Chapter 3 Flashcards
deoxyribonucleic acid (DNA)
the chemical composition of the molecules that contain the genes, which ate the chemical instructions for cells to manufacture various proteins
chromosome
one of the 46 molecules of DNA (23 pairs) that virtually every cell of the human body contains and that, together, contain all the genes. other species have more or fewer chromosomes
gene
a small section of a chromosome; the unit for the transmission of heredity
gamete
a reproductive cell (sperm for males and ova for females) each containing 23 chromosomes
zygote
the single cell formed when two gametes (sperm and ovum) come together
genome
the full set of genes that are the instructions to make an individual member of certain species
allele
a variation that makes a gene different in some way from other genes for the same characteristics. many genes never vary; others have several possible alleles
epigenetics
the study of how environmental factors affect genes and genetic expression
microbiome
all the microbes (bacteria, viruses, etc.) with all their genes in a community
genotype
an organism’s entire genetic inheritance, or genetic potential
homozygous
referring to two genes of one pair that are exactly the same in every letter of their code
heterozygous
referring to two genes of one pair that differ in some way. typically one allele has only a few base pairs that differ from the other member of the pair
23rd pair
the chromosome pair that, in humans, determines sex
XY
a 23rd chromosome pair that consists of an X-shaped chromosome from the mother and a Y-shaped chromosome from the father, an XY zygote becomes a male
XX
a 23rd chromosome pair that consists of two X-shaped chromosomes, one from the mother and the father, an XX zygote becomes a female
stem cells
cells from which any other specialized type of cell can form
In Vitro fertilization (IVF)
fertilization that takes place outside a woman’s body (as in a glass laboratory dish). procedure involves mixing sperm with ova that have been surgically removed from the ovary. if a zygote is produced, it is inserted into a woman’s uterus where it can develop
monozygotic twins
twins who originate from one zygote that splits apart very early in development
dizygotic twins
twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time
phenotype
the characteristics of a person, including appearance, personality, intelligence, etc.
human genome project
an international effort to map the complete human genetic code. the effort was essentially completed in 2001, though analysis is ongoing
dominant
reflected in the phenotype. dominant genes have more influence on traits than recessive genes do
recessive
hidden, not dominant. recessive genes are carried int he genotype and are not evident in the phenotype, except in special circumstances
carrier
a person whose genotype includes a gene that is not expressed in the phenotype. the carried gene occurs in half the carrier’s gametes and thus is passed on to half of the carriers children. if such a gene is inherited from both parents, the characteristic appears in the phenotype
