GeneticsGenetics& &

HeredityHeredity

Who was Gregor Mendel?

Who was Gregor Mendel?

• Austrian monk who studied mathematics and science

• As a boy he experimented with pea plants

• 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?

What is GENETICS?

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

• The nucleus of a cell contains genetic material– DNA

• Chromosomes– Genes

www.kent.edu/projects/cell/page7.htm

Genetic Material

Genes

• Genes are short sections of chromosomes

• Genes come in pairs and offspring inherit one copy of each gene from each parent http://www.accessexcellence.org

Genes come in pairs

• Since chromosomes come in pairs (one from mom, one from dad) Genes come in pairs

http://anthro.palomar.edu/biobasis/images/karyotype_male.gif

Define the following terms:

• Heredity• Allele• Trait

Define HEREDITY

The passing of traits from parent to offspring

Allele

• Alleles are different versions of a gene

• Every gene has two or more alternatives

http://library.thinkquest.org

Define TRAIT

• Characteristic or a way of looking, thinking, or being

• Traits that are genetic are passed down through the genes from parents to offspring

Describe RECESSIVE

Describe RECESSIVE

• A trait that is covered over, or dominated, by another form of that trait and seems to disappear

• Shown with a lower-case letter

• Example: c, d

What is HOMOZYGOUS?

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 (BB)

• When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive (bb)

What is HETEROZYGOUS?

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 (Bb)

• Since the dominant gene will be expressed, they are said to be heterozygous dominant

Describe DOMINANT

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

Define GENOTYPE

An organism's genetic makeup

Or the lettersExample: Bb, bb, BB

Define PHENOTYPE

Define PHENOTYPE

Outward physical appearance and behavior of an organism

Example: black hair

What is a PUNNETT SQUARE?

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:

http://www.borg.com/~lubehawk/psquare.htm

List the 3 Principles of Heredity

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?

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?

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