Chapter 3 Flashcards
When did Gregor Mendel study pea plants?
From 1856 - 1868
Why did Gregor Mendel choose pea plants?
Fast growing, many individuals can grow at once, have clear phenotypic traits, and are easy to cross/breed.
Define trait/trait versions
Physical characteristics and their variants
Define selfing
When an individual plant pollinates itself
Define cross
When one plant is bred with another
Define hybridization
Pea plant with one trait version is bred with a pea plant with a different trait version.
Define P1 Generation
Parental generation
Define F1 Generation
First filial generation. Children of parents
Define F2 generation
Second filial generation. Grandchildren of parents.
Define monohybrid crosses
Hybridization in which individuals only differ in 1 trait.
In monohybrid crosses of homozygous plants, what phenotypes will the F1 and F2 generation have?
F1 - only one trait version / phenotype (dominant allele shows)
F2 - mix of both trait versions
What are unit factors?
What Mendel called alleles.
Define homozygous
Organism with the same 2 unit factors /alleles
Define heterozygous
Organism that has 1 of EACH unit factor / allele
Define dominant
One trait version masks the other when both are present.
Define recessive
One trait version is masked when the other is present.
Define phenotype
An organism’s observable characteristics.
Define genotype
Organism’s underlying alleles
How many unit factors do diploid somatic cells have?
2 unit factors - corresponding to the 2 homologous chromosomes.
What is a punnet square?
Way to visual crosses. Shows what could happen if you cross 2 parents together.
Define testcross
Allows you to determine the genotype of a dominant individual.
Done by crossing the unknown dominant individual with a homozygous recessive individual.
What would the results of a test cross tell us?
If offspring all have the dominant phenotype, then the unknown’s genotype is homozygous dominant.
If offspring have a mix of dominant-phenotype and recessive-phenotype, the unknowns genotype is heterozygous dominant.
Define dihybrid cross
Crossing individuals that differ in 2 traits.
Define trihybrid cross
Cross between individuals that differ in 3 traits.
Define product law
Probability of multiple independent events is co-occurring. Is the product of their individual probabilities
Define independent assortment
Each homologous chromosome randomly picking a side in metaphase I
What are the odds that all maternal chromosomes end up on the same side in metaphase I?
1 / (2^23)
(incredibly low)
Define a chi squared test
Determines if the actual ratio differs from the expected ratio, or if the difference is due to chance.
Statistical test comparing observed and expected results.
What are the steps to a chi squared test?
1) Establish a null hypothesis
2) Obtain data
3) determine expected results
4) Find the chi squared value
5) determine degrees of freedom
6) Use df and chi square value to find probability (using given table)
7) Determine if you can reject the null hypothesis
Define null hypothesis
Default hypothesis assumed to be true
(Ex. no real difference between expected and observed offspring ratios)
How can you determine the expected results?
What is the expected offspring ratio? Use product law.
What is the chi-squared equation?
chi-square value =
the sum of [((O - E)^2) / E ]
E = expected
O = observed
What symbol is a female
circle
Define pedigree charts
Charts that reveal the distribution of phenotypes in a family. Helps to keep track and predict heritable diseases/conditions.
How do you know if you can reject the null?
If the p-value is less than or equal to 0.05 THEN you can reject the null.
What symbol is a male
Square
What symbol is when sex is unknown
Diamond
What symbol is for affected individuals
Shaded in / colored
What symbol is for parents who are unrelated to each other
(circle) - (square)
What symbol is for parents who are related to each other
(circle) = (square)
How are offspring of parents labeled/ordered?
By birth order. Oldest is on the left —> youngest to the right
What symbol is for fraternal twins?
A branch that stems into 2.
What symbol is for identical twins?
A branch that stems into 2 that has a second horizontal line (denoting =)
What does the “p” mean?
Proband.
Define consanguineous parents
Parents related to eachother
Define dizygotic twins
Fraternal. Not identical. Formed from 2 distinct zygotes
Define monozgotic twins.
Identical. Formed from same zygote.
Define proband
(p). Person who was first noticed to have the condition. FIRST CASE.
Define carrier
Someone who has the allele for a disease but does NOT have the disease. Generally heterozygous for it
What are the odds that an offspring is both yellow and round if 1 parent is GgWw and the other parent is GgWw?
9/16 odds for yellow and round
With a GgWw X GgWW cross, what is the probability of a GgWW offspring?
1/8 probability
Assuming a GGww x GgWw cross what are the odds of:
a) yellow, wrinkled
b) yellow, round
c) green, wrinkled
d) GGWw offspring
e) Ggww offspring ?
a) 1/2
b) 1/2
c) 0
d) 1/4
e) 1/4
With a cross between DdGgWw x DdGgWw , what are the odds for:
a) tall, yellow, and round
b) tall, green, and round
c) ddGGWw
a) 27/64
b) 9/64
c) 1/32
