INTRODUCTION TO GENETICS Ms. Wassum

Traits Traits are the different forms of a characteristic that you may exhibit Ex: Blue or Brown Eyes Traits are inherited from our parents Therefore, when we talk about genetics, we are talking about sexual reproduction

Chromosomes Every cell in a human body has 23 pairs of chromosomes – half from our mother, half from our father Genes are found on chromosomes We have about 20,000-25,000 genes Each gene holds a code that tells our body to make a certain protein The protein that is made determines a Specific trait. Ex: Blue eye pigment or Brown eye pigment

Alleles The different forms of a gene that can exist Ex: Curly hair gene or straight hair gene Dominant – ‘Strongest Allele’ – If it is present, you will have that trait. We use upper case letters for dominant alleles Recessive – ‘Weakest Allele’ – This won’t show up unless there are two of them. We use lower case letters for recessive alleles

Genotype The actual alleles you have for a trait Ex: For eye color, you inherit B from dad and b from Mom Your genotype is Bb If there is a dominant allele, the genotype is written with the upper case first. (Never write bB) Your genotype is the genes you have

Genotype (Cont’d) If you have two copies of the same allele for a trait (BB or bb), then you are HOMOZYGOUS for that trait If you have two different alleles for a trait (Bb), then you are HETEROZYGOUS for that trait

Phenotype How the genes actually show up, or how they are expressed So, if your genotype is Bb, Where B is brown And b is blue The phenotype would be Brown eyes Phenotype is the physical appearance

Karyotype-Normal A picture of the chromosomes found in an individual. Used to determine abnormalities.

Karyotype - Abnormal There are three copies of chromosome 21 – there should only be two copies. This is a karyotpe of a female with Down’s Syndrome.

Quiz Time You inherit the gene for freckles (F) from dad, and the gene for no freckles (f) from mom 1. What would your genotype be? Ff 2. What would your phenotype be? You would have freckles 3.Which allele is dominant? F (freckles)

Quiz Time You inherit the gene for no allergies (a) from dad, and the gene for allergies (A) from mom 1. What would your genotype be? Aa 2. What would your phenotype be? You would have allergies 3.Which allele is dominant? A (allergies)