Genetics Test IV

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Nucleoid: - Structure holding compact double stranded DNA
Mitchondrial DNA (mtDNA): - Double stranded close circle that replications semiconservatively
- Free of chromosomal proteins that are characteristic of eukaryotic DNA
- No introns
- Replication is depended on enzymes encoded by nuclear DNA
Introns: - "Intervening sequences"
- Gene stuffers
- Areas of genes which do not code for phenotype
Chloroplast DNA (cpDNA): - Much larger than mitochondrial DNA
- Circular, double stranded, repulicated semiconservatively, and free of the assosciated proteins characteristic of eukaryotic DNA
Polytene Chromosomes: - Found in various tissues and in the larvae of some flies and in several species of protozoans and plants
- Represent paired homologs
that undergo many rounds of repulication without strand separation or cytoplasmic division
Chromomeres: - Lateral condensations of material along the axis of a chromosome
Lampbrush Chromosome: - Characteristic of most vertebrate oocytes as well as the spermatocytes of some insects
- Meiotic Chromosomes
- Extended, uncoiled versions of the meiotic chromosomes
- Represent DNA that has been uncoiled from the central chromomere axis during transcription
Chromatin: - Components of chromosome that uncoil and are present in the interphase stage of the cell cycle
Histones: - Highly conserved proteins found only in the nucleus of numerous organisms
- Contain large amounts of the positively charged amino acids lysine and arginine, making it possible for them to bond electrostatically to the negatively charged phosphate groups of nucleotides
- Play an important role in chromatin structure
Chromatin Structure: - Digestion of chromatin by certain endonucleases such as microccal nuclease, yields DNA fragments that are approximately 200 bp
- Consist of some type of repeating unit
- Chromatin fibers are composed of linear arrays of spherical particles (called NUCLEOSOMES), which resemble beads on a string
Solenoid: - Formed during the helical winding of the nucleosome strands
- 30 nm fiber that consists of numerous closely coiled nucleosomes
- Condense the eukaryotic fiber by a factor of 5
Chromatin Remodeling: - A process in which chromatin must change its structure in order to accomodate protein-DNA interactions
Acetylation: - Process resulting from the action of histone acetyltransferase (HAT)
- Adds an acetyl group to the positively charged amino group present on the side chain of the amino acid lysine, changing the net charge of the protein by neutralizing the positive charge
Methylation and Phosphorylation: - Chemical processes that result from the action of enzymes called methyltransferases and kinases
Semiconservative Replication: - The two strands of the parents double helix unwind
How does condensation occur?: - Double stranded helical DNA binds with histones to form a nucleosome which becomes a chromatin fiber (like beads on a string)
Histone H1: - Keepds DNA in place on the nucleosome
Heterochromatin: - Tightly Coiled, dark straining
- Non coding chromosomes that contains no genes
- Determines chromosome structure
- Primarily found in centromeres and telomeres
- Remains densely coiled throughout cell cycle
Euchromatin: - Part of the chromosome that remains uncoiled
- Tightly coiled only during metaphase
Position Effect: - The position of a gene or group of genese relative to all other genetic material may affect their expression
Repetitive DNA: - Rapid reassosciation characteristic of multiple DNA fragments composed of identical or nearly identical nucleotide sequences
High Repititive DNA: - COnsists of short sequences repeated a large number of times
- Present as tandem repeats clustered in very specific chromosomal areas known to be heterochromatic- the regions flanking centromeres
Karyotype: - An alignment of chromosomes based on size and shape
Constitutive Heterochromatin: - Always found in centromeres and telomeres
- Noncoding regions of chromosomes contain HR/MR type nucleotides
Facultative Heterochromatin: - Potential to become whole chromosome x inactivation
- Example: barr body where whole chromosome is non coding
Exons: - Coding part of gene
- Determins phenotype
TATA Box: - A highly conserved sequence which serves as the binding site for RNA polymerase (start site of transcription) called the promotor region of a gene
CCAAT Box: - Site at which DNA binding proteins attach and modulate the rate and copies of a gene made
Enhancer: - Specific DNA sequences shared by genes to which proteins bind to coordinate gene activity
Solitary Euchromatin: - A single copy of a gene (haplid); 2 copies in a diploid situation
- Comprises bulk of euchromatin
Duplicated Euchromatin: - Duplicated gene sequences in the genome
- Consist of very similar nucleotides
- Each codes for a similar polypeptide but have a distinctly different function
- Arise from unequal crossover during meiosis
Mutligene Families: - Genes of identical or closely related DNA sequences which share similar function and chromosomal location are most often used or synthesized at different types
- Example: globin genes- embryonic, fetal, adult mammals
Pseudogene: - Nonfunctional sequences due to significant substitution or deletions in the nucleotide sequence
Transcrption: - First step in the conversion of information stored as genotype (DNA) to phenotype (RNA)
- Occurs in the nucleus
- Occurs during G1 or G2 (period when genes coding for cellular organelle proteins are synthesized)
- Starts at TATA box- defines which nucleotides will be transcribed
Steps of Translation: 1.) Recognition- TATA Bod
2.) Initiation- Binding of RNA polymerase
3.) Elongation- Movement of RNA polymerase
4.) Termination- GC rich regions
5.) Processing- Cap and tail addition; intron removal
Recognition: - RNA polymerase recognizes and binds at the TATA box
Initiation: - RNA polymerase chooses one strand for transcription, called the SENSE STRAND
Elongation: - RNA polymerase moves down DNA strand synthesizing RNA
- Growing RNA strand is complementary to DNA
- Introns and exons are both transcribed
Termination: - Termination site is reached causing release of both mRNA and RNA polymerase
mRNA: - Messenger RNA
- Template for translation
tRNA: - Delivers amino acids one by one to the growing peptide chain at the ribosome
- Clover leaf structure
rRNA: - Ribosomal RNA
- COmbines with proteins (30-50) to form subunits of the ribosome
- Site of translation
Processing: - Past transcription addition of cap and tail
- Intron Removal
Post- Transcriptional Modification: - 5' cap added to mRNA (made of guanine)- serves as ribosome recognition site
- Poly A tail added to the 3' end of mRNA- protects mRNA from degradation in the cytoplasm (added by poly A polymerase)
Splicing Mechanisms: - Intron removal
- Autocatalytic RNA and splicesosome
Autocatalytic RNA: - Ribozymes
- Splicing mechanism accuring most commonly in RNA
- The intron itself contains the enzymatic activity necessary for its removal
Spliceosome: - A large complex consisting of proteins and RNAs which excises introns in the nucleus of cells
- RNA component: snRNAs (small nucleotide RNA strands)
- Protein component: u=enzyme with excision activity
Translation: - Conversion of mRNA to amino acids
Storage Units: - mRNA --> Peptide
- Ribonucleotide --> Amino Acid
3 Nucleotides: 1 Codon: 1 Amino Acid
Feactures of Genetic Code: 1.) Written in linear form
2.) Coded in triplets
3.) Unambiguous (1 codon: 1 amino acid)
4.) Degenerate (1 amino acid can be coded for by more than one codon)
5.) Specific start (AUG) and stop (UAA, UGA, UAG) codons
6.) Commaless (no pauses)
7.) Non-overlapping
8.) Universal
3 Main Players in Translation: 1.) Ribosome (rRNA and proteins)- construction site
2.) Transfer RNA (tRNA)- delivery system
3.) Messenger RNA (mRNA)- message
Steps in Translation: 1.) tRNA Charging
2.) Initiation
3.) Elongation
4.) Termination
Anticodon Loop: - Structure on tRNA
- Complementary to codon
Acceptor Site: - Structure found on the 3' end of tRNA
- Site where amino accids attach
tRNA Charging: - tRNA molecules are linked with Amino Acid
Aminoacyl Synthetase: - Directs the charging of each tRNA
Ribosome (SITE): - Consists of Ribosomal RNA and ribosomal proteins
- Large and small subunits assosciate to form the ribosome
Proteins: - The end product of genes
- Function is cell shape and integrity
- Structural components of cells
- Everyday housekeeping functions
Peptide Bonds: - Combine 2 amino acids
R-Groups: - Unique for each one of the 20 Amino Acids
1.) Non-polar (Hydrophobic): Repels water
2.) Poplar (hydrophyilic): attracts water
3.) Positively Charged
4.) Negatively Charged
Electrophoresis: - Technique for separating proteins in a support medium based on size and/or charge
- Separation is achieved by passing an electric field across the medium
Translation Initiation: - Always start with the first AUG you findon the 5' end
P Site: - Petidyl
- Peptide
A site: - Acetyl
- Aceptor
Small Ribosomal Subunit: - Binds to the mRNA at the initiation site
Charged tRNA: - Charged tRNA with the specific anticodon for the start site binds at the triplet in the P site of the small subunit
Peptidyl Transferase: - Peptide bonds that link two amino acids and cause the releas of tRNA at P site
Pleiotrophy: - Many traits are controlled by the expression of multiple genes
Posttranslational Modification: - N and C- terminus amino acids are removed or modified
- Methyl groups of phosphates are added to particular amino acids
- Carbohydrate side chains be attached
- Chains may be shortened
- Metals may be added
Primary Peptides: - Sequence of amino acids in the peptide
Secondary Peptides: - Configuration in space/ interaction between amino acids
- Alpha helix: spiral chain of amino acids stabilized by H bonds; right handed helix with 3.6 amino acids/turn
- Beta pleated sheets: Single polypeptide chain folded back on itself or several running parallel to each other
Tertiary Peptides: - Conformation; 3D configuration
- Polar hydrophilic groups are onthe surface
- Non-polar hydrophobic groups on the inside
Quarternary Peptides: - Assosciation of multiple peptides
- Applies only to proteins composed of more than one polypetide chain
- Proteins with quarternary structure are colled OLIGOMERIC PROTEINS (hemoglobin)
Summary or proteins: - Protein function is dependent on shape
- Shape is determined by amino acids
- Amino acid composition is determined by nucleotide sequences
- Mutations can alter amino acid composition which can alter function of protein

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