Chap 3- Punnett Squares, etc. Flashcards
Why did Mendel choose garden peas?
-They are easy to grow, have true-breeding strains
-could have controlled mating: self-fertilization or cross-fertilization
-grow to maturity in one season
-have observable characteristics with two distinct forms
What had Mendel discover?
The basis for the transmission of hereditary traits
What did the monohybrid cross reveal?
How one trait is transmitted from one generation to another generation
What does monohybrid cross involve?
Crossing a single paid of contrasting traits
Sequence of parents in monohybrid
P1 generation- Parents
F1- P1’s offspring
F2- F1’s self fertilization result
In monohybrid, what traits do F2 generation exhibit?
3/4 exhibit the same trait as F1 generation and 1/4 of contrasting traits that disappeared in F1 generation
What is a similarity in F1 and F2 generation?
The results were identical regardless of which is the pollen parents and which is the source of ovum (reciprocal cross)
What do genes serve as?
The basic unit of heredity and are passed unchanged from generation to generation, various traits expressed by each individual plant
What are unit factors in pairs?
what controls genetic characters in individual organisms
What is dominance/Recessiveness?
One unit factor is dominant and the other is recessive
What is segregation?
Paired unit factors segregate (Separate) independently during gamete formation
Where are units of inheritance, called genes, found?
In alleles
What is genotype?
The genetic makeup of an individual for a specific trait (DD, Dd, dd)
What is phenotype?
Physical expression of the genetic makeup (tall and dwarf)
Homozygous genotype
has identical alleles (DD, dd)
Heterozygous genotype
Two different alleles (Dd)
What does the punnett square allow?
for genotypes and phenotypes resulting from a cross to be visualized
What is a testcross used for?
to determine whether an individual displaying the dominant phenotype is homozygous or heterozygous for that trait
What is dihybrid cross (two-factor cross)?
A cross involving two pairs of contrasting traits is a dihybrid cross, which generates a unique F2 ratio
What does Mendel’s fourth postulate state?
-During gamete formation, segregation pairs of unit factors assort independently of each other
-Two pairs of contrasting traits are inherited independently during gamete formation
-All possible combinations of gametes will form with equal frequency
What does product law of probabilities allow?
For all frequencies of all possible F2 phenotypes to be calculated
What occurs when two independent events occur simultaneously?
the combined probability of the two outcomes is equal to the product of their individual probabilities of occurrence
Where can testcross be applied?
When an individual expresses two dominant traits but whose genotypes are unknown
In testcross, what is crossed with F2?
a homozygous recessive genotype
Example: GGWW or GgWw cross with ggww to determine genotype of unknown
What did Mendel demonstrate in regards to trihybrid?
That the identical processes of segregation and independent assortment apply
What is the forked-line method?
A branched diagram that uses simple application of the laws of probability and can be used to solve crosses involving any number of gene pairs, providing that all gene pairs assort independently of each other. Works with dihybrid or trihybrid
What did Mendel suggest heredity resulted in?
discontinuous variation- offspring are not a blend of the parental phenotype
What did the chromosomal theory of inheritance propose?
Genetic material is found in all living organisms, contained with chromosomes which are transmitted from generation to generation
What is diploid number?
The specific number of chromosomes in each somatic cell nucleus diploid organism. It is the characteristic to that species
-Gametes formed during meiosis have half the number of chromosomes; haploid (n)
Where do each pair of homologous chromosomes separate?
during gamete formation; each gamete receive one member from each pair of chromosomes
What is the locus?
location of a gene on a given chromosome
What are genetic ratios and what do they predict?
Genetic ratios are expressed as probabilities and they predict the outcome of each fertilization event
What is the range of probability?
0.0 (not occur) to 1.0 (will occur)
What is calculated as using the product law?
Two independent events occurring at the same time
- The probability of both events occurring is the product of the probability of each individual event
What is the sum law
To calculate the probability that the possible outcomes of two event are independent of one another, but can be accomplished in more than one way
What does chi-square evaluate?
the influence of chance of genetic data; used to test how well the data fit the null hypothesis
-Degrees of freedom are taken into account bc the greater number of categories, the more deviation is expected as a result of chance
What is the degrees of freedom equal to?
n-1, where n is the number of different categories into which each datum point may fall
After degrees of freedom is determined, what may be interpreted?
X^2 in terms of a corresponding probability value (p)
What is the chi square X^2 used for?
to test how well the data fit the null hypothesis
What does the p value enable us to do?
Reject or fail the null hypothesis
p values b/w 0.5 and 1.0 indicate that the observed deviation will be obtained by chance alone 5 percent or more of the time
Null hypothesis
No significant difference between two groups
Alternative hypothesis
Significant difference between the two groups
What is a pedigree
shows a family tree with respect to a given trait. Pedigree analysis reveals patterns of inheritance of the trait being studied
In a pedigree, what are women designated as and what are male, unknown?
Female- circle
Male-square
Unknown- diamond
In pedigree, what does shading indicate?
expression of phenotype
In pedigree, what does a dot represent?
Heterozygous individuals that do not express that trait but are known as carriers
In pedigree, what do diagonal lines indicate?
twins from vertical line connected to sibship line.
In identical, diagonal lines linked by horizontal line
In fraternal, twins lack this connecting line
In pedigree what does a diagonal line through them indicate?
Deceased individual
What is proband (p)?
The individual for who the pedigree was constructed
What is albinism?
The first illustrates the inheritance of a recessive trait
The second illustrates the inheritance of a dominant trait
