Genetics test

Gene

sections of DNA in a chromosome that instruct cells to create certain proteins.

Chromosome

a thread-like structure found in the nucleus of a cell. Chromosomes are made up of proteins and DNA organised into genes. Most cells contain 2 pairs of 23 chromosomes (46 total). The exception to this are sex cells, which contain 1 pair of 23 chromosomes (23 total)

DNA

A double-helix-like molecule that contains the genetic information needed for the development and functioning of an organism

Allele

Alleles are variations of a genetic sequence found in a particular region of a chromosome. An individual inherits two alleles for each gene, one from each parent

Genotype

The term genotype refers to the alleles an individual inherited for a particular trait.

Phenotype

The observable characteristics in an individual resulting from the expression of a trait

Homozygous

The term “homozygous” refers to an individual possessing two of the same alleles for a trait

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Heterozygous

Heterozygous refers to an individual possessing differing alleles for a trait. Usually, one allele is dominant and one is recessive, making the individual a carrier. However, in some cases, both traits can be dominant or recessive

autosomal trait

An autosomal trait is passed down from one parent to a child. The sex of the parent or the child does not influence how the trait is passed down

sex-linked trait

A sex-linked trait is a trait that is influenced by the sex of the parent or child. This is because such traits are inherited through the sex chromosomes.

dominant trait

A dominant trait only needs 1 allele of that trait to be displayed. If an individual has 2 of the same dominant alleles, they are considered homozygous dominant. However, if they have only one copy of the dominant trait, they are considered heterozygous and a carrier for the recessive trait.

recessive trait

recessive traits need 2 of the same allele to be displayed

Prophase

During the stage of prophase, the cell prepares for division: the chromosomes condense and the nucleus starts to break down. The two centrosomes move to opposite ends of the cell.

Metaphase

During metaphase, the chromosomes line up along the middle of the cell

Anaphase

During anaphase, the chromosomes separate and are dragged away from each other. The chromosomes are separated by a structure called the mitotic spindle which is attached to the centrosomes.

Telophase (mitosis)

Two nuclei form, each with its own set of identical DNA. These are known as “daughter cells”

Telophase (meiosis)

Four nuclei form, each with its own set of unique DNA. These are known as “gametes”

Co-dominance

Co-dominance is when an individual possesses two alleles that are both dominant and both expressed. For example, when a chicken with white feathers breeds with a chicken with black feathers, the result is an offspring chicken that possesses both black and white feathers

**incomplete dominance**

Incomplete dominance is when an individual possesses 2 non-dominant alleles. These alleles are both partially expressed, thus creating a third, intermediate phenotype. An example of such is wavy hair, which comes as a result of an individual who possesses both curly and straight hair alleles.

simple inheritance

Simple inheritance refers to when the appearance of an inherited trait is controlled by a single gene