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36 Cards in this Set

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5 Element Model (Mendel's Conclusions)
1) Parents don't directly transmit physiological traits to offspring, they merely give info about those traits (DNA).
2) Progeny receive one copy of info from each parent.
3)Genes have alternate forms (alleles). Same alleles fuse during fertilization> homozygous. Different alleles fuse>heterozygous.
4)Some alleles dominant (expressed) or recessive (unexpressed unless homozygous).
5) Alleles don't blend or alter each other.
6)Alleles segregate during gamete formation and remain distinct (meiosis).
total set of alleles
physical characteristic resulting from allele expression
What were the results of Mendel's monohybrid experiments?
(flower color)
F1: All plants purple (purple x white = purple) Purple dominant, white recessive.
F2: 705/929 purple, 224/929 white (3:1 ratio)
F3: 1/4 white 2/4 purple and white 1/4 purple (1:2:1 ratio)
one trait examined

example: flower color
How are Punnett squares used to predict inheritance characteristics?
Allows symbolic analysis and prediction of traits that will be present (dominant vs. recessive; heterozygous vs. homozygous, etc.) when organisms of a certain genotype cross.
-Inheritance was once viewed as being "borne through fluid," usually blood, that led to blending of offspring.
-It referred to the breeding of domestic animals, such as horses
-Tracing bloodlines through pedigrees helps to find the origin of genetic issues and how they are passed through dominant and recessive traits
-example: glaucoma
Gregor Mendel
"Grandfather of modern genetics"
-1800's Abbott in Viennan monastery
-Used science to learn about heredity and the first to use math to quantify his results!
-Used the garden pea as experimental model
Why was the garden pea a good experimental model to study inheritance patterns?
1) It had been extensively used in the past by other scientists (science based on past work)
2)Large # of varieties: 7 distinguishable traits
3)Self-fertilizing: both male and female sex organs within flower so gametes can fuse to form offspring (seeds)
4)Small and easy to grow: many experiments quickly
5) Can prevent self-fertilization by removing male parts and then fertilize w/ pollen from another plant for a cross.
Mendel's 7 Distinguishable Traits
1) Flower color
2) Seed color
3) Seed texture
4) Pod color
5) Pod shape
6) Flower position
7) Plant height
How are traits passed from generation to generation?
1) Parents transmit info about physiological traits through genes. Progeny receive 1 copy of each gene from each parent.
2) Alleles are dominant or recessive and segregate during gamete formation (meiosis). Inherit two alleles for each gene.
3) Chromosomes are the vehicle (genes for traits reside on them)
4) Homologous chromosomes separate during gamete formation
Why is there variability among members of the same species?
1) Genes have alternate alleles
a) Gametes w/ same allele fuse:homozygous
b) Gametes w/ diff. allele fuse: heterozygous
2) Parents transmit info through genes and progeny receive 1 copy of each gene from each parent
3) Polygenic Inheritance
4) Pleiotrophy
5)Genes may have more than two alleles
6) Dominance is not always complete
7) Phenotypes may be affected by the environment
8) DNA: the sequence of nucleotides varies
Polygenic Inheritance
More than one gene affects a single trait

Example: height--continuous distribution of trait in a population results in a range of small differences from cumulative effects of multiple genes
One gene (allele) can affect multiple traits

Example: Cystic fibrosis, sickle cell anemia
Example of genes having more than two alleles
Blood types
Dominance is not always complete
1) Incomplete dominance
Incomplete dominance
heterozygote is intermediate in appearance

Example: Japanese 4 O'Clock: Red flower and white flower > pink flower. This is NOT allele blending.
Each allele has an effect and both are seen in a heterozygote

Example: Human blood types
Human blood types
1) Gene encodes for the enzyme that adds sugars to RBC surface
2) Gene has 3 alleles ( I^A galactosamine, I^B galactose, i no sugar) and 2 are given, one from each parent
3) Antibodies will attack other blood types, except O because it doesn't have sugar for antibodies to attack.
Patterns of Heredity
1) Occurs within a species
2) Transmitted from parent to offspring
a) chromosomes act as the vehicle
Different forms of a gene
Encodes info about a physical trait on nucleic acid
Dihybrid cross
Examining two traits at a time (example: seed color, seed texture)
Dominant vs. Recessive
Animal and plant cells are diploid paired chromosomes.
- Receive one copy from each parent
The dominant allele is when its physically identical to homozygous
The passing of traits from parent to offspring through genes that carry information for physical characteristics.
Mendel's Experimental Design
1) Plants of specific trait allowed to self-fertilize for multiple generations until strain was true-breeding (having uniform offspring).
2) Performed reciprocal crosses w/ true breeding strains w/ different traits. Result: F1 generation
3) Offspring (hybrids) from reciprocal crosses were allowed to self fertilize for multiple generations. Result: F2 generation.
(At each step, Mendel counted number of offspring with each trait)
Having uniform offspring. Achieved by allowing plants of a specific trait to self-fertilize.
Hybrid offspring
Result of reciprocal crosses (true-breeding strains with different traits)
Reciprocal Cross
True-breeding strain of one trait X true-breeding strain of another trait
As in the garden pea, both male and female sex organs are enclosed, allowing formation of gametes within one plant. Important step for having true-breeding strains.
Phenotypic (visible) trait determined by genotype.
3:1 ratio
F2 generation, result of reciprocal cross. 705/929 purple, 224/929 white
1:2:1 ratio
F3 generation. Result of Pp x Pp
1 true breeding dominant: 2 non true dominant : 1 recessive.

(1/4 purple, 2/4 purple & white, 1/4 white)
F1 Generation
(flower color)
All purple suggesting that purple is dominant, white is recessive
F2 Generation
(flower color)
929 plants total
705/929 purple flowers, 224/929 white flowers
ratio: 3:1
F3 Generation
(flower color)
1/4 purple, 2/4 purple & white, 1/4 white
ratio: 1:2:1