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28 Cards in this Set
- Front
- Back
Inheritance |
-The transfer of traits from parent to offspring dna(genotype)→rna→protein→trait→phenotype |
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Trait |
A measurable or observable characteristic of a cell/organism, result of the expression of different alleles |
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Alleles |
Alternative forms of a gene; most genes have 2 types, dominant and recessive |
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Locus |
Segment of dna that has information controlling some aspect of the structure or function of an organism -alleles govern variations of the same characteristic and occupy corresponding loci (locations) on homologous chromosomes |
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Genotype |
Genetic makeup of an organism, often expressed as symbols -dominant homozygous, AA, always observed in the form of a trait -dominant heterozygous, Aa, dominant trait is expressed -recessive homozygous, aa, only time recessive trait is expressed |
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Phenotype |
Physical appearance of an organism, determined by genotype |
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Multiple genes on one chromosome |
Genes must be at the same location on a pair of homologous chromosomes to be considered alleles |
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Mendel's principles of inheritance |
Principle of segregation: alleles separate before gametes are formed; alleles remain intact during meiosis and recessive alleles are not "lost" and can reappear in subsequent generations -one allele per gametes |
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Mendel's principles of inheritance |
Independent assortment: alleles on nonhomologous (different) chromosomes are randomly distributed into gametes -gametes receive alleles based on where the chromosomes are located during separation -contributes to genetic recombination |
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Linked genes |
Genes on the same chromosome that tend to be inherited together in successive generations -an exception to the principle of independent assortment -some genetic recombination occurs as a result of crossing over events as well |
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Dominant traits |
Always expressed, represented by capital letters |
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Recessive traits |
Only observed if both alleles code for the same trait, represented by lower case letters |
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Types of genotypes |
Homozygous- both alleles for a trait are the same Heterozygous- alleles for a trait are different |
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Punnett square |
Predicts the ratios of offspring with a particular genotype or phenotype resulting from the combinations of gametes from two parents; predicts the outcome of a cross |
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Monohybrid (parental) cross |
Homozygous dominant alleles x homozygous recessive alleles = 4/4 heterozygous genotype, 4/4 dominant phenotype |
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Heterozygous (F1) cross |
Heterozygous alleles x heterozygous alleles = 1/4 homozygous dominant genotype, 2/4 heterozygous genotype, 1/4 homozygous recessive genotype, 3/4 dominant phenotype, 1/4 recessive phenotype |
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Test cross |
Determines the genotype of an individual who has a dominant trait by mating the individual with one who has the recessive trait then looking for a recessive offspring |
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Dihybrid cross |
Mating between individuals with different alleles at two loci (on homologous or nonhomologous chromosomes) |
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Independent events |
One event does not affect the outcome of the other event; chance has no memory |
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Product rule |
Probabilities of independent events are multiplied Ex: if the offspring of two individuals has a 1/4 chance of having hazel eyes, there is a 1/16 chance for them to have two children with hazel eyes since 1/4 * 1/4 = 1/16 |
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X-linked genes |
Found on the x chromosome, express unusual inheritance patterns with abnormal alleles more frequently expressed in male offspring; y chromosome is smaller than x chromosome and does not have corresponding alleles for some traits, so a female will have one dominant allele that will mask the recessive allele, but if the male only has a recessive allele that will be expressed |
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Incomplete dominance |
Heterozygote has a phenotype intermediate between those of its parents |
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Codominance |
Heterozygote simultaneously expressed the phenotypes of both types of homozygotes Ex: speckled chickens |
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Multiple alleles |
Three of more alleles for a given locus may exist within a population Ex: blood type |
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Pleiotrophy |
Ability of a single gene to have multiple effects of an organisms phenotype; single gene affects multiple traits |
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Polygenic inheritance |
Multiple independent pairs of genes may have similar and additive effects on the same characteristic (height, body shape, etc); multiple genes work together to affect one trait |
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mutation |
change in the nucleotide sequence |
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spontaneous mutations |
result from errors in base pairing during dna replication |