Biol 108: Ch 8 & 9: DNA Structure and Function & From DNA to Proteins.
DNA Replication and Repair.
-Order of nucleotide bases in a strand of DNA (DNA sequence) is Genetic information -Before a cell reproduces, it must duplicate its DNA so that it can provide a full set of DNA to an offspring -DNA duplicates itself in DNA Replication.
Mutations Overview:
-Small scale, permanent changes in the nucleotide sequence of DNA that may result from replication errors. -Mutations can change a gene's product.
rRNA and tRNA: the translators:
-ribosomes (containing rRNA and proteins) and tRNA's interact to translate an mRNA into a polypeptide -One large and one small ribosome unit joins with mRNA and the transport tRNA -tRNA's deliver AA's to ribosomes in the order specified by mRNA -rRNA enigmatically catalyzes the format of a peptide bond between AA's -Each tRNA has two attachment sites 1. A triple of nucleotides (anticodon) base pairs with an mRNA codon 2. Another attachment site binds to AA specified by the codon. -Transfer RNA's (tRNA's) with different anticodons carry specific AA's to a ribosome during translation of mRNA
DNA to RNA to Protein:
-the sequence of Amino acids in a polypeptide chain correspond to a sequence of nucleotide bases in DNA called a gene -Conversion of information in DNA to a protein occurs in 2 steps: transcription and translation.
Discovery of DNA
-100 years of experiments with bacteria and bacteriophages offer solid evidence that DNA, not Protein is the hereditary material of life. -in the late 1800's, Miescher found nuclei contain an acidic substance that was mainly composed of phosphorus and nitrogen, which later, found DNA. -In the early 1900's, Gutfith used strep to study two strains and determined hereditary materials.
Structure of DNA
-3 prime (3') carbon of a sugar is joined by a phosphate group to 5' carbon of the next sugar,forming 2 sugar phosphate backbones running in opposite directions. -Inside are paired bases (A to T and C to G). One base pair is when the A and T or the C and G are combined. Mutations occur when the bases are not lined up properly
What are the proofreaders of DNA?
-A DNA molecule is not always replicated correctly, so we have what is called DNA polymerase, which is the proofreader. -DNA repair mechanisms (ike polymerase) correct mismatches -When proofreading and repair mechanisms fail, an error becomes a mutation.
What is a Chromosome and what does it do?
-A chromosome is a structure consisting of DNA and Proteins. -It carries part of or all of the cell's genetic information -Eukaryotic cells have a number of chromosomes.
What is Chromosome Duplication?
-As the cell prepares to divide, the cell duplicates its chromosomes, so both offspring get a full set. -After chromosomes are duplicated, each consists of two DNA molecules called sister chromatids, which are attached to each other at a centromere. -A duplicate chromosome consists of two long, tangled filaments (sister chromatids) bunched into an X shape.
Sex Determination in Humans
-Body cells of human females contain 2 X chromosomes. Males have X and Y. -An embryo/person will randomly inherit one sex chromosome from some and one from dad. --> All eggs have 1 X and sperm will have either X or Y (50/50 chance) -If an X bearing sperm fertilizer an X bearing egg, the individual will be female. If sperm carries Y chromosome, the individual will be male.
From DNA to Proteins: Chapter 9
-DNA contains all of the instructions for building a new person -The linear order sequenced of the 4 bases in the DNA strand si the genetic information which occurs in sulfates called genes --->Genes: part of a DNA base sequence --->Specifies an RNA or protein product.
What is the Chromosome Structure?
-DNA in a nucleus is divided into chromosomes -At its most condensed, a duplicated chromosome is packed tightly into an X shape -A chromosome unravels as a single fiber (a hollow cylinder) formed by coiled coils. -Coiled coils consist of molecules of DNA and proteins. -DNA molecule wraps around a core of histone proteins forming "bead structures" called nucleosomes. -The DNA molecule has 2 strands twisted into a double helix.
DNA's building blocks
-DNA nucleotide ahs 5 carbon sugar, three phosphate groups, and one of four nitrogen containing bases: Adenine, guanine, thymine, and cytosine (A=T, C=G)
Process of Transcription:
-During transcription: DNA acts as template upon which strands of RNA 9transcripts) is assembled fro RNA nucleotides. -Each new RNA is complementary in sequence to the DNA Template --->G pairs with C, A pairs with U (Uracil instead of thymine)
More to know about DNA replication
-Each parental DNA single strand serves as a template for assembly of new one -The two parental DNA single strands remain intact and a new strand is assembled on the old strand. -Each new double-stranded DNA that forms consists of one old parent single strand and a new single strand -Each DNA strand has an unbounded 5' carbon at one end and and unbounded 3' carbon on the other end
What is the Chromosome number?
-Eukariotic DNA is divided among a number of chromosomes that differ in length and size. -The sum of all chromosomes in a cell of given type is chromosome number -Diploid cells have two of each type of chromosomes while haploid cells have one. -Each species has characteristic chromosome number -Diploid (2n) and Haploid (n) -Humans have 46 chromosomes -2 types of chromosomes (23 pairs) so the chromosome number is diploid (2n) -Each pari of chromosomes has 2 versions: one maternal and one paternal. -Sex chromosomes differ among males and females: the differences determine an individual's sex -all other chromosomes are called autosomes, which are the same in males and females. -Autosomes of a pair have the same length, shape, and centromere location and carry the same genes.
RNA and Eukaryotes
-Eukaryotes modify their RNA inside the nucleus, then slip it to the cytoplasm. -Introns: nucleotide sequence that are removed from a new mRNA, and exons are sequences the stay in the mRNA. -Sometimes, some eons are removed and the remaining ones are spliced together (alternative splicing) which enables one gene to encode different proteins.
Defects in Hemoglobin:
-Frameshift mutation: a depletion/insertion from DNA of the global (beta) gene causes a type of anemia (be a thalassemia). -Deletion: Mutation in which one or more base pairs are lost. -Insertion: mutation in which one or more base pairs are added EX: frameshift usually has drastic consequences because it garbles the genetic message: an amino acid substitution results in abnormally shaped red blood cells characteristics of sickle cell anemia.
Mutated genes and their protein products:
-If a mutation changes the genetic instructions encoded in the DNA, an altered gene product may result: EX: hemoglobin in blood consists of 4 polypeptides (globin) golden around heme (iron fe): various defects in the polypeptides can cause anemia.
What is DNA synthesis?
-Occurs in the 5' to 3' direction -Only one of the new DNA strands can be assembled in a single piece. The other forms in short segments called Okazaki fragments.
How are Transcription and Translation a part of gene expression?
-Process by which the information gene becomes converted to an RNA or protein.
What are the various technologies that involve cloning?
-Reproductive cloning: produces genetically identical individuals (clones). Artificial twinning that yields genetically identical individuals. -Somatic Cell nuclear transfer (SCNT): fuses adult cell with an enucleated egg. Method of reproductive cloning which a researcher removes a nucleus from an unfertilized egg, then inserts into the egg, a nucleus from an adult body cell. Soma in Somatic means body. EX: Dolly the sheep. -Therapeutic Cloning: Produces embryos that are used for Stem cell research.
Genetic Code:
-The protein: building info in mRNA consists of a sequence of 3 mRNA's (bases) codon; each codon is a code for particular amino acids. - the 4 bases (a, c, g, and u) can be combined into 64 different codons, which constitute the genetic code.
Codons and Amino Acids:
-There are 20 kinds of Amino Acids found in proteins and some AA's are specified by more than one codon. -Some codons signal the beginning and end of proteins synthesis: -AuG (methionine): starts codon translation. -UAA, UAG, UGA: stops codon translation -The order of mRNA codons determines the order of AA's in the polypeptide that will be translated from it
Converting a gene to RNA
-Transcription converts information in gene to RNA -Enzymes use the nucleotide sequence of gene as a template to synthesize a strand of complementary RNA.
What are Polysomes?
-Transcriptions and translation both occur in the cytoplasm of bacteria: translation begins before transcription is done, so polysomes 'balls' form **in bacteria and archaea, transcription and translation both occur in cytoplasm
Overvieww of RNA to Protein Translation
-Translatin is an energy intensive process by which a sequence of odors in mRNA is converted to a sequence of AA's in polypeptide chain. -Transfer RNA's deliver AA's to ribosomes which catalyze the formation of peptide bonds between AA's.
Translating the Code: RNA to protein:
-Translation converts info carried by mRNA into a polypeptide -Trans occurs in the cytoplasm -Trans proceeds in 3 stages: 1. initiation, 2. elongation, 3. termination **there are 6 total steps in translation
Process of converting mRNA to proteins:
-Translation: converts information in an mRNA to protein -mRNA carries a protein-building message encoded in the sequence of sets of 3 nucleotide bases. -mRNA is decoded/translated into a sequence of Amino Acids, resulting in polypeptide chains that folds into a protein.
What finishes transcription?
-When the polymerase reaches the end of the gene, the DNA and new RNA strands are releases: many strands can be produced quickly.
What are the 4 steps in DNA replication?
1. The two strands of DNA are complementary nucleotides and match up according to base pair. 2. DNA helices breaks the H bonds that hold the double helix together and the two DNA strands unwind. 3. Each parent single strand serves as a template for assembly of new DNA. DNA polymerase assembles a complementary strand of DNA for each of the parent strands. 4. DNA ligase seals any gaps that remain between bases of the 'ew' DNA, so a continuous strand forms.
What are the 3 types of RNA?
1. Transfer RNA (tRNA): delivers Amino Acids to ribosoms in the order specified by messenger RNA (mRNA) 2. Ribosomal RNA (rRNA): Main component of ribosomes. The structure from which polypeptide chains are built. 3. mRNA (messenger RNA)
What 7 factors can cause mutations?
1. Transposable elements: segment of DNA that can spontaneously move to a new location. 2. Mistakes occur during DNA replication 3. Environmental: Damage DNA 4. Natural or synthetic chemicals cause mutations 5. X-Rays: breaks down chromosome pieces 6. Radiation: EX: UV 7. Chemicals: ex: cigarette smoke: can impair replication and cause mispairing during replication or stop it entirely.
What is an RNA polymerase?
Adds nucleotides to the end of a growing transcript.
How is DNA transferred? How is it Organized?
-All organisms pass DNA to offspring -In cells, each DNA molecule is organized as a chromosome.
What is Transcription?
-Process by which an RNA is assembled from nucleotides using the base sequence of a gene as a template.
Base pair substitution:
-Type of mutation in which a single base pair changes: ex: sickle cell. -Substitution of valine for glutamic acid.
What are Bacteriophages?
Viruses that infects bacteria.
Karyotypes:
Shows autosomes and X/Y chromosomes. -Can reveal abnormalities in an individuals complement of chromosomes.
Discovery of DNA's Structure
James Watson and Francis Crick "discovered" DNA's structure based on years of research by other scientists, one of which was Rosaline Franklin, who died of radiation poisoning from experimenting with x-rays. She was the first person to discover the structure of DNA but is sedum credited.
More about RNA
RNA is single-stranded chain of 4 kinds of nucleotides. Like DNA, RNA has 3 phosphate groups, a sugar, and one of the four bases, but RNA is slightly different: --->The sugar in RNA is ribose, not deoxyribose. --->RNA users the base uracil instead of thymine.
