It's All In The DNA

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Genetics is the study of heredity or the patterns of inheritance of specific traits, relating to genes and genetic information.

Heredity is the passing of genetic information (DNA) from parent to offspring during sexual reproduction. Each sex cell (egg or sperm) of the parent organism (plant or animal) contains one-half of the genetic information or chromosomes needed to create a new organism.

Chromosomes are structures found in the nucleus of a cell. Chromosomes contain strands of genetic information or DNA. DNA stands for deoxyribonucleic acid. DNA strands are coiled to form a double helix or spiral ladder shape. Segments of a DNA strand code for specific traits. These segments are called genes. Genes typically come in pairs. One gene from the pair is called an allele.

General Resources for Genetic Standards

Standard L.4A.1

Obtain and communicate information about the relationship between genes and chromosomes to construct explanations of their relationship to inherited characteristics.
What is a Chromosome?
What is DNA and How Does it Work?
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Tongue Tasting Trivia

1. There are 10,000+/- taste buds inside our mouths, including the roofs of our mouth.

2. In general, girls have more tastebuds than boys.

3. Taste is the weakest of the five senses.

4. Insects have the most highly developed sense of taste.

5. Some insects have taste organs on their feet, antennae, and mouth.

5. Fish can taste with their fins, tail, and mouth.

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The Sense of Taste, CNS

Human Chromosome Chart

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. Scientists order these chromosomes by size for ease of study.

The 23rd pair, the sex chromosomes, differ between males and females. Females have two copies of the X chromosome, while males have one X and one Y chromosome. Therefore, males determine the sex of the next generation. Can you calculate the probability for the sex of four children born to the same Dad and Mom?

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Standard 7.L.4A.2

Construct explanations for how genetic information is transferred from parent to offspring in organisms that reproduce sexually.
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Mendel Researched Heredity Using Pea Plants

  • Mendel planted seeds from purebred "parent" plants.
  • He observed how some traits where visible generation to generation.
  • He observed how some traits were not visible generation to generation.
  • Mendel kept very accurate records for hundreds of individual plants.
  • He used statistical analysis (MATH) to study the traits of different generations.
  • Through his findings, he proposed that the traits were passed by parents.
  • He said the traits that were visible generation to generation were dominant.
  • He said the traits that were less visible or rarely visible were recessive.

dominant - a trait that is expressed if present

recessive - a trait is that is expressed if there is not a dominant trait

Traits That Mendel Observed Generation to Generation


trait = seed color

variation = the seed color is either yellow or green

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Why Pea Plants?

  • easy to grow
  • grow quickly
  • can be cross pollinated
  • few traits
  • two variations for traits

Mendel Conducted Monohybrid Experiments.

  • one trait at a time was followed
  • data was recorded on the variations generation to generation
  • a total of seven traits were followed and recorded
  • the data showed that some trait variations were more likely to show up
  • some trait variations were hidden

The Data Results

  • He called the trait variations that showed up dominant
  • He called the trait variations that were hidden recessive
  • He proposed that traits were controlled by two alleles
  • One allele came from the father and one came from the mother
  • The trait variation were passed down randomly as alleles

Mendel's Research Results Showed The Following:

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How Geneticists Say It

Inherited alleles form the genotype.

A genotype can be homozygous or heterozygous.

Phenotype is the expression or what we "see" due to genotype combinations.

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the genetic makeup of an organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits.
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How Mendel's pea plants helped us understand genetics - Hortensia Jiménez Díaz

Labs: Extracting DNA

See Academic page for PDF notes from this lesson.
How to extract DNA from strawberries
Extract DNA from a banana!

Standard 7.L.4A.3

Develop and use models (Punnett squares) to describe and predict patterns of the inheritance of monohybrid crosses (single genetic traits) from parent to offspring (including dominant and recessive traits, incomplete dominance, and codominance).
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Gregor Mendel's Punnett Squares
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Complete Dominance

  • form of dominance in heterozygous condition wherein the allele that is regarded as dominant completely masks the effect of the allele that is recessive.

Incomplete Dominance

  • traits are simultaneously blended together resulting in a new phenotype
  • RW = a pink carnation is expressed or a new phenotype occurs
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  • both traits are independently expressed within one organism
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Multiple Alleles

  • Crossing Alleles for Blood Type Traits

1. Check out the Punnett Square below.

2. How's it different from the punnet squares we have been constructing?

3. Can you explain why it is different?

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  • one characteristic is controlled by two or more genes
  • the genes can be large in quantity (# or amount) but small in quality (effect or result)
  • human polygenic inheritance include height, skin color, eye color and weight.
  • polygenes offer a greater variety of trait expression for a characteristic
  • chart below is an example of polygenic inheritance for human height
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Sex-Linked Gene

  • a gene located on chromosome #23; X (female) or Y (male)
  • the sex chromosome #23 carries one allele from each gene
  • it is a gamete cell, or haploid, that is able to fuse with another cell to form life
  • gamete is a Greek term which means to marry

Below is a very short list of sex-linked diseases. There are many many more.

Why do you think there are lots of diseases that originate in the DNA of chromosomes?

  1. Color Blindness
  2. Sickle Cell Anemia
  3. Tay-Sachs
  4. Muscular Dystrophy
  5. Cystic Fibrosis

The pedigree chart below outlines how a sex-linked disease might be passed through generations. Study the key and then the chart, carefully.

When shapes are connected by a line = they reproduce a new generation


1. Use bullet points to explain the information that the chart demonstrates.

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Incomplete Dominance, Codominance, Polygenic Traits, and Epistasis!

Standard 7.L.4A.4

Use mathematical and computational thinking to predict the probability of phenotypes and genotypes based on patterns of inheritance.
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Standard 7.L.4A.5

Construct scientific arguments using evidence to support claims for how changes in genes (mutations) may have beneficial, harmful, or neutral effects on organisms.

Exploring Mutations

1. Mutations are alterations to a DNA sequence. If one thinks of the information in DNA as a series of sentences, mutations are errors in spelling the words that make up those sentences. Sometimes mutations are inconsequential, like a misspelled word whose meaning is still quite clear. At other times mutations have stronger ramifications, like a sentence whose meaning is completely changed. (By Aparna Vidyasagar, Live Science Contributor | January 13, 2016)

2. A mutation is a relatively permanent change in hereditary material.

3. Mutations are grouped into three types:

  • Single Gene Disorder - defect in one gene
  • Chromosome Disorder - number or structure of chromosome is changed
  • Multifactorial Disorder - multiple genes impacted by environment or lifestyle

4. Mutations orginate in two ways:

  • Gamate (germ) cell mutations are passed by sexual reproduction.
  • Body (somatic) cell mutations occur randomly in an organisms.
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Queen Victoria Hemophilia Pedigree

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Standard 7.L.4A.6

Construct scientific arguments using evidence to support claims concerning the advantages and disadvantages of the use of technology (such as selective breeding, genetic engineering, or biomedical research) in influencing the transfer of genetic information.

Technology & Genetics

With the advancement of technology scientists are able to explore the genetic make up of organisms through various types of research. This exploration has led to different methods of research and medical treatments. Some methods of research are controversial.

Biomedical Research

- broad area of scientific investigations of biological processes and causes for disease

- some investigations are controversial

- investigations can include but are not limited to:

selective breeding - ancient practice of controlling reproduction externally

human genome project - international project which mapped human DNA

cloning - producing identical populations by extracting one parent's DNA to reproduce

stem cell research - using embryonic cells or adult stem cells to create specific cell types

genetic engineering -manipulating the DNA of an organism with own or another's DNA

gene therapy - genes are introduced into the body to treat disease

Selective Breeding

process by which humans use animal breeding and plant breeding

to selectively develop particular phenotype traits (characteristics)

by choosing which will reproduce and have offspring.

What is Selective Breeding


Modern day strawberries are the result of selective breeding which started around 1714 when a French naval officer found a large flowering strawberry plant in Chile. Strawberries were then sent to a French horticultural center where, by chance, the Chilean strawberry crossed with a North American species. The result was the development of the pineapple strawberry from which modern, large-fruited strawberries can be traced.
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1.Gene therapy is a rapidly growing field of medicine.

2.Genes are introduced into the body to treat diseases.

3.A healthy gene is introduced to the body with the hope of supplanting the diseased gene.

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Genetic Engineering


-the manipulation of DNA in order to produce new types of organisms;

-usually by inserting or deleting genes;

1982 - 1st transgenic animal (mice)

1990 - 1st transgenic plant (maize, wheat)

1993 - regulations put on genetically engineered organisms, or gmo

1994 - gmo tomato sold in USA

2004 - 8.25 million farmers in 17 countries were growing gmo crops


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