Genetics: VocabularyNucleusDNAChromosomeAlleleGeneTraitsDominant RecessiveGenotypePhenotypeHomozygousHeterozygous

NucleusOur cells are controlled by the nucleus. The

nucleus also contains our genetic information

(DNA- DeoxyriboNucleic Acid)

on structures called

Chromosomes.

ChromosomesHumans have 46 chromosomes in

each body cells or 23 pairs.

Pea Plants have 14 chromosomes in each cell or 7pairs.

Made of thousands of genes (over 60,000 in humans).

Each parent contributes half of each chromosome pair to their offspring.

Usually there is one pair of sex chromosomes

GenesThe genes on chromosomes have

control for different traits. For example a gene may control for eye color. All genes come in pairs.

Half of the pair coming from mother, the other half coming from father

Humans: 23 genes from mother (XX)

23 genes from father (XY)

Pea Plants 7 genes from mother (XX)

7 genes from father (XY)

Alleles

There are different forms of genes called alleles.

For example: eye color (gene) brown eyes, blue eyes, and green eyes (allele)

Dominant Allele vs Recessive AlleleIndividual C is the only one who will have blue eyes (recessive allele)

Because the allele for brown eyes is present, individual B and individual A will have brown eyes

Dominant Allele vs Recessive Allele

• Dominant alleleDominant allele – a trait that always shows up when the allele is present– Symbol – Capital letter (T)

• Recessive alleleRecessive allele – a trait that is covered up or masked when a dominant allele is present– Symbol – lower case letter (t)For example brown eyes (B) are dominant

over blue (b), and appear more often.

Allele: Eye Color B represents the dominant trait brown b represents the recessive trait of blue.

– the child could have B from one parent and B from the other = child with brown eyes

GENOTYPE: BB PHENOTYPE: Brown Eyes– the child could have B from one parent and b from

the other = child with brown eyesGENOTYPE: Bb PHENOTYPE: Brown Eyes– the child could have b from one parent and b from

the other = child with blue eyesGENOTYPE: bb PHENOTYPE: Blue Eyes

Any time the dominant gene appears, the offspring will have the dominant trait.

Gregor Mendel’s Pea Plant Experiment

Let’s Review: Beach Ball Activity

1. What is the phenotype for Bb when b= blue eye color and B= brown color?

2. What is a phenotype and a genotype?3. When does a phenotype for a recessive trait show

up in an organism?4. How many pairs of chromosomes do humans have?5. T = tall and t= short, what is the phenotype for Tt?6. T = tall and t= short, what is the phenotype for tt?7. T = tall and t= short, what is the phenotype for TT?8. Sex chromosomes for males is?