Genetics & Heredity

Who was Gregor Mendel? Austrian monk “Father of Genetics” Previous views of Inheritance Blending Spermists Ovists

“Father of Genetics” Mendel performed breeding experiments with garden peas Found mathematical patterns of inheritance His work was not appreciated until 1900, 16 years after his death

Mendel’s work Why breed peas? They were available in many varieties, inexpensive, short life cycle, simple procedures, easy to grow. The use of plants also allowed strict control over the mating. He chose to study only characters that varied in an ‘either-or’ rather than a ‘more-or-less’ manner.

Mendel’s Law of Segregation Each hereditary characteristic is controlled by two factors (alleles) that separate and pass into reproductive cells (gametes).

Mendel’s Law of Independent Assortment Pairs of inheritance factors (alleles) segregate independently of each other when sex cells (gametes) are formed.

What is GENETICS?

What is GENETICS? The study of how traits are inherited through the interactions of genes.

Mitosis vs Meiosis Mitosis- Part of the cell cycle where the DNA replicates and the cell divides into two genetically identical diploid daughter cells Meiosis- Reduction division process, occurring only in reproductive (gamete) cells. One diploid cell produces four haploid cells that are not genetically identical (i.e. grab-bag)

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

What is a GAMETE? -A sex cell (sperm or egg) -Has half the chromosomes of a normal body cell In humans, how many chromosomes do we have in a normal body cell? In our sex cells, how many chromosomes are there?

Define the following terms: Heredity Allele Trait

The passing of traits from parent to offspring 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 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

Describe RECESSIVE

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 a ZYGOTE? The cell produced by the union of two gametes, before it undergoes cleavage.

What is HOMOZYGOUS?

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

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

Describe CO-DOMINANCE

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

Define GENOTYPE

Define GENOTYPE -An organism's genetic makeup -Always deals with the letters

Define PHENOTYPE

Define PHENOTYPE -Outward physical appearance of an organism

Mendelian Inheritance in Humans dominant recessive Tongue Roller (T) Free Earlobes (F) Dimples (D) Widow’s Peak (P) No Hitchhiker’s Thumb (H) Can’t roll tongue (t) Attached lobes (f) No dimples (d) Straight hairline (w) Hitchhiker’s thumb (h)

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

What is a PUNNETT SQUARE?

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?

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