Exam 2 Mendelin Flashcards
If you were interested in deciphering heredity, what characteristics would you want in an organism
easy to grow/house
distinct traits that are easy to measure
short generation interval
produce many offspring
Components of scientific process
Formulate a hypothesis
experimental design
collect data
analyze data
interpret data
generate new hypothesis
To formulate a hypothesis you have to
observe stuff and be skeptical
a priori
from the earlier
prior knowledge
a posterior
from the later
Hypothesis
your belief on how things work
should be falsifiable
Mendel’s Hypothesis process
bred true/ control lines of round and wrinkled
Mendel’s experimental design/collecting data
cross the controls
get all round
cross again and wrinkle trait reappears
Mendel’s analyze/interpret data
Round 3:1 wrinkled
large number in the experiment
Mendel’s new hypothesis
2 particles of inheritance
R and r
Mendel’s Test model- make predictions
Crossed all of the F2 rounds to get the 3:1 ratio again
Test on a different trait to prove it
Gene
discrete factor of inheritence
Allele
alternative forms of a gene
Locus
specific location on a chromosome
Genotype
Combination of alleles
Homozygote
two identical alleles at locus
Heterozygote
two different alleles at locus
Phenotype
manifestation or appearance of a characteristic
Dominant
Phen1 is dominant to Phen2 if the F1 heterozygotes have Phen1
R
Recessive
r
Monohybrid cross
between two lines that breed true for one trait
Dihybrid cross
a breeding experiment between two organisms which are identical hybrids for two traits
Parental generation
F0 or P
F1
first filial generation
F2
second filial generation
Backcross
take the F1 offspring and breed with one of the parents
Reciprocal backcross
take the offspring of one generation and cross them back to the male or female parent
Mendel’s laws
First law- segregation
Second law- independent assortment
First law segregation
- each individual organism possesses two alleles encoding a trait (diploid)
- Alleles separate when gametes are formed
- alleles separate in equal proportions
Second Law Independent assortment
alleles at different loci separate independently
Probability
expresses the likelihood of the occurrence of a particular event
Conditional Probability
a probability that is modified by additional information that another event has occurred
Multiplication rule
stating that the probability of two or more independent events occurring together is calculated by multiplying the probabilities of each of the individual events
Addition rule
stating that the probability of any of two or more mutually exclusive events occurring is calculated by adding the probabilities of the individual events
Testcross
cross between an individual with an unknown genotype and an individual with the homozygous recessive genotype
Homozygous recessive is considered a
control
Wild type
the trail or allele that is most commonly found in natural (wild) populations
denoted with a +
superscripts and subscripts
added to distinguish between genes
Slash
used to distinguish the two alleles present in an individual genotype
underscore
indicates that any allele is possible
The two mechanisms of sex determination
chromosomal
environmental
The difference between sex chromosomes and autosomal chromosomes
throughout most of their length they are not homologous (gene sequence does not encode for the same characteristics
Pseudo autosomal region
the X and Y chromosomes are homologous at only these regions
essential for X=Y chromosome pairing in meiosis in the male
Sex refers to
the sexual phenotype
one difference between male and female gametes is
size
The mechanism by which sex is established is called
sex determination
Hermaphrodite
both sexes present in the same organism
Monoecious
individual have both male and female
Dioecious
individuals have either male or female reproductive structures
Examples of environmental sex determination
temperature determining sex in bearded dragons
Slipper limpets sex determination by where they are in the pile
Chromosomal theory of heredity
genes are present on chromosomes which serve as vehicles for segregation of genes in meiosis
XX-XO
simplest forms of chromosomal sex determination
female have two Xs, males only get one
Heterogametic
different sex with 2 different chromosomes
Homogametic
same chromosomes
XX-XY
sex determination that mammals use
females have XX
males have XY
X and Y pair in the _____ region
pseudoautosomal
ZZ-ZW
Common in birds, some reptiles, butterflies, some amphibians
males are ZZ, females are ZW
Turner Syndrome
XO
1:3000, usually sterile
Sometimes cells are XX and others are XO
Mosaic- cells in an individual have different composition of chromosomes
Poly X
XXX, XXXX
1:1000
better than Turner’s syndrome (at least have all of the cells)
no known cases of an individual without an X (never develop)
Kleinfelter syndrome
XXY, XXXY, XXXXY, XXYY
1:1000, usually sterile
XYY males
1:1000, usually normal
Sex determining region Y (SRY)
encodes a transcription factor that promotes differentiation of the testes
Mammals in early development have
undifferentiated gonads
Males are _____ for genes on the X chromosome
hemizygous
hemizygous
only one copy
montremes
5 copies
Dosage compensation
females have two copies, male have 1 copy of x-specific genes, affects the amount of protein produced
Lyon hypothesis
within the female cell, one of the 2 X chromosomes is inactivated
(happens early in development)
Genetic maternal effect
determination of phenotype by the genotype of the mother
Dominance
Phen1 is dominant to Phen2 if the F1 heterozygote have Phen1
Traits are
dominant or recessive
Incomplete Dominance
type of dominance in which the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes
Complete dominance
type of dominance in which the same phenotype is expressed in homozygotes (AA) and in heterozygotes (Aa)
only the phenotype of the dominant allele is expressed
Codominance
type of allelic interaction in which the heterozygote simultaneously expresses traits of both homozygotes
The nature of the dominance is relative to
the level at which the phenotype is examined
Penetrance
percentage of individuals with a particular genotype that express the phenotype expected of that genotype
Incomplete penetrance
A case in which some individuals possess the genotype for a trait but do not express the expected phenotype
Expressivity
degree to which a trait is expressed
Example- polydactyl
- some people have extra digits
-some have extra skin tags
Multiple alleles
Presence of more than 2 alleles at a locus in a group of diploid individuals: however each individual of the group has only two of the possible alleles
[n(n+1)/2]
number of genotypes possible
lethal allele
allele that causes the death of an individual organism, often early in development, so that the organism does not appear in the progeny of a genetic cross
Compound heterzygote
an individual who carries two different alleles at a locus that result in a recessive phenotype
Gene interaction
interaction between genes at different loci that affect the same characteristic
Epistasis
type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus
epistatic gene
gene that makes or suppresses the effect of a gene at a different locus
hypostatic gene
gene that is masked or suppressed by the action of a gene at a different locus
recessive epistasis
the recessive genotype at one locus makes the phenotype at a second locus
Dominant epistasis
a single copy of an allele at one locus masks the phenotype of a second locus
Duplicate recessive epistasis
two recessive alleles at either of the two loci are capable of suppressing a phenotype
Complementation Test
test designed to determine whether two different mutations are at the same locus (are allelic) or at different loci (nonallelic)
sex influenced
characteristic encoded by autosomal genes that are more readily expressed in one sex
sex limited
characteristic encoded by autosomal genes and expressed in only one sex
cytoplasmic inheritance
inheritance of characteristics encoded by genes located in the cytoplasm
usually contributed entirely by one parent
Genetic maternal effect
determination of the phenotype of an offspring not by its own genotype but by the nuclear genotype of its mother
Genomic imprinting
differential expression of a gene that depends on the sex of the parent that transmitted the gene
