Genetics – Genetics Test Answers – Flashcards
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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 traits from one generation to the next
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trait
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a specific characteristic that varies from one individual to another
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gene
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sequence of DNA that codes for a protein and thus determines a trait
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genome
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the entire "library" of genetic instructions in DNA that an organism inherits
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Gregor Mendel
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father of genetics
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allele
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alternative form of a gene (one member of a pair) located at a specific position on a specific chromosome (a letter)
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dominant allele
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an allele that produces the same phenotype whether its paired allele is identical or different (capital letter)
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recessive allele
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an allele that produces its characteristic phenotype only when its paired allele is identical (lowercase letter)
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genotype
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the combination of alleles located on homologous chromosomes that determines a specific characteristic or trait (the allelic combination such as Bb)
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phenotype
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the observable physical or biochemical characteristics of an organism, as determined by the genotype (the expressed trait such as brown eyes)
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homozygous
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term used to refer to an organism that has two identical alleles for the same trait (ex. BB or bb)
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heterozygous
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term used to refer to an organism that has two different alleles for the same trait (ex. Bb)
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Punnett square
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diagram showing the gene combinations that might result from a genetic cross
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gamete (sex cell)
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specialized cell involved in sexual reproduction (sperm or egg)
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probability
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the possibility of different outcomes (percentage or ratio)
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monohybrid cross
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a one-trait cross (ex. color)
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dihybrid cross
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a two-trait cross (ex. color & shape)
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P generation
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parental generation is the first generation involving two individuals that are mated to predict or analyze the genotypes of their offspring
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F1 generation
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first filial generation is the generation resulting immediately from a cross of the first set of parents (P generation)
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F2 generation
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second filial generation is the generation resulting from a cross between two F1 individuals
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purebred
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offspring that are the result of mating between genetically similar kinds of parents; opposite of hybrid; same as true breeding
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hybrid
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offspring that are the result of mating between two genetically different kinds of parents; opposite of purebred
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Principle of Dominance
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when individuals with contrasting traits are crossed, the offspring will express only the dominant trait
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Law of Segregation
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states that allele pairs separate, or segregate, during gamete formation
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Law of Independent Assortment
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states that genes for different traits can segregate independently during the formation of gametes
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non-Mendelian inheritance
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refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws (ex. incomplete dominance, codominance, multiple alleles, polygenic traits, sex-linked traits)
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incomplete dominance
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when one allele is not completely dominant over the other, or blending occurs (ex. Red + White = Pink)
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codominance
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occurs when BOTH alleles of a gene are expressed in an individual (ex. Black + White = Black & White Speckled)
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multiple allele traits
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traits that are controlled by more than two alleles (ex. ABO blood typing = A allele, B allele, & O allele)
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polygenic traits
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a trait controlled by two or more genes; produce a wide range of phenotypes
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sex-linked traits
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a trait genetically determined by an allele located on the sex chromosome
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pedigree chart
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a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next
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chromatin
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unraveled and long DNA (during interphase)
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chromosome
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condensed, coiled, and shorted DNA (this occurs during mitosis and meiosis)
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chromatids
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the two identical halves of a single replicated eukaryotic chromosome and joined at the centromere
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homologous chromosomes
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chromosome pairs of approximately the same length, centromere position, and staining pattern, with genes for the same characteristics at corresponding places (one homologous chromosome is inherited from the mother; the other from the father)
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daughter cells
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new cells
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mitosis
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a type of cell division that results in two genetically identical daughter cells each with the same number of chromosomes of the parent cell
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meiosis
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a type of cell division that results in four genetically different daughter cells each with half the number of chromosomes of the parent cell (also known as reduction division)
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sexual reproduction
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process by which two cells from different parent unite to produce the first cell of a new organism
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asexual reproduction
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process by which a single parent reproduces by itself
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crossing over
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process in which homologous chromosomes exchange portions of their chromatids during meiosis (also called gene shuffling)
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genetic variation
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genetic differences within a species
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fertilization
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a process in sexual reproduction in which a sperm unites with an egg to make the first cell of a new organism, or zygote
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zygote
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fertilized egg
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somatic cell
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body cell (non-sex cell)
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haploid (N)
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term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes (Humans N = 23)
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diploid (2N)
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term used to refer to a cell that contains both sets of homolgous chromosomes (Humans 2N = 46)
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chromosomal mutation
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mutation that affects the number or structure of whole chromosomes
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deletion chromosomal mutation
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a mutation that involves the loss of all or part of a chromosome
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duplication chromosomal mutation
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a mutation that produces extra copies of parts of a chromosome
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inversion chromosomal mutation
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a mutation that reverses the direction of parts of a chromosome
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translocation chromosomal mutation
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a mutation that occurs when part of one chromosome breaks off and attaches to a different chromosome
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nondisjunction
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the most common error in meiosis and occurs when homologous chromosomes fail to separate
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trisomy
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a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities
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polyploidy
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condition in which an organism has extra sets of chromosomes because a complete set of chromosomes failed to separate during meiosis (ex. 3N or 4N)
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DNA fingerprinting
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an individual's unique sequence of DNA base pairs, determined by exposing a sample of the person's DNA to molecular probes
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genetic engineering
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the process of making changes in the DNA code of living organisms
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genetically modified organism (GMO)
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one that has artificially acquired one or more genes from the same or different species
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plasmid
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circular DNA found in bacteria
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recombinant DNA
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DNA produced by combining DNA from different organisms (DNA is cut out of one organism and recombined with another organism's DNA)
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enzyme
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protein that speeds up chemical reactions in organisms
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restriction enzyme
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DNA-cutting enzymes found in bacteria
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biotechnology
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the use of living organisms or other biological systems in the manufacture of drugs or other products or for environmental management, as in waste recycling
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karyotype
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a picture of an organism's genome and can be used for chromosomal anlysis
