Change to the quizzes
More questions – closer to what you may see on the exam
The midterm will not be as easy as what we’ve been getting in the quizzes
There are a series of tougher questions on MyLearning for prep stuff.
Genes, Evolution and Environment
What do they have to do with psych?
- Genes can “program” people to act a certain way
- Certain disorders may be caused by a change in the gene
- Predisposition (more susceptible) to… being an alcoholic
o The environment triggers it
Genes or Environment
- A rectangle is four sides – two of each are parallel and two are longer than the others. But they
equally contribute to the rectangle.
Functional units of heredity
Composed of DNA
Specify the structure of proteins
Located on chromosomes
Genes are transmitted to the next generation. Genes lead to the making of proteins – proteins make
cells. Cells make every living thing. ANALOGY TIME: Genes are recipes – like for chocolate cake :3
Rod-shaped and found in the nucleus of every cell
Sperm cell and each egg cell contain 23 chromosomes (human)
Fertilized egg contains 46 arranged in pairs
Made of DNA
Chromosomes contain thousands of genes
- Human ~ 35,000 genes (or recipes)
Genes are made of four amino acids
- Thymine Chromosomes are made of two DNA strands – you have a ladder. Each side is a strand of DNA. The
ladder is made of steps connecting the two sides – made of bases which are combinations of two amino
acids. You twist it and then you end up with a big twisted elastic band made of DNA.
Or it’s a book – the cover and the back cover thing and in the middle are the pages (which are the amino
acids. Each step is a page made of two amino acids. If it was a recipe book – can a recipe take more than
one page? – the gene can be several pages (or bases) long.
Comparative Sequence Sizes (Bases)
Yeast (chromosome 3)
- 350 thousand
Smallest human chromosome(Y)
- 50 million
Largest human chromosome (I)
- 250 million
Entire human genome
- 3 billion
A gene is a series of pages that makes a recipe. When the protein is made, the coil unravels and a copy of
the recipe will be made. Some pages (bases) are more important than others. Some are active and some
The genotype dictates the proteins (recipes) that will be made. They end up as the phenotype (what we
can observe) – lead to different features or traits.
Small Differences can Count for a lot
Small genetic sequence differences can have major impact on the expression of genes
- Changes transcription factors and the making of proteins
- Alters growth periods of the brain
There is a 1.5% difference between a chimpanzee and a human
Genetic of Chromosomal Anomalies
4% of all pregnancies suffer from chromosomal abnormalities
Majority = miscarriages
Only 0.5% of born babies have chromosomal abnormality
- Many die soon after birth
- Of those that survive, most suffer from Down syndrome
Mutations can be beneficial, but they’re not usually. Most often they lead to mental deficit, physical
Down’s Syndrome – Trisomy 21
- Usually, humans have 23 pairs of chromsomes
- In this case, 3 for chromosome 21 o Gene mutation (egg or sperm)
1/691 live births
Women who have children older are more at risk, but men can pass it on too.
Distinct physical signs
- Short and stocky stature
- Oval, upward slanting eyes
- Most can read, write and do math
Mortality around age 40 is high
- Brain degenerated looks like late stage Alzheimer’s
Heredity and Evolution
Measures the total proportion of variance in a trait that is due to genetic variance
Looking at what is transmitted or inherited
Genes vs Environment calculation
0 = environment
1 = genetic
Not precise, but can be influenced by a number of things
How is a trait more likely to get transmitted?
The process of humans selecting certain variety of traits of an organism of others
Is this often the case?
Let’s consider the case of the dogs…
Take the smallest poodles and breed til you get a miniature.
Artificial Selection and Psych
Why would artificial selection be beneficial to psych?
Could it be used to understand the genetic basis of behaviour and disorders?
Alcoholism has long been considered to be due in part to genetic factors
For instance, children of alcoholics are more likely to also become alcoholics
Need for an animal model to determine the contributing genes.
Rats and Alcohol
Need a strain of rats that drink large amounts of alcohol
Need another strain that drinks very little Enables for genetic comparison
How do we get those strains? Through artificial selection or selective breeding
How would you start it? $100 to buy vodka and $900 to buy rats. How do you divide the rats? Give them
each a cage with alcohol in it – measure the bottle.
Take a large group of rats and determine the high and the low alcohol drinkers – very far away from the
average. Ignore the rest. Breed th