genetics & heredity...same traits. alleles can be heterozygous; having different traits....

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11/16/2017 1 Genetics & Heredity Biology I Turner College & Career High School 2017 Fertilization is the fusion of an egg and a sperm. Purebred (True breeding plants) are plants that were allowed to self- pollinate and the offspring will be exactly like the parent.

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Page 1: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Genetics & Heredity

Biology ITurner College & Career High School 2017

Fertilization is the fusion of an egg and a sperm.

Purebred (True breeding plants) are plants that were allowed to self-pollinate and the offspring will be exactly like the parent.

Page 2: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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The Work of Gregor Mendel

Austrian monk

Born in 1822.

Studied heredity.

Heredity: the passing on of characteristicsfrom parents to offspring.

Characteristics that are inherited are called traits.

First person to successfully predict how traits are transferred from generation to generation.

Used garden peas in his experiments.

The Father of Genetics

Mendel’s Work

Mendel carried out his work with garden peas.

Page 3: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Mendel’s Observations

Mendel noticed differences in:

Flower color

Flower position

Seed color

Seed shape

Pea pod shape

Pea pod color

Stem height

This led him to further experiment on the plants.

Why pea plants?

Reproduce sexually, which means that they produce male and female sex cells, called gametes.

In a process called fertilization, the male gamete unites with the female gamete.

The resulting fertilized cell, called a zygote, then develops into a seed.

Page 4: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Mendel’s Experiment

He took pollen from a male plant and dusted it onto a female plant.

Parental generation (p) = the original pair of plants

Female part

Transfer pollen

Pollen grains

Maleparts

Cross-Pollination

Offspring

(F1) = first filial generation

(F2) = second filial generation

His first experiments are called monohybrid crosses because they only deal with ONE single trait (height, color)

mono means “one”

Page 5: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Mendel’s Experiments

Purebred: offspring where all previous generations have the same trait. Ex: a purebred short plant came from short parent plants.

First, he crossed a purebred purple with a purebred white.

Result of F1 Generation: all plants had purple flowers.

Parent Plants

F1 Generation

Mendel’s 2nd Experiment

Crossed two of the purple offspring from the F1 generation.

The F2 generation resulted in some offspring having purple flowers and others having white flowers

Parent Plants

F1 Generation

F2 Generation

Page 6: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Conclusions

Each organism has two factors that control each of its traits.

These factors are genes and that they are located on chromosomes.

Genes exist in different forms called alleles.

The principal of dominancestates that some alleles are dominant and others are recessive.

Tall pea plant

Short pea plant Tall pea plant

All Tall pea plants

3 tall: 1 short

P1

F1

F2

Mendel called the observed trait dominantand the trait that disappeared recessive.

Mendel concluded that the allele for tall plants is dominant to the allele for short plants.

Tall pea plant Short pea plant

All tall plants

F1

T T t t

T t

T t

P1

Page 7: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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F1

T tT T

3

Tall Tall Short

1

Tall

F2

Law of Segregation

The way an organism looks and behaves is called its phenotype. Ex. Tall, yellow

The allele combination an organism contains is known as its genotype. Ex. TT, Tt

An organism’s genotype can’t always be determined by its phenotype.

Tt x Tt Cross

T t t t

Tall Tall

T t T t

An organism is homozygous for a trait if its two alleles for the trait are the same. (True-breeding)

Exp. TT or tt

An organism is heterozygous for a trait if its two alleles for the trait differ from each other. (Hybrid)

Exp. Tt

Page 8: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Segregation Summary

Each trait has two genes, one from the mother and one from the father.

Traits can be either dominant or recessive.

A dominant trait only needs one gene in order to be expressed.

A recessive trait needs two genes in order to be expressed.

Egg and sperm are sex cells called gametes.

Segregation is the separation of alleles during gamete formation.

Genetics & Probability

Probability = the likelihood that a particular event will occur

Ex. Coin flipping: 1/2 probability that coin will flip head/tail

If you flip the coin 3 times what's the probability of flipping 3 heads?

1/2 x 1/2 x 1/2 = 1/8

*Past outcomes do not affect future ones!!*

The principles of probability can be used to predict the outcomes of genetic crosses.

What is the probability of parents having two male offspring in a row? (1/2 x 1/2=1/4)

Page 9: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Genetics & Probability

The likelihood that a particular event will occur is called probability.

Each trait has two genes, one from the mother and one from the father.

Alleles can be homozygous; having the same traits.

Alleles can be heterozygous;having different traits.

Question 1

The passing on of characteristics from parents to offspring is __________.

D. allelic frequency

C. pollination

B. heredity

A. genetics

The answer is B.Genetics is the branch of biology that studies heredity.

Page 10: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Question 2

What are traits?

Answer

Traits are characteristics that are inherited. Height, hair color and eye color are examples of traits in humans.

Question 3

Gametes are __________.

D. fertilized cells that develop into adult organisms

C. both male and female sex cells

B. female sex cells

A. male sex cells

The answer is C.

Organisms that reproduce sexually produce male and female sex cells, called gametes.

Page 11: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Question 4

Which of the following genotypes represents a animal that is homozygous dominant for a trait?

a. KK

b. Kk

c. kk

Question 5

Which of the following genotypes represents a plant that is homozygous recessive for height?

c. tt

b. Tt

a. TT

Page 12: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Punnett Squares

The gene combination that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square.

These are used to predict and compare the genetic variations that will result from a cross.

The types of gametes go on the top and left sides of the square.

The possible gene combinations appear in the four boxes.

Punnett Squares

If you know the genotypes of the parents, you can use a Punnett square to predict the possible

genotypes of their offspring.

Page 13: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Making a Punnett Square

You try this one…

A A

A

a

A A

A

a

AA AA

Aa Aa

Possible Children: ½ (50%) AA = trait A purebred

½ (50%) Aa = trait A hybrid

100% will show the trait

Page 14: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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More Practice

For a gene determining hair color (B); where both parents are heterozygous for blue hair.

B = dominant allele; blue hair

b = recessive allele; yellow hair

B b

B

b

Parent 1 = Bb

Parent 2 = Bb Possible Children

Possible Children: ½ (50%) Bb = blue hair

¼ (25%) BB = blue hair

¼ (25%) bb = yellow hair

BB Bb

Bb bb

More Practice

Smooth (N) Constricted (n)

Yellow (g) Green (G)

Axial (A) Terminal (a)

Tall (T) Short (t)

Round (R) Wrinkled (r)

Yellow (g) Green (G)

Purple (A) White (a)

Seed Shape

Seed Color

Flower Color

Pod Shape

Pod Color

FlowerPosition

Stem Height

Page 15: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Exploring Mendelian Genetics

Independent Assortment

1. Genes segregate independently.

2. The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.

3. Independent assortment helps account for the many genetic variations observed in plants, animals and other organisms.

Page 16: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Summary of Mendel’s Principals

Genes are passed from parent to offspring.

Some forms of a gene may be dominant and others recessive.

In most sexually producing organisms, each adult has two copies of each gene: one from each parent. These genes are segregated from each other when gametes are formed.

The alleles for different genes usually segregate independently of one another.

Beyond Mendel:Dominant & Recessive Alleles

Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.

Cases in which one allele is not completely dominant over another are called incomplete dominance.

Example: White (W) and Red (R) are both dominant in a flower. If WW x RR the F1

generation would be WR = pink.

Page 17: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Incomplete Dominance

Incomplete: Think PINK!

RR x WW

RW x RW

RR : RW : WW

Co-dominance

Codominance is when both alleles contribute equally to the phenotype.

Examples: Feathers, flowers, cattle.

Page 18: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Polygenic Inheritance

Polygenic inheritance the kind of inheritance in which the trait is produced from the cumulative effects of many genes.

In humans, height, weight, and skin and eye color are examples of polygenic inheritance

MEIOSISA type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Page 19: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Review:

Characteristics of Living Things

Living things are made up of cells.

Unicellular: one celled organisms.

Multicellular: manycelled organisms.

Living things reproduce to make offspring of the same species.

Sexual reproductionAsexual reproduction

Review:

Characteristics of Living Things

Page 20: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Living things grow and develop

Review:

Characteristics of Living Things

1. What type of cell division is the diagram above?

2. What phase of cell division the arrow pointing to?

Page 21: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Meiosis is

Reduction Division

Chromosome number is cut in half by separation of homologous chromosomes in diploid cells

Meiosis

Every individual has two sets of chromosomes.

One from the mother; one from the father.

When the chromosomes pair up for the same trait they are called homologous chromosomes.

A cell that contains pairs of homologous chromosomes is said to be diploid or 2n.

Gametes (egg /sperm) have only one chromosome

and are said to be haploid or n.

Page 22: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Chromosome Numberin Body Cells vs. Gametes

Gametes

Haploid (n) - have 1 set

Body Cells

Diploid (2n) - have 2 sets

Phases of Meiosis

Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.

Meiosis I: The homologous chromosomes line up but, then they crossover, exchanging genetic information.

Meiosis II: The two cells produced now enter a second division.

Start with 2 the two new cells and get 4 differentcells each with 23 chromosomes.

Page 23: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Variation

During normal cell growth, mitosis produces daughter cells identical to parent cell (2n to 2n)

Meiosis results in genetic variation by shuffling of maternal and paternal chromosomes and crossing over.

No daughter cells formed during meiosis are genetically identical to either mother or father

During sexual reproduction, fusion of the unique haploid gametes produces truly unique offspring.

Crossing Over: Meiosis I

Chiasmata: site of crossing over, occur in synapsis. Exchange of genetic material between non-sister chromatids.

Crossing over produces recombinantchromosomes.

Results in variations in daughter cells.

Page 24: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Crossing Over

Meiosis I Meiosis II

Results of Meiosis

Spermatogenesis: the process in which spermatozoa are produced from male germ cells by way of meiosis.

Oogenesis: the production of an egg cell (ovum).

Results: 4 viable haploid (n) sperm and 1 viable haploid (n) egg.

All gametes are genetically different.

Page 25: Genetics & Heredity...same traits. Alleles can be heterozygous; having different traits. Question 1 The passing on of characteristics from parents to offspring is _____. D. allelic

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Results in 4 haploid (n) cells.

Differs in male and female.

Genetically different from each other & the original cell.

Summary of Meiosis II

Human Cells 2n=46.

Sperm Cell

23 chromosomes

Gamete is haploid (n)

Egg Cell

23 chromosomes

Gamete is haploid (n)

White Blood Cell

46 chromosomes

Body cell is diploid (2n)