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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
- -2 chromosomes
- -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.
- -chromosomes condense
- -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
- -spindle apparatus
- -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
- -nuclei reappear
- - 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
- -double helix
- -backbone- sugar-diphosphate
- -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.
- three stages:
- 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
- 2. elogation
- 3. termination
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
DNA that has been artifically made
Cuts strands of DNA at specific location