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)

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

GENE 4 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 3 10 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 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 8

Genotypes vs. Phenotypes (p. 230) 24 Genotype- genes in an organism that are 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) 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.

14 Law of Segregation 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

PUNNET SQUARE 15 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 the disorder/disease is autosomal. Autosomal doesn’t affect just one sex.

Is it autosomal or X-linked?

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?