Genetic Variation and Mutation Test Review

SEX CHROMOSOMESXX---Female

XY---Male

Multiple Alleles

• Traits that have more than 2 phenotypes

• Example Blood Type

• A, B, O

• Sex-linked traits occur more often in males---ex hemophilia and colorblindness

• How to find a genetic disorder?• a. analysis of pedigree• Genetic counseling• Prenatal testing

• Pedigree Basics… Squares are males Circles are females….colored in shapes have trait….non---colored do not have trait

Crossing Over• When chromosomes exchange genetic

information that leads to more varations in the population

Gives most variation in a population…• Crossing over• Recombination of parents genes through---

Sexual reproduction (MEIOSIS)• Mutations

• Organisms with different traits that cross produce more variations in their offspring

• Populations with many different traits/variations have a better chance to survive---especial when the environment changes

• Mutations can lead to variations in a population because they change an organism’s PHENOTYPE

Mutations

• A mutation is ANY change in the DNA that causes a change in the phenotype or appearance

• They can be harmful, helpful or neutral

Nonsense Mutation

• When the nucleotide/base of DNA is changed and this causes the codon to be translated into a STOP codon instead of amino acid

• Creates a protein we cant use

Silent Mutation

• When a nucleotide/base is changed but is translated as the same amino acid….causeing no problems

• Missense Mutation• When a nucleotide/base is changed…causing

the codon to be translated into a DIFFERENT amino acid causing problems

Frame shift Mutations

• When you insert one or more nucleotides/bases into the DNA strand causing the codons and reading of those codons to shift

• Also can happen when one or more nucleotide/base is deleted….

Nondisjunction

• Failure of chromosomes to separate during Meiosis

• Causes Monosomy---one less chromosome in cell

• Causes Trisomy---one more chromosome in the cell

• Example Down Syndrome, Edward’s Syndrome and Klinefelter’s

• Body cell mutations:• Affect the person with it….such as mutated

skin cells…when they divide they pass on the mutation to that new skin cell.

• Cant be passed on because they do not affect the egg and sperm…AKA Gametes

• Germ cell mutations or mutations of the gametes…results in the offspring’s phenotype being changed.

Chromosomal Mutations

• Inversion----piece of chromosome breaks off and reattaches to the SAME in the reverse order

• Deletion---piece of chromosome breaks off and is gone

• Translocation---piece of chromosome breaks off and reattaches to the DIFFERENT in the reverse order

• OPEN ENDED QUESTIONS….Know them….

X-linked Cross• Normal Female----carrier• Normal Male• XN Xn• XN YResults: XN XN 50% females normal noncarriers

XN Xn 50% females normal carrier

Xn Y 50% All males with disorderXN Y 50% All males normal

• Sex-Linked Traits• Found on SEX CHROMOSOMES…usually X• Both sexes can have trait…males more likely• Hemophilia and Colorblindness• Sex Limited Traits• Found on Autosomes• Only 1 sex expresses the trait• Beard growth or Milk Production• Sex-Influenced Traits• Found on Autosomes• Both sexes……• Baldness

THIS IS THE CHART

• STUDY Nondisjunction Notes….

• GET OUT YOUR NOTES AND LOOK AT THESE PICTURES

• KARYOTYPE Pictures for • Monosomy, Trisomy and DIPLOID