Biology Topic 6

Mitosis

Body cells, 2 Daughter Cells, Clones, 1 Division

Meiosis

Sex cells, 4 Daughter Cells, Unique, 2 Divisions

What are human gametes and how many chromosomes do they have?

Sperm and egg cells; 23 chromosomes.

What happens to the chromosome number when two gametes fuse in fertilisation?

It restores the full double number of chromosomes (46).

Describe the structure of DNA?

A polymer made of two strands forming a double helix.

What is a gene?

A small section of DNA on a chromosome that codes for a specific sequence of amino acids to make a protein.

What is the genome?

The entire genetic material of an organism.

What is a mutation?

A continuous, random change in the DNA base sequence.

What are alleles?

Different versions of the same gene.

What does homozygous mean?

Having two identical alleles for a particular gene (e.g., BB or bb).

What does heterozygous mean?

Having two different alleles for a particular gene (e.g., Bb).

What is a phenotype?

The physical characteristic expressed by an organism because of its alleles.

What type of allele causes Cystic Fibrosis?

A recessive allele.

What type of allele causes Polydactyly (extra fingers/toes)?

A dominant allele.

How many pairs of chromosomes determine sex in human body cells?

1 pair (XX for female, XY for male).

What is variation?

Differences in the characteristics of individuals in a population.

State the theory of evolution by natural selection?

Living things with characteristics best suited to their environment are more likely to survive and pass on their genes.

What is selective breeding?

Breeding plants or animals for specific, desirable genetic traits.

Give one major risk of selective breeding?

Inbreeding, which makes the breed more susceptible to disease or inherited defects.

What is genetic engineering?

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.

What are fossils?

The remains of organisms from millions of years ago, found in rocks.

Give one reason why a species might go extinct?

New predators, a new disease, rapid environmental change, or a catastrophic event.

Why do bacteria evolve rapidly to become resistant to antibiotics?

They reproduce very fast, and natural selection favors the mutated resistant strains.

Who developed the system for classifying living things into Kingdoms, Phylum, Class, Order, Family, Genus, and Species?

Carl Linnaeus.

Who introduced the modern 'Three Domain System' for classification?

Carl Woese.

Describe the two parts of a binomial scientific name?

The first part is the Genus, and the second part is the Species.

Who came up with the theory of evolution at the same time as Charles Darwin?

Alfred Russel Wallace (Triple Only).

What did Gregor Mendel discover by breeding pea plants?

That characteristics are passed down in predictable hereditary units (genes) (Triple Only).