Psych 1100-Chapter 6 (Genetics and Evolution)

What is a gene and what are they made of?

Basic physical and functional unit of heredity; contains biological instructions that determine inherited traits.

DNA (deoxyribonucleic acid), which stores genetic instructions for growth, development, survival, and reproduction.

What does dna produce?

Proteins, through RNA. DNA is transcribed into RNA, which carries instructions for protein synthesis.

What are the steps rna follows?

Transcription: cell creates RNA copy of specific DNA segment

Translation: RNA travels to ribosome

Assembly: other forms of RNA gather amino acids to construct proteins

What are proteins and their functions?

Worker molecules that:

• Build/repair cells (structural proteins)

• Speed up chemical reactions (enzymes)

• Send hormonal signals

• Transport substances (e.g., hemoglobin)

• Defend the body (antibodies)

• Enable muscle contraction

What is mitosis?

Cell division in regular cells Produces 2 genetically identical cells with the same chromosome number. Differences between cells result from differential gene activation.

What is meiosis?

Cell division in gametes (sperm/egg). One cell divides twice to produce 4 genetically unique haploid cells (23 chromosomes).

What are gametes?

Sperm and egg cells containing 23 chromosomes. They combine during fertilization to form a zygote with 46 chromosomes (23 pairs).

What determines gene expression?

The environment can switch genes on or off, influencing physical traits and behaviour.

What is genotype and phenotype?

Genotype: Genetic makeup inherited from parents.

Phenotype: Observable physical and behavioural traits resulting from genotype + environment.

What are dominant and recessive genes?

Dominant: Expressed with one or two copies (heterozygous or homozygous).

Recessive: Expressed only with two recessive copies (homozygous).

How do we know about dominant and recessive genes?

Through Gregor Mendel's pea plant experiments, which showed predictable inheritance patterns (bred wrinkled and smooth peas to determine heritability)

How are genes and behvaiour related?

Genes influence behavioural tendencies by affecting brain development, physiology, and other traits, but they do not determine behaviour alone

What are single gene behaviours?

Traits controlled by one gene; categorical (present or absent).
Examples:

• Fearfulness in Basenji–Cocker Spaniel hybrids

• Phenylketonuria (PKU)

What are polygenic characteristics?

Traits influenced by many genes, producing continuous variation (e.g., height, intelligence)

Selective breeding

Breeding organisms with desirable inherited traits to increase those traits in future generations.

(I.e breeding plants, animals for desirable traits)

What is epigenetics?

Study of how environment and behaviour alter gene expression without changing DNA sequence. Influenced by diet, stress, lifestyle, etc

Can leads to development of various cancers through gene mutation

What is dna methylation?

Addition of methyl groups to cytosine that usually silence ("turn off") genes without altering DNA.

Parts of epigenetics?

Gene silencing: Methyl groups block transcription

Selective access: Different cell types activate only needed genes (ensures only necessary genes are on for that specific cell type)

DNA packaging: Methylation tightens DNA around histones, reducing gene access.

What are the two main sources for genetic variability?

Reshuffling of genes that occurs in gamete reproduction

Mutations: errors occurring during DNA replication, causing the replication to be not quite identical to the original (more harmful than helpful, natural selection weeds them out)

What drives evolution?

Environmental change (climate change, food supply) leads to natural selection, favouring traits that improve survival and reproduction.

(Ex. Medium ground finch example)

What are the two different ways to explain behaviour?

Distal explanations: evolutionary purpose (i.e male song birds singing during the spring to attract a female for reproduction)

Proximate explanations: immediate biological mechanism causing behaviour mechanistic l (i.e bird registers more sunlight, triggers mechanism to produce testosterone making it sing)

What are four reasons traits may not currently have any function?

vestigial traits: served a purpose for ancestors but no longer functional (cravings for sugar and fat)

By-products of natural selection: the chin

Chance traits: inheritable characteristics from mutations had no influence on survival at all (genetic drift)

Once-adaptive emotions not useful in every situation (guilt)

What was the Robles with Paul Elkman’s experiment to determine universal facial expressions?

Participants chose from only six emotion labels, which may have biased results since humans describe emotions different universally (due to internal sensations, learned concepts, culture)

What is biological preparedness?

An innate tendency to learn certain associations more easily because they promoted survival

Is behaviour purely innate or learned?

No, it’s a mixture of both. Some sort of experience is always necessary for a behaviour to develop and manifest

What is homoloy and analogy?

Homology: similarity due to common ancestry

Analogy: similarity due to convergent evolution, not shared ancestry (similarity in habits and lifestyle)

What four mating patterns are there?

Polygyny: One male, many females (common in mammals; high female PI).

Polyandry: One female, many males (common in birds; high male PI).

Monogamy: One male and one female (similar PI).

• Social monogamy: Pair bond to raise offspring.

• Sexual monogamy: Mate exclusively.

Promiscuity: Multiple mating partners; investment spread across the group.

What is parental investment theory?

The parent investing more time, energy, and risk in offspring is generally more selective when choosing mates.

What is aggression and where does it come from?

Behaviour intended to harm members of the same species, often due to competition for limited resources. Males are generally more aggressive than females

What are cooperation and altruism?

Cooperation: helping others while also benefiting yourself (e.g hunting, raising young, predator defence)

Altruism: helping another at a cost to your own survival or reproduction

Altruism: kin selection and reciprocity theory

Kin selection: helping relatives increases the survival of shared genes (calling out to warn about predator)

Reciprocity: helping unrelated individuals with the expectation of future help (e.g vampire bats frequently sharing food with unrelated members of species)