Chapter 3

Question 1

proteins

Answer 1

three-dimensional molecules that serve a wide variety of functions through their ability to bind to other molecules

Question 2

nucleus

Answer 2

organelle found in all eukaryotic cells, contains DNA, RNA, and other things

Question 3

molecules

Answer 3

structures made up of two or more atoms; can combine with other molecules to form more complex structures

Question 4

DNA

Answer 4

double-stranded molecule that contains the genetic code; a main component of chromosomes

Question 5

RNA

Answer 5

single-stranded molecule similar in structure to DNA; three forms essential to protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

Question 6

cytoplasm

Answer 6

semifluid, gel-like substance contained within the cell membrane; nucleus and numerous structures involved w/ cell function found in cytoplasm

Question 7

protein synthesis

Answer 7

manufacture of proteins; assembly of chains of amino acids into functional protein molecules; directed by DNA

Question 8

mitochondria

Answer 8

structures contained within the cytoplasm of eukaryotic cells that convert energy, derived from nutrients, to a form that can be used by the cell

Question 9

ribosomes

Answer 9

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

Question 10

mitochondrial DNA (mtDNA)

Answer 10

DNA found in the mitochondria; inherited only from the mother

Question 11

somatic cells

Answer 11

all the cells in the body except those involved in reproduction

Question 12

gametes

Answer 12

sex cells (eggs and sperm); developed from precursor cells in ovaries and testes

Question 13

zygote

Answer 13

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

Question 14

nucleotides

Answer 14

basic units of the DNA molecule, composed of a sugar, a phosphate, and 1 of 4 DNA bases

Question 15

replicate

Answer 15

to duplicate; the DNA molecule is able to make copies of itself

Question 16

enzymes

Answer 16

specialized proteins that initiate and direct chemical reactions in the body

Question 17

complementary

Answer 17

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)

Question 18

hemoglobin

Answer 18

a protein molecule that occurs in red blood cells and binds to oxygen molecules

Question 19

hormones

Answer 19

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

Question 20

amino acids

Answer 20

small molecules that are the components of proteins

Question 21

messenger RNA (mRNA)

Answer 21

form of RNA that’s assembled on a sequence of DNA bases; carries the DNA code to the ribosome during protein synthesis

Question 22

codons

Answer 22

triplets of messenger RNA bases that code for specific amino acids during protein synthesis

Question 23

transfer RNA (tRNA)

Answer 23

type of RNA that binds to specific amino acids and transports them to the ribosome during protein synthesis

Question 24

mutation

Answer 24

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

Question 25

gene

Answer 25

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

Question 26

genome

Answer 26

the entire genetic makeup of an individual or species; in humans, it's estimated that the human genome comprises about 3 billion DNA bases

Question 27

noncoding DNA

Answer 27

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

Question 28

exons

Answer 28

segments of genes that are transcribed and are involved in protein synthesis (prefix "ex" = expressed)

Question 29

introns

Answer 29

segments of genes that are initially transcribed and then deleted; not expressed, and aren't involved in protein synthesis

Question 30

regulatory genes

Answer 30

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

Question 31

homeobox genes

Answer 31

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

Question 32

sickle-cell anemia

Answer 32

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

Question 33

point mutation

Answer 33

change in one of the four DNA bases

Question 34

chromosomes

Answer 34

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

Question 35

autosomes

Answer 35

all chromosomes except sex chromosomes

Question 36

sex chromosomes

Answer 36

in mammals, the X and Y chromosomes

Question 37

locus

Answer 37

position or location on a chromosome where a given gene occurs; the term is sometimes used interchangeably with gene

Question 38

alleles

Answer 38

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

Question 39

karyotype

Answer 39

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

Question 40

mitosis

Answer 40

simple cell division; the process by which somatic cells divide to produce two identical daughter cells

Question 41

meiosis

Answer 41

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

Question 42

recombination

Answer 42

the exchange of genetic material between paired chromosomes during meiosis; also called "crossing over"

Question 43

clones

Answer 43

organisms that are genetically identical to another organism; term may also be used to refer to genetically identical DNA segments, molecules, or cells

Question 44

random assortment

Answer 44

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)

Question 45

polymerase chain reaction (PCR)

Answer 45

method of producing thousands of copies of a DNA sample

Question 46

Human Genome Project

Answer 46

an international effort aimed at sequencing and mapping the entire human genome, completed in 2003