Chapter 4; Genetics and Cellular Function Flashcards
deoxyribonucleic acid (DNA)
the cell’s hereditary matter
nucleotides
consists of a sugar, a phosphate group, and a single or double-ringed nitrogenous base
double helix
the structure of DNA that resembles a spiral staircase
law of complementary base pairing
the fact that one strand governs the base sequence of the other
genes
the essential function of DNA is to carry information
chromatin
fine filamentous material
chromosomes
46 long filaments
histones
each “bead” if a disc-shaped cluster of eight proteins
nucleosomes
segments
core particle
the spool of histones with the DNA ribbon around them
linker DNA
short segment
chromosome territory
permeated with channels that allow regulatory chemicals to have access to the genes
sister chromatids
two parallel filaments
prophase
early stage of cell division, these chromatids coil some more until each one becomes another 10 times shorter and about 700 nm wide
centromere
two genetically, identical, rod-like sister chromatids joined together at a pinched spot
kinetochore
protein plaque that has a role in cell division
genomics
relatively young science concerned with the comprehensive study of the genome and how its genes and noncoding DNA affect the structure and function of the organism
genetic code
a system that enable these 4 nucleotides to code for the amino acid sequences of all proteins
base triplet
a sequence of 3 DNA nucleotides that stands for 1 amino acid
codon
a 3-base sequence
stop codons
signal “end of message”
start codon
first codon of a messenger RNA transcript translated by a ribosome
transcription
the step from DNA to mRNA
translation
the step from mRNA to protein
RNA polymerase
binds to the DNA and assembles the RNA
pre-mRNA
the RNA produced by transcription is an “immature” form
exons
molecules that contains segments that will be translated into a protein
introns
segments that must be removed before translation
alternative splicing
one gene can code for more than one protein
transfer RNA (tRNA)
a relatively small RNA, whose job is to bind a free amino acid in the cytosol and deliver it to the ribosome to be added to a growing protein chain
anticodon
a series of three nucleotides complementary to a specific codon of mRNA
initiator tRNA
the first tRNA to bind to a ribosome at the start of translation
ribosomes
the little “reading machines” found in the cytosol and on the outside of the rough ER and nuclear envelope
initiation
mRNA passes through a nuclear pore into the cytosol and forms a loop
small subunit
in charge of information flow during protein synthesis
large subunit
a long tunnel running from the PTC to the ribosomal proteins
polyribosome
the cluster of ribosomes, all translating the same as mRNA
chaperone
as a new protein is assembled by a ribosome, it Is often bound by an older protein
stress proteins (heat shock proteins)
they are produced in response to heat or other stress on a cell and help damaged proteins fold back into their correct functional shapes
post-translational modification
removing some amino acid segments, folding the protein and stabilizing it with disulfide bridges, adding carbohydrates, etc
transport vesicles
bubblelike things that are coated with a protein called clathrin
DNA helicase
an enzyme that opens up one short segment of the helix at a time, exposing its nitrogenous bases
replication fork
the point where the DNA is opened up like two halves of a zipper separating
DNA ligase
another enzyme that can join segments
regulatory protein (transcription activator)
any protein that influences the regions of a DNA molecule that are transcribed by RNA polymerase during the process of transcription
mutations
changes in DNA structure
G1 (First gap phase)
an interval between cell division and DNA replication
S (synthesis phase)
in which a cell makes a duplicate copy of its centrioles and all of its nuclear DNA
parental DNA
DNA that serves as the template for replication
daughter DNA
made by the addition of a nucleotide that is complementary to the parent strand of DNA
interphase
the time between M phases
G0 (G-zero) phase
the ordered sequence of events that occur in a cell in preparation for cell division
Mitosis
helps development of an individual from a one-second fertilized egg, growth of all tissues and organs after birth, replacement of cells that die, and repair of damaged tissues
Prophase
chromosomes condense and nuclear envelope breaks down
spindle fibers
the centrioles begin to sprout elongated microtubules
metaphase
chromosomes lie along the midline of cell
mitotic spindle
the spindle fibers now form a lemon-shaped array
Anaphase
centromeres divide in two
daughter chromosome
each chromatid is now regarded as a separated, single-stranded
telophase
chromosomes gather at each pole of cell
cytokinesis
division of the cytoplasm into two cells
cleavage furrow
crease around the equator of the cell, and the cell eventually pinches in two
growth factors
chemical signals secreted by blood platelets, kidney cells, and other sources
contact inhibition
the cessation of cell division in response to contact with other cells
cyclins
families of proteins
cyclin-dependent kinases (Cdks)
families of protein kinases first discovered for their role in regulating the cell cycle
G2IM checkpoint
late in the G2 phase, determines whether the cell is able to proceed to mitosis
heredity
the transmission of genetic characteristics from parent to offspring
karyotype
a chart that shows the 46 chromosomes out in order by size and other physical features
homologous chromosomes
the two members of each pair that are in each 23 chromosomes
sex chromosomes
chromosomes X and Y
autosomes
all the other chromosomes
diploid
any cell with 23 pairs of chromosomes
haploid
sperm and egg cells
germ cells
cells on their way to becoming sperm and eggs
somatic cells
all other cells of the body
segregated
separate
paternal
sperm
maternal
egg
locus
the location of a particular gene on a chromosome
alleles
one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome
dominant
more important gene
recessive
genes that are expressed in offspring only when inherited from both parents
cleft chin
deep dimple in the middle of the chin
homozygous
individuals with two identical alleles
heterozygous
homologous chromosomes have different alleles for that gene
genotype
the paired alleles that an individual possesses for a particular trait
phenotype
an observable trait
Punnett square
shows how two heterozygous parents with certain traits can show up on their kids
carriers
individuals who carry a recessive allele and may pass it on
genetic counselor
perform genetic testing or refer clients for tests, advise couples on the probability of transmitting genetic diseases, and assist people in coping with genetic disease
multiple alleles
some genes exist in more than two allelic forms
gene pool
collective genetic makeup
codominant
equally dominant
incomplete dominance
when two different alleles are present
polygenic (multiple-gene) inheritance
a phenomenon in which genes at two or more loci, or even on different chromosomes, contribute to a single phenotypic trait
pleiotropy
a phenomenon in which one gene produces multiple phenotypic effects
alkaptonuria
mutation of chromosome 3
sex-linked traits
carried on the x or y chromosome and therefore tend to be inherited by one sex more than the other
x-linked
located on chromosome X
polydactyly
the presence of extra fingers or toes
penetrance
the percentage of a population with a given genotype that actually exhibits the predicted phenotype
epigenetics
heritable changes beyond the level of the genome
DNA methylation
the addition of methyl groups to DNA
Pnider-Willi syndrome
either mutation or gene silencing leads to diverse effects including poor muscle tone, short stature, overeating, and childhood behavioral problems
