Psychology
Learning objective New title: Theilgaard (1984)
Learning Outcomes Recap the biological debate for criminality Learn about a new study
Biological explanations for criminal behaviour What can you remember about genes and chromosomes? List what facts you can remember without looking back in your book.
Biological explanations for criminal behaviour We all have genes. Let’s start at the beginning: Genetic Similarity: We All Have the Same Genes Each person has the same set of genes - about 20,000 in all. The differences between people come from slight variations in these genes. For example, a person with red hair doesn't have the "red hair gene" while a person with brown hair has the "brown hair gene." Instead, all people have genes for hair colour, and different versions of these genes dictate whether someone will be a redhead or a brunette.
Biological explanations for criminal behaviour The Basics of DNA Your body contains 50 trillion tiny cells, and almost every one of them contains the complete set of instructions for making you. These instructions are encoded in your DNA. DNA is a long, ladder-shaped molecule. Each rung on the ladder is made up of a pair of interlocking units, called bases, that are designated by the four letters in the DNA alphabet - A, T, G and C. 'A' always pairs with 'T', and 'G' always pairs with 'C'.
Biological explanations for criminal behaviour DNA is Organised Into Chromosomes The long molecules of DNA in your cells are organised into pieces called chromosomes. Humans have 23 pairs of chromosomes. Other organisms have different numbers of pairs - for example, chimpanzees have 24 pairs. The number of chromosomes doesn't determine how complex an organism is - bananas have 11 pairs of chromosomes, while fruit flies have only 4
Biological explanations for criminal behaviour Chromosomes: Boy or girl? A newly fertilised egg usually has 46 chromosomes, arranged in 23 pairs. One pair of these chromosomes decides whether the embryo will grow into a boy or a girl: the sex chromosomes, X and Y – named after their shapes. A fertilised egg with two X- chromosomes will grow into a girl, and one with one X and one Y will grow into a boy. The sperm cell has the deciding chromosome. It is from conception as to whether a person will become male XY or a female XX.
Biological explanations for criminal behaviour
Biological explanations for criminal behaviour Chromosomes: Sometimes, chromosomes are not so straight forward. Some families carry genes which creates a difference in their off spring. Haemophilia is one example of this:
Biological explanations for criminal behaviour Chromosomes: Adults and children with Downs syndrome are born with an additional chromosome on the 21st pair.
Biological explanations for criminal behaviour Chromosomes: Some people are born androgynous. This is when the genes have not dictated either a male gender or a female gender. This is when the second X or the Y chromosome is missing.
Biological explanations for criminal behaviour Chromosomes: The XYY gene. This has been linked to increased aggression and violence. Why would a female not have the XYY chromosome? We will look more in detail at this in a study by Theilgaard (1984)
Biological explanations for criminal behaviour Now read pages 176 – 177 about Theilgaard’s (1984) research. As you go through it create a grid using the following titles as subheadings: Aim, procedure, Participants, results, conclusion, strengths, weaknesses, ethics
Biological explanations for criminal behaviour Do you think that all new born males should be tested for the XYY chromosome? (8) Explain your answer showing that you have considered both sides, and include other biological evidence that is used for and against this method of predicting behaviour. Key words: Genes Self fulfilling prophecy SLT Role models