Genetics - Chapter 6 Flashcards
Miescher
investigated a compound found in nucleus of cell
called this compound nuclein, now known as DNA
Hammerling
verified that genetic material was in nucleus
used algae, where the nucleus is found in the foot section
when any part of the algae was cut off, that section grew back, however when the foot section was cut off, nothing grew back
Hershey and Chase
worked with bacterial viruses
showed that viruses inject only their DNA into bacteria to produce more viruses, nothing else
therefore DNA directed the production of new viruses, and is the hereditary material
Levene
discovered that DNA has 3 main components
pentose sugar
phosphate group
nitrogenous base (carbon-nitrogen rings)
Watson and Crick
built a model of DNA
showed the molecular structure (double helix), the three different components, and the linking between A and T, and C and G
this was the final determination of the structure of DNA
DNA
deoxyribonucleic acid
double helix
composed of 4 different types of nucleotides with each of the following nitrogenous bases
purines (adenine, guanine) = 2 carbon rings
pyrimidines (cytosine, thymine) = 1 carbon ring
Pairing of nucleotides
nucleotides bond between DNA strands via a hydrogen bond (force acting on the nucleotides)
purines bond with pyrimidines
A = T (2 hydrogen bonds), C = G (3 hydrogen bonds)
the two strands are antiparallel, the phosphate end of one matches with the sugar end of the other
Mutations in DNA
spontaneous = occurs randomly, not caused by outside factors (mistakes when DNA is copied)
induced mutations = occur because of exposure to a physical or chemical agen that causes a mutation
there are 3 means of chromosomal changes = point mutations, block mutations, chromosomal mutations
Point mutations
small scale change to one nucleotide in the sequence
can have disastrous, little, or no effect on the protein coded for
substitution = different base inserted
insertion = extra base added
deletion = base removed
inversion = base order reversed
Block mutations
large scale change to larger chunks of nucleotides in the sequence
Deletion
part of the chromosome is actually lost
due to viruses, radiation, chemicals
may carry a specific gene which may have a large effect on the host
cri du chat = deletion of chromosome 5
Duplication
gene sequence is repeated one or more times within a chromosome
at some point, too many repeats can affect the function of the gene
fragile X syndrome = form of autism and inherited intellectual disabilities in males
Inversion
gene segment momentarily becomes free from its chromosome and then reinserts itself in the opposite order
this can completely alter the gene’s activities
Translocation
Barbara McClintock proved that gene sequences can move from one part of a chromosome to another
these segments are referred to as transposons, or jumping genes
Chromosomal mutation
large error involving the whole chromosome
example = non-disjunction
Inheriting mutations
many mutations go unnoticed because they occur in parts of the DNA that do not code for genes
many others are corrected in the copying process
as a person ages, mutations occur more frequently
for a mutation to be passed on from one generation to the next, it must be located on the gametes
Bacterial resistance
antibiotics destroy bacteria by binding to the cell wall and weakening it
if a bacteria has gone through a certain mutation, the antibiotic will not be able to bind to the cell wall
since this mutation is beneficial, it will be passed on to future generations
Human Genome Project
13 year project to sequence the human genome and other species
initially, scientist from around the world collaborated to complete the HGP
Celera genomics, a private company headed by Craig Venter, was able to use computer technologies and private funding to “join the race”
Patenting of genes
gene sequences are being patented as an incentive for drug companies, allows a larger payout if there is a discovery
this poses a problem for researchers as they cannot study certain genes without fear of being sued
there are therefore some genes that may hold cures to certain diseases, but they are not being researched due to the presence of patents
The human genome
approximately 3 billion base pairs
contains coding regions and non-coding regions
coding regions = sections that actually code for a protein (genes), only 1-3% of the genome
non-coding regions = junk DNA, less understood
very little genetic variation within our species
Genomics
the study of genomes and the interactions of genes that result in phenotypes
functional genomics = study of the resulting function of genes
Mice and genomics
mice provide a surprisingly good model organism for humans due to their genetic similarity
knockout mice = mouse where researchers have inactivated an existing gene by replacing it with an artificial piece of DNA, which causes changes in phenotypes
Bioinformatics
uses computer technology to create and analyze biological information
today we have huge databases of protein and DNA information
DNA fingerprinting = pattern of bands on a gel that is unique to each individual
DNA banks
public can store blood or saliva samples for evidence
endangered species genomes stored
convicted criminal DNA is stored in many countries
Manipulating the genome
appropriate sections of the genome can be manipulated to allow for mass production of valuable proteins
examples = insulin, spider silk, pest-resistant food products
Recombiant DNA
DNA fragment that contains DNA from more than one source
engineered and typically used with bacterial plasmids
the desire is a plasmid that contains a section of desired DNA, or the gene of interest
Steps of recombinant DNA
restriction enzymes (enzymes that snips DNA at known sequences), snip either end of the gene of interest and the plasmid
same enzyme must be used in all 3 places
results in complementary sticky ends that can anneal to combine the two pieces
recombinant DNA reinserted into bacterial cell
bacteria now replicates rapidly and multiple copies of the gene of interest are achieved
