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1

Alternate forms of a single gene

Allele

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An allele whose phenotype is expressed in a Heterozygote, a trait that appears in the F1 hybrids (heterozygote resulting from matting between pure breeding parental strains showing antagonistic Phenotypes)

Dominant

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An allele whose phenotype is not expressed in a Heterozygote, a trait that remains hidden in the F1 hybrids (resulting from the mating between pure breeding parental strains having antagonistic Phenotypes) appears in the F2

Recessive

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A genotype in which the two copies of the gene that determine a trait are the same allele

Homozygous

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A genotype in which the two copies of a gene that determine a trait are different alleles

Heterozygous

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Hemizygous

a genotype for genes present in only 1 copy in an otherwise diploid organism (such as X linked genes in a male)

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Actual alleles present in an individual

Genotype

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An observable characteristic

Phenotype

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Cross between parents differing in only one trait

Monohybrid cross

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Cross between parents that differ in two traits

Dihybrid cross

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A cross used to determine the genotype of an individual showing a dominant phenotype by mating with an individual showing the recessive phenotype

Test cross

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A cross of an F1 individual with a parent or an individual with an identical phenotype to the parent

Back cross

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Pure breeding individuals whose progeny in subsequent generations will be studied for specific traits

Parental, P

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Progeny of the P generation that all look like the dominant parent, recessive gene is masked

First filial, F1

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Progeny of F1 interbreeding, both parental types reappear in a 3:1 ratio, (3 dominant, 1 recessive), shows blending is not true

Second filial, F2

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2 alleles for each trait separate (segregate) during gamete formation and then unite at random (one from each parent) at fertilization

Law of segregation

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During gamete formation different pairs of alleles segregate independently of each other

Law of independent assortment

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Dominance where a dominant allele completely masks the effect of the recessive allele in a heterozygous individual

Complete dominance

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When an F1 hybrid does not resemble either pure breeding parent; an intermediate phenotype where both parental alleles contribute to the phenotype. Can produce up to 9 different Phenotypes. Shades of purple flowers.

Incomplete dominance

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Both traits show up equally in the heterozygote's phenotype in the F1 cross (spotted lentils) 1:2:1 in the F2 generation (blood group alleles; a & b sugars)

Codominance

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DNA that encodes a protein or a particular type of RNA, basic unit of biological information (heredity)

Gene

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Of ours in individuals who have inherited 2 recessive alleles of the H gene and do not produce the H carbohydrate that is the precursor to the A &B antigens. They may possess either or both alleles but are unable to express them. Look like type O. Recessive Epistasis.

Bombay phenotype

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Phenomenon in which a single gene determines a number of distinct and seemingly unrelated characteristics

Plieotropy

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Multifactorial trait

Determined by two or more factors including multiple genes interacting with each other or one or more genes interacting with the environment

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Case of epistasis in which The epistatic allele is recessive. 9:3:4 labs

Recessive epistasis

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Genes working in tandem to produce a particular trait 9:7 sweet pea flowers

Complementary Gene action

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The effects of a dominant allele at one gene hides the effects of alleles at another gene 12:3:1 squash

Dominant epistasis 1 & 2

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Genes whose products serve the same function in a pathway, a mutant phenotype is observed only if both gene products are absent 15:1 maize

Redundant genes

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Indicates how many members of a population with a particular genotype shows the expected phenotype

Penetrance

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The degree or intensity with which a particular genotype is expressed in the phenotype

Expressivity