Genetics Flashcards

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Gene

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The gene is the basic physical unit of inheritance. Genes are passed from parents to offspring and contain the information needed to specify traits. Genes are arranged, one after another, on structures called chromosomes.

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Chromosome

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In the nucleus of each cell, the DNA molecule is packaged into thread-like structures calledchromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

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Allele

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An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent. If the twoalleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous.

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Genotype

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The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific characteristic under consideration.

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Phenotype

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The phenotype of an organism depends on which genes are dominant and on the interaction between genes and environment. Compare genotype. The outward appearance of an organism; the expression of a genotype in the form of traits that can be seen and measured, such as hair or eye color.

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Gamete

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a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

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Punnett Square

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The Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding experiment.

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Random Segregation

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Paternal and maternal chromosomes get separated in meiosis and the alleles with the traits of a character are segregated into two different gametes. Each parent contributes a single gamete, and thus a single,randomly successful allele copy to their offspring and fertilization.

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Crossing Over

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Chromosomal crossover (or crossing over) is the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes. It is one of the final phases of genetic recombination, which occurs during prophase I of meiosis (pachytene) during a process called synapsis.

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Independent Assortment

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law of independent assortment. the principle, originated by Gregor Mendel, stating that when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.

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Meiosis

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Meiosis i/maɪˈoʊsɨs/ is a specialized type of cell division which reduces the chromosome number by half. This process occurs in all sexually reproducing eukaryotes (both single-celled and multicellular) including animals, plants, and fungi.

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Fertilization

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the action or process of fertilizing an egg, female animal, or plant, involving the fusion of male and female gametes to form a zygote.

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Zygote

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A zygote (from Greek ζυγωτός zygōtos "joined" or "yoked", from ζυγοῦν zygoun "to join" or "to yoke"), is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo.

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Dominant

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most important, powerful, or influential.

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Recessive

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relating to or denoting heritable characteristics controlled by genes that are expressed in offspring only when inherited from both parents, i.e., when not masked by a dominant characteristic inherited from one parent.

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Homozygous

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Homozygous describes a genotype consisting of two identical alleles at a given locus, heterozygous describes a genotype consisting of two different alleles at a locus, hemizygous describes a genotype consisting of only a single copy of a particular gene in an otherwise diploid organism, and nullizygous refers to an ...

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Heterozygous

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A diploid organism is heterozygous at a gene locus when its cells contain two different alleles of a gene. The cell or organism is called a heterozygote specifically for the allele in question, therefore, heterozygosity refers to a specific genotype.

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Autosomal Inheritance

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There are four types of Mendelian inheritance patterns: Autosomaldominant. Autosomal recessive X-linked recessive. X-linked dominant.Autosomal: the gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes).

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X-Linked Inheritance

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X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome. Females have two Xchromosomes, while males have one X and one Y chromosome.

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Complete Dominance

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In complete dominance, the effect of one allele in a heterozygous genotype completely masks the effect of the other. The allele that masks the other is said to be dominant to the latter, and the allele that is masked is said to be recessive to the former.

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Codominance

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Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele usually will be expressed, while the effect of the other allele, called recessive, is masked.

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Incomplete Dominance

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Incomplete dominance (also called partial dominance) occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. For example, the snapdragon flower color is either homozygous for red or white.