exam 2 review Flashcards
prokaryotes
organisms whose cells lack a nucleus and other organelles
what does every organism require to drive reaction
source of energy
-light (photo)
-chemicals (chemo)
every organism requires what for synthesizing organic compounds
source of carbon
-CO2 or related compound (auto)
-organic carbon (hetero)
phototrophs
obtain energy from sunlight
chemotrophs
obtain energy from chemicals like iron
autrophs
need only CO2 or related compound as a carbon source to synthesize organic compounds
heterotrophs
need at least one organic nutrient source to synthesize organic compounds
auto means
CO2 or related compound
hetero means
organic carbon
which metabolic diversities are present in eukaryotes
photoautotroph and chemoheterotroph
what metabolic diversity are present in prokaryotes
-photoautroph
-chemautotroph
-photoheterotroph
-chemoheterotroph
energy source for chemoautrophs
inorganic chemicals
energy source for chemoheterotrophs
organic compounds
endosymbiosis
one organism lives inside the cell or cells of another organism
endosymbiont theory
Theory that mitochondria and plastids originated as prokaryotic cells engulfed by a host cell, The engulfed cell and its host cell then evolved into a single organism
how did chloroplast form from endosymbiosis
absorb photosynthetic prokaryote, then eventually became the chloroplast
how did mitochondria form form endosymbiosis
engulfed oxygen using prokaryote which over generations of cells became mitochondrion
what evidence supports the endosymbiont theory
-mitochondria and chloroplasts have their own DNA, ribosomes, double membranes
-mitochondria and chloroplasts replicate by binary fission
-DNA in mitochondria and chloroplasts similar to prokaryotes that had similar functions
what does the cell cycle consist of
interphase and mitotic (m) phase
when do chromosomes duplicate in cell cycle
S phase
true or false: cells spend the most tine in interphase
true
what does interphase include
cell growth and copying of chromosomes in preparation for cell division
what are the sub-phases of interphase
G1, S phase, G2
what is chromatin
combination of DNA and proteins
what does a chromosomes consist of
DNA molecule packed together with protein
how do chromosomes fit into the nucleus
through an elaborate multilevel system of packing
chromosome
thread like strands that contain genes
what proteins are responsible for the first level of packing in chromatin
histones
nucleosome
first level of packing in chromatin
allele
an alternate form of a gene, affects phenotype
during interphase, how is DNA usually found? what does it allow more of
-less condensed form called euchromatin
-allows more transcription
what can transcription machinery only work on
uncondensed DNA
what happens to DNA during mitosis and meiosis
DNA condenses into highly compact structures (chromsoomes)
homologous chromosomes
pair of chromosomes that have simaile but not identical genetic information. Carry same genes in same location, but have different alleles.
what is the highly condensed form of chromatin called
heterochromatin
what is n
number of distinct chromsomes
what is humans n
23
mitosis
cell division that results in diploid (2n) daughter cells with identical genetic information
sister chromatids
two identical copies of a single chromosome. They are identical to each other and the parent cell.
genes expressed in mitosis are
the same genes expressed in daughter cells as parent cells
meiosis
division that produces haploid (n) non identical daughter cells (gametes)
diploid
cell containing 2 sets of chromosomes, one from each parent
haploid
cell containing one set of chromosomes
gametes
haploid reproductive cells like an egg or sperm; unite during sexual reproduction to produce diploid zygote
G2 of interphase
metabolic growth and activity, preparation for cell division
-chromosomes uncondensed after being duplicated in s phase
centrosomes
structure that organize microtubles
centriole
structure composed of microtubules
prophase
chromosomes condense (consist of two sister chromatids)
-mitotic spindles begin to form
-centrosomes move away from each other
prometaphase
-nuclear envelope fragments
-chromosomes condense further
-microtubules attach to kinetochores of chromosomes
kinetochores
proteins on centromere
metaphase
-centrosomes at opposite ends/poles of cell
-chromosomes arrive and line up at metaphase plate
how many sister chromatids are lined up at the metaphase plate in humans
2
anaphase
-sister chromatids split and become chromosomes
-chromosomes move towards opposite ends of cells
telophase
-2 daughter nuclei form in the cell
-nuclear envelope arises from fragments of parent cell nuclear envelope and endomembrane system
cytokinesis
division of cytoplasm
what is the eukaryotic cell regulated by
signaling molecules
what can checkpoint signals influence
growth factors
growth factors
protein that stimulates other cells to divide
What might happen if the cell ignored these checkpoints and progressed through the cell cycle?
The cell would divide under conditions where it was inappropriate to do so. If the daughter cells and their descendants also ignored either of the checkpoints and divided, there would soon be an abnormal mass of cells. (This type of inappropriate cell division can contribute to the development of cancer.)
G1 checkpoint absence of go-ahead signal
cell exits the cell cycle and enters a non dividing state
G1 checkpoint if cell receives go ahead signal
the cell continues on cell cycle
why durinh M checkpoint in cell in mitosis does cell receives stop signal
when any of its chromosomes are not attached to spindle fibers
M checkpoint go ahead signal
-when all chromosomes are attached to spindle fibers and allows the cell to proceed into anaphase
what happens in meiosis I
separates homologous chromosomes
prophase I of meisosi
-spindle form, nuclear envelope fragments, chromosomes condenses
-chromosome pairs with homolog, allows crossing over at chiasmata
-microtubules attach to kinetochores at the centromere of each homolog
what happens in meiosis I but not mitosis
homologous chromosomes interact
crossing over
exchange in genetic material on chromosomes
chiasmata
x shaped region where crossing over has occurred in prophase i
centromere
Region on sister chromatid (on duplicated chromosomes) where it is most closely attached to its sister by proteins
what happens when centrosomes fuse, example?
leads to diversity and change in number of chromosomes among species
-chimps and humans have 2 chromosomes that fuse
metaphase I of meiosis
-Pairs of homologous chromosomes align at the metaphase plate
-both chromatids of one homolog attach to kinetochore microtubules from one pole
-independent assortment
independent assortment
1st meiotic division randomly sorts maternal and paternal homologs -> variation in offspring
anaphase I of meiosis
-homologous chromosomes pulled apart towards opposite ends/poles of cell
telophase I of meiosis
two haploid cells form, each chromosomes consist of two sister chromatids with regions of nonsister chromatid DNA
what follows immediately after meiosis I
meiosis II
difference between meiosis I and II
Meiosis I separates homologous chromosomes and meiosis II separates sister chromatids
when does DNA replication occur in mitosis
s phase
when does DNA replication occur in meiosis
occurs during interphase before meiosis I but not meiosis II
number of divisions in mitosis
one
number of divisions in meiosis
2
synapsis of homologous chromosomes in mitosis
does not occur
synapsis of homologous chromosomes during meiosis
occurs during prophase I
number of daughter cells in mitosis and composition
2 identical to parent cell
number of daughter cells in meiosis and composition
4 genetically different from parent cell
roles of mitosis
enables multicellular eukaryotes to arise from single cell; growth and repair; asexual reproduction in some species
roles of meiosis
produces gametes or spores; reduces number of chromosomes by half; introduces genetic variability
what is synapsis
pairing of two homologous chromosomes that occur during meiosis
where are operons found
prokaryotes
operon
cluster of functionally related genes that can be simultaneously controlled by a single promoter with an “on-off switch”
operator
portion of DNA that acts as the switch where repressesors attaches
repressor
protein that inhibits transcription
what is the function of the trp operson
turns the genes on and off the encode enzymes required to synthesize tryptophan
how does binding with the corepressor tryptophan affect the conformation of the trp repressor
alters the conformation or 3D structure of the protein so that it can bind to the operator
operator composition
DNA
repressor composition
protein
enzyme 2 (c) composition
protein
trpC compoistion
DNA
trp operon transcript composition
mRNA
when environmental tryptophan is low trp operon is active or inactive
active
when environmental tryptophan is low trp repressor is active or inactive
inactive
when environmental tryptophan is low the trp repressor is in
non-functional conformation in the cytoplasm
order these
_enzyme c is synthesized and folds into its functional form
-mRNA transcript is produced
-intracellular tryptophan increases
1)mRNA transcript is produced
2)enzyme c is synthesized and folds into its functional form
3) intracellular tryptophan increases
when environmental tryptophan is High trp operon is active or inactive
inactive
when environmental tryptophan is High the trp repressor is active or inactive
active
when environmental tryptophan is High the trp repressor is bound
to the operator
when environmental tryptophan is High what happens to RNA polymerase
it is blocked form proceeding with transcription down the length of the operon
when environmental tryptophan is High concentration of mRNA for operon genes after the operon is repressed
decreases
when environmental tryptophan is a High concentration of copies of the protein coded by trp c after the operon is repressed
decreases
when environmental tryptophan is High concentration intracellular tryptophan after the operon is repressed
decreases
A mutation in the trp repressor gene results in a repressor that can bind Trp, but cannot bind to the operator. What effect would this mutation have?
Transcription will proceed because the repressor cannot bind to the operator to block transcription. Trp mRNA and enzymes will continue to be made, resulting in an ever-increasing concentration of trp.
After a sufficient amount of time, the bacteria has a fully functioning set of enzymes producing tryptophan (Trp). If the bacteria produces more Trp than they use in synthesizing proteins, what happens to the intracellular Trp concentration and what effect does this have on the activity of the trp operon?
The intracellular trp concentration will increase until it binds to the repressor, blocking transcription of mRNA, translation of trp enzymes, and production of more trp.
. A mutation in trpC results in a non-functional enzyme. What effect do you expect on the
On the concentration of intracellular tryptophan? Production of trp operon mRNA?
Intracellular trp will decrease until there is none left or until the bacterium can take it up from the environment. Production of the trp operon mRNA will proceed once there is not enough intracellular trp available to bind to the repressor. The transcript encodes for the enzymes including trpC although no trp is made because the biosynthetic pathway cannot proceed properly.
with repressible operon but transcription is usually on but can be repressed when
a specific molecule binds to a repressor
active repsossor
bound to operator preventing transcription
inactive transcription
not bound to operator
with inducible operon transcription is usually off but
can be induced when a specific molecule binds to repressor
anabolic pathway
metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules
how are anabolic pathways controlled
repressible operon
energy from repressing the genes involved in biosynthesis when the end product is plentiful
saves energy
catabolic pathway
metabolic pathway that releases energy by breaking down complex molecules to simpler molecules
what are catabolic pathways controlled by
inducible operon
energy after inducing the genes involved in breaking down particular molecule only when that molecule is present
saves energy
genomes are ____ within all the cells in an organism
identical
what do differences between cell types result from
differential gene expression
differential gene expression
the expression of different sets of genes by cells with the same genome
true or false: all cell within an organism contain the same DNA
true
cell theory
All cells within an individual organism typically contain the same DNA, with some exceptions (such as immune system cells and germ cells), because they originate from a single fertilized egg (zygote) through a process called cell division
how does chromatin modification regulate gene expression
structural organization
-genes within highly packed heterochromatin are not usually expressed
true or false: genes within highly packed heterochromatin are generally expressed
false
histone acetylation
addition of an acetyl group to histone tail amino acids opens up chromatin and promotes transcription
what does addition of methyl groups condense chromatin inhibit
transcription
exon
expressed sequence, encodes protein
intron
intervening sequence that get removed, do not encode protein
upstream
before promoter
downstream
after promoter
control elements
segments of noncoding DNA that serve as binding sites for transcription factors
enhancer
segment of eukaryotic DNA containing multiple control elements, usually located far from genes whose transcription it regulates
poly-a-tail
sequence of 50-250 adenine nucleotides added onto the 3’end of pre mRNA
GTP cap
molecule added to 5’ end of eukaryotic mRNA which contributed to mRNA stability and processing
what is a transcription factor
a protein that promotes transcription
what is an example of general transcription factor
initiation complex
what is an example pf specific transcription factor
activators
general transcription factors
essential for the transcription of all protein-coding genes and initiate transcription
specific transcription factors
regulate gene expression of specific genes by binding to specific regions of those genes
what events trigger transcription
binding of the activator to proteins in the transcription initiation complex
roles of transcription factors
1) activator protein bind to distal control elements grouped as an enhancer in DNA
2)DNA bending protein brings the bound activators closer to the promoter
3)activators bind to some mediator proteins and general transcription factors, forming an active transcription initiation complex on promoter
mRNA processing only happens in
eukaryotes
how does regulation of gene expression in eukaryotes differ from regulation in bacteria
gene expression in bacteria is more simple and efficient and does not require coordination across different segments of DNA and as many moving parts (transcription imitation complex factors, as much cell signalling, mRNA proccessing) as eukaryotes.
how much of human genome encodes a protein
1.5%
cytoplasmic determinants come from
the mother
cytoplasmic determinants
A maternal substance, such as a protein or RNA, that when placed into an egg influences the course of early development by regulating the expression of genes that affect the developmental fate of cells
what causes cell differentiation in an early embryo
induction
induction
cells from one area of embryo influence another area via signals that affect gene expression
indcution can control the assignment of
body axes
master regulatory gene
a regulator gene at the top of a gene regulation hierarchy, particularly in cell differentiation
homeotic genes
any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells
hox genes are a type of
homeotic gene
what do hox genes hep with
correct positioning of body parts
where does expression of genes begin
anterior
homeobox found in
found across different invertebrates and vertebrates in the same organization on chromosomes
hox genes are ______ __________ genes and largely determine the final body plan of every animal species
highly conserved
enhancer
segment of DNA containing group of distal control elements
What kind of proteins do Hox genes encode?
transcription factprs
what do these genes do
Encode transcription factors that promote transcription of genes within specific body segment that encode a complex of proteins required to build a specific structure (antennae)
what do hox genes tell us about why all bilateral animals have similar body plans
Hox genes are highly similar across bilateral animals and must have been present in a common ancestor of bilateral animals
