Biology Genetics Vocabulary

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Genetics

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the study of heredity

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Heredity

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the passing of charactersitics from parents offspring

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Traits

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are specific inherited characteristics that vary from one indivial to another

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Gene

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a section of DNA on a chromosome that codes for a trait

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Allele

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a distinct form of a gene:usually two per trait(one from each parent)

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Dominant Allele

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a gene that is fully expressed even when two differet alleles are present
EX:GG or Gg both show a green pea

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Recessive Allele

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a gene that is expressed only when paired with another recessive allele;when paired with a dominant allele,the recessive trait is not expressed
EX:gg will show a yellow pea

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Purebred

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an organism that received the same form of a genetic trait from each parent
EX:green pea plant X green pea plant (GG X GG gives GG offspring)

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Hybrid

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an organism that recieved different forms of a genetic trait from each parent
EX:green pea plant X yellow pea plant (GG X gg gives Gg offspring)

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Punnett Square

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used to predict and compare the genetics variations that will result from a cross

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Monohybrid Cross

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a cross that involes only one pair of genetic traits

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Dihybrid Cross

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a cross that involves two pairs of genetic traits

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Genotype

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the genetic make-up of an organism
EX:GG or gg

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Phenotype

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the physical expression of a trait
EX:GG=green,Gg=green,gg-yellow

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Homozygous

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when both alleles for a trait are the same~purebred

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Heterozygous

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when the alleles for a trait are different~hybrid

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Incomplete dominance

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when two different alleles for the same trait combine but neither allele wins expression over the other;the heterozygous expression is somewhere between the homozygous expressions
EX:snap dragon plant (homzygouos red X homosygous white=pink offspring

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Co-dominance

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both alleles express themselves fully
EX:human bloodor white/black feathers on chickens

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Multiple alleles

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when genes have 3 or more alleles available in the population;an indiviual will still only carry 2 (on from each parents)
EX:human blood or rabbit fur color

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Polygenic traits

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a trait controlled by two or more genes
EX:eye color or skin color-determained by distribution of pigment and tone amount

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Pleiotropy

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when a single gene affects more than one trait
EX:sickle cell diesase(causes anemia,heart damage,physical weakness)

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Pedigree

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a chat that shows a trait and how it is inherited within a family;helps to predict certain alleles in offspring

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Carrier

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a person that carries a recessive gene that is not expresed;heterozygous recessive

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Sex-linked

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genes found in either X or Y sex chromosomes
EX:Red/Green Colorblindness is X-linked reccsive
Hemophilia(absence of normal clotting factor blood)is X linked recesive

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Sex limited Traits

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are expressed only in the presence of sex hormones and are only obseved in one sex or the other;are located on autosomes;typically do not appear until puberty when sex hormones are produced
EX:bright plumage in male birds;beards in men;milk production in females