Heredity

Reflection Questions……Using your graph answer the

following using complete sentences – page 68

• Did you share a trait with another classmate?

• Did you find a trait that was unique to you?

• Why do some of the traits have such a big difference in the number of students that have the trait and the number that do not have the trait?

• If we took a poll of the entire school would the results be similar? Explain your answer.

Vocabulary to Know!START YOUR FLASH CARDS NOW

• allele

• chromosome

• codominance

• DNA

• dominant allele

• gene

• genotype

• heredity

• heterozygous

• homozygous

• pedigree

• phenotype

• Punnett square

• recessive allele

• trait

Gregor Mendel

• Gregor Mendel is known as the father of Genetics

• He was an Austrian Augustinian monk and scientist who studied the inheritance of certain traits in pea plants

What did Mendel do??

• Gregor Mendel had two significant discoveries in the mid-nineteenth century:

• The first is that organisms have “factors” or what is more commonly known as genes, that control their physical traits

• Secondly, organisms pass on their genes to their offspring in predictable ways

Because of Gregor Mendel…….

• Scientist can now predict the likelihood that children, not yet conceived may inherit certain diseases

• Scientists are also using this knowledge of genetics to alter the biology of plants, animals and humans.

Heredity

• Heredity refers to the passing of traits from parents to their offspring.

• Genes control the traits that appear in those offspring. When organisms reproduce, they give genes to their offspring, and those genes cause traits to appear.

More About Heredity

• Each gene is a small piece of a long complicated molecule called DNA. DNA is an abbreviation for Deoxyribonucleic Acid.

• In the reproductive process, DNA arranges itself into structures called chromosomes found in the nucleus of the cell.

Write the term that matches each

definition.

1. A section of a DNA molecule that controls a trait is called ___________________.

2. The passing of traits from parents to offspring is known as ___________________.

3. _____________________ is a complicated molecule that contains genes.

4. A characteristic in an organism ___________________.

5. The structure into which DNA arranges itself: ___________________.

Answers!

• A section of a DNA molecule that controls a trait is called a Gene

• The passing of traits from parents to offspring is known as Heredity

• DNA is a complicated molecule that contains genes.

• A characteristic in an organism: Trait

• The structure into which DNA arranges itself: Chromosomes

Phenotype and Genotype

•Phenotype – Scientists can study traits by examining how organisms look on the outside. The outside expression of a gene is called a phenotype. Example: Chris has a widow’s peak. A scientist will say that Chris is expressing the widow’s peak phenotype.

Phenotype and Genotype

•Genotype – Humans have two copies of each gene, called alleles, one from the biological mother and one from the biological father. When a scientist determines which two alleles a person has, they are determining the person’s genotype.

Dominant vs. Recessive

• A dominant allele causes a widow’s peak in humans. Scientists use an upper case letter (W) to indicate a dominant allele and a lowercase letter (w) to indicate a recessive allele.

• The widow’s peak gene has three possible genotypes: WW, Ww, or ww. Chris has a widow’s peak. Therefore we know that he has at least one dominant allele. His genotype is either WW or Ww.

Homozygous vs. Heterozygous

• If a person has two identical alleles, in Chris’s case, if he has WW as his genotype, then he is homozygous dominant for the trait.

• If a person has a dominant and a recessive allele, in Chris’s case, if he has Ww as his genotype, then he is heterozygous.• Amy doesn’t have a widow’s peak. Write the

letters for her genotype. ____________• What is Amy’s genotype: homozygous

dominant or homozygous recessive? ______________________

Heterozygous or Homozygous??

• AA ____

• Bb ____

• Cc ____

• Dd ____

• Ee ____

• ff ____

• GG ____

• HH ____

Punnett Square

• A Punnett square shows the possible combinations of alleles that children can inherit when two people produce offspring.

• The Ameba Sisters help us to understand!

• https://www.youtube.com/watch?v=i-0rSv6oxSY&index=14&list=PLwL0Myd7Dk1F0iQPGrjehze3eDpco1eVz