Chap. 5 Understanding Inheritance Flashcards
To make you cry (68 cards)
Who was Gregor Mendel?
- 1812 to 1884
- an Australian Monk
- known as the father of genetics
What were two important features of Mendel’s work?
- Simplicity
2. Measured quantitatively
What are (more specifically) the important points of Mendel’s work?
- studied specific characteristics one at a time
- had no knowledge of mitosis, chromosomes, etc.
- studied common garden peas
- readily available and easy to grow
- reproduce quickly
- many different characteristics with two traits
- followed a classic approach to problem solving
- most of his work was destroyed after his death
Characteristic
A feature of an organism which can be expressed in one of two or more ways, which are known as traits
Trait
A distinct form of a characteristic
How did Mendel control the pollination of his pea plants?
He removed the young, immature stamens from flowers chosen to be the female parent. They were separated, covered, and then pollinated by Mendel
What were Mendel’s four conclusions after his monohybrid crosses?
- The original male and female contain different factors (alleles) (one for tall, one for dwarf)
- There must be a mix of the factors in the F1 generation because both traits reappear in F2
- There must be a separation of factors prior to self pollination in order to produce a hybrid offspring
- The tallness factor must be dominant over the dwarfness and the dwarfness is recessive
What is Mendel’s first law, the law of segregation?
- An individual contains factors (alleles) in pairs
- These factors segregate from one another and are distributed to different sex cells
- Each parent can only contribute one member of a pair of factors to their offspring
What is the relation of probability to genetics?
The probability of two or more independent events occurring together is the product of individual probabilities of each event occurring separately.
How do you do a test cross?
Cross a dominant phenotype (the one you are testing) with a known pure bred homozygous recessive plant to determine the genotype of the F1 plant. If 50% of each phenotype, heterozygous
What are the steps of Mendel’s method?
Let R represent the dominant allele
Let r represent the recessive allele
1. Describe the genotypes of the parents
2. Determine the possible gametes each parent could produce
3. Organize the possible gametes using a PUNNETT SQUARE
4. Analyze all the possible genotype combinations by summarizing their gene combinations as a word description and summarize how many zygotes of each combination are possible
5. For each genotype describe the corresponding phenotype and how many are possible
What is the ratio for a standard monohybrid cross?
3:1
What is the ratio for a standard (heterozygous) dihybrid cross?
9:3:3:1
What is Mendel’s second law, the law of independent assortment?
Members of different pairs of factors behave independently and assort independently during gamete formation.
What are conventions of a pedigree chart?
- Roman numerals symbolize generation
- Arabic numbers symbolize individuals within a generation
- birth order is indicated by drawing them from the oldest to the youngest
In pedigree charts an autosomal dominant allele:
- will usually be transmitted from a parent to at least 50% of the offspring
- will appear in every generation (probably)
- will be expressed in the appearance of the organism
- every individual should have at least one affected parent
- males and females should be affected with equal frequency
- two affected individuals may have unaffected children
In pedigree charts a recessive recessive allele:
- will occur in offspring but may be absent in parents or other relatives
- will be seen in about 25% of the offspring if both parents are heterozygous.
- Two affected individuals usually produce offspring all of whom are affected
- males and females are equally at risk
True breeding
Organisms that exhibit the same traits generation after generation
Cross
The fertilization of a female gamete of specific genetic origin with a male gamete of specific genetic origin
Genotype
The combination of alleles for any given trait or the organism’s entire genetic makeup
Phenotype
The physical and physiological traits of an organism
Homozygous
An organism that has two identical alleles of a gene
Heterozygous
An organism that has two different alleles of a gene
Test cross
A cross between a parent of unknown genotype and a homozygous recessive parent