2.1 What is Genetics?

DNA
Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA)

• You get 50% of your nuclear DNA from your mother and 50% from your father.
• You get 100% of your mitochondrial DNA from your mother.
• 99% of all people’s DNA is the same.
• We all have two eyes, two ears, one nose, two legs, two arms, heart, liver, brain, intestines, etc…

Chromosomes

• You have 23 pairs of chromosomes.
• The chromosomes are made of molecules of DNA.
• The 23rd chromosome determines your gender.
  • XX – for female
  • XY – for male
• You get a X chromosome from your mother.
You get a 2nd X or a Y chromosome from your father.

Genes

• Inside your chromosomes are specific parts that are called genes. The genes control specific parts of your looks and behaviours.
• For example, there are variations in the genes for eye color: brown, blue, green and variations of those colors.
• For example, there are variations in the genes for hair color: brown, blonde, black, grey, and red and variations of those colors.

Human Karyotype
A stained microscopic picture of your chromosomes. The dark bands and location of the centromere show the properties of each part of the chromosome. There are over 25 000 genes in the human karyotype.

Proteins
Proteins make up many parts of the cell and your body. They are structural, markers, hormones (messengers), etc…

Mitosis

• Over time your cells wear out and die. To replace them your cells reproduce to produce new replacement cells.
• The chromosomes duplicate, separate and form two daughter cells that should be identical to the original.
• This is how organisms replicate asexually (without a sexual partner).
• Mutations occur when the mitosis (copying) makes a mistake in the DNA of the daughter cell.

Meiosis

• This produces the sex cells (ova and sperm) called gametes. Each gamete contains parts of one of a pair of chromosomes (half your chromosomes).
• Each of your chromosomes is half from your father and half from your mother. When the chromosomes replicate there is a crossing over where the new chromosome is a combination of DNA from each of your father and mother’s chromosome, called a homologous chromosome, located in the haploid cell (gamete).
• When the gamete (haploid) from each parent combine to form a full set of 23 pairs of chromosomes unique to each child.

Selective breeding

• It is used by breeders to change the characteristics of animals or plants. It works faster than natural evolution.
• Eg. Faster racehorses, cows that produce more milk, larger apples, faster growing tomatoes, etc…

Discovering Genes Gregor Mendel was a monk who did extensive experiments breeding peas and determined how genes get passed from parent to daughter. He looked for easy to identify characteristics like color.

• He made purebreds
• ie. white + white always produce white;
• ie. purple + purple always produce purple.
• He made mix breeds
• ie. white + purple always produce purple
• The grandchildren are both purple and white.
• ie. purple mix + purple mix produce purple and white

Alleles are alternate forms of a gene. ie. You can carry the DNA gene (allele) for gene brown eyes and the allele for blue eyes.

• Daughter cells have two copies of each gene (allele).
• Dominant alleles (genes) are expressed when one or more allele is present.
• Recessive alleles (genes) are only expressed when both alleles are recessive.

Punnett Squares This show the probability of traits being passed from parent to child.

• Diagram - Homozygous dominant parents
• Diagram - Homozygous dominant and heterozygous parents
• Diagram - Heterozygous and homozygous recessive parents
• Diagram - Some genes are sex related.
• Colorblindness is dominant or recessive on the X chromosome.

2.2 Inheritance

Daughter cells have two copies of each gene (allele).
Dominant alleles (genes) are expressed when one or more allele is present.
Recessive alleles (genes) are only expressed when both alleles are recessive.

Punnett Squares
This show the probability of traits being passed from parent to child.
Diagram - Homozygous dominant parents
Diagram - Homozygous dominant and heterozygous parents
Diagram - Heterozygous and homozygous recessive parents
Some genes are sex related.
Colorblindness is dominant or recessive on the X chromosome.

2.3 DNA

DNA

• DNA is like a twisted ladder (double helix).
• Nucleotides are the chemical cross pieces. There are 4 nucleotides, A, C T & G.
• Adenine always binds with thymine.
• Cytosine always bind with guanine.
• When determining DNA you only list one side of the helix.
• Adenine always binds with thymine.
• Cytosine always bind with guanine.

DNA bases combine in groups of three to form amino acids. Amino acids combine to form proteins.

2.4 Mutations and Genetic Diseases

Factors That Increase Mutations

• Ionizing radiation (UV, X-rays)
• Cigarettes
• Medication (side effect)
• Pesticides

Tracing Genetic Disease: Pedigree Charts
By tracing your genetic lineage geneticists can determine the probability of traits.

Pedigree is used with animals to track desired traits for selective breeding.

Resistance in Bacteria Cells can transfer DNA from one cell to another using free DNA fragments (RNA) or plasmids (circular DNA fragment) in a process called transduction.

2.5 Genetic Technologies

DNA Fingerprinting
There are small differences between each person’s DNA. Those differences make your DNA identification (DNA fingerprint) Police use DNA fingerprints from saliva, blood or semen in order to identify criminals. It is also used to identify human remains.

Recently companies have been using DNA tests to let customers explore where they came from and who they are related to.
Also the companies have been making money selling the information to the police to look for unknown DNA samples from crime scenes.
The Golden state killer killed people in 1987 and was tracked down in 2015 because two of his cousins used DNA testing.
Always read the fine print!

Transgenics
GMO (genetically modified organisms) are created by transferring genes from one organism into another in a lab.
The mice in the picture have a transgenic gene from GFP (green fluorescent protein) that was transferred from a jellyfish into the mice. GFP is used because it easily shows scientists what part of the DNA was affected.
Several countries have banned GMO food. Canada has no GMO rules for food.

Applying Transgenics—Medicines and Gene Therapy
Scientists have begun to cure some genetic diseases through recombinant DNA which rewrites a part of the person’s DNA, often to produce a specific enzyme, hormone or other protein.
DNA can also be manipulated in bacteria to produce different affects like producing specific substances (medications, insulin) or eat types of pollution.

Eugenics
the dark side of genetic manipulation. Some groups (Nazis) believe that some genetics are superior (Aryans). They used this as justification to exterminate other groups (Jews, mentally handicap, LGTBQ, etc...).
Japanese and Nazi did horrific experiments on some prisoners of war without regards for the ethics and morally because everyone else was sub-human.
Unit 731 & Nazi (WW2), Standford prison experiment (1971) Nowadays all medical experiments go to an ethics board to make sure no undue stress or injury is inflicted on participants.

Chapter 2 Summary

Chapter 2 Review Questions

Unit A Conclusion PDF

Unit A Review Questions