6.4 Traits, Genes, and Alleles – Flashcards
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What does homologous chromosomes mean?
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pair of chromosomes that have the same genes at the same loci
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What does the phenotype describe?
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The physical characteristics
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What does a genotype show?
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The genetic makeup of genes
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How are alleles represented?
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Letters
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What do homozygous dominant alleles look like?
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TT
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What do Homozygous recessive alleles look like?
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tt
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What do heterzygous dominant alleles look like?
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Tt
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If an organism has a recessive trait, can you determine its genotype for that trait?
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Yes but it must be homozygous recessive
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What factors besides alleles affect phenotype?
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Environment
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QQ is ?
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Homozygous dominant
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What is an alternative form of a gene?
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Allele
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What is the opposite of homozyogous?
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Heterozygous
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What is the opposite of homozygous dominant?
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Heterozygous dominant
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Why does each parent contribute only one allele to the offspring?
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because during meiosis the chromosomes split apart
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The inheritance of traits follows the rules or probability
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Notes
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Genotypic ratio is?
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1:2:1
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Phenotypic ratio is?
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3:1
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What is a dihybrid cross?
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Cross that examines the inheritance of two different traits
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Suppose an organism had the genotype AABb. What two types of gametes could result from this allele combination?
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AB Ab
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What is the phenotypic ratio that results from a dihybrid cross between two organisms that are heterzygous for both traits?
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9:3:3:1
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Probabilty predicts____________ number of occurences, not the__________ number of occurrences
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Average;exact
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To calcuate the probability that two independent events will happen together, ___________ the probability of each individual event
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Multiply
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What is a testcross?
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A cross between an organism with an genotype and an organism with the recessive phenotype
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What is the independent in the law of independent assortment?
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The alleles
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What are two ways that sexual reproduction helps create and maintain genetic diversity?
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Independent assortment of chromosomes during meiosis and random assortment of gametes
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What does sexual reproduction create?
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New combination of alleles
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How is production of unique combinations and advantage to organisms species?
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Creates genetic diversity
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Why does each parent organism have four alleles ?
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Because two different alleles are involved
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Are chromosomes in a duplicated or unduplicated state when crossing over occurs?
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Duplicated
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The exchange of chromosome segements between homologous chromosomes is called _____________
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Crossing over
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The tendency for two genes that are located close together on a chromosome to be inherited together is called______
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Genetic linkage
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Sex chromosomes are?
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Chromosomes that determines an organisms sex
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Autosomes are?
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Chromosomes that do not play a direct role in sex determination
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How is a carrier different from a person who has a genetic disorder?
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They dont have the disease but can pass it on
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What are sex linked genes?
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Genes that are located on the sex chromosome
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In humans, how does a gamete from a male determine the sex of offspring?
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The male can pass on either an x or y chromosome
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For what are genes on the Y chromosome responsible?
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The development of male offspring
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How are sex linked genes expressed differently in the phenotypes of males and females?
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All of the genes on each chromosome will be expressed in a male. In females two copies of each gene can affect phenotype.
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How is the everyday meaning of carry related to the meaning of the term carrier in genetics?
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Carrier passes something on by carrying it to the offspring
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What is x chromosome inactivation?
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When one of the two x chromosomes is randomly turned off
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The same genes can have many versions
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Note
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Genes influence the development of traits
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Note
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Punnett squares illustrate genetic crosses
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Note
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A monohybrid cross invovles one trait
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Note
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A dihybrid cross involves two traits
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Note
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What is a gene?
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A piece of DNA that provides a set of instructions to a cell to make a certain protein.
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Sexual reproduction creates unique gene combination
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Note
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Crossing over during meiosis increases genetic diversity
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Note
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Two copies of each autosomal gene affect phenotype
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Note
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Males and females can differ in sex linked traits
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Note
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The inheritance of traits follow the rules of probability
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Note
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