Genetics and Heredity HEREDITY The passing of traits

Genetics and Heredity

HEREDITY § The passing of traits from parents to offspring.

TRAIT 2 § A characteristic of an organism § Examples include: height, skin color, eye color, freckles, nose shape, etc. § Traits are controlled by genes. § What traits did Mendel observe in pea plants? (p. 218)

26 GENETICS § Study of the passing on of characteristics from one organism to its offspring § Make sure #26 mentions Gregor Mendel! 1

4 GENE 3 10 • • § The set of information that a controls a trait It is a segment of DNA on a chromosome Genes come in 2 forms (allele-forms of a gene): a. DOMINANT: allele that will always be expressed (shown) in an offspring • Tries to PREVENT the expression of recessive gene What are some examples of alleles? (p. 221) Which alleles on page 221 are DOMINANT?

11 b. RECESSIVE: allele that will only be expressed if there are no dominant alleles present • Is prevented from showing up if there is a dominant allele present Which alleles on page 221 are recessive?

Dominant & Recessive § Example: § Eyecolor- Brown eyes are dominant and blue eyes are recessive. § A person can have a brown allele and a blue allele but still have brown eyes because the brown allele is dominant and hides the blue allele (it’s recessive).

Dominant & Recessive § Dominant alleles are represented with a capital letter. (Add this to Card #10) § Recessive alleles are represented with a lowercase letter. (Add this to Card #11) § R = Dominant § r = recessive § An organism is represented by two letters for each allele (or gene that comes from mom and dad)

Homozygous/Heterozygous (p. 230) 9 8 § Homozygous (purebred)-when a species has two identical (genes)alleles for a trait § Represented by the same 2 letters § Ex. BB (dominant) or bb (recessive) § Heterozygous (hybrid)-when a species has two different (genes) alleles for a trait § Represented by 2 different letters § Ex. Bb

Genotypes vs. Phenotypes (p. 230) 24 § Genotype- genes in an organism that are 25 § § § present Ex. Bb, bb or BB (Add to #24) Phenotype- an organism’s physical traits (or visible traits) Ex. Brown eyes, brown hair (Add to #25)

Law of Dominance 12 § This means if the two alleles are different, one usually wins out. § Think of sports. Dominance in sports means one team usually wins out.

Law of Independent Assortment 13 § § § Independent = by themselves Assortment = how things are sorted out This means if multiple traits get passed along, those alleles get sorted out each by themselves. § For example, getting one allele for one trait doesn’t mean you can only get a certain allele for another trait.

Law of Segregation 14 § Segregation means separating. § When reproductive cells are made, all the pairs of alleles separate. Each gamete contains 1 allele for each trait.

MUTATION § Change in a gene’s information (like a change in instructions)

Mutations can be: § HELPFUL § HARMFUL Examples include: Down’s syndrome, color blindness, albinism, sickle cell anemia § NEUTRAL

15 PUNNET SQUARE § A mathematical model used to predict the chances that offspring will inherit genes from their parents

SAMPLE PUNNET SQUARE

Practice problem #1 § Predict the genotypes for the fur color of the offspring of a brown, heterozygous hamster and a white homozygous hamster. Brown is dominant and white is recessive.

Problem #2 § Predict the gentoypes of the offspring of 2 white homozygous cows. Black is dominant over white.

#2

Problem #3 § Predict the genotypes of the offspring of 2 gray heterozygous rats. Gray is dominant over white, which is recessive.

#3

Practice problem #4 § What are the chances of having a girl or a boy baby? § How would you make a Punnett Square to show it?

#4

Pedigree Charts 7 § Pedigree: a chart of the genetic history of a family over several generations § They are used to find out the probability of a child having a disorder or a certain trait in a family.

Symbols on a Pedigree Female: Male:

Connecting Pedigree Symbols: § Examples of connected symbols: § Married couple § Children §

More symbols in a Ped. Chart:

Example of a ped. Chart: § What does a pedigree chart look like?

Interpreting a Ped. Chart: § 1. Determine if the pedigree chart shows an autosomal or X-linked disease/disorder. § If one sex in the pedigree is affected, it is X-linked. § It is a 50/50 ration between sexes, the disorder/disease is autosomal. Autosomal doesn’t affect just one sex.

Is it autosomal or Xlinked?

§ Autosomal…why? ?

Interpreting Ped. Chart cont. § 2. Determine whether the disorder is dominant or recessive. § If it is dominant, one of the parents must have the disorder/trait/disease. § It is is recessive, neither parent has to have the trait/disorder because they can be heterozygous (Bb).

Dominant or Recessive?

§ Dominant…. why? ?

Dominant or Recessive? ? ?

§ Recessive…. . why? ? ?

§ You are researching the inheritance of a red colored tongue in a lizard…. § Is it autosomal or X-linked? § Is it dominant or recessive?