<< Chapter < Page Chapter >> Page >

What results did Mendel find in his crosses for flower color? First, Mendel confirmed that he had plants that bred true for white or violet flower color. Regardless of how many generations Mendel examined, all self-crossed offspring of parents with white flowers had white flowers, and all self-crossed offspring of parents with violet flowers had violet flowers. In addition, Mendel confirmed that, other than flower color, the pea plants were physically identical.

Once these validations were complete, Mendel applied the pollen from a plant with violet flowers to the stigma of a plant with white flowers. After gathering and sowing the seeds that resulted from this cross, Mendel found that 100 percent of the F 1 hybrid generation had violet flowers. Conventional wisdom at that time would have predicted the hybrid flowers to be pale violet or for hybrid plants to have equal numbers of white and violet flowers. In other words, the contrasting parental traits were expected to blend in the offspring. Instead, Mendel’s results demonstrated that the white flower trait in the F 1 generation had completely disappeared.

Importantly, Mendel did not stop his experimentation there. He allowed the F 1 plants to self-fertilize and found that, of F 2 -generation plants, 705 had violet flowers and 224 had white flowers. This was a ratio of 3.15 violet flowers per one white flower, or approximately 3:1. When Mendel transferred pollen from a plant with violet flowers to the stigma of a plant with white flowers and vice versa, he obtained about the same ratio regardless of which parent, male or female, contributed which trait. This is called a reciprocal cross    —a paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross. For the other six characteristics Mendel examined, the F 1 and F 2 generations behaved in the same way as they had for flower color. One of the two traits would disappear completely from the F 1 generation only to reappear in the F 2 generation at a ratio of approximately 3:1 ( [link] ).

The Results of Mendel’s Garden Pea Hybridizations
Characteristic Contrasting P 0 Traits F 1 Offspring Traits F 2 Offspring Traits F 2 Trait Ratios
Flower color Violet vs. white 100 percent violet
  • 705 violet
  • 224 white
3.15:1
Flower position Axial vs. terminal 100 percent axial
  • 651 axial
  • 207 terminal
3.14:1
Plant height Tall vs. dwarf 100 percent tall
  • 787 tall
  • 277 dwarf
2.84:1
Seed texture Round vs. wrinkled 100 percent round
  • 5,474 round
  • 1,850 wrinkled
2.96:1
Seed color Yellow vs. green 100 percent yellow
  • 6,022 yellow
  • 2,001 green
3.01:1
Pea pod texture Inflated vs. constricted 100 percent inflated
  • 882 inflated
  • 299 constricted
2.95:1
Pea pod color Green vs. yellow 100 percent green
  • 428 green
  • 152 yellow
2.82:1

Upon compiling his results for many thousands of plants, Mendel concluded that the characteristics could be divided into expressed and latent traits. He called these, respectively, dominant and recessive traits. Dominant traits are those that are inherited unchanged in a hybridization. Recessive traits become latent, or disappear, in the offspring of a hybridization. The recessive trait does, however, reappear in the progeny of the hybrid offspring. An example of a dominant trait is the violet-flower trait. For this same characteristic (flower color), white-colored flowers are a recessive trait. The fact that the recessive trait reappeared in the F 2 generation meant that the traits remained separate (not blended) in the plants of the F 1 generation. Mendel also proposed that plants possessed two copies of the trait for the flower-color characteristic, and that each parent transmitted one of its two copies to its offspring, where they came together. Moreover, the physical observation of a dominant trait could mean that the genetic composition of the organism included two dominant versions of the characteristic or that it included one dominant and one recessive version. Conversely, the observation of a recessive trait meant that the organism lacked any dominant versions of this characteristic.

Questions & Answers

the properties of life
Clarinda Reply
response to the environment, reproduction, homeostasis, growth,energy processing etc.....
Pushpam
hello.
Daniela
hi
MacPeter
Good
Thomas
a complete virus particle known as
Darlington Reply
These are formed from identical protein subunitscalled capsomeres.
Pushpam
fabace family plant name
Pushpam Reply
in eukaryotes ...protein channel name which transport protein ...
Pushpam Reply
in bacteria ...chromosomal dna duplicate structure called
Pushpam
what is a prokaryotic cell and a eukaryotic cell
Matilda Reply
There are two types of cells. Eukaryotic and Prokaryotic cells. Prokaryotic cells don't have a nucleus or membrane enclosed organelles (little organs within that cell). They do however carry genetic material but it's not maintained in the nucleus. Prokaryotic cells are also one celled.
juanita
Prokaryotic cells are one celled (single celled).
juanita
Prokaryotic cells are Bacteria and Archea
juanita
Prokaryotic cells are smaller than Eukaryotic cells.
juanita
Eukaryotic cells are more complex. They are much bigger than Prokaryotic cells.
juanita
Eukaryotic cells have a nucleus and membrane bound organelles.
juanita
Eukaryotic cells are animals cells which also includes us.
juanita
Eukaryotic cells are also multicellular.
juanita
nice explaination
Amna
eukaryotic cells are individual cells .. but eukaryotes are multicellular organisms which consist of many different types of eukaryotic cells
Will
also eukaryotic cells have mitochondria. prokaryotic cells do not
Will
Good
John
in prokaryotes only ribosomes are present... in eukaryotes mitochondria ...glogi bodies ..epidermis .....prokaryotes one envelop but eukaryotes compartment envelop....envelop mean membrane bound organelles......
Pushpam
prokaryotic cell are cells dat have no true nuclei i.e no cell membrane while eukaryotic cell are cell dat have true nuclei i.e have cell membrane
Divine
grt
Thomas
we have 46 pair of somatic cell and 23 pair of chromosomes in our body, pls can someone explain it to me. pls
Matilda Reply
we have 22 pairs of somatic chromosomes and one pair of sex chromosome
Amna
thanks
Matilda
we have 23 pairs of chromosomes,22 pairs of somatic and one pair of sex chromosomes
Amna
23 chromosomes from dad & 23 chromosomes from mom 23 +23=46 total chromosomes
juanita
X & Y chromosomes are called sex cells, the very presence of a Y chromosome means the person is Male.
juanita
XX Female XY Male
juanita
If a Karyotype has more than 46 Chromosomes then nondisjunction occured. For example, having an extra chromosome 21 will cause Down Syndrome.
juanita
in mammal state the different vertebrae and their location in the body
Igbinigie Reply
what is a somatic cell
Senam Reply
somatic cells are body cells
juanita
somatic cell organised whole plant body part
Pushpam
what is biology
lilian Reply
what is biology
Dada Reply
The scientific study of life.
juanita
the study of life
Clarinda
good
Thomas
the virus that causes mumps in humans is composed of a protein outer Shell containing a core of DNA
Daniel Reply
Basic science and applied science question about cancer
Joyce Reply
what are the importance of ATPs
Olatunji Reply
How can biology be studied from a microscopic approach to a global approach
Joyce Reply
The large central opening in the poriferan body is called
Chynna Reply

Get the best Biology course in your pocket!





Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?

Ask