Alien Genetics A Science and Math Overlap

Genetics The field of biology that studies heredity (the passing of traits from one generation to the next)

Genes The section of DNA that codes for a certain trait. Every characteristic is controlled by a pair of genes – one from the organism’s mother, and one from its father. Alleles are the different forms of a gene.

The Law of Dominance If one or both alleles in an organism are for the dominant characteristic, then the organism will exhibit that dominant characteristic. The recessive characteristic will only be shown if both alleles are for that recessive characteristic.

Guessing game!!! For each allele pair, guess which one is dominant and which is recessive in humans: –Eye color: Brown or blue/grey/green/hazel?

Guessing game!!! For each allele pair, guess which one is dominant and which is recessive in humans: –Earlobes: Unattached (A) or attached(B)?

Guessing game!!! For each allele pair, guess which one is dominant and which is recessive in humans: –Number of digits: five fingers/toes on each hand/foot, or having extra fingers/toes?

The Law of Segregation Gametes are the sex cells (sperm and ovum) that combine to form a new offspring. Each gamete randomly gets one of each pair of alleles for each trait, so that when the two gametes combine, the offspring has a complete set of pairs.

Genotype The combination of alleles in an organism Homozygous: The two alleles for the trait are the same. Heterozygous: The two alleles for the trait are different.

Phenotype The trait that is displayed by the organism What genotypes – combinations of dominant and recessive alleles – would make an organism display the dominant trait? What genotypes would make the organism display the recessive trait?

Punnett Square A chart used to predict the possible genotypes (and phenotypes) of the offspring of a cross between two parent organisms From this, you can figure out the probability of each genotype (and phenotype) occurring in the offspring.

Haha!

Allele Representation The same letter is used to represent both alleles for a trait, but the capital is used for the dominant allele, and the lowercase is used for the recessive allele.

Our First Cross The alien species that we’re going to study follows the same genetics laws that we humans, here on Earth, do. In this alien species, having blue skin is a dominant trait and having green skin is a recessive trait. Let’s use B’s for blue skin and b’s for green skin.

Our First Cross The mom alien is homozygous with blue skin. What is her genotype? The dad alien is homozygous with green skin. What is his genotype?

A Punnett Square Looks Like…

Setting up the Punnett Square The two alleles from one parent go above the two columns, and the two alleles from the other parent go to the left of the two rows. BB b b

Filling in the Punnett Square Put the letter pair (one from the top, one from the side) in each box. B B b b Bb

Probability The likelihood of something happening In fraction form, the numerator is the number of desired outcomes (what you are looking for) and the denominator is the number of total outcomes (all of the possibilities). To change to a percent, divide numerator by denominator and multiply by 100.

Genotypes What are the possible genotypes in the offspring of a cross between a homozygous blue- skinned alien mom and a homozygous green-skinned alien dad? BB b b Bb

What is the probability of each genotype in the offspring of a cross between a homozygous blue- skinned alien mom and a homozygous green-skinned alien dad? BB b b Bb Genotypes

Phenotypes What are the possible phenotypes in the offspring of a cross between a homozygous blue- skinned alien mom and a homozygous green-skinned alien dad? BB b b Bb

Phenotypes What is the probability of each phenotype in the offspring of a cross between a homozygous blue- skinned alien mom and a homozygous green-skinned alien dad? BB b b Bb

Another Cross Let’s look at a different pair of aliens. In this pair, both parents are heterozygous with blue skin. What are the parents’ genotypes for skin color?

Complete the Punnett Square Try it on your own!

Check your Punnett Square Does yours match mine? Bb B b BBBb bb

Genotypes What are the possible genotypes in the offspring of a cross between a heterozygous blue- skinned alien mom and a heterozygous blue-skinned alien dad? Bb B b BBBb bb

Genotypes What is the probability of each genotype in the offspring of a cross between a heterozygous blue- skinned alien mom and a heterozygous blue-skinned alien dad? Bb B b BBBb bb

Phenotypes What are the possible phenotypes in the offspring of a cross between a heterozygous blue- skinned alien mom and a heterozygous blue-skinned alien dad? Bb B b BBBb bb

Phenotypes What is the probability of each phenotype in the offspring of a cross between a heterozygous blue- skinned alien mom and a heterozygous blue-skinned alien dad? Bb B b BBBb bb

Contact Information Christina Chuey Rene Fernandez