Week 1
Genes and evolution
1. What are chromosomes, DNA, and genes, and what is the relationship between the
three?
In each nucleus of each cell there are 23 chromosome pairs, this is 46 chromosomes
in total. Chromosomes consist of strands of DNA. DNA consists of genes. A gene is
a hereditary code which determine specific traits.
2. What is meant by genetic expression, genotype, and phenotype?
Genetic expression refers to a gene being turned on or off. For example: in skin cells
the genes for skin colour are turned on or expressed, in hair cells these same genes
are turned off or not expressed. A genotype is an organism’s specific set of genes. A
phenotype is expressed in the overt traits and behaviour of an organism and is
determined by the interaction between genotype and the environment.
3. Can you explain how genes are passed from parents to children?
A female egg and a male sperm cell both have 23 chromosomes containing genes.
When they combine they form 23 chromosome pairs containing genes from both the
male and female. Some genes are dominant, and some genes are recessive. If
there’s two different alleles dominant alleles will be expressed, and recessive alleles
won’t. Recessive alleles are only expressed if the two alleles are the same.
4. What is meant exactly by evolution through natural selection?
Evolution through natural selection means that organisms with traits that endanger
survival are less likely to reproduce because there is less chance of survival. Traits
that encourage survival are more likely to be passed on to next generations. This is
how genes improve.
5. Which role do evolution, genes, and environment play in behaviour?
Behaviour is a result of the continuous interaction between genes and environment.
Evolution influences genes. That’s how evolution alters behaviour over a long period
of time.
6. What is behavioural genetics and which methods are used here?
Behavioural genetics is a field of study focused on genetic and environmental
influences on behaviour. A research method in this field is the study of twins. Twins
have the same genes, so environmental influences are what causes differences
between two individual twins. Adoption studies.
7. What is meant by heritability?
Heritability is the passing of genes from parent to offspring. It is a combination of
Genetic variance
genetic and phenotypic variance: H= .
Phenotypic variance
, The brain and the nervous system
1. What are the structure and function of the neuron?