Extension information

Information from T1 W8 Science student copy

Explain how genetic information is passed from one generation to the next in your student copy. 

The egg and the sperm each have 23 chromosomes in them. When the sperm fertilizes the egg, the of the two chromosomes form a pair and combine alleles to make a gene. This is where the alleles come in.  

Explain how sexual reproduction give rise to variation 

Because sexual reproduction involves combination of genetic data, this causes generation later to have variation of features. It is done between two people, which based on the traits of the parents, can alter the appearance of the child. The dominant and recessive alleles play a huge role in deciding your traits, as combining them together can give a probability of which trait you are likely to possess. 

Describe how the pair of alleles determine your trait 

In the alleles, one is dominant, and one is recessive. We can use the Punnett square to help determine which gene is most likely to be produced and not. Using brown and blue eyes as an example, brown eyes can have the alleles BB (purebred brown), or Bb (dominant brown, recessive blue), and blue eyes can have the alleles bb (because it is not the dominant condition). If you have a parent with brown eyes (purebred) (BB) and blue eyes (bb) the child will one hundred percent, come out with brown eyes. However, if you have parents with non-purebred brown eyes (Bb) there is a 25% chance of the child coming out with blue eyes because of their grandparents' genes. 

Genotype: An organisms genetic information (alleles)

Phenotype: The features that we can see physically on a person based on their alleles (or genotype). 

Homozygous dominant: When an offspring receives two alleles of the dominant gene. 

Heterozygous: When an offspring receives both a dominant and recessive gene – the dominant one ruling over the recessive one. 

Homozygous recessive: When an offspring receives two alleles of the same recessive gene 

Phenotypic ratio: a numerical comparison of the physical traits that an individual may possess based off alleles. 

Genotypic ratio: a numerical comparison of how many different combinations of alleles an individual might have.  

How to find Genotypic ratio: Fill out a punnetts square and count how many allele combinations there are and then show that data in the form of a ratio. 

How to find Phenotypic ratio: Fill out a punnetts square and count how many physical traits there are likely to be, then show that data in the form of a ratio.