BASIC GENETIC PRINCIPLESCharacteristics of Living ThingsFactors that Influence IndividualityMendel and the Science of Genetics

Characteristics of Living Things

1. Species Characteristics – traits that are common to a particular speciese.g., characteristics of human race

2. Individual Characteristics – characteristics that make one individual member of a species different from anothere.g., sex, skin color, hair color, shape of eyebrows, structure of earlobes, presence of dimples, etc.

Factors that Influence Individuality

1. Heredity – transmission of genetic materials, or characteristics, from parents to offspring

2. Environment – contributes to an organism’s nature

Gregor Mendel and the Science of Genetics

Genetics• Deals with heredity and the

factors affecting transmission of characteristics from one generation to another

• Attempts to describe the similarities and differences among organisms (variation)

• Explains the characteristics transmitted from one parent generation to the next generation of offspring

Gregor Mendel

• An Austrian monk

• Experimented on heredity with garden peas

• Father of genetics

Why did Mendel choose pea plants?

1. They grow quickly.2. They reproduce by self-pollination.3. They also possess characteristics that can

easily be recognized like height, color of flowers, and shapes of seeds.

4. Pollination could be controlled in this group of plants with minimum work.

5. Garden peas could also produce enough offspring to conduct a study.

Pea Plant Experiment

Pea Plant Experiment

Results

Results

Mendel’s Principles

1. Independent Assortment- Traits are inherited independently of one another.

2. Dominance

- When pure parents with opposite traits are mated, the first generation shows only one trait (dominant). The other trait (recessive) is hidden.

3. Segregation- When hybrids are crossed, the opposite traits are separated into different offspring in a ratio of ¾ dominant and ¼ recessive.

Fundamentals of Genetics

1. Allele- different copies or forms of a gene controlling a certain traite.g., tallness (T) and shortness (t)

2. Homozygous / Pure- same alleles (e.g. TT and tt)

3. Heterozygous / Hybrid- different alleles (e.g., Tt)

Homozygous vs. Heterozygous

Genotypes and Phenotypes

1. Genotype- genetic makeup or the combination of genes of an organisme.g., TT – homozygous or pure tall, Tt – heterozygous or hybrid tall, and tt – short

2. Phenotype- physical trait of an organism as shown externally in its appearancee.g., tall and short

Genotypes and Phenotypes

Seat Work

Directions: Indicate if the following gene pairs are homozygous or heterozygous.

1. AA2. Rr3. aaBB4. MmNN5. PpQq

Seat WorkDirections: Write True if the statement is correct. Otherwise, change the underlined phrase/s to make the statement true.

1. Variation deals with the similarities among organisms.

2. Being four-legged is one of the individual characteristics of dogs.

3. Pure tall (TT) and hybrid tall (Tt) have different phenotypes.

4. Recessive traits are written in lower-cased form.

5. Differences that may occur between identical twins is influenced by heredity.

In a nut shell…

• Genetics is the study of ________ (similarities) and ________ (differences).

• Species characteristics differ from individual characteristics in the sense that _________.

• The three principles formulated by Mendel are _________.

• Homozygous differs from heterozygous in the sense that _________.

• Genotype differs from phenotype in the sense that ________.

Application of Mendelian Laws

Traits No. of People PercentageBlack Hair 20Brown Hair 32

TOTAL

What is more dominant? By how many percent?

Traits No. of People PercentageTongue Rollers 25

Non-Rollers 33TOTAL

Application of Mendelian Laws

Traits No. of People PercentageBlack Hair 20 38 %Brown Hair 32 62 %

TOTAL 52 100 %

What is more dominant? By how many percent?

Traits No. of People PercentageTongue Rollers 25 43 %

Non-Rollers 33 57 %TOTAL 58 100 %

Try some more…

What is more recessive? By how many percent?

Traits Clement

Stephen

Polycarp

Total Percentage

Dark 22 30 27Light 28 25 23

TOTAL

Traits Clement

Stephen

Polycarp

Total Percentage

Tall 18 28 25Short 32 22 25TOTAL

Try some more…

What is more recessive? By how many percent?

Traits Clement

Stephen

Polycarp

Total Percentage

Dark 22 30 27 79 51 %Light 28 25 23 76 49 %

TOTAL 50 55 50 155 100 %

Traits Clement

Stephen

Polycarp

Total Percentage

Tall 18 28 25 71 47 %Short 32 22 25 79 53 %TOTAL 50 50 50 150 100 %

Seat Work

What is more dominant? By how many percent?

Traits Blase Philomena

Justin Total Percentage

Tall 16 11 18Short 24 39 22TOTAL

Traits Blase Philomena

Justin Total Percentage

Curly 11 22 22Straight 18 16 33TOTAL

Seat Work

What is more dominant? By how many percent?

Traits Blase Philomena

Justin Total Percentage

Tall 16 11 18 45 35 %Short 24 39 22 85 65 %TOTAL 40 50 40 130 100 %

Traits Blase Philomena

Justin Total Percentage

Curly 11 22 22 55 45 %Straight 18 16 33 67 55 %TOTAL 29 38 55 122 100 %

Application of Mendelian Laws

Suppose Grace Lee, a chinky-eyed woman married President Noynoy Aquino, a wide-eyed man, what type of eyes do you think will their offspring have?

Application of Mendelian Laws

Suppose Grace Lee, a chinky-eyed woman married President Noynoy Aquino, a wide-eyed man, and chinky eyes were known to be dominant, what type of eyes do you think will their offspring have?

Application of Mendelian Laws

Suppose Grace Lee, a HETEROZYGOUS chinky-eyed woman married President Noynoy Aquino, a HOMOZYGOUS wide-eyed man, and chinky eyes were known to be dominant what type of eyes do you think will their offspring have?

Let’s try some more…

Black is known to be dominant trait over Caucasian skin. If a homozygous Caucasian woman married a homozygous African-American man, what will be the skin color of their offspring?

Let’s try some more…Brown eye is dominant over green. Determine the chance of having a child with brown eyes if Gabriel has heterozygous brown eyes and his partner Patricia has homozygous green eyes.

Seat Work

1. Jerome is a homozygous fat man. Joanne is a heterozygous thin woman. If thinness is dominant, what will be the possible outcome of their offspring?

2. Brown complexion is dominant over white complexion. Lester has homozygous brown complexion while his partner Ericka has heterozygous brown complexion. Determine the genotype, phenotype, genotypic and phenotypic ratios of their children.

Seat Work

3. Dark complexion is dominant over white. Luis has a heterozygous dark complexion while Harriet has a homozygous white complexion. Determine the genotypes, phenotypes, genotypic and phenotypic ratios of their offspring.

4. Both Toshiro and Francesca have heterozygous chinky eyes. If having chinky eyes is dominant over having wide eyes, determine the percentages of having chinky eyes and wide eyes in their offspring.

Application of Mendelian Laws: Dihybrid Test Cross

Pocahontas is a homozygous copper-toned, black haired woman who married John Smith a homozygous white, blond-haired man. If copper-toned skin and blond hair are dominant traits, what will be the phenotype of their children?

More on Dihybrid Test CrossAladdin is a homozygous copper-toned, skinny guy. Jasmine on the other hand, is also copper-toned and skinny but heterozygous. If copper-toned skin and skinny are both dominant, what will be the phenotype of their children?

More on Dihybrid Test Cross

Mufasa is a homozygous red-maned, long-tailed lion. Sarabi is a homozygous pink-maned, short-tailed lioness. If pink mane and long tail are dominant, what is the possible genotype of Simba, their child?

Seat Work

Ariel is a homozygous red-haired, wide-eyed woman. Eric is a heterozygous dark-haired, wide-eyed man. If dark hair and wide eyes are both dominant, what will be the phenotype of their possible child?

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