Genes - idexcel igcse biology

What is a gene?

A length of DNA that codes for a particular protein or characteristic.

What are chromosomes?

Structures made of DNA and proteins found in the nucleus of a cell.

How many chromosomes do humans have?

Humans have 46 chromosomes, arranged in 23 pairs.

What do sex chromosomes determine?

The sex of the individual; Female: XX, Male: XY.

What are alleles?

Different versions of a gene that can occupy the same position on a chromosome.

What is a dominant allele?

An allele that expresses its trait even if only one copy is present.

What is a recessive allele?

An allele that expresses its trait only when two copies are present.

What is genotype?

The genetic makeup of an individual, represented by the combination of alleles.

What is phenotype?

The physical expression or characteristic resulting from the genotype.

What is Mendelian inheritance?

The set of principles established by Gregor Mendel through his studies of pea plants.

What does the Law of Segregation state?

Each parent passes one of their two alleles for each gene to their offspring.

What is a monohybrid cross?

A genetic cross that studies the inheritance of one gene with two alleles.

What is co-dominance?

A situation where both alleles in a heterozygous individual contribute to the phenotype.

What is incomplete dominance?

A situation where the heterozygous phenotype is an intermediate between the two homozygous phenotypes.

What is a mutation?

A change in the sequence of DNA that can alter the function of a gene.

What are sex chromosomes?

Chromosomes that determine the gender of an individual; females have XX and males have XY.

What is cystic fibrosis?

A genetic disorder caused by a recessive allele, leading to thick mucus affecting lungs and digestive system.

What is sickle cell anemia?

A genetic condition caused by a mutation in the hemoglobin gene, resulting in sickle-shaped red blood cells.

What is genetic screening?

Testing individuals for genetic disorders or mutations.

What is genetic engineering?

The manipulation of an organism’s genome using biotechnology.

What are GM crops?

Genetically modified crops that can have improved resistance to pests or diseases.

What are sex-linked traits?

Traits that are carried on the sex chromosomes, often affecting males more due to having one X chromosome.

What is a Punnett square?

A diagram used to predict the outcome of genetic crosses.

What is a pedigree chart?

A diagram used to track the inheritance of traits within a family.