DNA MUTATIONS & GENETICS

LEWIS BIOLOGY 2013

CONCEPTS COVERED THIS UNITMutations (Point and Frame-shift)

Diseases caused by Mutations

Sickle Cell Anemia and Point Mutations

Genetics and Heredity

Gregor Mendel and the Pea Plants

Monohybrid Crossing

Alleles

Mendelian Genetics

Non-Mendelian Genetics

Dominance vs. Recessive

Co-Dominance

Incomplete Dominance

Multiple Alleles & Blood Typing

Sex-Linked Traits

Pedigree Analysis

Chapters 10 & 12-13 are a good resource to use for this unit! Please read ahead

TERMS YOU WILL ENCOUNTER THIS UNIT (CHAPTERS 10 AND 12 IN BLUE BOOK; DO NOT USE INTERNET DEFINITIONS!)

Heredity

Trait

Genetics

Gamete

Fertilization

Zygote

Pollination

Hybrid

Allele

Dominant

Recessive

Phenotype

Genotype

HomozygousHeterozygousCrossing overDiploidHaploidEggHomologous chromosomesMeiosisNondisjunctionSpermSexual reproductionCarrierFetuspedigree

Co-dominanceIncomplete dominanceMultiple allelePolygenic inheritanceSex chromosomeSex linked traitKaryotype

DISEASES COVERED THIS UNIT

Please research (and TAKE NOTES) and read ahead about the following genetic disorders:

Symptoms, causes, treatment, etc..

1. Klinefelter’s Disease

2. Turner’s Syndrome

3. Cystic Fibrosis

4. Sickle Cell Anemia

5. Trisomy 21 (Down Syndrome)

6. Phenylkentonuria (PKU)

ENVIRONMENTAL OR GENETIC??

The following list contains diseases that are either caused by environmental factors (smoking, diet, etc.) or because of mutated genes that are passed along by parents. Determine if each disease is caused by an environmental factor or genetic factor (mutation)—or both

1. Skin cancer

2. Lung cancer

3. Diabetes

4. PKU

5. Heart Disease

THE EXAM FOR THIS UNIT

The exam for this unit will be held between April 29-30.

Most of the material will cover: DNA, RNA, Protein Synthesis and Genetics—although older material will be on the exam.

The midterm will be weighed twice (as two test grades)

Please study ahead of time as it is comprehensive and cumulative.

As a resource, utilize Chapters 10, 12, & 13 in the Blue Glencoe Textbook

DNA MUTATIONS

There are two general types of mutations

Point and Frame-Shift

Mutagen: something that causes a mutation

Point Mutations: a genetic mutation in which only one of the nitrogenous bases is substituted (changed) to another. Only one amino acid is changed

Frame-shift Mutations: a genetic mutation in which one of the bases is added or deleted. This causes the rest of the DNA sequence to shift, changing the ENTIRE DNA/AMINO ACID SEQUENCE. THIS IS THE MOST DANGEROUS MUTATION. Potentially lethal

EXAMPLES OF POINT MUTATION

Sickle cell anemia is caused by a point mutation.

A single base is changed, causing the disease to occur

(FYI, those who have sickle cell are resistant to Malaria)

Normal Hemoglobin (blood) GGG-CTT-CTT-TTT

Sickled Hemoglobin (blood) GGG-CAT-CTT-TTT

Only one(1) of the amino acids will change

EXAMPLES OF FRAME-SHIFT MUTATIONS

One of the bases in a DNA sequence is either inserted or deleted, therefore causing the entire sequence to shift.

This will change the entire DNA sequence, thusly changing the entire AMINO ACID SEQUENCE.

THIS CAN BE LETHAL

NORMAL SEQUENCE: ATC – GAT – TTA – AAG

THE A WILL BE DELETED, AND THE REST OF THE BASES WILL SHIFT TO FILL ITS PLACE

MUTATED SEQUENCE: ATC – GTT – TAA –AG…..

GENETICS & HEREDITYCHAPTERS 10 &12

FATHER OF GENETICS

Gregor Mendel is the father of genetics (hence the term Mendelian Genetics).

• Mendel was an Austrian monk studied heredity (how traits are passed from parent to offspring)

• He was the first to be able to predict the outcome of one’s traits.

• This led to the field of genetics (branch of biology that studies heredity)

• He studied heredity using garden pea plants using the sex organs (yes, plants reproduce sexually..)

THE BIRDS & THE BEES…WELL JUST THE PLANTS

IN PLANT FERTILIZATION, THE MALE GAMETE UNITES WITH THE FEMALE GAMETE. THIS RESULTS IN A ZYGOTE

ZYGOTE

TERMS & ABBREVIATIONS

• Monohybrid cross: aka the ‘Punnett Square’, used to predict the traits of offspring

• P1: Parent generation (mom & dad)

• F1, F2, ..: Filial generations (the offspring, grandchildren etc.)

• Homozygous Dominant: AA

• Homozygous recessive: aa (this is the ONLY time recessive traits are shown)

• Heterozygous: Aa (the dominant trait is still expressed)

• Dominant: trait that is shown or expressed

• Recessive: trait that is hidden or disappears in the mating

• Alleles: forms of a gene

…MORE TERMS

Phenotype= the Physical appearance (color, size, shape, etc.)

Genotype = the gene or allele (Aa, AA, aa)

Example:

75% of the Offspring were Heterozygous Aa (genotype), meaning, they have Yellow eyes (phenotype)

25% of the offspring were Homozygous recessive aa (genotype), meaning they have white eyes (phenotype)

Joke: You’ve got some good jeans! Haha…Get it??

BASICS OF THE PUNNETT SQUARE: TRY THIS EXAMPLE

Alleles: Brown eyes: BB, Bb Blue Eyes: bb

Problem:Mom has blue eyes, and Dad is Heterozygous for Brown eyes.

Complete the Punnett Square and give the phenotype and genotype of the offspring

A a

a

a

BASICS OF THE PUNNETT SQUARE: ANSWER

Aa aa

Aa aa

Alleles: Brown eyes: BB, Bb Blue Eyes: bb

Problem:Mom has blue eyes, and Dad is Heterozygous for Brown eyes.

Complete the Punnett Square and give the phenotype and genotype of the offspring A a

a

a

Answer: Phenotype: 50% will have brown eyes50% will have blue eyes

Genotype: 50% Aa (heterozygous)50% (homozygous recessive)

ASSIGNMENT #2

Complete the Monohybrid Cross worksheet on my website. The worksheet has been upload, you may write your answers on your own paper OR print it at home!

Do not forget the rules of Mendelian Genetics!!!

If there is a capital letter (A, B, C…), this means the gene is dominant, and will mask (cover) the recessive gene (a, b, c)

MEIOSIS

HOW WE MAKE GAMETES (SPERM AND EGGS)

…NOT SEXUAL REPRODUCTION

REMEMBER…

We covered Meiosis when we talked about Mitosis.

Meiosis is a cell division of gametes…

In other words---it’s how guys make sperm, and ladies make eggs (ladies, you’re born with the eggs you have ) Guys continue Meiosis until they’re old…yuck

Meiosis is NOT SEXUAL REPRODUCTION

MEIOSISIn Meiosis, it’s a way of taking a person’s 46 chromosomes, and dividing them in half—so that parents only pass 23 chromosomes onto their offspring.

You’re the perfect blending of both of your parents.

46 chromosomes in dad’s sperm / 2 (meiosis) = 23 chromosomes

46 chromosomes in mom’s eggs / 2 (meiosis) = 23 chromosomes

23 chromosomes + 23 chromosomes = YOU

REVIEW: MITOSIS VS. MEIOSISMitosis Meiosis

Number of Divisions 1 2 (Meiosis I & Meiosis II)

Number of daughter cells 2 4

Purpose Making new body cells (liver, hair, skin, etc.)“somatic cells”

Making new sex cells “gametes” (sperm & eggs)

Chromosome # Diploid (2n) Haploid (n) -half

MEIOSIS VS MITOSIS

Organism Somatic cell (Mitosis)Diploid (2n)

Gamete (meiosis)Haploid (n)

Fruit fly 8 4

Garden pea 14 7

Corn 20 10

Tomato 24 12

Leopard frog 26 13

Apple 34 17

Human 46 23

Chimpanzee 48 24

Dog 78 39

Adder’s tongue fern 1260 630

EVENTS IN MEIOSISCrossing Over: Occurs in Prophase I, where the chromosomes break, and exchange genetic material

Nondisjunction: where the chromosomes fail to separate during Meiosis, this causes Trisomy 21 (Down Syndrome)

Crossing over

TO BE CONTINUED…NON-MENDELIAN GENETICS