AQA GCSE Combined Science Biology - inheritance, variation and evolution

inheritance, variation and evolution

What is DNA?

A molecule that carries genetic information and instructions for the cell.

Where is DNA found?

In the nucleus of cells, packaged into chromosomes.

What is a gene?

A section of DNA that codes for a specific protein.

What is a genome?

The entire set of genetic material in an organism.

Why is understanding the human genome important?

Helps with identifying genes linked to diseases, inherited disorders, and human migration.

What are the two types of reproduction?

Sexual and asexual reproduction.

What is sexual reproduction?

Involves the fusion of male and female gametes and results in genetic variation.

What is asexual reproduction?

Involves only one parent and produces genetically identical offspring (clones).

What is meiosis?

A type of cell division that produces gametes with half the number of chromosomes.

What is a gamete?

A sex cell (sperm or egg in animals; pollen or ovule in plants).

How many chromosomes do human body cells have?

46 (23 pairs).

How many chromosomes do human gametes have?

23 (single set).

What is fertilisation?

The fusion of male and female gametes to form a zygote.

What is a zygote?

A fertilised egg cell.

What is a genotype?

The genetic makeup of an individual.

What is a phenotype?

The physical characteristics shown.

What is a dominant allele?

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

What is a recessive allele?

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

What is homozygous?

Having two of the same alleles (e.g., TT or tt).

What is heterozygous?

Having two different alleles (e.g., Tt).

What is cystic fibrosis?

A genetic disorder of the cell membranes caused by a recessive allele.

What is polydactyly?

A genetic disorder causing extra fingers or toes, caused by a dominant allele.

What is genetic screening?

Testing embryos or individuals for the presence of genetic disorders.

What is variation?

Differences in characteristics due to genes, environment, or both.

What is natural selection?

The process by which organisms with advantageous traits survive and reproduce.