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Alleles
Alternative forms of genes. An organism as two alleles for each trait - inheriting one from their mother and one from their father.
Monohybrid Cross
When only one trait is being studied in a cross.
P Generation
Parental generation of a cross
F Generation
The progeny generation or filial generation. (F1, F2, etc)
True Breeding
When a plant is homozygous for the trait being studied. When a monohybrid cross occurs between two true breeding parents, then the F generation will all be heterozygous or homozygous for the studied trait depending on the true breeding parents.
SA- Testcross
A true breeding recessive parent (always the case) can be crossed with a parent showing a dominant phenotype to determine if the experimental parent is homozygous or heterozygous.
SA Dihybrid Cross
When two traits are being studied in a cross. The traits must be located on separate chromosomes or variation will only occur in the instance of crossing over. Based on the Law of Independent Assortment
Incomplete Dominance
When progeny phenotypes are apparent blends of parental phenotypes. Ex
Codominance
Occurs when multiple alleles exist for a given gene. Each dominant allele is fully dominant when combined with a recessive allele, but when two dominant alleles are present the phenotype is the result of both dominant alleles being expressed simultaneously. Ex-BLOODTYPE
What makes Drosophila melanogaster great for teh study of genetics?
Short life cycle. Reproduces often. Reproduces in large numbers. Its chromosomes are large and easily recognizable in shape. Its chromosomes are few (N=4) . Mutations occur relatively frequently.
Central Dogma of Molecular Genetics
DNA can self-replicate. DNA can be transcribed into RNA. RNA can be translated into proteins.
Nucleotide
Basic unit of DNA. In DNA they are composed of a phosphate group bound to a deoxyribose sugar bound to a base. In RNA, the sugar is a ribose. Two types
Purine
A type of nucleotide. Adenine & Guanine. Another five member N-containing ring is fused to the six member N-containing base ring.
Pyrimidine
Type of nucleotide. Cytosine & Thymine. The base is only the six membered N-containing ring.
Characteristics of the DNA double-helix
The helical backbone consists of the sugar-phosphate chain. Adenine always interacts with thymine by two hydrogen bonds. Guanine always interacts with cytosine by three hydrogen bonds.
SA; DNA Replication
The double stranded DNA helix begins to unwind into two single strands - the parent and the template strand. Each parent or template strand undergoes complementary base-pairing to synthesize the two new daughter strands. Since each daughter helix contains a parent strand, DNA replication is semiconservative. One daughter strand is the leading strand and the other the lagging strand. The leading strand is continually synthesized by DNA polymerase in the 5' -> 3' direction. The lagging strand is discontinuously synthesized in a series of short segments called Okazaki fragments. This is because DNA polymerase only synthesizes in the 5' -> 3' direction. Overall growth of the lagging strand occurs in the 3' -> 5' direction.
Explain the degeneracy or redundancy of the genetic code.
There are 20 amino acids but there are 64 possible codons to specify them. Therefore, it is that most amino acids have more than one codon to specify them.
SA- RNA vs. DNA
RNA is usually present as a single strand rather than a double. Also a polynucleotide structure. DNA has a deoxyribose sugar, while RNA has a ribose sugar. Uracil is substituted for thymine in RNA. RNA can be found in the nucleus AND the cytoplasm. DNA is transcribed into RNA. RNA is translated into proteins.
mRNA
Messenger RNA. Carries the complimentary DNA sequence from the nucleus to the ribosomes where protein synthesis occurs. mRNA is monocistronic or one mRNA codes for one polypeptide.
tRNA
Transfer RNA. Found in the cytoplasm, it brings amino acids to the ribosome to aid in mRNA translation. There is at least one tRNA for each amino acid. The tRNA has a dual function of binding to the animo acid and recognizing the specific mRNA codon with its anitcodon. Each amino acid has a aminoacyl-tRNA synthetase which has an active site that binds to the amino acid and the tRNA to catalyze their attachment and form an aminoacyl-tRNA complex.
rRNA
Ribosomal RNA. A structural component of ribosomes and is most abundant of the RNA types. It is synthesized in the nucleus.
Transcription
The process by which DNA is synthesized into an mRNA molecule in the nucleus. The mRNA then leaves the nucleus by nuclear pores into the cytoplasm.
Translation
The process by which mRNA codons are translated into a sequence of amino acids to make a polypeptide or protein. This process occurs in the cytoplasm by a ribosome with the use of mRNA, tRNA carrying amino acids, enzymes, and other proteins.
Aminoacyl-tRNA Synthetase
The enzyme which has an active site to bind a specific animo acid and tRNA molecule and catalyze the synthesis of a aminoacyl-tRNA complex. Each amino acid has its own aminoacyl-tRNA synthetase.
SA- Ribosome
A free or membrane bound structure which translates mRNA into a polypeptide. Composed of two subunits: small subunit which binds to the mRNA and a large subunit that binds the the protein. Ribosomes have three active sites: 1) mRNA attachment 2) P site or peptidyl-tRNA binding site for the tRNA attached to the growing peptide 3) A site or aminoacyl-tRNA complex binding site for the incoming aminoacyl-tRNA complex.
P Site
Peptidyl-tRNA binding site on a ribosome. For tRNA attached to the growing peptide.
A Site
Aminoacyl-tRNA binding site on a ribosome. For the incoming aminoacyl-tRNA complex.
SA- Peptide Synthesis
Three phases: initiation, elongation (includes translocation), termination. 1) Initiation begins when a ribosome binds to the 5' end of an mRNA molecule. The ribosome scans the mRNA until it finds the start codon and binds the initiator aminoacyl-tRNA complex, methionine-tRNA. 2) In elongation the next aminoacyl-tRNA complex with the complementary anticodon binds to the A site. A peptide bond is formed between the amino acid in the A site and the amino acid of the growing peptide in the P site. Translocation then occurs when the mRNA is advanced three nucleotides in the 5' -> 3' direction to release the uncharged tRNA and move the peptidyl-tRNA from the A site to the P site so that a new aminoacyl-tRNA complex may bind at the A site. 3) When a termination codon appears in the A site, the ribosome terminates translation. These termination codons do not translate for an amino acid.
Nondisjunction
When homologous chromosomes fail to separate in meiosis I or sister chromatids fail to separate in meiosis II. Offspring or zygotes of these gametes may be trisomy or monosomy for a given chromosome. Can also occur with the sex chromosomes. Trisomy
Monosomy
When nondisjunction occurs during meiosis and the zygote has only one copy of a chromosome - one from one parent and non from the other, which experienced nondisjunction.
SA- Chromosomal Mutation
A change in the genetic information of a cell located in the DNA. Can be caused by environmental factors or occur simultaneously. If it occurs in somatic cells, the individual may develop a tumor. If it occurs in the gamete cells, the mutation will be carried to the offspring. Most mutations occur in regions of the DNA that do not code for proteins and will remain silent. If they do occur in a protein coding sequence, they are usually recessive or deleterious
Colchicine
A chemical compound that is a mutagenic agent and prevents spindle formation, resulting in polyploidy.
Point Mutation
A nucleic acid is replaced by another. Usually involves one to three nucleotides. May or may not result in an amino acid change. If the mutation does not change the protein it is a silent mutation. If the mutation causes the codon to change to translating another amino acid it is a missense mutation. If the mutation results in the change to a stop codon, it is a nonsense mutation. These mutations may or may not be lethal, depending on the nature of the amino acid for which it changed. These mutations do not change the length of the genome. Missense Mutation
Nonsense Mutation
When a point mutation results in the mutated codon translating for a stop codon.
Frameshift
A genetic mutation that is the insertion or deletion of nucleic acids. They result in a change in the length of the genome and are usually lethal.
Phenylketonuria
PKU Genetic disorder that results in the inability to produce enzymes to metabolize phenylalanine. This results in the body building up concentrations of phenylalanine and its by-products leading to mental retardation.
Sickle-Cell Anemia
Genetic disorder which results in red blood cells becoming sickle shaped because they contain defective hemoglobin. Ultimately the blood is less efficient at carrying oxygen.
Plasmids
Cytoplasmic, circular DNA found in bacteria. It is experimentally used to regulate many microorganisms, because one or more genes can be inserted into them.
Nucleoid
Region of a bacteria cell where a single circular chromosome is located.
Bacterial Gene Replication
Replication begins at a unique origin of replication and proceeds in both directions, 5' -> 3', simultaneously.
Episome
Plasmid capable of integration into the bacterial genome.
Bacterial Transformation
Bacterial mechanism for genetic variance among asexual reproducing strands. process by which a foreign chromosome fragment, plasmid, is incorporated into the bacterial chromosome via recombination. The new genetic material becomes inheritable. Bacterial Conjugation
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