Chapter 14 (Classical Genetics) Flashcards
What principles account for the transmission of traits from parents to offspring?
parents pass on discrete heritable units—genes—
that retain their separate identities in offspring.
Who started the foundation for modern genetics?
Gregor Mendel
What did Mendel use for his experiments?
pea plants
Why did Mendel use pea plants?
generation of many offspring
What did Mendel choose to track?
only characteristics that showed up in two alternate forms (like color purple and white)
What did Mendel use to begin his experiments with?
true-breeding pea plants
What is the P generation?
parental generation
What is the F1 generation?
1st generation (offspring of parents)
What is the F2 generation?
offspring of the first generation
What is hybridization?
mating, or crossing, of two true-breeding varieties
What were the laws that Mendel discovered?
Law of Independent Assortment and Law of Segregation
How did the pea experiment contribute to the Law of Segregation?
F1 generation had distinct colors matching either one of the parents, no blending happened. Rather, one trait disappeared then reappeared
What was the phenotypic ratio of the F2 generation in the pea experiment?
3:1
What was the genotypic ratio of the F2 generation in the pea experiment?
1:2:1
What is a phenotype?
physical appearance
What is a genotype?
genetic makeup
What does a punnet square describe?
all possible results and statistic predictions of a genetic cross
How do you represent a dominant allele?
capital letter
How do you represent a recessive allele?
lowercase letter
What can a genotype be of a dominant phenotype be?
ex: PP or Pp
What accounts for variations of different genes?
alternate versions of the gene existing on a locus as an allele
How many alleles are inherited for each trait?
2 alleles per trait (each from parent)
If two alleles at a locus differ then how does it affect the effects of dominance and recessive-ness
dominant allele determines the appearance while recessive allele has no affect on appearance
What is the Law of Segregation?
2 alleles separate during gamete formation and end up in different gametes
What is homozygote/homozygous?
organism that has a pair of identical alleles for a gene, TRUE BREEDING
What is heterozygous/heterozygote?
an organism that has two different alleles for a gene, NOT TRUE BREEDING
What did Mendel follow to come up with the law of independent assortment?
following two traits (like color and shape)
What is a monohybrid cross?
cross between only one hybrid and a true-breeding
What is a dihybrid cross?
cross between two hybrids
What is the phenotypic ratio for a dihybrid cross?
9:3:3:1
What does the Law of Independent Assortment State?
genes are packaged into gametes in all possible allelic combinations, as long as each gamete has one allele for each gene and do so independently
What does the Law of Independent Assortment apply to?
alleles on different chromosomes that ARE NOT HOMOLOGS or genes that are very far apart
Do you multiple or add when it comes to calculating probability with two or more independent events happening sequentially?
multiply
Do you multiple or add when you want to calculate the probability that one or more events will happen?
add
What should the probability for a set of outcomes equal?
1
What are the situations in which Mendelian genetics doesn’t apply to a single gene?
When alleles are not completely dominant or recessive
When a gene has more than two alleles
What is complete dominance?
one allele always looks like one of the two parents (one plant always purple with purple and white parents)
What are the degrees of dominance?
complete dominance, incomplete dominance, codominance
What is incomplete dominance?
one allele not dominant over the other, phenotype is like a mix of parent varieties (red and white allele make pink offspring)
What is codominance?
two alleles each affect the phenotype in separate, distinguishable ways (blood type)
What is pleiotrophy?
Most genes, however, have multiple phenotypic effects (ex: gene that determines color also determines thickness of the coating of that color) (ex: cystic fibrosis, sickle cell)
What are the effects of a single gene?
degree of dominance, multiple alleles, pleiotrophy
What are the effects of multiple genes?
idea that expression of gene #2 depends on the expression of gene #1, but gene #1 becomes inactive, then the expression of gene #2 will not occur
What is epistasis?
phenotype depends on the activation of 2 or more genes
What does polygenic inheritance include?
quantitative characters
Epistatic interactions of modifications of which ratio?
9:3:3:1
What are quantitative characters?
the measurable phenotype that depends on the action of many genes working together (aka height and skin color)
What kind of inheritance pattern does quantitative variation indicate (aka a curve)?
polygenic inheritance
How is a genotype related to phenotype in terms of the environment?
with a range of phenotypic possibilities due to environmental influences
What is a pedigree?
the family tree that describes the interrelationships of parents and children across generations
Dominantly inherited disorders are caused by..
presence of only 1 dominant allele
Recessively inherited disorders show up by…
individuals homozygous for the allele
What are carriers?
heterozygotes carry a recessive allele but have normal phenotype
Why does recessive inheritance of a gene increase when mating within a family?
people with recent common ancestors are more likely to carry the same recessive alleles than are unrelated people
What are the possibilities of trait patterns in a pedigree?
autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, Y-linked
Are sex-linked disorders common more in women or men?
men
For a recessive sex-linked trait to be expressed, what does a female need?
homozygous (2 recessive X)
For a recessive sex-linked trait to be expressed, what does a male need?
one recessive X allele
