Another example: Flower color

For example, flower color:

P = purple (dominant)

p = white (recessive)

If you cross a homozygous Purple (PP) with a homozygous white (pp):

P P p p

P p ALL PURPLE (Pp)

Cross the F1 generation:

P p P p

P P P p

P p

p p

P

p

P pGenotypes:1 PP2 Pp1 pp

Phenotypes: 3 Purple 1 White

Mendel’s Principles

• 1. Principle of ___________________:

One allele ________________ another, one allele was _________________ over the other in the F1 generation.

• 2. Principle of ____________________:

When ______________ are formed, the pairs of hereditary factors (_________) become ________________, so that each sex cell (egg/sperm) receives only ________ kind of gene.

Human case: CF• Mendel’s Principles of Heredity apply universally

to all organisms.

• Cystic Fibrosis: a lethal genetic disease affecting _________________.

• Caused by mutant ______________ gene carried by 1 in 20 people of European descent (12M)

• One in 400 Caucasian couples will be both carriers of CF – 1 in ____ children will have it.

• CF disease affects ______________ in tissues – mucus is accumulated in lungs, causing infections.

Inheritance pattern of CF

IF two parents ___________ the recessive gene of Cystic Fibrosis (c), that is, they are ___________________ (C c), one in four of their children is expected to be __________________ for CF and have the disease:

C C C c

C c

c c

C c

C

c

C C = normalC c = carrier, no symptomsc c = has cystic fibrosis

Probabilities…

• Of course, the 1 in 4 probability of getting the disease is just an expectation, and in reality, any two carriers may have normal children.

• However, the greatest probability is for 1 in 4 children to be affected.

• Important factor when prospective parents are concerned about their chances of having affected children.

• Now, 1 in 29 Americans is a symptom-less carrier (Cf cf) of the gene.

Gaucher Disease• Gaucher Disease is a rare _______________ disease.

It causes _____________-storage disorder (lipids accumulate in spleen, liver, bone marrow)

• It is the most common genetic disease affecting _____________ people of Eastern European ancestry (1 in 500 incidence; rest of pop. 1 in 100,000)

Principle of Independent Assortment

• Based on these results, Mendel postulated the 3. Principle of __________________________:

“Members of one gene pair _______________ independently from other gene pairs during ______________ formation”

Genes get ______________ – these many combinations are one of the advantages of sexual reproduction

Relation of gene segregation to meiosis…

• There’s a ________________ between the movement of chromosomes in meiosis and the segregation of __________ that occurs in ___________

Beyond Mendelian Genetics: Incomplete Dominance

Mendel was lucky!Traits he chose in thepea plant showed up very clearly…One allele was _______________ over

another, so ________________ were easy to recognize.

But sometimes phenotypes are not very obvious…

Summary of Genetics

• Chromosomes carry _________________ info (genes)• Chromosomes (and genes) occur in __________• New _________________ of genes occur in sexual

reproduction• Monohybrid vs. Dihybrid crosses• Mendel’s Principles:

– _____________________: one allele masks another

– _________________: genes become separated in gamete formation

– ________________ Assortment: Members of one gene pair segregate independently from other gene pairs during gamete formation

Meiosis

Genes• Tens of thousands of genes• Lined up on chromosomes

Chromosomes

• Occur in ___________ (Male, Female)

• _____________—A cell with two of each kind of chromosome is said to be diploid, or _______, number of chromosomes

Gametes

• Male (__________) and Female (_________)

• Contain one of each kind of chromosomes.

• A cell with one of each kind of chromosome is called a ________________ and is said to contain a haploid, or _____, number of chromosomes.

Homologous Chromosomes

• Pair chromosomes are called __________________ chromosomes—determine __________________.

• Gene for same trait– same order,– chromosomes in a

homologous pair are not always identical.

• (Chromosome 4 contains 3 traits Mendel Studied)

MeiosisFrom the Greek word meioun,

meaning “to diminish”.

Cell division that results in a _____________ containing ___________ the number of chromosomes of its parents.

Meiosis• Divisions: Meiosis ____ and Meiosis ______• Begins with

one diploid (___) cell four haploid (___) cells.

• Sex cells (_________________) haploid.• Sperm fertilizes an egg-results in zygote

(diploid)• Zygote develops by ______________ into a

multi-cellular organism.• Reproduction —Production and subsequent

fusion of haploid sex cells.

Interphase

• Chromosomes _____________ • Chromosome

– two identical sister ________________ held together by a ____________________

Prophase I• Chromosomes coil up and a

_______________ forms.• Homologous chromosomes

comes together, matched gene by gene, to form a four-part structure called a _____________.

• Chromatids pair so tight that sometimes non-sister chromatids from homologous chromosomes sometimes exchange genetic material in a process known as ___________________.

Crossing Over• Exchange of ______________ material• Any location • Several locations at once• Humans-Two to three crossovers for each pair of

homologous __________________.

Metaphase I• ___________________ attaches to a spindle

fiber• ____________________________ pull the

tetrads into the middle, or equator, of the spindle.• Chromosomes are lined up side by side as

tetrads.

Anaphase I• Chromosomes

__________________ and move to opposite ends of the cell.

• Centromeres holding the sister chromatids together do not ___________ like they do in anaphase of mitosis.

• Ensures that each new cell have only one chromosome from each ______________ pair.

Telophase I

• ______________ is broken down

• Chromosomes _______________

• Cytoplasm divides 2 new cells.

• ____________ of genetic information of original cell (one chromosome from each homologous pair)

• Another cell division needed

Meiosis II

• Newly formed cells go through short _______________ (*chromosomes don’t replicate*)

• _______________ II—Spindle forms in each of the two new cells and the spindle fibers attach to the chromosomes.

• _______________ II—The chromosomes, still made up of sister chromatids, are pulled to the center of the cell and line up randomly at the equator.

• _______________ II—Centromere of each chromosome splits, allowing sister chromatids to separate and move to opposite poles.

• _______________ II—Nuclei reform, spindles break down, and cytoplasm divides.

Meiosis Results

• Four ______________ sex cells have been formed from one original _____________ cell.

• Each haploid cell contains one ____________________ from each homologous pair.

• Haploid cells become ______________, transmitting the genes they contain to offspring.

The History of DNA

Early WorkFriedrich Miescher, 1869, first isolates a substance from the nucleus of cells that he calls “______________.” His student, Richard Altmann, calls the substance “___________________________.”

Biochemists identify two types of nucleic acids, later called ____________ and ________________.

In 1929, ____________________________________ at the Rockefeller center identifies the four bases of DNA.

What Does DNA Do?Though early researchers knew that DNA was found in chromosomes, they doubted that it was the hereditary material. There were only four bases. How could four bases code for all sorts of proteins?

Some researchers, including Linus Pauling, thought that the protein also found in chromosomes was probably the hereditary factor.

Frederick Griffith

In 1928, Frederick Griffith carried out experiments on pneumonia _________________________ in _____________.

Discovery: something in __________________________________ virulent bacteria could be transferred to live, harmless bacteria and make them virulent.

Griffith’s Experiment

Oswald Avery

Avery continued working with Griffith’s findings in hope of discovering what factor in bacteria carried the trait of virulence.

Isolated proteins, carbohydrates, nucleic acids and applied them to non-virulent bacteria. Only __________________________________ (DNA) caused a change.

Avery’s Work

Erwin Chargaff

Chargaff studied DNA itself, in hopes of providing some clues about its _______________________.

Discovered that there are always _____________________ amounts of the bases Adenine and Thymine, and equal amounts of Cytosine and Guanine.

Chargaff proposed that these bases _______________ with one another in some way.

Wilkins and Franklin

Rosalind Franklin and Maurice Wilkins worked with __________________ crystalography to find more clues about the ________________________ of DNA.

Franklin’s X-ray images suggested a ______________________ structure.

Franklin and Wilkins

Watson and Crick

James Watson and Francis Crick were also working on discovering the structure of DNA.

Applied Chargaff’s rule, assumed that _________ always pairs with _______, ______ with __________.

Watson was not entirely convinced of the helical structure that _____________________ had suggested, and his critique of her work led her to doubt herself.

Watson and CrickWilkins consulted with Watson and Crick. Without Franklin’s knowledge, he handed them the data that he and Franklin had worked on.

Watson immediately recognized the significance. He and Crick went to work on a model of DNA.

The First DNA Model

DNA structure

DNA is made up of _________ bases. RNA also has four bases, but has _______________ instead of ________________.

DNA structure

Across the DNA double-ladder, _______ always pairs with ______, _________ always pairs with _______ because of the number of hydrogen bonds the bases form.

DNA structure

The DNA ladder forms a ___________________, or helical, structure, with the two sides held together with _______________________ bonds.