Whose got Genes?

Genes, Heredity, & DNA

What are genes?Genes are a segment of DNA on a chromosome that controls a particular trait.

Genes are located on the chromosomes in the nuclei. Each organims has a fixed number of chromosomes.Humans have 23 pairs (46) chromosomes.Genetics is the study of how traits are passed on from one generation to another

                                  

So what is DNA?

DNA is a complex molecule (polymer) found in all living things.The primary function of DNA is to store and transmit genetic information that tells cells which proteins to make and when to make them.

DNA TRIVIA

An idea about size: An average cell nucleus is about 6 micrometers in diameter.

The total length of the DNA in the human genome is 1.8 meters.

There must be several levels of coiling and super coiling in DNA

Who was Gregor Mendel?

Who was Gregor Mendel?

Austrian monk who studied mathematics and scienceAs 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. 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 organismGenes come in pairs and offspring inherit one copy of each gene from each parent

Define the following terms:

HeredityAlleleTrait

Define HEREDITY

The passing of traits from parent to

offspring

Define ALLELE

The different forms of a trait that a gene may haveOne form of a gene

Define TRAIT

Ways of looking, thinking, or beingTraits 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 Hidden when the other copy of the gene contains the dominant allele.A recessive allele shows up only when there is no dominant allele presentShown with a lower-case letter

What is HOMOZYGOUS?

What is HOMOZYGOUS?

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

What is HETEROZYGOUS?

What is HETEROZYGOUS?

When alleles occur in different formsWhen offspring inherit one dominant gene and one recessive gene, they are said to be heterozygousSince 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 traitTrait 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

Define PHENOTYPE

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 combineA way to show phenotype & genotypeA 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 allelesAn uppercase letter stands for a dominant allele Lowercase letters stand for recessive alleles

Introduction to Punnett Squares:

A Punnett Square is a chart drawn to determine the probable results of a genetic cross. To be able to draw a Punnett Square, you must know the genotype of both parents.

R r

R RR

Rr

r RR

rr

Punnett Squares

Sample Problem 1.   In roses, red flowers are dominant over white flowers. What are the possible offspring when a homozygous red rose is crossed with a homozygous white rose.

homozygous red rose = RR

homozygous white rose = ww

Generation 1

homozygous red rose = RR

heterozygous red rose = Rw

homozygous white rose = ww

Generation 2

homozygous red rose = RR

heterozygous red rose = Rw

homozygous white rose = ww

Generation 3

List the 3 Principles of Heredity

List the 3 Principles of Heredity

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

References

Slideshow adapted from http://www.science-class.net/PowerPoints/Genetics.htm