{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?