chapter 14 a and 14b Flashcards
define hereditary
the transmission of traits from parents to their offspring
define trait
any characteristics of an individual
what is the blending hypothesis
the idea that parental traits blend so that their offspring have intermediate traits
what is the particulate hypothesis
the idea that parents pass on discrete heritable units (genes)
(mendel and his pea plants helped him figure this one out)
what is the inheritance of acquired characteristics hypothesis
parental traits are modified through use and then passed on
what are polymorphic traits
trait that appears more commonly in two or more different forms (ex: purple vs white flowers)
what are pure lines
organism that produces offspring identical to themselves when self fertilized
p vs F1 and F2 generation
p = grandparents
F1 =parents
F2 = grand babies
what is a monohybrid cross
what ratio are these offspring
mating between two parents that are both heterozygous for one gene
3:1 only one has recessive genes only
define genotype
the combination of alleles found in an individual
what is mendel’s principle of segregation
the two members of each gene pair must segregate. They separate into different gamete cells during formation of eggs and sperm in the parents
what is a dihybrid cross
a dihybrid cross is a mating between parents that are both heterozygous for 2 traits
independent assortment vs dependent assortment. which one supported mendels result
o Independent assortment: alleles of different genes are
transmitted independently of each other.
o Dependent assortment: the transmission of one allele
depends on the transmission of another.
accurate = principle of independent assortment
in a dihybrid cross what is the phenotypic ratio of the F2 generation
9:3:3:1
what is a testcross
a homozygous recessive parent is mated with a parent that has a dominant phenotype but unknow genotype
what is the multiplication rule
states that the probability of two or more independent events will occur together is the product of their individual probabilities
what is the rule of addition
states that the probability that any one of two or more exclusive events will occur is calculated by adding together their individual probabilities
what part or cell division is responsible for Mendel’s principle of segregation
the physical separation of alleles during meiosis I
the genes for different traits assort independently of one another at meiosis I because they are located on different homologous chromosomes
- different nonhomologous chromosomes assort independently of one another
wild type vs mutant
wild type is the most common phenotype for each trait
mutants are individuals with traits caused by mutations
what does the SRY gene on the Y chromosome do
encodes a protein that is the trigger for male development
are pure lines always homozygous
yes
do all of the genes on the sex chromosomes relate to the sex of the individual?
No, they produce proteins that have other functions
what is sex linkage
the general term for genes being on either sex chromosome
a gene located on the x chromosome is x - linkage
when genes are close together on the same chromosome they are _____
what is linkage
linked
linkage is the tendency of genes to be inherited together because they are on the same chromosome
why are we only analyzing the male offspring in the fruit fly experiment
only have one copy of that gene on x chromosomes. Females have 2 copies. one on each chromosome
when does cross over occur in meiosis
prophase I
what is the frequency of recombination?
a measure of the distance between linked genes
when 2 genes are found on separate chromosomes the ratio of 1:1:1:1
how likely are two genes found on the same chromosome located very far apart for crossover to occur.
likely to occur. would be unlikely if closer together
why is the frequency of recombination 0 - 50%
because only 2 chromatids from two chromosomes can crossover (only 2 out of 4 bunny ears)
what is multiple allelism
when there are more than 2 alleles of a gene in a population
ex: humans have 3 common alleles for blood types o,a,b
what is codominance
neither allele is dominant or recessive to the other. heterozygous display the phenotype of both alleles
Ex: AB blood type
what is incomplete dominance
other alleles display incomplete dominance
heterozygotes have an intermediate phenotype
ex: pink flowers and white flowers made light pink flowers (Rr)
what is epistasis
the expression of many genes depends on the presence of absence of other genes
two or more genes work together to control a single trait.
genes that modify the phenotypic expression of other genes is said to show epistasis
ex: chickens and their combs
what is a pedigree
a family tree that describes the interrelationships of parents and children across generations
inheritance patterns of a particular traits can be traced and described using pedigrees
pedigrees can also be used to make predications about future offspring using multiplication and addition rules
define carriers
heterozygous individuals who carry the recessive allele but are phenotypically normal
dominant alleles that cause lethal disease are ___ and arise by _____
rare, mutation
