Chapter 3 Flashcards
proteins
three-dimensional molecules that serve a wide variety of functions through their ability to bind to other molecules
nucleus
organelle found in all eukaryotic cells, contains DNA, RNA, and other things
molecules
structures made up of two or more atoms; can combine with other molecules to form more complex structures
DNA
double-stranded molecule that contains the genetic code; a main component of chromosomes
RNA
single-stranded molecule similar in structure to DNA; three forms essential to protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)
cytoplasm
semifluid, gel-like substance contained within the cell membrane; nucleus and numerous structures involved w/ cell function found in cytoplasm
protein synthesis
manufacture of proteins; assembly of chains of amino acids into functional protein molecules; directed by DNA
mitochondria
structures contained within the cytoplasm of eukaryotic cells that convert energy, derived from nutrients, to a form that can be used by the cell
ribosomes
structures composed of a form of RNA called ribosomal RNA (rRNA) and protein; found in a cell’s cytoplasm and are essential to the manufacture of proteins
mitochondrial DNA (mtDNA)
DNA found in the mitochondria; inherited only from the mother
somatic cells
all the cells in the body except those involved in reproduction
gametes
sex cells (eggs and sperm); developed from precursor cells in ovaries and testes
zygote
cell formed by the union of an egg cell and sperm cell; contains the full complement of chromosomes (46 in humans); has the potential of developing into an entire organism
nucleotides
basic units of the DNA molecule, composed of a sugar, a phosphate, and 1 of 4 DNA bases
replicate
to duplicate; the DNA molecule is able to make copies of itself
enzymes
specialized proteins that initiate and direct chemical reactions in the body
complementary
in genetics, referring to the fact that DNA bases form pairs (base pairs) in a precise manner; ex: adenine only bonds to thymine (these are complementary because one requires the other to form a complete DNA pair)
hemoglobin
a protein molecule that occurs in red blood cells and binds to oxygen molecules
hormones
substances (usually proteins) that are produced by specialized cells and that travel to other parts of the body, where they influence chemical reactions and regulate various cellular functions
amino acids
small molecules that are the components of proteins
messenger RNA (mRNA)
form of RNA that’s assembled on a sequence of DNA bases; carries the DNA code to the ribosome during protein synthesis
codons
triplets of messenger RNA bases that code for specific amino acids during protein synthesis
transfer RNA (tRNA)
type of RNA that binds to specific amino acids and transports them to the ribosome during protein synthesis
mutation
a change in DNA; the term can refer to changes in DNA bases (specifically called point mutations) as well as to changes in chromosome number and/or structure
gene
sequence of DNA bases that specifies the order of amino acids in an entire protein, a portion of a protein, or any functional product, such as RNA; a gene may be composed of thousands of DNA bases
genome
the entire genetic makeup of an individual or species; in humans, it’s estimated that the human genome comprises about 3 billion DNA bases
noncoding DNA
DNA that does not direct the production of proteins; however such DNA segments produce thousand of molecules (ex: RNA) that are involved in gene regulation; thus the term noncoding is misleading
exons
segments of genes that are transcribed and are involved in protein synthesis (prefix “ex” = expressed)
introns
segments of genes that are initially transcribed and then deleted; not expressed, and aren’t involved in protein synthesis
regulatory genes
genes that influence the activity of other genes; direct embryonic development and are involved in physiological processes throughout life; critically important to the evolutionary process
homeobox genes
evolutionarily ancient family of regulatory genes that directs the development of the overall body plan and the segmentation of body tissues; there are at least 20 families of homeobox genes
sickle-cell anemia
severe inherited hemoglobin disorder in which red blood cells collapse when deprived of oxygen; results from inheriting two copies of a mutant allele; the type of mutation that produces the sickle-cell anemia allele is a point mutation
point mutation
change in one of the four DNA bases
chromosomes
discrete structures composed of DNA and proteins found only in the nuclei of cells; chromosomes are visible under magnification only during certain phases of cell division
autosomes
all chromosomes except sex chromosomes
sex chromosomes
in mammals, the X and Y chromosomes
locus
position or location on a chromosome where a given gene occurs; the term is sometimes used interchangeably with gene
alleles
alternate forms of a gene; occur at the same locus on paired chromosomes and thus govern the same trait, but because they’re different, their action may result in different expressions of that trait
karyotype
chromosomes of an individual, or what is typical of a species, viewed microscopically and displayed in a photograph; chromosomes are arranged in pairs and according to size and position of the centromere
mitosis
simple cell division; the process by which somatic cells divide to produce two identical daughter cells
meiosis
cell division in specialized cells in ovaries and testes; meiosis involves two divisions and results in four daughter cells, each containing only half the original number of chromosomes; these cells can develop into gametes
recombination
the exchange of genetic material between paired chromosomes during meiosis; also called “crossing over”
clones
organisms that are genetically identical to another organism; term may also be used to refer to genetically identical DNA segments, molecules, or cells
random assortment
chance distribution of chromosomes to daughter cells during meiosis; along with recombination, random assortment is an important source of genetic variation (but not new alleles)
polymerase chain reaction (PCR)
method of producing thousands of copies of a DNA sample
Human Genome Project
an international effort aimed at sequencing and mapping the entire human genome, completed in 2003
