nucleic acids are unique in their ability to direct their own replication from monomers
process by which a DNA molecule is copied & how cells repair their DNA
DNA & proteins
Watson & Crick?
1953-created double-helical model for the structure of DNA
Genetic trait of pathogenicity be transferred btwn bacteria?
result: when killed pathogenic bacteria w/heat & then mixed all remains w/ living bacteria of non-pathogenic strain, becomes pathogenic
discovery of the genetic role of DNA
study Streptococcus pneumonae(bacterium)=> 2 strains:
1 pathogenic(disease causing)
more evidence tht DNA is genetic material
change in genotype & phenotype due to the assimilation of external DNA by a cell
little more than DNA
enclosed by a protective coat => protein
Chase & Hershey?
performed experiment showing that DNA is the genetic material of a phage
T2 (E.Coli) => injected w/ radioactive isotope: P & S
IMPT: provided evidence tht nucleic acids rather then proteins are hereditary material
1: base composition varies btwn species
2: w/in a species, # of A-T base are equal & C-G base are equal
A=T (2 H bonds)
C=G (3 H bonds)
Wilkins & Franklin ?
produced X-ray diffraction of DNA
presence of 2 strands accounts
Key features of DNA structure?
sugar PO4 backbones of the 2 strands
held by H bonds btwn nitrogenous bases (paired in the interior of helix)
partial chemical structure?
strong covalent bonds link units of ea. strand while weaker H bonds hold one strand to the other
oriented in opposite directions
A & G
C & T
Purine + Purine?
Pyrimidine + Pyrimidine?
Purine + Pyrimidine?
width is uniform diameter
DNA pairing - template strand?
2 strands: complementary -> ea. store the info necessary to reconstruct the other
both daughter molecule will consist of 1 intact parent & 1 newly synthesized strand
2 parental strands while other daughter molecule will consis of 2 newly synthesized strands
daughter molecule contains a mixture of old & new DNA
Messelson & Stahl?
experiment supported the semiconservative model of DNA replication
Origins of replication?
replication of DNA molecule -> short stretches of DNA having a specific sequence of nucleotides
Y-shaped region where parental strands of DNA are being unwound
enzymes that participate in the unwinding -> untwist the double-helix at the replication forks, separating the 2 parental strands & making them available as template strands
single strand binding proteins?
bind to the unpaired DNA strands keeping them from re-pairing
relieves the strain of twisting by breaking, swiveling & rejoining DNA strands
Primer synthesized by enzyme primase
Nitrogenous bases of DNA?
T -> thymine
along w/ 5 C-sugar=> deoxyribose (covalently bonded)
nitrogenous base T?
nitrogenous base A?
nitrogenous base C?
nitrogenous base G?
very critical to DNA structure?
nucleotide? (nucleic acid?
sugar + nitrogenous bases + P
focused on 3 mains:
transforming agent -> DNA
Phage head is made up of...?
cytosine makes up 38% of the nucleotides in a sample of DNA from an organism...percentage of nucleotides in this sample would be thymine..?
What also holds the bonds btwn stacked pairs of DNA?
Van der Waals interactions
What is function of DNA polymerase III?
add nucleotides to end of a growing DNA strand
New DNA strand elongates only in the 5' to 3' direction b/c..?
DNA polymerase can only add nucleotides to the free 3' end
3' prime end?
always OH group
5' prime end?
always PO4 group
Transfer RNA(#1) attached to amino acid lysine enters ribosome, and binds to growing peptide on the other tRNA(#2) in ribosome already..where does tRNA(#2) move to after this bonding of lysine to the polypeptide?
Sickle cell disease is result of what kind of mutation?
Which point mutation would most likely have a catastrophic effect on functioning of a protein?
base deletion near the start of a gene
What to expect of a eukaryotic cell lacking telomerase?
reduction in chromosome length
Transfer RNA(#1) attached to amino acid lysine enters ribosome, and binds to growing peptide on the other tRNA(#2) in ribosome already..when ribosome reaches a stop codon on mRNA, no corresponding tRNA enters A site..if translation reaction were to be experimentally stopped, which would u isolate?
assembled ribosome w/ a polypeptide attached to tRNA in P site
Particular triplet of bases in the nontemplate strand of DNA is AAA...anticodon in tRNA tht binds to mRNA codon is..??
What is meant by description of "antiparallel" regarding strands tht make up DNA?
5' to 3' direction of 1 strand runs counter to the 5' to 3' direction of the other strand
RNA polymerase moves in which direction along DNA?
3'->5' along template strand
Protein synthesis sequence..?
1) small ribosomal subunit binds w/ mRNA
2) aminoacyl-tRNA binds to A site
3) peptide bond forms btwn new amino acid & polypeptide chain
4) tRNA translocates to P site
5) tRNA leaves P site, & P site remains vacant
RNA polymerase differs from DNA polymerase?
RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis
THECATATETHERAT...how put this in framshift mutation?
Synthesis of lagging strand?
Each Okazaki fragment on lagging strand must be primed separately (1&4)
DNA polymerase III?
forms Okazaki fragments
elongates each Okazaki fragement adding on to its primer
leading strand: continuously synthesizes the leading strand, adding on to the primer
DNA polymerase I?
aka "proof reading" or backfilling w. DNA from RNA
leading strand: removes primer from the 5' end of leading strand & replaces it w/ DNA on the adjacent 3' end
Lagging strand: removes the primer from the 5' end of ea. fragment & replaces it w/ DNA, adding on to the 3'end of adjacent fragment
fills in (seals) all spots on lagging base
leading strand: joins the 3'end of DNA tht replaces the primer to the rest of the leading strand
lagging: joins the Okazaki fragments
cuts H bonds
cause to unwind
single strand binding protein
hepls to unwind & not get it tight
Steps of DNA replication?
4) primase (RNA polymerase)
5) DNA polymerase III
6)DNA polymerase I
process by which DNA directs the synthesis of proteins
provide the instructions for making specific proteins
any kind of RNA on a DNA template
actual synthesis of RNA under the direction of DNA
carries a genetic message from the DNA to the protein
synthesizing machinery of the cell
Gene to Protein?
DNA ----> RNA ------> proteins
(transcripts) (translation) (gene product)
mRNA->rRNA->tRNA message of DNA to protein
actual sunthesis of a polypeptide, which occurs under the direction of mRNA
occurs on ribosomes
Uracil substitutes for T (except for T w/ A it will be U)
Only find U in...?
translation & transcription occurs together
DNA is not separated by nuclear membranes from ribosomes & other proteins -synthesizing
mRNA produced by transcription is immediately translated w/o add. processing
RNA transcripts are modified before becoming true mRNA
nuclear envelope separates transcription from translation in space/time
transcription occurs=> nucleus
translation occurs=> cytoplasm
How many bases corresponds to amino acid?
encoded as sequence of nonoverlapping base triplets, or codons
Triplets of nucleotide bases?
smallest units of uniform length tht can code for all amino acids
genetic instruction for a polypeptide chain are written in the DNA as a series of codons
Codon in mRNA..?
is either translated into amino acid or serves as a translational stop signal
3rd base in sequence
catalyzed by RNA polymerase which pries the DNA strands apart & hooks together the RNA nucleotides
follows same base-pairing rules as DNA, except tht in RNA U subs for T
stages of transcript??
DNA sequence where RNA polymerase attaches & initiates transcription
signals the intiation of RNA synthesis
stretch of DNA tht is transcribed into RNA molecules
RNA polymerase moves along DNA, continues to untwist double helix, exposing 10-20 DNA bases at a time for pairing w/ RNA nucleotides
Alteration of mRNA ends..?
ea. end of pre-mRNA mol. is modified in particular way:
5'end receives a modified nucleotide cap
3'end gets poly-A tail
removes introns & joins exons
Are molecules of tRNA all the same?
each carries specific amino acid on 1 end
each has an anitcodon on other end
consists of single RNA strand tht is only about 80 nucleotides long
joins each amino acid to correct tRNA
Ribosome has 3 binding sites for tRNA..?
2) A site
3) E site
starts & active
3 stages of translation?
1) initiation ->w/AUG
2) elongation -> gets longer & longer
3) termination -> protein
changes in the genetic material of cell
changes in just one base pair of gene
Types of point mutations?
base-pair substitutions => replacement of 1 nucleotide & its partner w/another pair of nucelotide
base-pair insertions or deletions => result in frameshift
continuity of life is based on the reproduction of cells
integral part of cell cycle
life of a cell from time it first formed from a dividing parent cell until its own division into 2 daughter cells
Organisms depend on cell division for..?
development from a fertilized cell (reproduction)
repair (aka tissue renewal)
Cell division results from..?
daughter cells w/ identical genetic info-> DNA
special type of cell division tht produce sperm/eggs?
all DNA in cell constitutes this
consist of single DNA molecule or # of DNA molecules
DNA molecules in cell are packages into this
replication/distribution of so much DNA is manageable
2 sets of chromosomes (46 chromosomes ->2 sets of 23 ea.parent)
reproductive cells =>sperm & eggs
have half as many chromosomes as somatic cells
1 set of chromosomes
eukaryotic cells consists of this
complex of DNA & protein tht condenses during cell division
building material of chromosomes
Cell divison consists of...?
division of nucleus
division of the cytoplasm
gametes are produced by variation of cell division
yields nonidentical daughter cells tht have only 1 set of chromosomes, half as many as parent cell
Cell cycle ?
mitotic (M) phase
Mitotic (M) phase?
mitosis & cytokinesis
shortest part of cycle
cell growth & copying of 90% of chromosomes in preparation for cell division
longer part of cycle
cell is about to divide, grows& copies its chromosomes in preparation for cell division
divided into subphases:
1)G1 phase ("1st gap")
3)G2 phase ("2nd gap")
cell duplicated during which phase?
Mitosis is divided into 5 phases?
composed of centrosomes & the microtubules that extend from them
radial arrays of shorter microtubules tht extend from centrosomes
regions in animal's cells tht organize the microtubules of spindle
contains 2 centrioles
G2 of interphase?
nucleur envelope encloses nucleus
nucleus=>1 or more nucleoli
1 centrosomes have formed by duplication of single centrosome
chromosomes=>duplicated during S phase, can't be seen individually b/c not condensed
chromatin fibers become more tightly coiled->discrete chromosomes
2 identical sister chromatids joined at their centromeres (cohesins)
mitotic spindle being to form
centromeres move away from ea. other ->propelled by microtubules
nuclear envelope fragments
microtubules extending from ea. centrosome can now invade nuclear area
ea.2 chromatids have kinetochore
some of microtubules attach to kinetochore
kinetochore microtubules->pulling back & forth like tug of war
centrosomes=>opp poles of cells
chromosome convene @ metaphase plate
for ea. chromosome -kinetochore of sister chromatids are attached to kinetochore microtubules coming from opp poles
cell cycle control system ?
similiar to a clock
cyclically operating set of molecules in cell that triggers & coordinates key events in cell cycle
cell does not receive the go-ahead signal, exit the cycle, switching into nondividing state
2 types of regulatory proteins?
cyclin-dependent kinases (Cdks)
protein tht gets its name from its cyclically fluctuating concentration in cell
kinase to be active
enzymes tht activate or inactivate other proteins by phosphorylating them
some give go-ahead signals @ G1 & G2 checkpoints
molecular control of cell cycle
cyclin-Cdk complex tht triggers a cell's passage past G2 checkpoint into M phase
Density dependent inhibition?
crowded cells stop dividing
must be attached to substratum in order to divide
signaled to cell cycle via pathways involving plasma membrane proteins & elements of cytoskeletons linked to them
What amino acid sequence will be generated based on this following mRNA condon seq?
A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence NH2-phe-leu-ile-val-COOH would be..?
3' AAA-GAA-TAA-CAA 5'
Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?
normal cell converted to cancerous cell by a process called..?
physical or chemical expression of heredity
identical gene pairs on homologous chromosomes
non-identical gene pairs on homologous chromosomes
individual will be hybrid for trait in question
allele tht is phenotypically expressed in homozygous or heterozygous state
allele masks presence of recessive allele
allele tht is only expressed when homozygous
recessive trait only appears when dominant allele is absent
actual physical appearance/characteristic of organism
genetic makeup of organism based on alleles present
discovered basic principles of heredity by breeding garden peas in carefully planned experiments
heritable feature tht varies among individuals such as flower color
At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork:3' C C T A G G C T G C A A T C C 5'..
RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?
5' A C G U U A G G 3'
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests...?
that the parents were both heterozygous.
Two characters that produce a 9:3:3:1 phenotypic ratio in the F2 generation should have which of the following properties?
The genes controlling the characters obey the law of independent assortment
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt × BBtt will have black fur and long tails?
In a cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.How many genes must be responsible for these coat colors in Labrador retrievers?
Drosophila (fruit flies) usually have long wings (+) but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg). If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?
All +bt +vg heterozygotes
A 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is a sign of
Which of the following is an example of polygenic inheritance?
Skin pigmentation in humans
A woman has six sons. The chance that her next child will be a daughter is
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
XCXc and XCY
Males are more often affected by sex-linked traits than females because
males are hemizygous for the X chromosome
states that, if a population is not evolving, then the frequencies of alleles and genotypes in that population will remain constant from one generation to the next. Further, this principle allows us to predict what the genotype frequencies will be in a non-evolving population. We can conclude that a population may be evolving if its genotype frequencies differ from those predicted by the Hardy-Weinberg principle.
Which of the following are basic components of the Hardy–Weinberg model?
Frequencies of two alleles in a gene pool before and after many random matings
Which of the following statements is not a part of the Hardy–Weinberg principle?
The genotype frequencies in the offspring generation must add up to two.
True or false? The Hardy–Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating
Which of the following evolutionary forces results in adaptive changes in allele frequencies?
What genotype frequencies are expected under Hardy–Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q= 0.2 for a particular gene?
The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively
Which of the following evolutionary forces could create new genetic information in a population?
When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
the gene involved is on the X chromosome
A man with Klinefelter syndrome (47, XXY) is expected to have any of the following EXCEPT
What is a nondisjunction?
An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell
When can nondisjunction occur?
Nondisjunction errors can occur in meiosis I, when homologous chromosomes fail to separate, or in either mitosis or meiosis II, when sister chromatids fail to separate.
Which syndrome is characterized by the XO chromosome abnormality?
What kind of cell results when a diploid and a haploid gamete fuse during fertilization?
A triploid cell
Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?
A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.