Unit 8: Mendelian Genetics Flashcards
Gregor Mendel started experimenting with ___ varieties of ____ and selected varieties he would use in his experiments to verify if they were __________ (_________).
Started experimenting with 34 varieties of peas and selected varieties he would use in his experiments to verify they were pure-breeding (homozygous).
What approach did Mendel use in his experiment?
Mendel was the first to use this quantitative approach to understanding heredity.
What inheritance pattern did Mendel’s experiment show?
Mendel showed that inheritance of at least some traits was more of a discontinuous inheritance.
What are Mendelian Traits?
We call these traits that follow simple dominant recessive patterns “Mendelian Traits”
What is Mendel’s first law?
Principle of segregation- Each diploid organism has two alleles for a characteristic. These two alleles segregate randomly when gametes are formed, and one allele goes into each gamete.
What is Mendel’s second law?
What is Mendel’s third law?
Law of Dominance- When two different alleles are present in an individual, only the trait encoded by one of them- the “dominant” allele is observed in the phenotype.
What is a genotype?
The two alleles that an individual has at a given gene is called a genotype.
What is homozygous dominant?
2 dominant alleles (TT)
What is heterozygous?
2 different alleles (Tt)
What is homozygous recessive?
2 recessive alleles (tt)
What are the four characteristics of an autosomal dominant trait?
- Male-to-male transmission can occur.
- Males and females transmit the trait with equal frequency.
- All generations are affected.
- Transmission stops after a generation where no one inherits the mutation.
What are the three characteristics of an autosomal recessive trait?
- Males and females can be affected and transmit the gene, unless it causes death before reproductive age.
- The trait can skip generations.
- Parents of an affected individual are heterozygous or have the trait (Unaffected parents can be carriers (heterozygous, Aa. If both parents have the condition (aa), all their children will inherit it (aa).
What are the two effects of mutations?
- Loss of function
- Gain of function
What is a loss of function mutation?
No protein made (enzyme deficiencies). Usually recessive.
What is a gain of function mutation?
Different (toxic) form of protein or too much made. Usually dominant.
When are chromosomes that carry each allele oriented randomly?
During metaphase I, the two chromosomes which carry each of these alleles are oriented randomly.
What is the genotypic ratio and phenotypic ratio of a Bb x Bb where homozygous dominant BB is Purple and homozygous recessive bb is white?
Phenotypic ratio: 3/4 purple 1/4 white or (3:1)
Genotypic ratio: 1/4 BB 1/2 Bb 1/4 bb or 1:2:1
What is a forked-line diagram?
The forked-line diagram is used to determine gamete genotypes and frequencies.
What is the rule of independent events?
Past events have no influence on future events.
Ex. If a coin is tossed 5 times, and each time a head appears, the chance that the next toss will be heads is still 1/2.
What is the product rule?
The chance that two or
more independent events will occur together is equal to the product of the probabilities of each individual event.
What is the addition rule?
The chance of an
event occurring when that event can occur two or more different ways is equal to the sum of the probabilities of each individual event.
Ex. Since an offspring can have at least one dominant allele in two different ways (AA or Aa), we add their probabilities: 1/4 + 2/4 = 3/4
When you role a dice, the probability of getting either a three or a four is 1/6 + 1/6 = 2/6 = 1/3.
