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AP Biology Genetics

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Recessive
gene that produces its characteristic phenotype only when its allele is identical
Genotypes
the version of genes someone has. (Not visible)
Heterozygous
two different versions of that trait
Homozygous
two of the same trait
Dominant
gene that produces the same phenotype in an organism whether or not the allele is identical
Testcross
method of determining genotype
Monohybrid experiments
testcrosses that check for a dominance relationship between two alleles at a single locus
Punnett Squares
used to calculate the probability of a genotype
Law of Segregation
"Diploid cells have pairs of genes, or pairs of homologous chromosomes. The two genes of each pair are separated from one another during meiosis, so they end up in different gametes."
Dihybrid crosses
done to determine dominance relationship between alleles at two loci
law of Independant Assortment
"Genes are sorted into gametes independently of other genes"
Codominance
two nonidentical alleles of a gene are both fully expressed in heterozygotes, so neither is dominant or recessive
Incomplete Dominance
one allele of a pair isnt fully dominant over its partner, so heterzygote's phenotype is between that of the homozygotes
Epistasis
Interactions between different gene products.
Pleiotrophy
one gene that influences multiple traits
Fibrilin
fibers that give elasticity to tissues of heart, skin, blood vessels, tendons, and other body parts.
Linkage Groups
all genes on a chromosome
Tyrosinase
enzyme that affects the coat color of Himalayan rabbits
Continuous Variation
other traits that occur in a range of small differences
bell curve
the type of curve if a trait shows continuous variation
Camptodactyly
finger shape and movement are abnormal
Karyotyping
diagnostic tool that helps determine the individual's diploid set of chromosomes
Acondroplasia
cartilage model of skeleton doesnt form properly. caused by an autosomal dominant allele
Huntington's Disease
involuntary muscle movements increase as nervous system deteriorates. Caused by an autosomal dominant allele
Galactosemia
Malnutrition, diarrhea, vomiting, damage to eyes, liver and brain, eventual death. caused by a recessive autosomal inheritance
Progeria
mutated allele produces hutchinson-gilfork progeria syndrome. accelerated rate of aging and short life span.
Hemophilia A
x-linked recessive disorder; interferes with blood clotting.
Duchenne Muscular Dystrophy
muscle degeneration. genes of X encodes dystrophin, structural/support protein muscle cells
Duplications
normal chromosomes have DNA sequences that are duplicated several times
Deletion
loss of some portion of a chromosome
Cri-du-chat
(cry of the cat) deletion of chromosome 5 causes mental impairment and an abnormally shaped larynx
inversion
part of the DNA sequence within the chromosome becomes oriented in the reverse direction, with no loss
Translocation
part of a broken chromosome attaches to a different chromosome or to a different part of the same one
polyploid
cells that normally have 3+ types of each chromosomes
nondisjunction
1+ pairs of chromosomes do not seperate properly during mitosis or meiosis
Down syndrome
only tricomis individuals who reach adulthood. upward slanting eyes, deep crease across sole of foot and palm of hand. moderate to severe mental impairment and heart problems
Klienfelter's syndrome(XXY)
outcome of nondisjunction. feminizing effects: small testes and prostate glands, low sperm count, sparse body hair, enlarged breasts
XYY syndrome
taller than average, mild mental temperament
Prenatal
before birth
embryo
up to 8 weeks after fertilization
fetus
8+ weeks after fertilization
Amniocentesis
a syringe withfraws 20mL of amniotic fluid, which contains shed fetal cells and fetal waste
genetic screening
routine testing for alleles associated with genetic disorders. provides info on reproduction risks