bio test chapters 10-11 :(

s a d n e s s s s s s s s s s s s s s s s s

Griffith

tried to develop a vaccine against pneumonia by studying a harmless and pathogenic strain that causes the disease. When he killed the pathogenic and mixed the remains with the harmless bacteria, some living bacterial cells became pathogenic.

Bacteriophages (phages)

Viruses that infect bacteria exclusively

Hershey and Chase

grew bacteriophage so that the protein was radioactive; after going into the centrifuge after injection, the radioactivity was in the liquid. Then, they grew bacteriophage so that the DNA was radioactive; after going into the centrifuge after being injected, the radioactivity was in the pellet.

Phages infecting bacterial cells

after the virus attaches to the host bacterial cell, it injects DNA into the host. Once injected, the viral DNA causes the bacterial cells to produce new phage proteins and DNA molecules which cause the cell to lyse, releasing the new phages

Watson and Crick

Discovered the structure of DNA

Nucleotide

molecule consisting of a nitrogenous base, a phosphate group, and a sugar

Polynucleotide

Nucleotide polymer chain

Phosphate group in nucleotide

phosphorus at center with four surrounding oxygens

Sugar in nucleotide

five carbon atoms, rest depends on ribose or deoxyribose

Basic

Nitrogenous bases are ______

Single ring, pyrimidines

thymine or uracil and cytosine (__), ______

Double ring, purines

adenine and guanine (__), ______

2

A pairing with T/U has __ hydrogen bonds

3

C pairing with G has __ hydrogen bonds

Semiconservative model for DNA replication

each of the two daughter molecules have one old strand from the parental molecule and one newly created strand (created through complementary base pairing)

Origins of replication

Where the replication of chromosomal DNA begins, proceeding in both directions (creating bubbles) until they fuse and there are two daughter DNA molecules

DNA polymerase

enzyme that links DNA nucleotides to a growing daughter strand; adds nucleotides only to 3’ → 5’ direction.

Okazaki fragments

to make the daughter strand, polymerase must work from the forking point. New strands are synthesized in short pieces as the fork opens up, called this

DNA ligase

pieces the Okazaki fragments into a single DNA strand

Proteins

__ are the links between genotype and phenotype

transcribed, translated

DNA ____ to RNA ____ to protein

Codons

the flow of information from gene to protein is based on triplet code; these are the triplets found in RNA

61

out of the 64 triplets code for amino acids

AUG

has a dual function; codes for Met and can also provide signal for the start of a polypeptide chain

UAA, UGA, UAG

don’t designate amino acids; serve as stop codons, ending translation

RNA polymerase

transcription enzyme that moves along the gene, forming a new RNA strand by following base-pairing rules

Promoter

acts as a binding site for RNA polymerase, determines where transcription starts

Terminator

RNA polymerase adds RNA nucleotides until it reaches a sequence of DNA bases called this, ending the gene

mRNA

conveys genetic messages from DNA to translation machinery of cell; transcribed from DNA, information in it translated into polypeptides

RNA processing

adding cap at 5’, tail at 3’, introns removed, exons spliced together

Introns

noncoding regions of RNA

Exons

coding regions, part of a gene that are expressed

tRNA

transfers amino acids to a growing polypeptide in a ribosome; picks up the appropriate amino acids, and recognizes appropriate codons in the mRNA

Anticodon

complementary to a codon triplet on mRNA

Ribosomes

coordinate functioning of mRNA and tRNA and catalyzes synthesis of polypeptides; made up of a large and small subunit, each made up of rRNA and proteins; has binding side for mRNA on small subunit and binding sites (P site and A site) for tRNA on large subunit

initiation

mRNA binds to small ribosomal subunit, tRNA base-pairs with start codon (carries Met). then, the large ribosomal subunit binds to the small one, and initiator tRNA fits into P site on the ribosome, and will hold the growing polypeptide. The A site is ready for the next tRNA.

Elongation

anticodon of incoming tRNA molecule pairs with mRNA codon in the A site. Then, the polypeptide from the tRNA in the P site separates and attaches to the amino acid carried by the tRNA in the A site. Then, the P site tRNA leaves and the tRNA from the A site moves to the P site

Stop codon

ends elongation; the completed polypeptide is freed and the ribosome splits back into separate subunits

Mutation

any change to genetic information of a cell or virus

Silent mutation

when the resulting protein still has the same amino acids

Missense mutation

changes one amino acid to another (varying effects)

Nonsense mutation

changes amino acid codon to a stop codon (typically resulting protein will not function properly)

Frameshift mutation

when number of nucleotides inserted or deleted is not a multiple of three (typically disastrous effects)

Mutagens

mutations caused by physical or chemical agents (like radiation)

Virus

infectious particle with a bit of nucleic acid wrapped in a capsid and sometimes a membrane envelope

Capsid

protein coat

Lytic cycle

results in lysis of host cell and release of newly produced viruses

Lysogenic cycle

DNA replication occurs without destroying the host cell

Similarities + differences in lytic and lysogenic cycles

Both lytic and lysogenic cycles begin when phage DNA enters the bacterium and forms a loop. Then, in the lytic cycle, DNA immediately turns a cell into a virus producing factory and the cell lyses. However, in the lysogenic cycle, viral DNA is inserted into the bacterial chromosome and once inserted the phage DNA is called prophage and most of its genes are inactive. Every time the cell prepares to divide, it replicates phage DNA as well. Sometimes an environmental signal can switch over from lysogenic to lytic cycle.

RNA

many animal viruses have _____ instead of DNA as their genetic material

Replication cycle of a typical enveloped RNA virus

the viral envelope fuses with the cell’s membrane allowing the protein-coated RNA to enter the cytoplasm. Enzymes digest the protein coat. An enzyme that entered as part of the virus then uses the RNA genome as a template for making complementary strands of RNA. This synthesizes new viral proteins. After, the new coat proteins assemble around the new viral RNA and the viruses leave

Retrovirus

an RNA virus that reproduces by means of a DNA molecule (reverse DNA → RNA flow of information); has reverse transcriptase

Reverse transcriptase

catalyzes reverse transcription; synthesis of DNA on RNA template

HIV (a retrovirus) behavior in a cell

reverse transcriptase makes a DNA strand and adds a complementary DNA strand to it. The resulting DNA enters the cell’s nucleus and inserts into the chromosomal DNA. The host’s RNA polymerase transcribes the incorporated DNA into RNA and this can be translated to viral proteins. New viruses from these components leave the cell and infect others.

Prion

consists solely of a misfolded form of a normal brain protein; clumps together with other prions, disrupting brain functions

transformation, transduction, conjugation

3 ways bacteria can transfer DNA

transformation

uptake of foreign DNA from surrounding environment

transduction

transfer of bacterial genes by a phage

conjugation

physical union of two bacterial cells and the DNA transfer between them

F factor

piece of DNA that determines ability of a donor E. coli cell to carry out conjugation

F factor’s behavior during conjugation

integrated into donor bacterium’s chromosome; when this cell conjugates, the donor chromosome replicates at F factor’s origin of replication. Once inside the recipient cell, the transferred donor genes can recombine with crossing over.

Plasmid

The F factor can also exist as one _______

One plasmid F factor behavior during conjugation

the F factor replicates when the donor cell mates with a recipient cell and transfers one whole copy in linear rather than circular form to the recipient cell. The transferred plasmid re-forms a circle in the recipient cell, and the cell becomes a donor

R plasmids

carry genes for enzymes that destroy antibiotics

Gene regulation

turning on and off of genes, helps organisms respond to environmental changes

Gene expression

genotype → phenotype process

Gene expression

The control of _________ makes it possible for cells to produce specific kinds of proteins when and where they are needed

Promoter

a site where the transcription enzyme, RNA polymerase attaches and initiates transcription

Operator

between the promoter and enzyme genes, a DNA control sequence that acts like a switch; determines whether RNA polymerase can attach to the promoter and start transcribing the genes

Operon

cluster of genes with related functions, along with the control sequences (on-off switch controls the whole cluster)

Repressor

turns transcription off by binding to the operator and blocking attachment of RNA polymerase to the promoter

Regulatory gene

located outside operon, codes for the repressor

Activators

proteins that turn operons on by binding to DNA and stimulating gene transcription; they make it easier for RNA polymerase to bind to the promoter, rather than blocking RNA polymerase, as repressors do

Differentiation

when cells become specialized in structure and function, fulfilling a distinct role

Differentiation

During the cell divisions that lead from a zygote to an adult in a multicellular organism, individual cells must undergo ___________

Histones

a protein molecule important in DNA packing. Eukaryotic chromatin consists of equal parts DNA and this protein.

Histones

attach to the DNA double helix, two loops of DNA for every 8.

DNA methylation

plays a role in turning genes off

Epigenetic inheritance

inheritance of traits transmitted by mechanisms not directly involving nucleotide sequence, such as chemical modification of histones or DNA bases

X chromosome inactivation

one of the two X chromosomes in each cell inactivated at random

Barr body

the inactive X in each cell condensed into a compact objectT

Transcription factors

to function, eukaryotic RNA polymerase requires the assistance of these proteins (as they function in initiating or regulating transcription). They bind to DNA or to other proteins that bind to DNA

Enhancers

The first step in initiating gene transcription of all protein-coding genes is binding of activator proteins to DNA control sequences called ___________

Enhancers

located far away on the chromosome from the gene, DNA control sequences

transcription

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A DNA-bending protein twists the DNA strand and brings the bound activators close to the promoter. The bound activators interact with other transcription factor proteins which bind at the gene’s promoter. This large assembly of proteins facilitates attachment of RNA polymerase to the promoter and initiation of ____

Alternative RNA splicing

regulation at RNA-processing level in which multiple mRNA are produced from the same primary transcript depending on which segments are treated as exons and introns

proteins

A lot of DNA remains not transcribed into _______. However, a significant amount of the genome is transcribed into functioning but non-protein-coding RNAs

microRNAs (miRNAs)

RNA molecules that associate with one or more proteins in a complex that can degrade or prevent translation of mRNA with a complementary sequence (degrades if entirely complementary - translation blocked if partially complementary)

Small interfering RNAs (siRNAs)

RNA molecules that associate with one or more proteins in a complex that can degrade or prevent translation of mRNA with a complementary sequence (very similar to miRNA)

RNA interference (RNAi)

blocking of gene expression by siRNAs

Homeotic gene

master control gene that regulates groups of other genes that determine the anatomy of parts of the body

Nucleic acid hybridization

can find the mRNA by using this technique, the base pairing of one strand of a nucleic acid to a complementary sequence on another strand (complementary molecule = nucleic acid probe, labeled with fluorescent tag)

DNA microarray

detects and measures expression of thousands of genes at a time

Complementary DNAs (cDNAs)

complementary to one of the mRNAs in a DNA microarray

Signal transduction pathway

series of molecular changes that convert a signal on a target cell’s surface to a specific response inside the cell

Totipotent

a cell that has potential to give rise to all different types of cells within an organism

Clone

organism produced through asexual reproduction, or, in this context, an individual created by asexual reproduction (no fusion of sperm and egg)

Regeneration

regrowth of lost body parts

Nuclear transplantation

how animals can be cloned, when the nucleus of one cell is placed into another cell

Reproductive cloning

replaces nucleus of an egg cell or zygote with a nucleus from an injected adult somatic cell, after a few days, the cell divisions forming a blastocyst. Then, the blastocyst is implanted into the uterus of a surrogate mother. The cloned animal will be genetically identical to the donor of the nucleus