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Genetics > Principles Of Heredity > Flashcards

Principles Of Heredity Flashcards

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1
Q

Null Hypothesis

A

– A hypothesis where there is no difference between groups or no relationship between variables.

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2
Q

Allele

A
  • One of two or more alternative forms of a gene.
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3
Q

Locus (Loci)

A
  • Position on a chromosome where a specific gene is located.
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4
Q

Genotype

A
  • The set of alleles possessed by an individual organism.
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5
Q

Gene

A
  • An inherited factor that helps determine a trait.
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6
Q

Scientific Method

A
  • The process of observing, asking questions, and seeking answers through tests and experiments
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7
Q

Monohybrid Cross

A
  • Cross between two individuals that differ in a single characteristic.
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8
Q

P (parental) Generation

A
  • The first generation in a genetic cross.
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9
Q

Phenotype

A
  • Appearance or manifestation of a characteristic.
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10
Q

F1 (filial 1) Generation

A
  • Offspring of the parents in the P generation in a genetic cross.
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11
Q

Homozygous

A
  • Having two identical alleles at a locus.
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12
Q

Heterozygous

A
  • Having two different alleles at a locus.
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13
Q

Recessive

A
  • Refers to an allele or a phenotype that is expressed only in homozygotes (aa); this allele is not expressed in a heterozygote (Aa) phenotype.
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14
Q

Concept Of Dominance

A
  • Principle of heredity discovered by Mendel stating that when two different alleles are present in a genotype, only one of them—the dominant allele—is observed in the phenotype.
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15
Q

Dominant

A
  • Refers to an allele or a phenotype that is expressed in homozygotes (AA) and in heterozygotes (Aa); only this allele is expressed in a heterozygote phenotype.
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16
Q

F2 (filial 2) Generation

A
  • Offspring of the F1 generation in a genetic cross; the third generation of a genetic cross.
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17
Q

Probability

A
  • Likelihood of the occurrence of a particular event; more formally, the number of times that a particular event takes place, divided by the number of all possible outcomes. Values range from 0 to 1.
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18
Q

Mendel’s First Law of Segregation

A
  • Principle of heredity discovered by Mendel that states that each individual diploid organism possesses two alleles at a locus and that these two alleles separate when gametes are formed, one allele going into each gamete.
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19
Q

Punnett Square

A
  • Shorthand method of determining the outcome of a genetic cross. On a grid, the gametes of one parent are written along the upper edge, and the gametes of the other parent are written down the left side. Within the cells of the grid, the alleles in the gametes are combined to form the genotype of the progeny.
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20
Q

Backcross

A
  • Cross between an F1 individual and either of the parental genotypes.
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21
Q

Genotypic Ratio

A

– The ratio of the different genotypes possible in the offspring of a cross.

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22
Q

Addition Rule

A
  • Rule stating that the probability of any of two or more mutually exclusive events is calculated by adding the probabilities of the events.
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23
Q

Multiplication Rule

A
  • Rule stating that the probability of two or more independent events taking place together is calculated by multiplying their probabilities.
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24
Q

Phenotypic Ratio

A
  • The ratio of the different phenotypes possible in the offspring of a cross.
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25
Q

Dihybrid Cross

A
  • Cross between two individuals that differ in two characteristics.
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26
Q

Wild Type

A
  • The trait or allele that is most commonly found in natural (wild) populations.
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27
Q

Testcross

A
  • Cross between an individual with an unknown genotype and an individual with the homozygous recessive genotype.
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28
Q

Mendels Second Law Of Independent Assortment

A
  • Principle of heredity discovered by Mendel that states that genes encoding different characteristics (genes at different loci) separate independently; applies to genes located only on different chromosomes or to genes far apart on the same chromosome.
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29
Q

Degrees Of Freedom (df)

A
  • Degrees of freedom = n -1, where n is the number of classes. For a genetic cross, n is the number of phenotypes.
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30
Q

Table Of Critical Values Of The Chi-Square Distribution

A

– It is a reference table that lists chi-square critical values. A chi-square critical value is a threshold for statistical significance for certain hypothesis tests and defines confidence intervals for certain parameters.

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31
Q

Chi-Square Goodness-Of-Fit Test

A
  • Statistical test used to evaluate how well a set of observed values fit the expected values. The probability associated with a calculated chi-square value is the probability that the difference between the observed and the expected values is due to chance.
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32
Q

Formula (Chi-Square)

A
  • The sum of the (observed minus the expected) squared divided by the expected.
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33
Q

Pedigree

A
  • Pictorial representation of a family history, essentially a family tree that outlines the inheritance of one or more characteristics.
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34
Q

Consanguinity

A
  • Mating between closely related people.
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35
Q

Sex Chromosome

A
  • Chromosomes that differ in number or morphology in males and females.
36
Q

Autosomes

A
  • Chromosome that is the same in males and females; a nonsex chromosome.
37
Q

Proband

A
  • The person from whom the pedigree is initiated.
38
Q

Sex - Sexual Phenotype

A
  • usually male or female.
39
Q

Gender

A
  • A sexual category assigned by an individual or others based on behavior and cultural practices.
40
Q

Pedigree Analysis

A

– Use to determine if the mode of inheritance is recessive, dominant, autosomal, or sex-linked. Moreover, it also determines the probability of an individual or offspring being affected in the given cross.

41
Q

Sex Determination

A
  • Specification of sex (male or female). Sex-determining mechanisms include chromosomal, genic, and environmental sex-determining systems.
42
Q

Heterogametic Sex

A
  • The sex (male or female) that produces two types of gametes with respect to sex chromosomes. For example, in the XX-XY sex-determining system, the male produces both X-bearing and Y-bearing gametes.
43
Q

Homogametic Sex

A
  • The sex (male or female) that produces gametes that are all alike with respect to sex chromosomes. For example, in the XX-XY sex-determining system, the female produces only X-bearing gametes.
44
Q

Genic Sex Determination

A
  • Sex determination in which the sexual phenotype is specified by genotypes at one or more loci, but there are no obvious differences in the chromosomes of males and females.
45
Q

Pseudoautosomal Region

A
  • Small region of the X and Y chromosomes that contains homologous gene sequences.
46
Q

Sex - Determining Region Y (SRY) Gene

A
  • The male-determining gene in mammals, located on the Y chromosome.
47
Q

Sex - Linked Characteristic (Y - linked; X - linked)

A
  • Characteristic determined by a gene or genes on sex chromosomes. A Y-linked characteristic is one that is determined by a gene or genes on the Y chromosome. A X-linked characteristic is one that is determined by a gene or genes on the X chromosome.
48
Q

XX-X0 Sex Determination

A
  • The female is XX and is the homogametic sex. The male is the heterogametic sex but only has one sex chromosome. The male in XX-XO systems produce gametes with (X) or without (O) a sex chromosome.
49
Q

ZZ - ZW Sex Determination

A
  • The female gamete determines the sex of the offspring. Males are the homogametic sex (ZZ), while females are the heterogametic sex (ZW).
50
Q

Barr Body

A
  • Inactivated X chromosome that appears as a condensed, darkly staining body in the nuclei of most cells of female placental mammals.
51
Q

Environmental Sex Determination

A

– Sex is determined fully or in part by environmental factors.

52
Q

Hemizygosity

A
  • Possession of a single allele at a locus. Males of organisms with XX-XY sex determination are hemizygous for X-linked loci because their cells possess a single X chromosome.
53
Q

XX - XY Sex Determination

A

– Females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two different kinds of sex chromosomes (XY), and are called the heterogametic sex. The male gamete determines the sex of the offspring.

54
Q

Dosage Compensation

A
  • A mechanism to equalize the amount of protein produced by X-linked genes and autosomal genes. In placental mammals, dosage compensation is accomplished by the random inactivation of one X chromosome in the cells of females.
55
Q

Lethal Allele

A
  • Allele that causes death at an early stage in development—often before birth—so that some genotypes do not appear among the progeny.
56
Q

Dominant Lethal Allele

A
  • kills both heterozygotes and homozygotes.
57
Q

Codominance

A
  • Type of allelic interaction in which the heterozygote simultaneously expresses the phenotypes of both homozygotes.
58
Q

Recessive Lethal Allele

A
  • kills individuals that are homozygous for the allele
59
Q

Expressivity

A
  • Degree to which a trait is expressed.
60
Q

Penetrance

A
  • Percentage of individual organisms having a particular genotype that express the expected phenotype.
61
Q

Incomplete Penetrance

A
  • The genotype does not always produce the expected phenotype.
62
Q

Complete Dominance

A
  • Type of dominance in which the same phenotype is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote.
63
Q

Incomplete Dominance

A
  • Type of dominance in which the phenotype of the heterozygote falls in between the phenotypes of the two homozygotes.
64
Q

Multiple Alleles

A
  • Presence of more than two alleles within a group of organisms; however, each diploid member of the group has only two of the possible alleles.
65
Q

Compound Heterozygote

A
  • An individual that carries two different alleles at a locus that result in a recessive phenotype.
66
Q

Gene Interaction

A
  • Interaction between genes at different loci that affect the same characteristic.
67
Q

Dominant Epistasis

A
  • when the dominant allele of one gene hides the expression of all alleles of another gene
68
Q

Hypostatic Gene

A
  • Gene that is masked or suppressed by the action of a gene at a different locus.
69
Q

Epistasis

A
  • Type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus.
70
Q

Recessive Epistasis

A
  • When the recessive allele of one gene hides the expression of all alleles of another gene.
71
Q

Epistatic Gene

A
  • Gene that masks or suppresses the effect of a gene at a different locus.
72
Q

Temperature-Sensitive Allele

A
  • An allele that is functional only at certain temperatures.
73
Q

Genetic Maternal Effect

A
  • The phenotype of the offspring is determined by the genotype of the mother.
74
Q

Cytoplasmic Inheritance

A
  • Inheritance of characteristics encoded by genes located in the cytoplasm. Because the cytoplasm is usually contributed entirely by one parent, these types of characteristically are usually only inherited from one parent.
75
Q

Sex-Influenced Characteristic

A
  • Characteristic encoded by autosomal genes that are more readily expressed in one sex. For example, an autosomal dominant gene may have higher penetrance in males than in females, or an autosomal gene may be dominant in males but recessive in females.
76
Q

Sex Limited Characteristic

A
  • Characteristic encoded by autosomal genes and expressed in only one sex. Both males and females carry genes for these types of characteristics, but the characteristics appear in only one of the sexes.
77
Q

Epigenetics

A
  • Phenomena due to alterations in DNA that do not include changes in the base sequence; often affects the way in which DNA sequences are expressed. Such alterations are often stable and heritable in the sense that they are passed to descendant cells or individuals.
78
Q

Phenocopy

A
  • Phenotype produced by environmental factors alone that is the same as the phenotype produced by a genotype.
79
Q

Discontinuous Characteristic

A
  • Characteristic that exhibits only a few easily distinguished phenotypes. An example is seed shape, in which seeds are either round or wrinkled.
80
Q

Pleiotropy

A
  • Ability of one gene to affect multiple characteristics.
81
Q

Continuous Characteristic

A
  • Characteristic that displays a large number of possible phenotypes that are not easily distinguished, such as human height.
82
Q

Polygenic Characteristic

A
  • Characteristic encoded by genes at many loci.
83
Q

Quantitative Characteristic

A
  • Continuous characteristic that displays a large number of possible phenotypes or is encoded by multiple genetic factors.
84
Q

Multifactoral Characteristic

A
  • Characteristic determined by multiple genes and environmental factors.
85
Q

The Mitochondrial Eve Theory

A

– A theory in which mitochondrial DNA in modern humans was inherited from one common female ancestor in Africa approximately 200, 000 years ago.

Genetics (13 decks)

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