one side but flipped to otherside
24Fragile X Syndrome
second most common cause of MR
25What is the patho of Fragile X Syndrome?
chromatin fails to condense during mitosis
affects males>females
26What is the clinical manifestations of Fragile X Sydnrome?
MR
long face, large mandible, large everted ears
hyperextensible joints, high-arched palate
mitral valve prolapse
macroorchidism (difficult reproduction)
27Genotype
gene composition
28Phenotype
outward appearance
29Dominant
observable affects
30Recessive
hidden effectd
31Carrier
has diseases gene but phenotypically normal
32Transmission dominant inheritance
delayed age of onset
penetrance and expressivity
33Characteristic of transmission dominant
males = females in transmission
no skipped generations
transmit to 1/2 their offspring
34Recurrence Risk of transmission dominant
probability of disease is subsequent offspring
35Transmission recessive inheritance characteristics
males = females
disease many be seen in siblings of affected individuals but usually not in parents
36Consanguinity
mating of related individuals
37Recurrence Risk Recessive
1/4 normal homozygous
1/2 carriers and phenotypically normal
1/4 homozygote with disease