Genetics & Heredity

Who was Gregor Mendel?

Austrian monk who studied mathematics and science As a boy he could predict the possible types of flowers and fruits that would result from crossbreeding two plants in his father’s garden

Who was Gregor Mendel? Curiosity about the connection between the color of a pea flower and the type of seed that same plant produced inspired him to begin experimenting with garden peas in Made careful use of scientific methods, which resulted in the first recorded study of how traits pass from one generation to the next.

What is GENETICS?

The study of how traits are inherited through the interactions of genes.

What is a GENE?

The material that controls which traits are expressed in an organism Genes come in pairs and offspring inherit one copy of each gene from each parent

Define the following terms: Heredity Allele Trait

Define HEREDITY The passing of traits from parent to offspring

Define ALLELE The different forms of a trait that a gene may have One form of a gene

Define TRAIT Ways of looking, thinking, or being Traits that are genetic are passed down through the genes from parents to offspring

Describe RECESSIVE

A trait that is covered over, or dominated, by another form of that trait and seems to disappear Hidden when the other copy of the gene contains the dominant allele. A recessive allele shows up only when there is no dominant allele present Shown with a lower-case letter

What is HOMOZYGOUS?

Both alleles [forms of the gene] are the same When offspring inherit two dominant genes, (one dominant gene from each parent) they are said to be homozygous dominant When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive

What is HETEROZYGOUS?

When alleles occur in different forms When offspring inherit one dominant gene and one recessive gene, they are said to be heterozygous Since the dominant gene will be expressed, they are said to be heterozygous dominant

Describe CO-DOMINANCE

When an organism has two different alleles for a gene that does not follow the dominant/recessive pattern The organism shows a trait that is a blend of the traits represented by the two alleles Also called INCOMPLETE DOMINANCE

Describe CO-DOMINANCE For example: The gene for the color of some flowers has one allele for red and one for white. When both alleles are present, neither is dominant, and the flower color is pink

Describe DOMINANT

A trait that covers over, or dominates, another form of that trait Trait that always shows up, even when only one of the two alleles is in the dominant form Shown by a capital letter

Define GENOTYPE

An organism's genetic makeup

Define PHENOTYPE

Outward physical appearance and behavior of an organism

What is a PUNNETT SQUARE?

A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine A way to show phenotype & genotype A chart that shows all the possible combinations of alleles that can result when genes are crossed

What is a PUNNETT SQUARE? Letters stand for dominant and recessive alleles An uppercase letter stands for a dominant allele Lowercase letters stand for recessive alleles

Read More About Punnett Squares Here: square.htm

List the 3 Principles of Heredity

Traits are controlled by alleles on chromosomes An allele’s effect is dominant or recessive When a pair of chromosomes separate during meiosis the different alleles for a trait move into separate sex cells

What is meant by MULTIPLE ALLELES?

A trait that is controlled by more than two alleles is said to be controlled by multiple alleles Traits controlled by multiple alleles produce more than three phenotypes of that trait

What is meant by MULTIPLE ALLELES? For Example: The alleles for blood types in humans are called A, B, and O The O allele is recessive to both the A and B alleles

What is meant by MULTIPLE ALLELES? When a person inherits one A allele and one B allele for blood type, both alleles are expressed The person has the blood phenotype AB

What is meant by MULTIPLE ALLELES? A person with phenotype A blood inherited an A and an O allele (AO) ~OR~ an A and an A allele (AA)

What is meant by MULTIPLE ALLELES? Someone with phenotype B blood has the genotype BB or BO This person inherited either a B and an O allele ~OR~ Two B alleles

What is meant by MULTIPLE ALLELES? A person with phenotype O blood has the genotype OO

What is POLYGENIC INHERITANCE?

Occurs when a group of gene pairs acts together to produce a trait The effects of many alleles produces a wide variety of phenotypes