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meiosis produces

haploid gametes

fertilization produces

diploid zygotes

autosomes

nonsex chromosomes

the letter O signifies the

absence of a sex chromosome

heterogametic sex

when males produce two different types of gametes with respect to the sex chromosomes

homogametic sex

when females produce gametes that are all the same with respect to the sex chromosomes

pseudoautosomal region

small region of the X and Y chromosomes that contains homologous gene sequences

genic sex determination

sex determination in which the sexual phenotype is specified by genes at one or more loci, but there are no obvious differences in the chromosomes of males and females

genomic imprinting

differential expression of a gene that depends on the sex of the parent that transmitted the gene. If the gene is inherited from the father, its expression is different from that if it is inherited from the mother

genic balance system

sex determining system in which sexual phenotype is controlled by a balance between genes on the X chromosome and genes on the autosomes

Turner Syndrome

1. females
2. underdeveloped secondary sex characteristics
3. sterile
4. chromosome complement - XO

Klinefelter Syndrome

1. feminine males
2. small testes, sterile
3. reduced facial hair
4. chromosome complement - cells have one or more y chromosome, XXY, XXXY, XXYY

Poly-X females

1. females
2. few are sterile, most menstruate regularly
3. severity of mental retardation increases with the amount of X chromosomes
4. chromosome complement - XXX+

Barr Body

condensed, darkly staining structure that is found in most cells of female placental mammals and is an inactivated X chromosome

When does random X inactivation takes place?

Early in development, within the first weeks of development

dominance

the idea that an individual organism possesses two different alleles for a characteristic, but the trait encoded by only one of the alleles is observed in the phenotype

incomplete dominance

an intermediate phenotype between two homozygotes

codominance

the heterozygote expresses the phenotypes of both homozygotes (think AB blood type)

Dominance

Phenotype of the heterozygote is the same as the phenotype of one of the homozygotes.

Incomplete Dominance

Phenotype of the heterozygote is intermediate (falls within the range) between the phenotypes of the two homozygotes

Codominance

Phenotype of the heterozygote includes the phenotypes of both homozygotes

dominance is an __________ ______________

allelic interaction

an allelic interaction is

the interaction between the products of genes

Incomplete Penetrance

Refers to a genotype that does not always express the expected phenotypes. When an individual will possess the genotype but does not always express the phenotype - EX. polydactyly

Penetrance

Percentage of individuals with a particular genotype that express the phenotype expected of that genotype

Expressivity

the degree to which a character is expressed

(T or F) Incomplete Penetrance and variable expressivity are due to the effects of other genes and to environmental factors that can alter or completely suppress the effect of a particular gene.

T

lethal allele

causes the death of an individual organism, often early in development, and so the organism does not appear in the progeny of a genetic cross. Recessive lethal alleles kill individual organisms that are homozygous for the allele; dominant lethals kill both heterozygotes and homozygotes

An example of a dominant lethal allele is:

Huntington's Disease

Multiple Alleles

presence in a group of individuals of more than two alleles at a locus

gene interaction

type of interaction between the effects of genes at different loci (genes that are not allelic)

epistatic gene

a gene that does the masking

epistasis

type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus

hypostatic gene

gene that is masked or suppressed by the action of a gene at a different locus

when a probability associated with the chi-square value is >.05

there is a good fit between the observed results and the ratio

complementation test

test designed to determine whether two different mutations are at the same locus (are allelic) or at different loci (are nonallelic).

complementation

two different mutations in the heterozygous condition are exhibited as the wild-type phenotype; indicates that the mutations are at different loci

cytoplasmic inheritance

inheritance of characteristics encoded by genes located in the cytoplasm, because cytoplasm is usually contributed entirely by only one parent, most cytoplasmically inherited characteristics are inherited from a single parent

sex-influenced characteristics

encoded by autosomal genes that are more readily expressed in one sex.

sex-limited characteristics

characteristic determined by a gene or genes on sex chromosomes

genetic maternal effect

determines the phenotype of an offspring. offspring inherits genes for the characteristics from both parents, but the offspring's phenotype is determined not by its own genotype but by the nuclear genotype of its mother

epigenetics

Phenomena due to alterations to DNA that do not include changes in the base sequence; often affect the way in which DNA sequences are expressed. Alterations are often stable and heritable in the sense that they are passed from one cell to another

Norm of Reaction

range of phenotypes produced by a particular genotype in different environmental conditions

Sex-linked characteristics

Genes located on the sex chromosome

Sex-influenced characteristics

Genes on autosomal chromosomes that are more readily expressed in one sex

Sex-limited characteristics

Autosomal genes whose expression is limited to one sex

Genetic maternal effect

Nuclear genotype of the maternal parent

Cytoplasmic inheritance

Cytoplasmic genes, which are usually inherited entirely from only one parent

Genomic imprinting

Genes whose expression is affected by the sex of the transmitting parent

Phenocopy

phenotype that is produced by environmental effects is the same as the phenotype produced by a genotype

discontinuous (meristic) characteristics

have a few easily distinguished phenotypes (blood type)

continuous characteristics

characteristics that exhibit a continuous distribution of phenotypes (height, weight)

continuous characteristics are also called

quantitative characteristics

polygenic characteristics

characteristics that are encoded by genes at many loci

pleiotropy

one gene affects multiple characteristics

multifactorial characteristics

many continuous characteristics both polygenic and influenced by environmental factors

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