Lecture 9 Flashcards
What did people think before Mendel?
Inheritance is a blend of parent phenotypes and there is no recessive or dominant alleles
Why did Mendel choose peas?
They had distinct phenotypes, they were easy to grow, it was easy to set up crosses
What is the n number of peas?
2n=14 so it is diploid
What is the life cycle of the pea?
One year
What is the female part of the pea plant?
The stigma and ovule
What is the male part of the pea plant?
The filament and anther. This is within the stamen
How did Mendel do Cross pollination?
He took pollen from the anther of one plant and brushed it onto the sigma of the other plant and cut off the anthers
How many pea characters did Mendel begin with?
7
How many true breeding lines to Mendel have?
14
What are True breeding strains?
Population of organisms that produce offspring with specific parental traits that remain constant from generation to generation
Why was Mendel successful when other weren’t?
Because he made pure-breeding strains for genetic crosses
He also used discontinuous traits
He also noticed repeatable ratios
What is a Genetic Cross?
An experiment in which males and females of a model organism are mated to produce offspring
What is Hybridization?
A cross between two true-breeding individuals from distinct populations
What are the offspring of a hybridization cross known as?
Hybrids (monohybrids for one character, dihybrids for two characters)
What is a Monohybrid Cross?
A Genetic cross between two individuals that are identically heterozygous for a given gene e.g. A/a
What is a Reciprocal cross?
The same as a monohybrid cross except the phenotypes of the male and female are reversed
What are Monohybrids?
The offspring that are the result of a cross between two true breeding opposite homozygous alleles
What is Mendel’s first law?
Heredity is controlled by discrete factors (genes)
What is Mendel’s second law?
Alternative versions of genes explain the variation with respect to characters/traits (alleles)
What is Mendel’s third law?
An individual inherits one allele from each parent and therefore each gene exists as pair
What is Mendel’s fourth law?
Alleles in an individual may differ so that one allele is dominant and determines the phenotype
What is the Law of Segregation or Mendel’s first law created by Mendel?
The two alleles in a diploid organism separate during gamete formation, ensuring that an egg or sperm cell only receives one of the alleles
What is Random Fertilization?
Any male gamete can join with any female gamete
What a Test Cross used to test?
To test if an individual expressing a dominant trait is homozygous or heterozygous
What causes a wrinkled pea?
A mutation in a gene that makes an enzyme that converts starch to branched starch. Wrinkles peas don’t have this
How did Mendel tell if genes were linked?
He crossed true-breeding lines for a single trait and crossed them to create dihybrids
What are Dihybrids?
Plants that were heterozygous for 2 traits that were created by crossing two pure breeding parents YyRr
What is the Law of independent assortment?
The idea that genes could be inherited independently of each other
What would the ratio be if the cross was dependant?
The ratio would be 3:1 phenotypically
What would the ratio be if the cross was Independent?
9:3:3:1 phenotypically
What is the nomenclature for genes on different chromosomes?
A/a; B/b
What is the nomenclature for genes on the same chromosome?
AB/ab
What is a test cross for a Dihybrid cross?
Crossing an unknown with the dominant phenotypes with homozygous recessive genotype to determine the unknown genotype
What does Mendel’s Second law state?
Two different genes assort their alleles independently in gamete formation if they are found on different chromosomes
What is probability?
The chance that an event will occur
How can you calculate probability?
Number of times an event occurs/ total number of events
What is Synteny?
Two or more genes are located on the same chromosome and are physically linked
What is genetic linkage?
When genes are located near each other on the same chromosome tend to be transmitted as a unit
What are syntenic blocks?
Evolutionary conserved regions of chromosomes that display the same order of genes in different species
What is a Map unit?
A measurement that correlates amount of recombination seen with the distance between genes
What does it mean if genes are less than 50 mu apart?
They do not assort independently
What does it mean if genes are more than 50 map units apart?
They assort independently even though they reside on the same chromosome
What does a recombination frequency of 50% indicate?
The 2 gene are on the same chromosome 50 mu apart
The 2 gene loci are on the same chromosome more than 50 mu apart
The 2 gene loci are on separate chromosomes
If genes are unlinked what will the ratio of parents to recombinants in a dihybrid test cross?
1:1:1:1
