Chapter 3 Flashcards
DNA
- deoxyribonucleic acid
- the chemical composition of the molecules that contain the genes, which are the chemical instructions for cells to manufacture various proteins
chromosome
- one of the 46 molecules of DNA (in 23 pairs) that virtually each cell of the human body contains and that, together contain all the genes
- other species have more or fewer
gene
- a small section of a chromosome; basic unit for the transmission of heredity
- consists of a string of chemicals that provide instructions for the cell to manufacture certain proteins
allele
- a variation that makes a gene different in some way from other genes for characteristics
- many genes never vary; others have several possibilites
genome
-the full set of genes that are the instructions to make an individual member of a certain species
gamete
-a reproductive cell—that is, a sperm or ovum that can produce a new individual if it combines with a gamete from the other sex to make a zygote
zygote
-the single cell formed from the union of two gametes, a sperm and an ovum
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
- most genes are _______
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 determines sex in humans
- the other 22 pairs are autosomes–inherited equally by males and females
XX
- a 23rd chromosome pair that consists of two X-shaped chromosomes, one each from the mother and the father
- ___zygotes become females
XY
- a 23rd chromosome pair that consists of an X-shaped chromosome from the mother and a Y-shaped chromosome from the father
- ___zygotes become males
stem cells
-cells from which any other specialized type of cell can form
monozygotic (MZ) twins
- twins who originate from one zygote that splits apart very early in development
- aka identical twins
- other monozygotic multiple births (such as triplets and quadruplets) can occur as well
dizygotic (DZ) twins
- twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time
- aka fraternal twins
ART
- assisted reproductive technology
- a general term for the techniques designed to help infertile couples conceive and then sustain a pregnancy
IVF
- in vitro fertilization
- 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 woman’s ovary–if a zygote is produced, it is inserted into a woman’s uterus, where it may implant and develop into a baby
phenotype
-the observable characteristics of a person, including appearances, personality, intelligence, and all other traits
polygenic
-referring to a trait that is influenced by many genes
multifactorial
-referring to a trait that is affected by many factors, both genetic and environmental, that enhance, halt, shape, or alter the expression of genes, resulting in a phenotype that may differ markedly from the genotype
epigenetic
-referring to environmental factors that affect genes and genetic expression–enhancing, halting, shaping, or altering the expression of genes and resulting in a phenotype that may differ markedly from the genotype
Human Genome Project
- an international effort to map the complete human genetic code
- essentially completed in 2001, though analysis is ongoing
dominant-recessive pattern
-the interaction of a heterozygous pair of alleles in such a way that the phenotype reflects one allele (dominant gene) more than the other (recessive gene)
carrier
- a person whose genotype includes a gene that is not expressed in the phenotype
- the carried gene occurs in half of the carrier’s gametes and thus is passed on to half of the carrier’s children
- if such a gene is inherited from both parents, the characteristic appears in the phenotype
X-linked
-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
copy number variations
-genes with various repeats or deletions of base pairs
heritability
-a statistic that indicates what percentage of the variation in a particular trait within a particular population, in a particular context and era, can be traced to genes
down syndrome
- a condition in which a person has 47 chromosomes instead of the usual 46, with 3 rather than 2 chromosomes at the 21st site
- people with Down syndrome typically have distinctive characteristics, including unusual facial features, heart abnormalities, and language difficulties
- aka trisomy-21
fragile X syndrome
- a genetic disorder in which part of the X chromosome seems to be attached to the rest of it by a very thin string of molecules
- the cause is a single gene that has more than 200 repetitions of one triplet
genetic counseling
-consultation and testing by trained experts that enable individuals to learn about their genetic heritage, including harmful conditions that they might pass along to any children they may conceive
PKU
- a genetic disorder in which a child’s body is unable to metabolize an amino acid called phenylalanine
- unless the infant immediately begins a special diet, the resulting buildup of phenylalanine in body fluids causes brain damages, progressive mental retardation, and other symptoms
