Genetics Unit Test Vocabulary Flashcards Preview

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Flashcards in Genetics Unit Test Vocabulary Deck (42):
1

genetics

the science of heredity and of the mechanisms by which traits are passed from parents to offspring

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heredity

the passing of genetic traits from parent to offspring

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trait

a genetically determined characteristic

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pollination

the transfer of pollen from the male reproductive structures (the anthers) to the tip of a female reproductive structure (the pistil) of a flower in angiosperms or to the ovule in gymnosperms

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self-pollination

the transfer of pollen grains from an anther to the stigma of the same flower or to the stigma of another flower on the same plant

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cross-pollination

a reproductive process in which pollen from one plant is transferred to the stigma of another plant

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true-breeding

describes organisms or genotypes that are homozygous for a specific trait and thus always produce offspring that have the same phenotype for that trait

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P generation

parental generation, the first two individuals that mate in a genetic cross

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F1 generation

the first generation of offspring obtained from an experimental cross of two organisms

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F2 generation

the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation

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dominant

in genetics, describes an allele that is fully expressed whenever the allele is present in an individual

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recessive

in genetics, describes an allele that is expressed only when no dominant allele is present in an individual

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law of segregation

states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

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law of independent assortment

the law that states that genes separate independently of one another in meiosis

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allele

one of the alternative forms of a gene that governs a characteristic, such as hair color

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genotype

the entire genetic makeup of an organism; also the combination of genes for one or more specific traits

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phenotype

an organism's appearance or other detectable characteristic that results from the organism's genotype and the environment

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homozygous

describes an individual that has identical alleles for a trait on both homologous chromosomes

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heterozygous

describes an individual that has two different alleles for a trait

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probability

the likelihood that a possible future event will occur in any given instance of the event

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monohybrid cross

a cross between individuals that involves one pair of contrasting traits

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Punnett square

a graphic used to predict the results of a genetic cross

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genotypic ratio

the ratio of the genotypes that appear in offspring

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phenotypic ratio

the ratio of phenotypes produced by a cross

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test cross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

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complete dominance

a relationship in which one allele is completely dominant over another

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incomplete dominance

a condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully

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codominance

a condition in which both alleles for a gene are fully expressed

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dihybrid cross

a cross between individuals that have different alleles for the same gene

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sex chromosome

one of the pair of chromosomes that determine the sex of an individual

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autosome

any chromosome that is not a sex chromosome

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sex-linked trait

a trait that is determined by a gene found on one of the sex chromosomes, such as the X chromosome or the Y chromosome in humans

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linked gene

one of a pair of genes that tend to be inherited together

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chromosome map

a diagram of gene positions on a chromosome

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map unit

in chromosome mapping, an increment of 1 percent in the frequency of crossing-over

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germ-cell mutation

mutation that occurs in an organism's gametes

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somatic-cell mutation

a mutation that occurs in a body cell

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lethal mutation

a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive

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pedigree

a diagram that shows the occurrence of a genetic trait in several generations of a family

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carrier

in biology, an individual who has one copy of a recessive autosomal allele that causes disease in the homozygous condition

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genetic disorder

an inherited disease or disorder that is caused by a mutation in a gene or by a chromosomal defect

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multiple alleles

more than two alleles (versions of the gene) for a genetic trait