Invitation to the Lifespan Ch 2
zygote - ✔✔ correct answer The single cell that is formed from the fusing of two gametes, a sperm
and an ovum
DNA(deoxyribonucleic acid) - ✔✔ correct answer The molecule that contains the chemical
instructions for cells to manufacture various proteins.
chromosome - ✔✔ correct answer One of the 46 molecules of DNA (in 23 pairs) that each cell of the
human body contains and that, together, contain all the genes.
gene - ✔✔ correct answer A small section of a chromosome; the basic unit for the transmission of
heredity. Consists of a string of chemicals that provide instructions for the cell to manufacture certain
proteins.
gamete - ✔✔ correct answer A reproductive cell; that is, a sperm or an ovum that can produce a new
individual if it combines with a gamete from the other sex to form a zygote.
allele - ✔✔ correct answer Any of the possible forms in which a gene for a particular trait can occur.
genotype - ✔✔ correct answer An organism's entire genetic inheritance, or genetic potential.
phenotype - ✔✔ correct answer The observable characteristics of a person, including appearance,
personality, intelligence, and all other traits.
genome - ✔✔ correct answer The full set of genes that are the instructions to make an individual
member of a certain species.
XX - ✔✔ correct answer A 23rd chromosome pair that consists of two X-shaped chromosomes, one
each from the mother and the father; the zygote becoming a female.
XY - ✔✔ correct answer A 23rd chromosome pair that consists of an X-shaped chromosome from the
mother and a Y-shaped chromosome from the father; the zygote becoming a male.
monozygotic twins - ✔✔ correct answer Twins who originate from one zygote that splits apart very
early in development; identical twins.
, Invitation to the Lifespan Ch 2
dizygotic twins - ✔✔ correct answer Twins who are formed when two separate ova are fertilized by
two separate sperm at roughly the same time; fraternal twins.
additive gene - ✔✔ correct answer A gene that adds something to some aspect of the phenotype. Its
contribution depends on additions from the other genes, which may come from either the same or
the other parent.
dominant-recessive pattern - ✔✔ correct answer The interaction of a pair of alleles in such a way
that the phenotype reveals the influence of one allele (the dominant gene) more than that of the
other (the recessive gene).
carrier - ✔✔ correct answer A person whose genotype includes a gene that is not expressed in the
phenotype. Such an unexpressed gene occurs in half the carrier's gametes and thus is passed on to
half the carrier's children, who will most likely be carriers, too. Generally, the characteristic appears
in the phenotype only when such a gene is inherited from both parents.
X-linked - ✔✔ correct answer A gene carried on the X chromosome. If a male inherits an X-linked
recessive trait from his mother, he expresses that trait because the Y from his father has no
counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to
express them.
germinal period - ✔✔ correct answer The first two weeks of prenatal development after conception,
characterized by rapid cell division and the beginning of cell differentiation.
embryonic period - ✔✔ correct answer The stage of prenatal development from approximately the
third through the eighth week after conception, during which the basic forms of all body structures,
including internal organs, develop.
fetal period - ✔✔ correct answer The stage of prenatal development from the ninth week after
conception until birth, during which the fetus grows in size and matures in functioning.
stem cells - ✔✔ correct answer Cells from which any other specialized type of cell can form
implantation - ✔✔ correct answer The process, beginning about 10 days after conception, in which
the developing organism burrows into the tissue that lines the uterus, where it can be nourished and
protected as it continues to develop.
zygote - ✔✔ correct answer The single cell that is formed from the fusing of two gametes, a sperm
and an ovum
DNA(deoxyribonucleic acid) - ✔✔ correct answer The molecule that contains the chemical
instructions for cells to manufacture various proteins.
chromosome - ✔✔ correct answer One of the 46 molecules of DNA (in 23 pairs) that each cell of the
human body contains and that, together, contain all the genes.
gene - ✔✔ correct answer A small section of a chromosome; the basic unit for the transmission of
heredity. Consists of a string of chemicals that provide instructions for the cell to manufacture certain
proteins.
gamete - ✔✔ correct answer A reproductive cell; that is, a sperm or an ovum that can produce a new
individual if it combines with a gamete from the other sex to form a zygote.
allele - ✔✔ correct answer Any of the possible forms in which a gene for a particular trait can occur.
genotype - ✔✔ correct answer An organism's entire genetic inheritance, or genetic potential.
phenotype - ✔✔ correct answer The observable characteristics of a person, including appearance,
personality, intelligence, and all other traits.
genome - ✔✔ correct answer The full set of genes that are the instructions to make an individual
member of a certain species.
XX - ✔✔ correct answer A 23rd chromosome pair that consists of two X-shaped chromosomes, one
each from the mother and the father; the zygote becoming a female.
XY - ✔✔ correct answer A 23rd chromosome pair that consists of an X-shaped chromosome from the
mother and a Y-shaped chromosome from the father; the zygote becoming a male.
monozygotic twins - ✔✔ correct answer Twins who originate from one zygote that splits apart very
early in development; identical twins.
, Invitation to the Lifespan Ch 2
dizygotic twins - ✔✔ correct answer Twins who are formed when two separate ova are fertilized by
two separate sperm at roughly the same time; fraternal twins.
additive gene - ✔✔ correct answer A gene that adds something to some aspect of the phenotype. Its
contribution depends on additions from the other genes, which may come from either the same or
the other parent.
dominant-recessive pattern - ✔✔ correct answer The interaction of a pair of alleles in such a way
that the phenotype reveals the influence of one allele (the dominant gene) more than that of the
other (the recessive gene).
carrier - ✔✔ correct answer A person whose genotype includes a gene that is not expressed in the
phenotype. Such an unexpressed gene occurs in half the carrier's gametes and thus is passed on to
half the carrier's children, who will most likely be carriers, too. Generally, the characteristic appears
in the phenotype only when such a gene is inherited from both parents.
X-linked - ✔✔ correct answer A gene carried on the X chromosome. If a male inherits an X-linked
recessive trait from his mother, he expresses that trait because the Y from his father has no
counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to
express them.
germinal period - ✔✔ correct answer The first two weeks of prenatal development after conception,
characterized by rapid cell division and the beginning of cell differentiation.
embryonic period - ✔✔ correct answer The stage of prenatal development from approximately the
third through the eighth week after conception, during which the basic forms of all body structures,
including internal organs, develop.
fetal period - ✔✔ correct answer The stage of prenatal development from the ninth week after
conception until birth, during which the fetus grows in size and matures in functioning.
stem cells - ✔✔ correct answer Cells from which any other specialized type of cell can form
implantation - ✔✔ correct answer The process, beginning about 10 days after conception, in which
the developing organism burrows into the tissue that lines the uterus, where it can be nourished and
protected as it continues to develop.
