6. Inheritance, Variation and Evolution

What is sexual reproduction?

Sexual reproduction involves the fusion of male and female gametes, producing genetically different offspring.

What is asexual reproduction?

Asexual reproduction involves only one parent, no gamete fusion, and produces genetically identical offspring (clones).

What process forms gametes?

Meiosis.

How many gametes are produced in meiosis?

Four genetically different gametes with half the chromosome number.

What restores the full number of chromosomes after fertilisation?

The fusion of gametes.

What is DNA?

A polymer made of two strands in a double helix.

What is a gene?

A section of DNA that codes for a specific protein.

What is the genome?

The entire genetic material of an organism.

Give two benefits of the Human Genome Project.

Identifying genes linked to disease and tracing human migration patterns.

What is an allele?

A different form of a gene.

Define genotype.

The combination of alleles an organism has.

Define phenotype.

The physical characteristics expressed by the genotype.

What is a dominant allele?

An allele that is always expressed, even if only one copy is present.

What is a recessive allele?

An allele that is only expressed if two copies are present.

What does homozygous mean?

Having two identical alleles for a trait.

What does heterozygous mean?

Having two different alleles for a trait.

What causes polydactyly?

A dominant allele.

What causes cystic fibrosis?

A recessive allele.

What is embryo screening?

Testing embryos for genetic disorders.

What are the sex chromosomes for a female?

XX.

What are the sex chromosomes for a male?

XY.

What causes variation in a species?

Genetic differences, environmental factors, or both.

What is a mutation?

A random change in DNA.

What is evolution?

A change in inherited characteristics over time via natural selection.

Who developed the theory of natural selection?

Charles Darwin.

What is speciation?

The formation of a new species when populations become too different to interbreed.

What is selective breeding?

The process of humans breeding plants or animals for desired traits.

Give two risks of selective breeding.

Inbreeding and increased risk of genetic disorders.

What is genetic engineering?

Modifying the DNA of an organism by inserting genes from another.

Give two uses of genetic engineering.

GM crops with resistance or yield traits; bacteria producing human insulin.

What is a GM crop?

A crop whose DNA has been genetically modified.

Give one concern about GM crops.

Possible effects on wild species and human health.

(HT only) What are the main steps of genetic engineering?

Isolate gene with enzymes → insert into vector → transfer to cells early in development.

What are fossils?

Remains or traces of organisms from millions of years ago.

How are fossils formed?

Hard parts don’t decay, replacement by minerals, or preserved traces.

Why is the fossil record incomplete?

Many early life forms were soft-bodied or destroyed by geological activity.

What is extinction?

When no individuals of a species remain.

Give three causes of extinction.

New predators/diseases, environmental changes, catastrophic events.

How does antibiotic resistance develop?

Mutation creates resistant strain → survives → reproduces → spreads.

Give three ways to reduce antibiotic resistance.

Avoid unnecessary use, complete full courses, restrict agricultural use.

Why is antibiotic resistance a major concern?

New antibiotics are slow to develop and resistance can spread rapidly.

What is the Linnaean classification system?

Kingdom, Phylum, Class, Order, Family, Genus, Species.

What is binomial naming?

A two-part scientific name using genus and species.

What are the three domains of life?

Archaea, Bacteria, and Eukaryota.

What is an evolutionary tree?

A diagram showing evolutionary relationships using genetic and fossil evidence.