DNA and Protein Synthesis Flashcards
DNA
Deoxyribonucleic acid
Located in nucleus
Made of nucleotides
Nucleotide
Composed of phosphate group, deoxyribose sugar and nitrogenous base
Relationship between DNA, genes and chromosomes
Both chromosomes and genes are made of DNA
A gene is a section of DNA which codes for a particular characteristic
Chromosomes are tightly wound DNA which only appear in the nucleus at the start of cell division.
DNA Replication (steps)
- DNA is unzipped by an enzyme called helicase
- The nucleotides of template are exposed
- Primers (short segments of DNA) are needed to start the process. (Produced by enzyme= RNA primase) (DNA polymerase then add bases to template strand)
- Ligase joins DNA strands together (DNA is re zipped) two identical DNA molecules are produced
Neucleic Acids
DNA= deoxyribonucleic acid RNA= ribonucleic acid
Transcription
Occurs in nucleus
DNA unzips at the region to be copied
RNA polymerase attaches to DNA at promoter
Free nucleotides create mRNA
Uracil attaches to adenine
Transcription stops and RNA polymerase detaches from DNA releasing mRNA
Introns
Are non coding segment of DNA in eukaryotic cells
Exons
Coding segments of DNA that are involved in gene expression
Translation
mrna moves into the cytoplasm
mRNA binds with a ribosome
Begins at a start codon
tRNA contains an anti codon
tRNA anticodon binds with mRNA codon releasing amino acid
Polypeptide chain continues to grow until stop codon is reached
Polypeptide forms a protein, travels to endoplasmic reticulum
Eukaryote
Nucleoid region No membrane bound organelles Plasmids Flagellum No histone
Prokaryote
Membrane bound organelles
Nucleus
Histones
Mitosis (interphase)
DNA is replicating, chromosomes are not visible
Mitosis (prophase)
Chromosomes become visible, nucleolus and nuclear membrane disappear. Chromosomes appear as 2 chromatids joined by centromere. Crossing over occurs
Mitosis (metaphase)
Chromatids line up along the equator, spindle fibres appear and attach to centromere.
Mitosis (anaphase)
Centromere divides and the pair of chromatids seperate. Each pulled to opposite poles as spindle fibres shorten
Mitosis (telophase)
Cytokensis occurs
2 identical daughters cells produced
Meiosis (interphase)
Chromosomes replicate forming sister chromatids joined at centromere. Centrosome replicates forming two centrosomes
Meiosis (prophase 1)
Chromosomes condense. Diploid number of chromosomes appear as long thin threads, they shorten and thicken. Crossing over occurs, nuclear membrane disappears. Spindle forms
Meiosis (metaphase 1)
Pairs of chromatids line at the equator. Random assortment
Meiosis (anaphase 1)
Chromosomes move towards the poles pulled by spindle fibres. Sister chromatids stay attached at centromere and move as one unit
Meiosis (telophase 1)
Spindle disappears
Cytokinesis occurs
Two haploid cells form
Meiosis (prophase 2)
Spindle apparatus forms, crossing over may cause sister chromatids to not be genetically identical.
Meiosis (metaphase 2)
Sister chromatids line up at equator and attach to spindle fibres
Meiosis (anaphase 2)
Centromeres seperate and sister chromatids are pulled apart and move to opposite poles.
Meiosis (telophase 2)
Chromosomes reach poles and spindle disappears. Nuclei form, chromosomes begin condensing, nuclear membrane reappears, nucleolus becomes visible and cytokinesis occurs. Four daughter cells form
Gene expression
Is the production of proteins
Environmental factors
Climate Toxins Altitude Disease Soil pH Food availability Light availability Temperature
Himalayan Rabbits
Pigment gene influenced by temperature
Gene active when 15-25 Degrees celsius
Fur turns black in colder temp
30+ degrees no pigmentation
Point Mutation
Occurs when a single nitrogenous base is changed
Insertion or Deletion
Addition or deletion of a single base
Can have dramatic affects as they cause a frameshift
Substitution
When a single base is swapped with a different one
Silent substitution
The single change results in the same amino acid being produced
Non sense substitution
Results in a stop codon
Mis sense substitution
The substitution results in a different amino acid
Chromosomal mutation
Results from 2 or more breaks in the DNA helix and rearrangement of segments
Deletions
Usually fatal
Occurs when a strand is broken in two places and the segment is lost
Results in a shorter chromosome
Inversion
Cause of disorders
Chromosome breaks in 2 places and the segment rotates 180 degrees before rejoining
Translocation
Often results in cancer
Occurs when a segment of one chromosome breaks off and attaches to another chromosome
Duplications
Usually harmful (can result in beneficial traits) An extra copy of a section of a chromosome is made and then inserted into another region on the same chromosome or another chromosome.
