Genetics

Question 1

Genetics

Answer 1

When organisms reproduce, information is passed from parents to offspring on the chromosomes in the gametes (sex cells)

The way in which inherited characteristics are passed on from parents follows a pattern. The study of this pattern of inheritance is called genetics.

Question 2

Phenotype

Answer 2

The physical characteristics that an organism shows are referred to as its
phenotype, e.g. hair colour, stem length.

Question 3

Genotype

Answer 3

This combination of genes (the genetic make-up of the organism) is called the genotype.

Question 4

Alleles

Answer 4

Genes are parts of chromosomes, which code for a particular characteristic. Genes can exist in more than one form. A pair of genes may contain two of the same form, or two different forms.
The characteristics of an organism are mainly controlled by the combination of different forms of gene in a pair.

The different forms of a gene are called alleles.

Body cells carry two alleles, one inherited from each parent.
Therefore, each gamete carries one allele of the gene.

Question 5

Polygenic inheritance

Answer 5

Many of the features possessed by an individual in terms of their phenotype have been caused by the interaction of the alleles of several genes. This is referred to as polygenic inheritance. Skin colour in humans and seed mass in plants are good examples of this.

Question 6

Dominant and Recessive alleles

Answer 6

Alleles can be either dominant or recessive.

Capital letters are used for dominant genes and small case for recessive genes.
If BB is genotype then the dominant gene is shown in the phenotype.
If Bb is genotype then the dominant gene is shown in the phenotype.
If bb is genotype then the recessive gene is shown in the phenotype.