Chapter 9: Mendelian Genetics And Mutation Flashcards Preview

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Flashcards in Chapter 9: Mendelian Genetics And Mutation Deck (68):
1

theory of blending inheritance

proposed that traits present on the parents mixed together like paint to produce a new combination in the offspring

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horticulture

the artificial selection of plants

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hybridizing

the process of crossing two different types of plants

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true breeding

strains of plants that contain only one form of a trait

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reciprocal cross

an experimental cross in which 2 different forms of a trait are interchanged between male and female plants

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monohybrid cross

an experiment that uses parent varieties (or strains) differing in a single trait

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self-crossing/self-fertilization

a plant is pollinated with its own pollen as opposed to pollen from another plant

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genes

heritable factors; discrete unit of hereditary information

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alleles

alternate forms of a gene

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homozygous

has two identical alleles for a given trait

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heterozygous/hybrid

has two different alleles for a given trait

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genotype

an allelic combination

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phenotypes

the physical expression of genes

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recombination

the occurrence of an offspring whose phenotype differs from that of the parent

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test-cross

crossing an organism of an unknown genotype with a homozygous recessive individual to determine the unknown genotype; the ratio of phenotypes in the offspring determines the unknown genotype

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inheritance

the way traits are passed on from generation to generation

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back cross

a test cross with the homozygous recessive parent (a reverse test cross)

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Punnett square

invented by Reginald Punnett in 1905. It is a grid that shows all the possible gametes formed by each of the parents and all of the possible genotypes and phenotypes in the offspring.

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dihybrid

a breeding experiment that uses parental varieties differing in two traits

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independent assortment

the alleles for the two different traits must assort independently with respect to one another

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meiosis

a type of cell division in sexually reproducing organisms which results in gametes with half of the chromosome number of the original cell

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recombination

a process in meiosis that results from homologous chromosomes segregating into different gametes, resulting in multiple possible allele combinations

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the multiplicative law of probability

the probability of two independent events co-occurring is the product of their individual probabilities

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trihybrid

a breeding experiment that uses parental varieties differing in three traits

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sickle cell anemia

caused by a defective hemoglobin protein in red blood cells which causes the cells to deform to a sickle shape and triggers blood clotting and other symptoms

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the additive rule

the probability of one or another of two mutually exclusive (or separate) events occurring equals the sum of their individual probabilities

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intermediate inheritance

the heterozygote genotype has a unique phenotype which is intermediate to the two parental phenotypes; neither allele dominates

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codominance

both alleles of a heterozygote are distinctly expressed

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antigen

a foreign substance that does not belong to a particular host organism and elicits an immune response

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antibody

an immunoglobulin produced by B cells which binds to antigens, and in doing so function in immune response

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pedigree

information categorized into a family tree which traces the inheritance of various traits (including disorders) throughout generations

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Mendel's 3:1 ratio

describes that in the F2 generation, dominant and recessive traits will occur 3-to-1

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Mendel's 9:3:3:1 ratio

the result of a dihybrid cross, where out of 16 individuals, 9 represent both dominant traits, 3 represent one dominant trait, 3 represent another dominant trait, and 1 represents the recessive traits.

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epistasis

one gene's expression modifies or suppresses another gene

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albino

characterized by a complete lack of pigment

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quantitative characters

traits that vary in population along a continuum, because there is more than one existing phenotype

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polygenic inheritance

two or more genes have an additive affect on one phenotypic character

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locus

the location of a gene

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pleiotropy

one gene can affect many traits

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lethal recessive

a condition that is lethal in the homozygous condition

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dominant allele

in the heterozygote, the allele that is fully expressed

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recessive allel

in the heterozygote, the allele that is completely masked

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mutation

a recessive allele results in a defective enzyme

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structural disorder

one defective, dominant allele results in a phenotypic effect

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over-dominance

a population level phenomenon where the heterozygote has a selective advantage over either homozygote (ex: those will sickle-cell anemia are resistant to malaria)

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linked genes

genes that stay on the same chromosomes

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parental phenotypes

the offspring have an appearance which is identical to one of the parents

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recombinant phenotypes

the offspring have an appearance which differs from either of the parents

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map unit

a way of calculating the relative distance between genes, calculated by dividing the number of recombinants by the total number of offspring times 100

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sex chromosomes

the pair of chromosomes that determine the sex of an organism

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sex-linked gene

a gene located on a sex chromosome

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chromosome theory

the theory that Mendel's heritable factors are located on chromosomes

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hemizygous

having a total of one allele for a given trait; a condition that is associated with genes located on sex chromosomes

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Barr bodies

the inactive X chromosome present in each cell of the female which has been condensed into a compact object

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mosaic

in art, the term is used to describe a pattern; in biology, it is used to describe patchiness in a characteristic

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autosome

a chromosome that is not directly involved in sex determination; in humans there are 22 of these chromosomes

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sex chromosomes

the chromosomes that are responsible for sex determination; in humans there is only one pair of these chromosomes

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aneuploidy

a deviation in the chromosome number such that certain chromosomes are present in extra copies or are absent

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polyploidy

a deviation in the chromosome number such that the organism has more than two complete sets of chromosomes

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nondisjunction

a pair of homologous chromosomes or sister chromatids fail to separate properly during meiosis or mitosis

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karyotype

a technique in which an individual's metaphase I chromosomes are examined in order to determine their number and characteristics

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deletion

the loss of a piece of chromosome during cell division, resulting in a fragment which lacks a centromere

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syndrome

having a number of phenotypic effects

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point mutation

a mutation that affects a single nucleotide of the DNA strand

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silent mutation

the base pair substitution has no phenotypic effect

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missense

the base pair substitution causes one amino acid to be substituted for another amino acid

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nonsense

the base pair substitution causes an amino acid-specifying codon to be changed to a stop codon; the prematurely shortened protein is usually not functional

68

frameshift

if the number of nucleotides, inserted or deleted, is not a multiple of three, this can occur. The result is an improper grouping of codons leading to a changed protein product.