Chapters 11/12/13 Flashcards
any eukaryotic chromosome that is not a sex chromosome; are present in the same number and kind in both males and females
autosome
the fusion of two haploid gamete nuclei to form a diploid zygote nucleus
fertilization
a haploid reproductive cell
gamete
during zygote development, cells that are set aside from the somatic cells and that will eventually undergo meiosis to produce gametes
germ-line cells
the morphology of the chromosomes of an organism as viewed with a light microscope
karyotype
the position on a chromosome where a gene is located
locus
any of the cells of a multicellular organism except those that are destined to form gametes (germ-line cells)
somatic (cell)
the first round of cell division - referred to “reductive division” because homologous chromosomes separate
meiosis I
the second round of cell division
meiosis II
The diploid (2n) cell resulting from the fusion of male and female gametes (fertilization)
zygote
The process of producing offspring through an alternation of fertilization (producing diploid cells) and meiotic reduction in chromosome number (producing haploid cells).
sexual reproduction
A mechanism of genetic recombination that occurs only in eukaryotic organisms, in which two chromosomes trade segments; can occur between nonhomologous chromosomes as well as the more usual exchange between homologous chromosomes in meiosis.
recombination or crossing over
One of two or more alternative states of a gene.
allele
The genetic constitution underlying a single trait or set of traits.
genotype
The realized expression of the genotype; the physical appearance or functional expression of a trait.
phenotype
A single genetic cross involving two different traits, such as flower color and plant height.
dihybrid cross
mendel’s second law of heredity, stating that genes located on nonhomologous chromosomes assort independently of one another
law of independent assortment
Describes a case in which two or more alleles of a gene do not display clear dominance. The phenotype of a heterozygote is intermediate between the homozygous forms.
incomplete dominance
Describes a case in which two or more alleles of a gene are each dominant to other alleles but not to each other. The phenotype of a heterozygote for codominant alleles exhibits characteristics of each of the homozygous forms.
codominance
Interaction between two nonallelic genes in which one of them modifies the phenotypic expression of the other.
epistatsis
an allele that is expressed when present in either heterozygous or the homozygous condition
dominant allele
the offspring resulting from a cross between a parental generation - in experimental crosses, these parents usually have different phenotypes
first filial (f1) generation
having two different alleles of the same gene
heterozygous
having two identical alleles of the same gene
homozygous
the mating of unlike parents
hybridization
Mendel’s first law of heredity, stating that alternative alleles for the same gene segregate from each other in production of gametes
law of segregation
condition in which an individual allele has more than one effect on production of the phenotype
pleiotrophy
a diagrammatic way of showing the possible genotypes and phenotypes of genetic crosses
punnett square
an allele that is expressed only when present in a homozygous condition, but is “hidden” by the expression of a dominant allele in the heterozygous condition
recessive allele
in genetics, a characteristic that has alternative forms
trait
The offspring resulting from a cross between members of the first filial (F1) generation
f2 generation
describes a mode of inheritance in which more than one gene affects a trait
polygenic inheritance
The theory stating that hereditary traits are carried on chromosomes.
chromosome theory of inheritance
A trait determined by a gene carried on the X chromosome and absent on the Y chromosome.
sex-linked (x-linked) gene
A phenomenon by which the expression of genes carried on sex chromosomes is kept the same in males and females, despite a different number of sex chromosomes
dosage compensation
A deeply staining structure, seen in the interphase nucleus of a cell of an individual with more than one X chromosome, that is a condensed and inactivated X. Only one X remains active in each cell after early embryogenesis.
Barr body
The failure of homologues or sister chromatids to separate during mitosis or meiosis, resulting in an aneuploid cell or gamete.
nondisjunction
The condition in an organism whose cells have lost or gained a chromosome;
aneuploidy
The process of evaluating the risk of genetic defects occurring in offspring, testing for these defects in unborn children, and providing the parents with information about these risks and conditions.
genetic counseling
Genetic disease usually caused by presence of an additional chromosome 21 (trisomy 21). This can also be due to a translocation of material from chromosome 21 to another chromosome. The translocated chromosome combined with two normal copies of chromosome 21 produces the same effect as trisomy. The syndrome is characterized by growth reductions, characteristic facial structure, and mild to moderate intellectual disability.
down syndrome
describes a condition in which a chromosome has been lost due to a nondisjunction during meiosis, producing a diploid embryo with only one of these autosomes
monosomic
a chromosome that is related to sex
sex chromosome
a permanent change in cell’s DNA; includes change in nucleotide sequence, alteration of gene position, gene loss or duplication, or insertion of foreign sequences
mutation
describes the condition in which an additional chromosome has been gained due to a nondisjunction during meiosis, and the diploid embryo therefore has three autosomes.
triomic
A cross in which only a single trait with two variations is considered is called a(n) ____
cross or single factor cross.
monohybrid
