Nucleic Acids Pt 2 Flashcards
Upon DNA replication
Large dna molecules interacts with histone proteins to fold long DNA molecules.
Histone DNA complexes are called
Chromosomes
A chromosome is about
15% by mass DNA and 85% by mass protein
Cells of different kinds of organisms have
Different numbers of chromosomes
Number of chromosomes in human, mosquto frog, dog and turkey
Human 46
Mosquito 6
Frog 26
Dog 78
Turkey 82
Chromosomes occur in
Matched (homologus) pairs
46 chromosomes of a human cell constitue
23 homologus pairs
It is directly under the direction of DNA
Protein synthesis
Proteins are responsible for the formation of
Skin,hair,enzymes,hormones
Protein synthesis can be divided into two phases
Transcription
Translation
A process by which DNA directs the synthesis of of mRNA molecules
Transcription
A process which mRNA is deciphered to synthesize a protein molecule
Translation
Sugar unit in the backbone of RNA is
Ribose
The base thymine found in DNA is replaced by
Uracil in RNA
RNA is a ___ while DNA is double stranded
Single stranded
RNA molecules are much smaller than DNA molecules ranging
From 75 nucleotides to a few thousand of nucleotides
Formed directly by DNA transcription
Heterogeneous nuclear RNA (hnRNA)
Post transcription processing converts
hnRNA to mRNA
Carries instructions for protein synthesis
MessengerRNA mRNA
Facilitates the conversion of hnRNA to mRNA
small nuclear RNA (snRNA)
Small nuclear RNA contains
100 to 200 nucleotides
Combines with specific proteins to form ribosomes .physical site of protein synthesis
Ribosomal RNA rRNA
Delivers amino acids to the sites of protein synthesis
Smallest nucleotide units
Transfer RNA tRNA 75-90 nucleotide units
Transcription 2 step process
Synthesis of hnRNA and editing to yield mRNA molecule
DNA to RNA to nucleus
A segment of a DNA base sequence responsible for the production of a specific hnRNA/mRNA molecule
GENE
Most human genes are (size)
1000-3500 long
All of the genetic material (total DNA)
Genome
human genome is about____ genes
20k to 25k
Excision of introns and joining of exons
Splicing
A gene segment that codes for genetic information
Exon
A DNA segments that interrupt a genetic message
Intron
The splicing process is driven by
snRNA
A process by which several different proteins variants are produced from a single gene
Alternative splicing
All of the mRNA molecules that can be generated from the genetic material in a genome
Transcriptome
Transcriptome is different from a
Genome
Responsible for the biochemical complexity created by splice variants obtained by hnRNA
Transcriptome
Base sequence of an mRNA molecule
A,C,G and U
A three nucleotide sequence in an mRNA molecule that codes for a specific amino acied
Codon
Assignment of the 64 mRNA codons to specific acids
Genetic code
3 of the 64 codons are
Termination codons/ stop signals
tRNA molecules as intermidiaries deliver amino acids to
MRNA
Important features of the tRNA stucture
- The 3’ end of tRNA is where an amino acid is covalently bonded to the tRNA
- The loop opposite to the open end of tRNA is the site for a sequence of 3 bases called an anticodon
A process in which mRNA codons are deciphered to synthesize a protein molecule
Translation
An rRNA comples serves aa the site of protein synthesis
Ribosome
An error in base sequence reproduced during DNA replication
Errors in genetic information is passed on during transcription
Altered info can cause changes in amino acid seq
Have profound effect on an organism
Mutation
Two common types of mutations
Point mutation
Frameshift mutation
Mutations are caused by
Mutagens
A substance or agent that causes a change in the structure of a gene
Mutagens
Two important types of mutagens
Radiation and chemical agents
Mutagenic cause cancers
Ultraviolet xray, radioactivity and cosmic radiation
HNo2 mutagenic
Convert cytosine to uracil
Nitrites nitrates and nitrosamines can form
Nitrous acid in cells
Normal conditions mutations are
Repaired by repair enzymes
Tiny disease causing agents with outer protein envelope and inner nucleic acid core
Viruses
Can not reproduce outside their host cells (living organ
Viruses
Invade their host cells to reproduce and in the process disrupt the normal cell’s operation
Viruses
Virus invade
Bacteria plants animals and humans
Common disease of viral origin
Cold, small pox, rabies, influenza,hepatitis and AIDS
Inactive virus or bacterial envelope
Antibodies produced against inactive viral or bacterial envelopes will kill the active bacteria and viruses
Vaccines
E.coli cells of a specific strain containing the plasmid of interest are treated with chemicals to dissolve their membranes and release the cellular contents
Dissolution of cells
The cellular contents are fractioned to obtain plasmids
Isolation of plasmid fraction
Restriction enzymes are used to cleave the double stranded DNA
Cleavage of plasmid DNA
Using the same restriction enzyme the gene of interest is removed from a chromosome of another organism
Gene removal from another organism
Gene-plasmid splicing
The gene from step 4 and the opened plasmid from step 3 are mixed in the presence of the enzyme DNA ligase to splice them together
The recombinant DNA prepared in step 5 are transferred to a live E.coli culture where they can be replicated transcribed and translated
Uptake of recombinant DNA
Transformed cell can reproduce a large number of identical or
Clones
Are the cells that have descended from a single cell and have identical DNa
Clones
Given bacteria grow very fast within few hours
1000s of clones will be produced
Each clone can
Synthesize the protein directed by foreign gene it carries
A method for rapidly producing copies of a DNA nucleotide sequence
Polymerase chain reaction PCR
Allws to produce billions of copies of a specific gene in a few hours
Polymerase chain reaction PCR
Any abnormality in the number of chromosomes
Aneuploidy
Common aneuploidies
Trisomy 21
Trisomy x
Klinefelters syndrome
Also known as down syndrome
Trisomy 21
Super female syndrome
Trisomy x or triple x
Xxy syndrome male extra x chromosome
Klinefelter syndrome
