A segment of DNA that codes for the basic unit of heredity; transmitted from one generation ot the next.
The location of a gene on a chromosome
Mandelians 4 Principles
1. alternative versions of genes cause variations in inherited characteristics in offspring.
2. every organism inherits one one allele from each parent.
3 if 2 alleles are different, dominant allele will be fully expressed in offspring, recessive allele will have no noticeable effect in offspring
4. the 2 alleles for each character separate during gamete production.
- determines if an individual showing dominant trait is homozygous or heterozygous.
- homozygous dominant = dominant phenotypes
- heterozygous = ratio of dominant to recessive
cross involving the study of one character (ex. flower color)
Cross involving the study of multiple characters.
F1 hybrids have the apparance between 2 parents. (ex. red and white flowers make pink flowers)
Gene has more then 2 alleles. (ex. human blood type)
a single gene gives off more then one effect
gene at one locus alters gene at another locus.
two or more genes have one effect on a single character.
Sex linked inheritance
inheritance from the sex genes x and y.
regulates gene dosage in females.
members of a pair of homologous chromosomes don't separte right during mieosis 1; result is one gamete recieve 2 copies of chromosome while the other recieves none. offspring will have incorrect chromosome number.
Cells with 46 chromosomes
-4 DNA strands
-both chromosomes of each pair carry the same genes that control inherited characteristics
contain half the # of chromosomes; sperm and egg.
Cell duplicated its DNA; each chromosome has 2 identical sister chromatids.
-2 sister chromotids attach at centromere
-synapsis occurs (joining of homologous chromosomes) forming tetrads (new structure)
-crossover occurs (dna from one homologue is cut and exchanged for another)
-nuclear envelope desinigrates
-spindle attaches to homologues
homologues line up at metaphase plate
chromosomes move toward opposite ends of the cell.
telophase 1 and cytokenesis
-move until they reach opposite poles
-hapliod set of chromosomes
-2 sister chromotids
-sister chromotids move toward plate
-chromosomes at metaphase plate
-prepare to move toward opposite poles
-centromeres of sister chromotids separate
-move toward opposite cells
Telophase and cytokenesis
-chromosomes move all the way to opposite ends
- cytokenesis occurs
-4 daughter cells have hapliod number of chromosomes
events that occur in mieosis that don't occur in mitosis
1. synapsis and crossover
2. metaphase 1- homologues are at plate rather then individual chromosomes
3. anaphase 1- sister chromotids of each duplicated chromosome stay attached
-nitrogous bases (Adanine, guanine, cytocine, and thymine)
-Backbones are antiparallel- right = 5-3 left = 3-5
6 major points of DNA replication
1. begins at origin of replication
2. protiens bind to origin of replication and separate strands (5-3 direction)
3. DNA polyinerase catalyse elongation of new dna at replication fork
4. poly. adds new nucleotides to to chain
5. replication occurs continuously on 5-3 strand (leading strand)
6. the 3-5 is copied in a series of segments called Okazaki fragments and sealed by DNA Ligase
produces rna using DNA template; takes place in nucleus.
1. initiation- Poly2 transcribes mRNA; binds to promotor using protiens (transcription factors)
2. elongation- rna poly moves along dna untwisting and adding new nucleotides to the 3 end.
3 Termination- poly detaches; rna transcript is released
Carries genetic message of DNA to protien making ribosomes.
production of a peptide chain using mRNA; occurs in ribosomes. Instructions for the peptide chain written in triplet code. (series of three nucleotide groups.) (codons)
transfers amino acids to ribosome;
3 ribosome binding sites
p site- hold trna that carries peptide chain
a site- holds trna that carreis amino acid thats added to next chain
e site- exit
three stages of translation
1. initiation- first codon is always AUG
Three parts of Operon
1. operator- controls access of rna poly.
2. promotor- rna poly attaches
3. genes of operon
-The operon (gene) is normally on but can be turned off.
-anabolic- builds essential organic molecules.
-respessor protien is inactive
-an access of the organic molecule produced by the operon can attach to repressor protien and activate it.
-protien binds to operator site turning it off.
-normally off but can be activated
-catabolic- breaks down foods
-repressor protien is active
-inducer binds to and inacivates protiens which detaches protien from operon allowing the operon gene to be activated