Heredity

Heredity

Standard

• SC.7.L.16.1 : Understand and

explain that every organism
requires a set of instructions
that specifies its traits, that this
hereditary information (DNA)
contains genes located in the
chromosomes of each cell, and
that heredity is the passage of
these instructions from one
generation to another.

Essential and Guiding Questions

Essential Question

• How are traits inherited?

Guiding Questions

• What is heredity?

• What did Gregor Mendel discover about heredity?

• How are traits inherited?

• What are the exceptions of complete dominance?

Learning Goals

I can summarize Mendel’s findings.

Summarize

I can explain how dominant and recessive traits differ.

Explain

I can describe DNA’s role in determining traits

Describe

I can identify the relationship between genes and alleles

Identify

I can identify the relationship between genotype and phenotype

Identify

I can describe the relationship among genes ,traits, and characteristics

Describe

I can discuss complete and incomplete dominance and codominance.

Discuss

I can distinguish between inherited and acquired characteristics.

Distinguish

I can provide examples of environmental factors that may affect phenotype.

Provide

Lesson Vocabulary

• heredity: the passing of genetic material from parent to offspring

• gene: one set of instructions for an inherited trait

• allele: one of the alternative forms of a gene or characteristic, such as hair color

• genotype: the entire genetic makeup of an organism: also the combination of genes for one or more specific traits

• phenotype: an organism's appearance or other detectable characteristic

Multiple Choice

The passing of genetic material from parent to offspring is

• gene

• heredity

• dominant

• recessive

Multiple Choice

• An organism's appearance or other detectable characteristic is _________.

• genotype

• recessive

• dominant

• phenotype

Multiple Choice

• One set of instructions for an inherited trait is ________.

• genotype

• Allele

• gene

• recessive

Multiple Choice

• The entire genetic makeup of an organism: also the combination of genes for one or more specific traits is ________.

• genotype

• gene

• phenotype

• allele

Multiple Choice

• One of the alternative forms of a gene or characteristic, such as hair color

• genotype

• heredity

• gene

• allele

Lesson Vocabulary

• dominant: describes the allele that is fully expressed when carried by only one of a pair of homologous chromosomes

• recessive: in genetics, describes an allele that is expressed only when no dominant allele is present in an individual

• incomplete dominance: a condition in which two alleles are expressed such that the phenotype of a heterozygous individual is an intermediate of the phenotypes of the two homozygous parents.

• codominance: a condition in which two alleles are expressed such that the phenotype of a heterozygous individual is a combination of the phenotypes of the two homozygous parents

Dropdown

​

Select answer

: describes the allele that is fully expressed when carried by only one of a pair of homologous chromosomes

​

Select answer

: in genetics, describes an allele that is expressed only when no dominant allele is present in an individual

​

Select answer

: a condition in which two alleles are expressed such that the phenotype of a heterozygous individual is an intermediate of the phenotypes of the two homozygous parents.

​

Select answer

: a condition in which two alleles are expressed such that the phenotype of a heterozygous individual is a combination of the phenotypes of the two homozygous parents

What is heredity?

• The passing of genetic material

from parent to offspring is called
heredity.

• Imagine a kitten, the kitten

has blue eyes like its mother
and orange fur like its
father.

• How did the kitten get these

traits?

• These traits are a result of

information stored in the
kitten’s genetic material.

Dropdown

The passing of genetic material from parent to offspring is called ​

Select answer

.

What did Gregor
Mendel discover
about heredity?

•A monk named Gregor Mendel performed the first major
experiments investigating heredity.

•Mendel lived in Austria during the 1800s and studied science
and mathematics before becoming a monk.

•He began studying the inheritance of traits among pea plants
in the monastery’s garden.

•He studied seven different characteristics of pea plants:
flower color, pod color, pod shape, seed color, seed shape, as
well as, flower and pod position.

•A characteristic is a feature that has different forms in a
population.

•Mendel studied each characteristic separately, always
starting with plants that were true-breeding for that
characteristic.

•A true-breeding plant is one that will always produce
offspring with a certain trait when allowed to self-pollinate.

•Each of the characteristics that Mendel studied had two
different forms.

• For example, the color of a pea could be green or
yellow.

•These different forms are called traits.

Dropdown

A monk named ​

Select answer

performed the first major
experiments investigating heredity.​

Traits depend on inherited factors

• In his experiment with seed pod color, Mendel took two sets of plants,

one true-breeding for plants that produce green seed pods.

• Instead of letting the plants self-pollinate as they do naturally, he paired

one plant with the pollen of another plant.

• He did this by fertilizing one plant with the pollen of another plant.

• He called the plants that resulted from the plants as the first

generation.

• All of the plants resulted in green seed pods.

• Mendel called this trait the dominant trait.

• Because the yellow trait seemed to recede, or fade away, he called it a

recessive trait.

Traits depend on
inherited factors
continued

•Mendel let the first-generation of plants self-pollinate.

•He called the offspring that resulted from this self-
pollination the second generation.

•About three-fourths of the second-generation plants
had green seed pods and about one-fourth had yellow
seed pods.

•The trait that seemed to disappear in the first
generation reappeared in the second generation.

•Mendel hypothesized that each plant must have two
heritable “factors” – one from each parent- for yellow
pod color.

•A plant with one yellow factor and one green factor
would produce green pods because producing green
pods is a dominant trait.

•This plant could still pass on the yellow factor to the
next generation.

Multiple Choice

Which trait is dominant?

• Yellow

• Green

Multiple Choice

Which trait is recessive?

• Yellow

• Green

Open Ended

How can you tell what pea pod color is dominant and recessive?

How are traits inherited?

• Mendel’s experiments and conclusions have been the

basis for much of the scientific thought about heredity.

• His ideas can be further explained by our modern

understanding of the genetic material DNA.

• What Mendel called “factors” are actually segments of

DNA known as genes!

Genes Are Passed from
Parents to Offspring

•Genes are segments of DNA found in chromosomes that
give instructions for producing a certain characteristic.

•Humans, like many other organisms, inherit their genes
from their parents.

•Each parent gives one set of genes to the offspring.

•The offspring then has two versions, or forms, of the same
gene for every characteristic- one version from each parent.

•The different versions of a gene are know as alleles.

•Genes are often represented by letter symbols.

•Dominant alleles are shown with a capital letter, and
recessive alleles are shown with a lower case letter. An
organism with two dominant or two recessive alleles is said
to be homozygous for that gene.

•An organism that has one dominant and one recessive
allele is heterozygous.

Dropdown

Dominant alleles are shown with a ​

Select answer

letter, and
recessive alleles are shown with a ​

Select answer

letter. An
organism with two dominant or two recessive alleles is said

Select answer

for that gene. An organism that has one dominant and one recessive
allele is ​

Select answer

.

Open Ended

Which pair of pair of alleles are
heterozygous and how do you know?

Open Ended

Which pair of pair of alleles are
homozygous? How do you know?

Multiple Choice

If one parent is homozygous dominant for red flower and the other parent is homozygous recessive for yellow flower color. What will be the phenotype of the offspring?

• red flower

• yellow flower

• orange flower

Multiple Choice

If one parent is homozygous recessive and the other parent is homozygous dominant. What will the genotype of the offspring?

• Homozygous recessive

• Heterozygous

• Homozygous dominant

Genes Influence Traits

• The alternate forms of genes, called alleles, determine the

traits of all living organisms.

• The combination of alleles that you inherited from your

parents is your genotype.

• Observable traits are phenotype.

• The phenotypes of some traits follow patterns similar to

the ones that Mendel discovered in pea plants.

• That is, some traits are dominant over others.

Dropdown

The combination of alleles that you inherited from your parents is your ​

Select answer

. Observable traits are ​

Select answer

. The phenotypes of some traits follow ​

Select answer

similar to the ones that Mendel discovered in pea plants.

That is, some traits are ​

Select answer

over others.

Genes Influence Traits Continued

Apply

• The girls in this photograph have

different types of hair. Is hair
type a genotype or a
phenotype?

Many Genes Can
Influence a Single
Trait

• Some characteristics, such as the color of your skin, hair, and eyes are the

result of several genes acting together.

• Different combinations of alleles can result in different shades of eye color.

• Because there is not always a one-to-one relationship between a trait and a

gene, many traits do not have simple patterns of inheritance.

Multiple Choice

Some characteristics, such as the color of your skin, hair, and eyes are the result of several genes acting together.

• True

• False

A Single Gene
Can Influence
Many Traits

• One gene influences mor than

one trait.

• For example a single gene causes

the white Siberian tiger to have
white fur.

• If you look closely, you will see

that the tiger also has blue eyes.

• The gene that affects fur color

also influences eye color.

Multiple Choice

One gene influences more than one trait.

• True

• False

A Single Gene Can Influence Many Traits

•Many genetic disorders in humans are linked to a single gene but
affect many traits.

•For example the genetic disorder sickle cell anemia occurs in
individuals who have two recessive alleles for a certain gene.

•This gene carries instructions for producing a protein in read blood
cells.

•When a person has sickle cell anemia alleles, the body makes a
different protein.

•This protein causes red blood cells to be sickle or crescent shaped
when oxygen levels are low.

•Sickle-shaped blood cells can stick in blood vessels, sometimes
blocking the flow of blood.

•These blood cells are also more likely to damage the spleen.

•With fewer healthy red blood cells are also more likely to damage the
spleen.

•With fewer healthy red blood cells, the may not be able to deliver
oxygen to the body’s organs.

•All of the traits associated with sickle cell anemia are due to a single
gene.

The Environment Can
Influence Traits

•Sometimes, the environment influences an organisms phenotype.

•The artic fox has a gene that responsible for coat color.

•This gene is affected by light. In the winter, there are fewer hours of daylight,
and the hairs that make up the artic fox’s coat grow in white. In the summer,
when there are more daylight hours the hairs in the coat grow in brown.

•Both genes and the environment contribute to the organism’s phenotype.

•The environment can influence human characteristics as well. For example,
your genes may make it possible for you to grow to be tall, but you need a
healthy diet to reach your full height potential.

• Traits that are learned in one’s environment are not inherited. For example,
your ability to read and write is an acquired trait-a skill you learned.

•You were not born knowing how to ride a bike, and if you have children, they
will not be born knowing how to do it either.

•Acquired traits are traits that learned in an organisms environment.

Multiple Choice

The environment never influences an organisms phenotype.

• True

• False

What are the exceptions
to complete dominance?

• The characteristics that Mendel chose

to study demonstrated complete
dominance, meaning that
heterozygous individuals show the
dominant trait.

• Some human traits, such as freckles

and dimples, follow the pattern of
complete dominance, too.

• However, other traits do not.

• For traits that show incomplete

dominance or codominance, one trait
is not completely dominant over
another.

Multiple Choice

In incomplete dominance or codominance, one trait
is completely dominant over
another.

• true

• false

Incomplete Dominance

•In complete dominance, each allele in a
heterozygous individual influences the
phenotype.

•The result is a phenotype that is a blend of the
phenotypes of the parents.

•One example of incomplete dominance is found
in the snapdragon is crossed with a true-
breeding white snapdragon, all of the offspring
are pink snapdragons.

•Both alleles of the gene have some influence.

•Hair texture is an example of incomplete
dominance in humans.

•A person with one straight hair allele and one
curly-hair allele will have wavy hair.

Multiple Choice

In incomplete dominance, each allele in a
heterozygous individual influences the
phenotype.

• True

• False

Multiple Choice

If one parent is homozygous dominant for red flower and the other parent is homozygous recessive for white flower color. What will be the phenotype of the offspring if the two genes are incomplete dominance?

• white

• red

• pink

Codominance

•For a trait that shows codominance, both of the alleles in a
heterozygous individual contribute to the phenotype.

•Instead of having a blend of the two phenotypes,
heterozygous individuals have both of the traits associated
with their two alleles

•An example of codominance is shown in the genes that
determine human blood type: A, B, and O. The alleles are
responsible for producing small particles on the surface of
red blood cells called antigens.

•The A allele produces red blood cells coated with A
antigens.

•The B allele produces red blood cells coated with B
antigens.

•The O allele does not produce antigens.

•The A and B alleles are codominant.

•So, someone with one A allele and one B will have type AB
blood.

Multiple Choice

DNA contains genes that provide instructions for inherited traits. What is the relationship between the genes and chromosomes?

• Genes are segments of DNA that are located on the chromosomes of each cell.

• Genes are made up of thousands of chromosomes.

• Genes correspond to the phenotype, While chromosomes correspond to the genotype.

• Chromosomes correspond to the phenotype, while genes correspond to the genotype.

Open Ended

Summarize what you have learned today. Use at least 3 sentences.

Poll

How well do you think you understand heredity?

• I do not understand it at all.

• I kind of understand but need more practice.

• I understand very well and will do well on my next quiz or assessment.

• I can teach it.