17.4

Monohybrid inheritance

12 flashcards to master Monohybrid inheritance

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Definition Flip

What is meant by 'inheritance' in biology?

Answer Flip

Inheritance refers to the transmission of genetic information from parents to offspring, resulting in offspring resembling their parents.

Example: a tall pea plant inherits genes for tallness from its parent plants.
Definition Flip

Define 'genotype' and provide an example.

Answer Flip

Genotype is the genetic makeup of an organism, specifically the alleles it possesses for a particular gene.

Example: a pea plant might have the genotype 'Tt' for plant height, where 'T' represents the allele for tallness and 't' represents the allele for dwarfism.
Definition Flip

What is the 'phenotype' of an organism?

Answer Flip

Phenotype refers to the observable characteristics or traits of an organism, resulting from the interaction of its genotype and the environment.

Example: a pea plant with the genotype 'Tt' might have a tall phenotype.
Definition Flip

Describe the term 'homozygous'.

Answer Flip

Homozygous means having two identical alleles for a particular gene.

Example: a pea plant that has two alleles for tallness (TT) is homozygous dominant, while one with two alleles for dwarfism (tt) is homozygous recessive.
Key Concept Flip

What does it mean for an organism to be 'pure-breeding'?

Answer Flip

A pure-breeding organism is homozygous, meaning it has two identical alleles for a trait. When two identical homozygous individuals breed, they will always produce offspring with the same phenotype for that trait.

Example: crossing two homozygous tall pea plants (TT x TT) will always produce tall pea plants.
Definition Flip

Define 'heterozygous'.

Answer Flip

Heterozygous means having two different alleles for a particular gene.

Example: a pea plant with one allele for tallness (T) and one allele for dwarfism (t) is heterozygous (Tt).
Key Concept Flip

Explain why a heterozygous individual is not pure-breeding.

Answer Flip

A heterozygous individual is not pure-breeding because it carries two different alleles for a trait. This means it can produce gametes with either allele, leading to offspring with different combinations of alleles and thus potentially different phenotypes.

Definition Flip

What is a 'dominant' allele?

Answer Flip

A dominant allele is expressed in the phenotype even when only one copy is present in the genotype.

Example: in pea plants, the allele for tallness (T) is dominant over the allele for dwarfism (t), so a plant with the genotype Tt will be tall.
Definition Flip

Explain what a 'recessive' allele is.

Answer Flip

A recessive allele is only expressed in the phenotype when two copies are present in the genotype (i.e., when the individual is homozygous recessive).

Example: in pea plants, the allele for dwarfism (t) is recessive, so a plant must have the genotype tt to be dwarf.
Key Concept Flip

Describe the purpose of a 'test cross'.

Answer Flip

A test cross is used to determine the unknown genotype of an individual showing a dominant phenotype. It involves crossing the individual with a homozygous recessive individual. The phenotypes of the offspring reveal the unknown genotype.

Definition Flip

Explain 'codominance' with an example.

Answer Flip

Codominance occurs when both alleles in a heterozygous individual contribute to the phenotype.

Example: in shorthorn cattle, the alleles for red coat (CR) and white coat (CW) are codominant. Heterozygous individuals (CRCW) have a roan coat, showing both red and white hairs.
Key Concept Flip

Explain how red-green color blindness is an example of sex linkage.

Answer Flip

Red-green color blindness is a sex-linked trait because the gene responsible for it is located on the X chromosome. Because males only have one X chromosome, they are more likely to express the recessive color blindness allele if they inherit it, while females need to inherit the allele on both X chromosomes.

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17.3 Meiosis 18.1 Variation

Key Questions: Monohybrid inheritance

What is meant by 'inheritance' in biology?

Inheritance refers to the transmission of genetic information from parents to offspring, resulting in offspring resembling their parents.

Example: a tall pea plant inherits genes for tallness from its parent plants.
Define 'genotype' and provide an example.

Genotype is the genetic makeup of an organism, specifically the alleles it possesses for a particular gene.

Example: a pea plant might have the genotype 'Tt' for plant height, where 'T' represents the allele for tallness and 't' represents the allele for dwarfism.
What is the 'phenotype' of an organism?

Phenotype refers to the observable characteristics or traits of an organism, resulting from the interaction of its genotype and the environment.

Example: a pea plant with the genotype 'Tt' might have a tall phenotype.
Describe the term 'homozygous'.

Homozygous means having two identical alleles for a particular gene.

Example: a pea plant that has two alleles for tallness (TT) is homozygous dominant, while one with two alleles for dwarfism (tt) is homozygous recessive.
Define 'heterozygous'.

Heterozygous means having two different alleles for a particular gene.

Example: a pea plant with one allele for tallness (T) and one allele for dwarfism (t) is heterozygous (Tt).

About Monohybrid inheritance (17.4)

These 12 flashcards cover everything you need to know about Monohybrid inheritance for your Cambridge IGCSE Biology (0610) exam. Each card is designed based on the official syllabus requirements.

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