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Genetics. Genotypes, Phenotypes, Punnett Squares, and Karyotypes. Genotypes. Genotypes are the specific combinations of the genes you get from your dad and mom. They are written as a combination of 2 letters (cases where there are more than 2 exist). Understanding Genotypes.
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Genetics Genotypes, Phenotypes, Punnett Squares, and Karyotypes.
Genotypes • Genotypes are the specific combinations of the genes you get from your dad and mom. • They are written as a combination of 2 letters (cases where there are more than 2 exist)
Understanding Genotypes Anytime a capital letter is present, it represents a dominant gene. Dominant means overpowering. Anytime a lower-case letter is present, it represents a recessive gene. Recessive is understood to be weaker.
Genotype Examples Gene for hair type can look like this. F - dominant gene (carries gene for straight hair) f - recessive gene (carries gene for curly hair) Possible Genotypes: FF (2 dominants) Ff (1 of each) ff (2 recessives)
Phenotypes Phenotypes are the characteristics that a person shows. They are based on the two letter combination of letters (genotype)
Phenotype Examples No Freckles is a dominant trait Freckles is a recessive trait Genotype: FF -> Phenotype: No Freckles Genotype: ff -> Phenotype: Freckles Genotype: Ff -> Phenotype: No Freckles Genotype: fF -> Phenotype: No Freckles
Paper Activity. You are going to get strips of paper. Some are colors, some are clear. Follow the directions on the wall to complete the activity.
Punnett Squares • Punnett Squares are tools that we use to try to predict what genotypes are possible when two people have children. • A punnett square can tell us what percent chance two people have of having a child with a certain phenotype (characteristic)
Setting Up a Punnett Square. • Make a square • Draw a vertical line cutting the square in half. • Draw a horizontal line cutting the square in half. • You should have 4 equally sized squares.
Setting Up a Punnett Square Mom f F • Put Dad’s Genotype (two letters) on the side. 1 in front of each row.) • Put Mom’s Genotype(2 letters) on top. 1 on top of each column. F DAD f
Setting Up a Punnett Square • Fill in each box with the gene from dad. F f
Setting Up a Punnett Square f F • Fill in each box with a gene from mom
Setting Up a Punnett Square MOM F f F D AD f
In this case, you have three possible combinations. • FF - No Freckles • Ff - No Freckles, but carries gene for freckles (f) • Ff - freckles
What chance do these two people have of having a child that cannot roll his/her tongue? Rolling tongue is a dominant = Shaded (capital letters) Non rolling tongue is recessive = Nonshaded (lower-case letters) Dad Mom Mom’s Geno: tt Mom’s Pheno: Can not roll Dad’s Geno: TT Dad’s Pheno: Can roll
What chance do these two people have of having a child that cannot roll his/her tongue? Rolling tongue is a dominant = Shaded (capital letters) Non rolling tongue is recessive = Nonshaded (lower-case letters) Dad Mom Mom’s Geno: tt Mom’s Pheno: Can not roll Dad’s Geno: Tt Dad’s Pheno: Can roll
What chance do these two people have of having a child that cannot roll his/her tongue? Rolling tongue is a dominant = Shaded (capital letters) Non rolling tongue is recessive = Nonshaded (lower-case letters) Dad Mom Mom’s Geno: TT Mom’s Pheno: Can roll Dad’s Geno: Tt Dad’s Pheno: Can roll
Karyotypes • A Karyotype is a picture of all your chromosomes nicely paired and organized so that a genetic counselor can identify any possible conditions. • A normal karyotype would contain 46 total chromosomes or 23 pairs of chromosomes…all labeled.
Karyotype Info • It costs a lot of money to have a karyotype done. • Most people that get one are people concerned that their child will have a certain condition • A karyotype is made early in the pregnancy. • A karyotype can give parents and doctors time to prepare (specialists on hand a birth, additional screening done after birth, etc).
How to make a karyotype • Take a picture of all your chromosomes • Cut out all the chromosomes • Pair them up based on length and banding pattern (sometimes where the centromere is located) - think of a bar code.