Chapter 5 (Excluding 5.3) Flashcards
What plant did Gregor Mendel use for his experiments?
He choose Pea plants (Pisum Sativum)
Why was Gregor Mendel’s choice of pea plants a good one?
- Readily available
- Short generation time
- Showed many traits
What is a trait?
A specific characteristic or feature exhibited by an organism (such as flower colour of a plant)
What does it mean to self-fertilize?
The same plant provides the male and female gamete
What does true breeding/pure breeding mean?
An organism that exhibits the same traits generation after generation
How did Gregor Mendel control his pea plant experiments?
He selectively fertilized a female gamete with a specific male gamete in a process called a cross
What is a Cross also referred as?
Cross-pollination
Describe the steps in Gregor Mendel’s experiments
- Used pure breeding ( genetically identical) lines of peas and looked at 7 different traits
- Crosses a pure breeding plant with a plant of the opposite trait (white x purple). Called this P generation
- Recorded data on offspring called First Filial (F1)
- Self pollinated F1
- Recorded data on offspring; Second Filial (F2)
- Always 3:1 ratio
What is a Monohybrid cross?
A cross of 2 individuals that differ by one trait
What is the Mendelian ratio?
The ratio of 3:1 in the F2 generation
What is the Law of Segregation?
Says that traits are determined by pairs of alleles that segregate during meiosis so that each gamete receives one allele
What are alleles?
Different forms of a gene and diploid organisms have 2 alleles for each trait
What else does the Law of segregation say about pairs of pairs of alleles?
One allele is dominant, while another is said to be recessive
What does Dominant mean?
The form of a trait that always appears when an individual has an allele for it (only one is needed to show trait)
What does Recessive mean?
The form of a trait that only appears when an individual has 2 alleles for it
What else does the Law of Segregation say?
- Inherited traits are determined by 2 alleles of a gene
- These 2 alleles segregate into each gamete of the parents during meiosis
- Each gamete contains one of the alleles
- When fertilized, each offspring has one allele from each parent (total of 2)
- The trait expressed will depend on they inherit dominant or recessive alleles
What does expression of the recessive trait require?
An individual needs to have 2 alleles for the trait (only recessive)
What is a genotype?
The combination of alleles in an organization (Ex. Yy, yy, YY)
What is a Phenotype?
The physical and physiological traits of an organism. The expression of a genotype is called the phenotype
What does it mean to be Homozygous for a trait?
An individual has 2 identical alleles for that trait (Ex. YY or yy)
What does it mean to be Heterozygous for a trait?
An individual has 2 different alleles for a gene (Ex. Yy)
What are used to analyze the results of crosses?
Punnett Squares (Made by Reginald Punnett)
What do Punnett Squares do?
Uses Mendel’s Law of Segregation to show all possible offspring that could be formed from the gametes of the parents
What do the 4 squares in a Punnett Square represent?
They represent the 4 possible combinations and the chance of each of them occurring (each square represents 1/4 or 25%)
