1 / 8

Understanding Alleles and Genes in Inheritance

Learn about alleles, genes, phenotypes, genotypes, and Punnett squares in inheritance. Explore the concepts of dominance, recessiveness, homozygous, and heterozygous alleles.

antoinettej
Download Presentation

Understanding Alleles and Genes in Inheritance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Review Each person inherits two alleles for each gene, one allele from each parent. • What is an allele? • What is a gene? • Define phenotype. • Define genotype. The basic unit of heredity. The physical appearance or visible traits displayed by offspring. The genetic makeup or allele combination present in offspring.

  2. PunnettSquare What is it? A graphical grid showing the potential offspring allele combinations from two parents.

  3. Punnett Squares are grids that show the potential offspring of two parents. PARENT T T OFFSPRING P A R E N T t Tt Tt Tt t Tt KEY: T = Tall t = short

  4. Background • Professor Reginald Punnett, (1875-1967) a British geneticist created the Punnett square, a tool in genetics which is still used by biologists today to predict the probability of possible genotypes of offspring.

  5. Begin by drawing a grid. Next, you put the genotype (allele combination) of one parent across the top and that of the other parent down the left side.  1st parent: T T 2nd parent: t t Constructing a Punnett square TT x tt T T t t KEY: T = Tall t = short Note: Capital letters denote dominance

  6. Next, all you have to do is fill in the boxes with the potential offspring combinations. BUT HOW??? Like a multiplication table, combine each column-head letter and row letter into the empty squares.  Constructing a Punnett square TT x tt 1 2 T T 1 & 3 2 & 3 3 t Tt Tt 1 & 4 2 & 4 4 t Tt Tt KEY: T = Tall t = short

  7. Interpreting a Punnett SquareWhat does it tell us? TT x tt 1st parent: TT Phenotype?_________ 2nd parent: tt Phenotype?_________ Tall T T Short t Tt Tt Tt Offspring: ____ Phenotype?_______ All Tall t Tt Tt TT x tt One parent dominant homozygous, other parent recessive homozygous. KEY: T = Tall t = short

  8. New Terms having 2 identical alleles for a trait • Homozygous: • Heterozygous: • Dominant: • Recessive: having 2 different alleles for a trait the term dominant gene refers to the allele that causes a phenotype that is seen a gene that does not produce its effect when it occurs with a dominant gene, but produces its effect only when there are two copies of it

More Related