Bell Ringer 32211 Take note packet and worksheet

Bell Ringer 3/22/11 Take note packet and worksheet from front table Turn in HW and permission slips/$ Respond to the following: § Which is more detrimental (harmful), a frameshift mutation or a point mutation and why? § What is a mutagen? Give one example.

MUTATIONS & HUMAN GENETICS Chapter 11. 3, Chapter 12

Mutations (11. 3) § Mutation = change in DNA sequence § Mutations can be caused by errors in replication, transcription, translation, cell division, or external agents § Mutations in reproductive cells can affect potential offspring (ex: inheritable genetic disorders) § Mutations in body cells do not get passed onto offspring (ex: if an individual develops skin cancer)

Types of Mutations § Point Mutations = a change in a single DNA base pair § Frameshift Mutations = a single base is added or deleted from DNA

What do the terms “missense” and nonsense” mean? What do you notice about the amino acid each codes for?

§ Chromosomal Mutations = missing or extra pieces of chromosomes, switched pieces, extra chromosomes § occurs frequently in plants, “super sized strawberries” § Few C. M. ’s get passed onto offspring because the zygote dies or the mature offspring cannot reproduce

For each #, what is different between the chromosome on the left to the on the right?

§ Mutation of genetic material will affect the proteins produced

Polyploidy in strawberries Wild type Commercially propagated varieties Each cell is 1 n Each cell is 8 n 8 copies of each chromosome!

Polyploidy in Dianthus

Cause & Repair § Some mutations are spontaneous § Mutagen = any agent that causes DNA change (ex: harmful chemicals, radiation) § Cells have repair mechanisms and special enzymes that can fix incorrect DNA

Prepare for notes: To start, answer the following ? s in your notes: Here is the original sentence: THE CAT ATE THE RAT For all questions below, show the words in the sentence are affected. 1. A ‘C’ is added after the 1 st C above. THE CCA TAT ETH ERA T 2. An ‘R’ is added after the 1 st R above. THE CAT ATE THE RRA T 3. The first ‘A’ is changed to an ‘S’. THE CST ATE THE RAT 4. The first ‘R’ is changed to an ‘L’. THE CAT ATE THE LAT 5. Of the 4 changes above, which was more detrimental to the overall meaning of the sentence?

DNA repair § “Proofreading” is performed by enzymes like DNA ligase. § Such repair mechanisms work very efficiently, although they are not perfect. § Thus, it is still best to avoid situations that would expose us to mutagens.

HUMAN TRAITS Chapter 12, Section 1

Pedigree § Pedigree = map of inheritance of genetic traits Copy this down! from generation to generation Married Offspring Female Does NOT have trait Male Has trait Shading does NOT show dominant or recessive! ONLY the presence of the trait!

Karyotype § Chromosomes come in pairs, inherited from parents § Karyotype = a chart of chromosome pairs, can be used to visualize chromosomal abnormalities § Chromosomes are organized by size and centromere location § Humans have 23 pairs of chromosomes, 46 total chromosomes

§ Autosomes = any chromosome that isn’t a sex chromosome § In humans – Chromosome pairs 1 -22 § Sex Chromosome = genes that determine an individual’s gender (X and Y) § In humans – Chromosome pair 23 § XX = female § XY = male § Sex chromosomes are the last pair on the karyotype

Genetic counseling § Pedigree can help us understand the past & predict the future § Thousands of genetic disorders are inherited as simple recessive traits § from benign conditions to deadly diseases § albinism § cystic fibrosis § Tay sachs § sickle cell anemia § PKU

Genetic testing sequence individual genes

Recessive diseases § The diseases are recessive because the allele codes for either a malfunctioning protein or no protein at all § Heterozygotes (Aa) § carriers § have a normal phenotype because one “normal” allele (the dominant one) produces enough of the required protein

Heterozygote crosses § Heterozygotes as carriers of recessive alleles Aa x Aa female / eggs male / sperm A a AA AA Aa Aa A Aa a carrier Aa Aa aa carrier disease A Aa a

Cystic fibrosis (recessive) § Primarily whites of European descent § strikes 1 in 2500 births § 1 in 25 whites is a carrier (Aa) § normal allele codes for a membrane protein that transports Cl- across cell membrane § defective or absent channels limit transport of Cl- & H 2 O across cell membrane § thicker & stickier mucus coats around cells § mucus build-up in the pancreas, lungs, digestive tract & causes bacterial infections § without treatment children die before 5; with treatment can live past their late 20 s

Tay-Sachs (recessive) § Primarily Jews of eastern European (Ashkenazi) descent & Cajuns (Louisiana) § strikes 1 in 3600 births § 100 times greater than incidence among non-Jews § non-functional enzyme fails to breakdown lipids in brain cells § fats collect in cells destroying their function § symptoms begin few months after birth § seizures, blindness & degeneration of muscle & mental performance § child usually dies before 5 yo

Sickle cell anemia (recessive) § Primarily Africans § strikes 1 out of 400 African Americans § high frequency § caused by substitution of a single amino acid in hemoglobin § when oxygen levels are low, sickle-cell hemoglobin crystallizes into long rods § deforms red blood cells into sickle shape § sickling creates pleiotropic effects = cascade of other symptoms

Dominant Heredity § Caused by dominant allele (A) § Freckles, Widow’s peak, Hitchhickers thumb, Huntington’s disease (brain degeneration, doesn’t appear until later in age), immunity to poison ivy § Individual will display the dominant phenotype if its genotype is heterozygous or homozygous dominant (Aa or AA) http: //www. zerobio. com/drag_gr 11/pedigree_overview. htm

Huntington’s chorea (dominant) § Dominant inheritance 1872 § repeated mutation on end of chromosome 4 Testing… Would you want to know? § mutation = CAG repeats § glutamine amino acid repeats in protein § one of 1 st genes to be identified § build up of “huntingtin” protein in brain causing cell death § memory loss § muscle tremors, jerky movements § “chorea” § starts at age 30 -50 § early death § 10 -20 years after start

Genetics & culture § Why do all cultures have a taboo against incest? § laws or cultural taboos forbidding marriages between close relatives are fairly universal § Fairly unlikely that 2 unrelated carriers of same rare harmful recessive allele will meet & mate § but matings between close relatives increase risk § “consanguineous” (same blood) matings § individuals who share a recent common ancestor are more likely to carry same recessive alleles

When Heredity Follows Different Rules Chapter 12, Section 2

Incomplete Dominance § Complete Dominance = one allele completely dominates over another § Incomplete Dominance = phenotype of a heterozygote is in between the dominant & recessive phenotypes, appearance of a third phenotype § Think painting! (YY=yellow and yy=blue, what would Yy=?

RR rr Rr Rr RR Rr Rr rr

Codominance § Both alleles for a gene are expressed in a heterozygous individual § Neither allele is dominant or recessive § Ex: Blood type (A, B, AB, O)

Sex Determination & Sexlinked Inheritance § The 23 rd pair of chromosomes determines an individuals sex § Males XY, X from mom & Y from dad § Females XX, both mom & dad give an X § Sex-linked Traits = traits controlled by genes on sex chromosomes

Sample test for color blindness § Write down A-D and what you see appear in each circle.

4 Sex-Linked Traits: § Normal Color Vision: A: 29, B: 45, C: --, D: 26 § Red-Green Color. Blind: A: 70, B: -, C: 5, D: § Red Color-blind: A: 70, B: -, C: 5, D: 6 § Green Color-Blind: A: 70, B: --, C: 5, D: 2

§ § Red-Green colorblindness Hemophilia (blood doesn’t clot properly) Male Pattern Baldness Duchenne Muscular Distrophy (muscular degeneration leading to eventual paralysis)

§ Majority of sex-linked traits are found on the X-chromosome § Why do you think this might be? ? § Look back in your notes to the karyotype that was for the male. § X-linked traits display more in males (1 copy of X chrom. ) § XRY or Xr. Y in males § XRXR or XRXr or Xr. Xr

Polygenic Inheritance § Characteristics that are influenced by several genes § The picture to the right shows 3 genes affecting skin pigmentation

What connection can you make to latitude and skin pigmentation?