genetics & heredity mr. nigh. who was gregor mendel?
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GeneticsGenetics& &
HeredityHeredity
Mr. NighMr. Nigh
Who was Gregor Mendel?
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 1856.
• Gregor Mendel 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.
What is a GENE?
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
Describe RECESSIVE
• A trait that is covers over, or is 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
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
CompleteDominance
Describe INCOMPLETE DOMINANCE
Describe INCOMPLETE 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
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 petals are half white and half red.
Co-Dominance
Define GENOTYPE
Define GENOTYPE
An organism's genetic makeup
Ex.RR Rr rr
Define PHENOTYPE
Define PHENOTYPE
Outward physical appearance and behavior
of an organismEx.Blue flowers, Green Seeds etc.
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 ex. RR
• When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive ex. rr
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 ex. Rr
• Since the dominant gene will be expressed, they are said to be heterozygous dominant
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
• A lowercase letter stands 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