Page 122 - Cardiac Nursing

0:4
0/0
0/0
1
1
0:4
6/2
q
xd
q
xd
3
3
009
7-1
e 9
8 A
10.
10.
7-1
0 A
Pa
Pa
g
M
M
M
ta
ta
ra
p
p
p
ra
LWBK340-c04_
LWB
LWB K34 0-c 04_ p p pp097-110.qxd 30/06/2009 10:40 AM Page 98 Aptara
04_
0-c
K34
g
e 9
0 A
09
09
g
6/2
q
8 A
3
009
98 PA R T I I / Physiologic and Pathologic Responses
DISPLAY 4-1 Definitions
Amino acids. The building block for proteins. Humans before it is threaded into ribosomes for translation into
require 20 amino acids as building blocks. protein.
Chromosome. An arrangement of tightly packed and coiled Mutation. An alteration in a gene or segment of DNA; muta-
DNA and protein. Diploid cells such as the human body tions are largely accidental and unproductive. On rare oc-
cells have 23 sets of chromosomes; haploid cells such as casions, mutations can be dangerous and/or even benefi-
gametes—-sperm or ova—-have only a single set of chro- cial. Thus, mutations can lead to variation in the
mosomes. phenotype of an organism.
DNA. Deoxyribonucleic acid, the double helix, which codes Phenotype. The physical structure and/or composition of an
for the proteins and other elements necessary to organism, or group of organisms. Genotypes expressed in
construct an organism. and operating in the context of a given environment(s)
Exon. Regions of DNA that are expressed, coding for RNA determine phenotype.
and/or protein. Protein. Genes often encode for proteins, which help form
Gamete. A sex cell, such as egg or sperm, capable of joining and regulate all organisms. Proteins are molecular
with an opposite gamete (egg plus sperm) to make a machines composed of strings of 20 different types of
zygote. amino acids. Proteins can in turn form complexes,
Gene. A gene is a segment of DNA or RNA that performs a which interact to perform more complex actions and
specific function; usually, it is a segment of DNA that functions.
codes for some molecular product, often a protein. Aside Ribosomes. Ribosomes are complexes of RNA and protein,
from the nucleotides that code for the protein, a gene which use the information encoded in mRNA to assemble
also consists of segments that determine the type, quan- specific proteins out of amino acids via a process termed
tity, and timing of protein expression. Genes can produce translation.
different combinations of proteins under different stimuli. RNA. Ribonucleic acid; an intermediate, complementary
Genome. The sum total of genetic material in an individual copy of DNA. mRNA is used by ribosomes as templates
organism. for the construction of proteins.
Genotype. A relative term that can refer to a particular nu- Sex chromosomes. In humans, the X and Y chromosomes.
cleotide position, or even an entire segment of DNA. A Two X chromosomes result in a female gender, while an X
genotype has two components, one from the same posi- chromosome and a Y chromosome result in a male gen-
tion on each chromosome. der. Other species have different types of sex
Intron. In most eukaryotic cells, introns are segments of chromosomes.
DNA that are a component of gene structure but do not Synteny. Segments of chromosomes, which contain the
generally code for proteins. Introns are processed out of same sequence of genes, which are shared between differ-
transcribed messenger RNA (mRNA), or spliced out, ent organisms.
each of us unique. DNA is an exquisitely small yet extremely long around proteins called histones. DNA in the human genome is
molecule that lacks the tensile strength to remain unprotected dur- arranged into 24 distinct chromosomes (i.e., 22 autosomes and two
ing cell division. Accordingly, DNA molecules are packaged into sex chromosomes), physically separate molecules that range in length
tightly coiled units called chromosomes, found in the nucleus of every from about 50 million to 250 million base pairs. The two sex chro-
cell. Chromosomes consist of the double helix of DNA wrapped mosomes determine gender; two copies of the “X” chromosome re-
sult in female gender, while one copy each of the “X” and “Y” chro-
mosomes determines male gender (Fig. 4-3). There are 23 pairs of
chromosomes in the normal diploid genome in humans (i.e., 22
Sugar
■ Figure 4-1 The four DNA bases. Each DNA is made up of the
sugar 2 -deoxyribose linked to a phosphate group and one of the four ■ Figure 4-2 The DNA molecule consists of two antiparallel, com-
bases depicted above. plementary strands of nucleotides that pair A
T or G
C.