Mendel & Pea Plants
Who was the monk that performed experiments with pea plants and is known as the "father of genetics"?
Gregor Mendel
What is the purpose of a Punnett square?
To predict possible genotypes of offspring from parental alleles
Name the two scientists credited with discovering the double-helix structure of DNA.
James Watson and Francis Crick
What is a gene?
A segment of DNA that codes for a trait
If purple flower color (PP) is dominant and white (pp) is recessive, what phenotype does Pp show? Draw a Punnett Square to Help
Shows purple
Name one pea plant trait Mendel studied
flower color, seed shape, seed color, pod shape, pod color, flower position, stem length
Draw a 2x2 Punnett square for a cross between two heterozygous parents (use the letter T)
What shape describes the structure of DNA?
Double helix.
What is an allele?
One form of a gene (example: allele for purple vs allele for white)
Which allele (dominant or recessive) must be present in two copies to show its trait?
Recessive
If Mendel crossed true-breeding purple-flowered pea plants with true-breeding white-flowered pea plants, what color were all plants in the first generation (F1)?
All purple
From the a TT x tt cross, what is the expected genotype ratio? (Give as proportions a TT : Tt : tt)
0 : 4 : 0
List the three main parts of a DNA nucleotide.
Sugar (deoxyribose), phosphate, nitrogenous base
Define "homozygous" and give an example of both homozygous dominant and homozygous recessive using the letter A
Two of the same alleles. AA - dominant trait shows, aa - recessive trait shows
If a plant shows the recessive phenotype, what can you say about its genotype?
It has two copies of the recessive gene (tt)
Define "true-breeding" in terms of Mendel’s experiments.
True-breeding means parents always produce offspring with the same trait when self‑fertilized.
If the ratio for hair color (brown being dominant to blonde) looks like this, what is the PHENOTYPE ratio?
TT - 1 Tt - 2 tt - 1
Brown - 3
Blonde - 1
What are the nitrogen pairs?
Thymine & Adenine
Cytosine & Guanine
Define "heterozygous" and give an example using the letter A
Two different alleles. Aa - Dominant trait shows
A plant is homozygous recessive for pod shape (rr). If crossed with a heterozygous plant (Rr), what fraction of offspring will be homozygous recessive? Draw a Punnet Square to help
In Mendel’s pea experiments, what fraction (or percent) of the second generation (F2) had the recessive trait when he crossed two F1 plants? (Provide percent or fraction.)
About 1/4 or 25%
A pea plant with genotype tt is crossed with a plant of unknown genotype that shows the dominant trait. SOME of the offspring show the recessive trait. What is the unknown genotype?
Tt
how many chromosomes do humans have? How many pairs is that?
46 total - 23 pairs
Explain the difference between genotype and phenotype and give one example showing both.
Genotype is the genetic makeup (example: Aa); phenotype is the physical trait shown (example: purple flowers)
Two tall plants are crossed. Some offspring are short. What does this tell you about the genotypes of the parent plants?
they are both heterozygous