chapter 6.3 -6.4 and chp. 7. what is genetics? genetics- the study of heredity heredity- the...

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Chapter 6.3 -6.4 and Chp. 7

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Gregor Mendel “Father of Genetics”  Australian monk that worked with pea plants to discover many details of genetics.  Mendel's Experiments  Mendel chose pea plants as his experimental subjects, mainly because they were easy to cross and showed a variety of contrasting traits (purple vs white flowers, tall vs short stems, round vs wrinkled seeds)  Pea plants usually self-pollinate- when pollen fertilizes the egg of the same plant  Mendel would cross pollinate pea plants which he used pollen from one plant to fertilize(pollinate) the egg of another pea plant.

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Page 1: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Chapter 6.3 -6.4 and Chp. 7

Page 2: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

What is genetics? Genetics- The study of heredity Heredity- the passing of traits from parents to

offspring. Traits- a specific characteristic Ex: eye color,

heightHow are DNA-Genes-Chromosomes related?•DNA – Deoxyribonucleic

acid- the genetic code of life •DNA wound tightly makes up a gene•Stacks of genes make up a chromosome•Gene-chemical factors that determine traits

gene

CHROMOSOME

Page 3: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Gregor Mendel “Father of Genetics” Australian monk that worked with pea

plants to discover many details of genetics. Mendel's Experiments Mendel chose pea plants as his

experimental subjects, mainly because they were easy to cross and showed a variety of contrasting traits (purple vs white flowers, tall vs short stems, round vs wrinkled seeds) Pea plants usually self-pollinate- when pollen

fertilizes the egg of the same plant Mendel would cross pollinate pea plants which

he used pollen from one plant to fertilize(pollinate) the egg of another pea plant.

Page 4: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Mendel chose true-breeding lines of each plant/trait he studied (true breeding lines always produced offspring of the same type)

He crossed a true breeding plant with a plant of the opposite trait (purple x white). He called this the Parental (P) generation.

He recorded data on the offspring of this cross (First Filial, F1)

He self pollinated the F1 offspring

He recorded data on the offspring of the second generation, calling it the Second Filial generation (F2)

Page 5: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Mendel’s Analysis of his Experiments The F1 generation always displayed one trait

(he later called this the dominant trait) The F1 generation must have within it the

trait from the original parents - the white trait The F2 generation displayed the hidden trait,

1/4 of the F2 generation had it (he later called this hidden trait the recessive trait)

Each individual has two "factors" that determine what external appearance the offspring will have. (We now call these factors genes or alleles)

Page 6: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Mendel established three principles (or Laws) from his research 1. The Principle of Dominance and

Recessiveness - one trait is masked or covered up by another trait

2. Principle of Segregation - the two factors (alleles) for a trait separate during gamete formation

3. Principle of Independent Assortment - factors of a trait separate independently of one another during gamete formation; another way to look at this is, whether a flower is purple has nothing to do with the length of the plants stems - each trait is independently inherited

Page 7: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Modern Genetics~ Punnett Squares There are 2 alleles(genes) that determine traits. Alleles are represented by letters. Ex: Bb,bb,BB Dominant allele- the stronger allele;

represented by a capital letter EX: Brown eyes =B Recessive allele- the weaker allele;

represented by a lower case letter Ex: Blues eyes=b

When a Dominant and recessive are paired, the Dominant allele will show in the appearance of the organism the recessive will not.

Example: Bb- the child will have Brown eyes

Page 8: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Genotype- genetic make up **when asked for the genotype give the

two alleles(letters) Ex: Bb or BB or bbPhenotype- physical characteristics

** When asked for the phenotype look at the alleles(letters) then give what the child would look like: Ex: Brown eye or Blue eyes

Homozygous (aka.Pure Bred)- having the same alleles for a trait Ex: BB or bb

Heterozygous (aka. Hybrid)- having different alleles for a trait. Ex: Bb

Page 9: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Bb

?

Mom’s alleles

B B

Father’s Alleles

bb

Problem: What are the combinations if the mother has BB and father has bb

•The top alleles drop down into the boxes & side alleles go in the boxes across.•Write the capital letter first.

Page 10: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Genetics and Probability

Probability- the likelihood that a particular event will take place.

Ex: when flipping a coin the likelihood that it will land on head is ½. If flipping twice the likely hood is 1/2X1/2=1/4

Each event is an independent event.

Page 11: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Probability of a Punnet Square It can be expressed as a fraction, percent or

ratio. Punnett Square that have 4 squares the

probability is out of 4. Ex: 1 out of 4 = ¼ or 25% ; 2 out of 4 = ½ or 50%

BB

b

b

Genotype: BB=25% or ¼ Bb=50% or 2/4 bb=25% or ¼

Ratio = 1:2:1 Phenotype:

Brown eyes =75% or ¾Blue eyes = 25% or ¼Ratio: 3:1

B=Brown eyesb = blue eyes

Page 12: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

T= Tongue rollert = Non tongue roller

Punnett Square practice problem: Fill in the square and give the probabilities in percent and the ratios

Genotypes:

Heterozygous:

Homozygous:

Phenotypes:

T tTt

This cross is a monohybrid cross= crosses 1 trait both parents are hybrids. The Ratio is always 1:2:1

Page 13: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

2 Factor CrossesThese two factors come from the 4 possible allele pairs of gametes according to the law of independent assortment

Ratio:

9:3:3:1

Mom=RrYyDAD=RrYy

Possible Gametes= RY, Ry, rY, ry

This is a Dihybrid cross- 2 traits are crossed at one time and both parents were hybrid for both traits.

Ratio is always 9:3:3:1

Page 14: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Incomplete Dominance Incomplete Dominance- When traits

are neither dominant nor recessive. Hybrids produce mixed traits Ex: Red flower x White flower produces

all pink flowers Codominance- When Both alleles

contribute to the phenotype. Example: instead of a mixture being produced both traits are produced Ex: Brown hair cow x White hair cow

produces cows that have both brown & white hairs .

Page 15: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-
Page 16: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Multiple Allele Traits Multiple Allele Traits- Traits that

are controlled by more than two alleles. Blood type in humans is controlled by three alleles: A, B, and O Phenotype Genotype

A AA or AO

B BB or BO

AB AB only

O OO only

Page 17: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Sample of Multiple Allele Crosses

Page 18: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Sex-linked traits Traits that are on one of the sex

chromosomes ( X or Y ) but not the other. Example: red/green color blindness

carried on the X chromosome If the trait is on the X chromosome

then it may be represented by Xc.

X Xc. = (Female)a carrier but not in the phenotype

Xc. Xc. = (Female)trait shows in phenotype

Xc. Y= (male) trait shows in phenotype

Page 19: Chapter 6.3 -6.4 and Chp. 7. What is genetics?  Genetics- The study of heredity  Heredity- the passing of traits from parents to offspring.  Traits-

Sex Linked Punnett Square

XhXh XhX

XhY XY

Xh

Xh

X

Y

h- represents balding