Upload
doris-watson
View
220
Download
0
Tags:
Embed Size (px)
Citation preview
psyc
hlot
ron.
org.
uk
Evolution
Cars kill many more people than spiders. So why are phobias of spiders much more
common than phobias of cars?
psyc
hlot
ron.
org.
uk
Today you will…
Learn about• The role and influence of
genes in humans
Learn how to• Describe biological
structures• Distinguish between
biological and psychological concepts
psyc
hlot
ron.
org.
uk
How many can you define?
• Gene• Genetics• Heredity• Genotype• Phenotype• Dominant gene• Recessive gene
psyc
hlot
ron.
org.
uk
What are genes?
• Genes are bits of DNA which make proteins– These proteins cause physiological responses in
the body• An organism’s genes convey information
about how to construct that organism from one generation to the next
psyc
hlot
ron.
org.
uk
Genetics and heredity
• Genetics is the study of how genes influence physical and behavioural characteristics
• Heredity refers to the traits, tendencies and characteristics inherited from our parents/ancestors
psyc
hlot
ron.
org.
uk
Genotype vs Phenotype• Genotype: the whole set of genetic information
carried by the organism• Phenotype: the physical manifestation of the
genotype. Only some genes carried in the genotype will be expressed in the phenotype.
psyc
hlot
ron.
org.
uk
• Why might a characteristic encoded in the genotype not be expressed in the phenotype?
psyc
hlot
ron.
org.
uk
• How does this example illustrate the concepts of phenotype and genotype?– John and Alan are identical twins who were
separated at birth. Alan was raised in a very impoverished environment. John is substantially taller than Alan.
psyc
hlot
ron.
org.
uk
Remember...
• Just because it’s in the genotype that doesn’t necessarily mean it’ll be expressed in the phenotype:– The environment influences gene expression– Some genes are recessive and some are dominant
psyc
hlot
ron.
org.
uk
• Genes are organised in chromosomes, these come in pairs – you inherit one half of each pair from each parent– Dominant genes are always expressed – Recessive genes are expressed only in the absence
of a dominant gene
psyc
hlot
ron.
org.
uk
Which genes are expressed?
• Consider eye colour:B = brown eyes (dominant)b = blue eyes (recessive)
• So what colour eyes would a person have with the following gene pairs?– BB– Bb– bb
psyc
hlot
ron.
org.
uk
Dominant vs Recessive
Brown eyes Blue eyes
Dark hair Blond/red hair
Curly hair Straight hair
Colour vision Colour blindness
Normal sight Night blindness
Normal blood Haemophilia
Hearing Congenital Deafness
psyc
hlot
ron.
org.
uk
Explain why…
• Doug and Amber both have blonde hair. They have two children, Alex and Sam. Alex has red hair while Sam’s hair is dark brown.
psyc
hlot
ron.
org.
uk
Heritability
O 1
100 % down to genes
100 % down to environment
The extent to which the variability found in a characteristic or trait is hereditary is known as the heritability coefficient (score from 0 to 1)
For example, eye colour is solely determined by genes so has a heritability coefficient of 1. Height is slightly influenced by environment and has a heritability coefficient of 0.9
psyc
hlot
ron.
org.
uk
What about psychology?
• Where would you place these traits?
• Memory, extraversion, academic achievement, verbal reasoning, intelligence, spatial reasoning
O 1
100 % down to genes
100 % down to environment