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{Genetics
Review
Involves several different genes for one trait like eye color, skin tone and color, height (humans), wheat kernel color
These are called Polygenes
Polygenic Inheritance
Skin color has three alleles: ABC for dominant and abc for recessive
The darkest skin tone is AABBCC and the lightest is aabbcc
Possible gametes for both the mom and dad are: abc, abC, aBc, Abc, aBC, ABc, AbC, and ABC
Distribution of results will be a bell curve!
Example
Punnett Grid
Mendel’s laws worked with genes on separate chromosomes – Law of Independent Assortment
Many genes are found on a single chromosome and they will separate together with crossing over being a way to create ‘recombinants’
Linked Genes and Genetic Variety
Occurs when there are linked genes – An offspring that possesses the characteristics from both parents as crossing over has occurred and the linked genes transfer between homologous chromosomes
The further apart the genes are on a chromosome, the better the chance of producing recombinant gametes and organisms
Recombinant
Steps: Denature the DNA – heat it to 95 oC, breaking
the H bonds between the nucleotide bases Annealing where the DNA is cooled and the
Primers – small strands of DNA that bind to target DNA on the strand – bind to the complementary sequence and specify the DNA to be amplified
Heated now to the optimal temp – 72oC, so the DNA Polymerase extends the primers using the target DNA as the template
This process is repeated 20 – 35 times!! Exponential growth
PCR
Uses an electrical current to move negatively charged DNA particles through a current carrying Gel
They move due to size and charge When stained they create a banded
pattern and similarities between different samples indicate a familial relationship
Used in forensic studies and paternity testing
Gel Electrophoresis and DNA Profiling
Completed in 2003 – Mapped all the genes in Human DNA
Helps to give a better understanding of how particular changes in coding can cause particular results – genetic disorders
Identifies specific genes – synthetic human hormones are used to produce human insulin for diabetics
Genetic screening to identify specific diseases like sickle-cell anemia and Huntington’s Disease
Human Genome Project
Manipulation of particular genes for a specific purpose
Specific genes are located and extracted and then used to modify the genetic code of another species
An example is inserting the gene code for creating insulin into a bacterium
Restrictive enzymes cut the DNA sequence at particular nucleotide sequences then ligase enzymes join them to another DNA strand with the same sequence
Lab Activity on Tuesday
Genetic Engineering
Cloning – Good or Bad?