Genetics exam for thurday Flashcards
What is a locus?
Position or place of the allele
What is an allele?
One of two or more alternative forms of a gene
What is a gene?
An inherited factor (encoded in the DNA) that helps determine a characteristic
What does hemizygous mean?
having only one copy of a gene or chromosome segment instead of the usual two.
What is autosomal?
Not on sex chromosomes, all other chromosomes
What is sex-linked
These traits are controlled by genes on the sex chromosomes, which are the X and Y chromosomes
What is a monohybrid cross?
a genetic cross that studies the inheritance of a single trait or gene in two organisms with different variations at a single genetic locus.
What is a dihybrid cross?
a breeding experiment that involves mating two organisms that are heterozygous for two traits.
What is a back cross?
a breeding technique in genetics that involves crossing a hybrid organism with one of its parents or a genetically similar organism. F1 gen X P
What is a test cross?
unknown genotype x homozygous recessive
what is a reciprocal cross?
The sexes of the parents are reversed.
What is nondisjunction?
the failure of chromosomes to separate properly during cell division (meiosis)
What is the principle of segregation?
Each diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete.
What is the principle of independent assortment?
alleles located on different chromosomes will sort independently
What are the P, f1, and f2 generations in a monohybrid or dihybrid cross?
p = parents
F1= offspring of parents
f2 = offpring of f1 cross
What is the binomial expansion?
(n!/ X! * (n-x)! ) *p^x * q^n-x
p equals the probability of one event
q equals the probability of the alternative event
n equals the total number of events
What is the product rule?
the probability of two or more independent events occurring together is calculated by multiplying the individual probabilities of each event
What is XO sex determination?
XX is female and XO is male, male is missing the Y chromosome
What is XY sex determination?
XX is female and XY is male, present system in humans
What is ZW sex determination?
ZZ is the male and ZW is the female. The male is homogametic and the female is heterogametic.
What is environmental sex determination?
Temperature and position of development can be factors of trait inheritance
In chromosomal sex determination, what are the homogametic sexes?
XX, ZZ,
In chromosomal sex determination, what are the heterogametic sexes?
XY, XO, ZY
What gene determines maleness in human bros?
SRY gene
What is X-linked?
Inheritance based on X chromosome
What is Y linked?
Inheritance based on the Y chromosome, trait is only in males and can only be passed to other male from father. if father has it, 100% of male offspring will have it too.
What dosage compensation mechanism is used in humans?
Inactivate one of the X chromosomes in the homogametic sex
What dosage compensation mechanism is used in Drosophila?
Increase transcription activity on the X chromosome in the heterogametic sex
What is incomplete dominance?
Both dominant and recessive show in various blends
What is penetrance?
% of individuals having a particular genotype that expresses the expected phenotype
What is incomplete penetrance?
when some individuals with a certain genotype do not express the expected phenotype.
What is codominance?
Both dominant and recessive are present but the phenotype is not an intermediate of the 2 but both show 100%.
What are lethal alleles?
Causes death at an early stage of development, so some genotypes may not appear among the progeny
What is gene interaction?
The effects of a gene at one locus depend on the presence of a gene at another locus. Genes exhibit independent assortment but do not act independently in phenotypic expression
What is epistasis?
One gene masks the effect of another gene
what is cytoplasmic inheritance?
Inheritance of mitochondrial DNA comes from only the mother. 100% mother.
What is the maternal effect?
The offspring’s phenotype is dependent on the mother’s genotype
What is expressivity?
the degree to which a trait is expressed
What is the difference between penetrance and expressivity?
“penetrance” refers to the proportion of individuals with a specific genotype who actually express the associated phenotype (whether they show the trait or not), while “expressivity” describes the degree to which a phenotype is expressed in individuals with the same genotype
What is sex-limited?
Expressed in only one sex, encoded by autosomal
What is sex-influenced?
Not limited to one sex, encoded my autosomal chromosomes
What is genomic imprinting?
differential expression of genetic material depending on whether it is inherited from the male or female parent
What is the purpose of a complementation test? How is it performed?
Determine whether mutations are at the same locus or at different loci. If the mutations are at the same locus, then the offspring will have the mutant phenotype and carry only the mutant alleles. If the mutations are at different locations, offspring will be heterozygous.
Homo Dom X HOMO rec
What is Turner syndrome and what is the genotype that goes with it?
XO genotype in females, short stature, webbed feet, narrow nails and low hairline
What is Klinefelter syndrome and what is the genotype that goes with it?
XXY, XXXY, XXXXY, etc. Extra chromosomes in male genotype. Only in males, small testes, large breasts, lack of body or facial hair
What are Poly X females and what is their genotype?
Females with more than 2 X chromosomes, taller, low muscle tone, learning disabilities, and developmental delays
What is dosage compensation?
The more copies of the chromosome/ gene, the more expression of that chromosome/ gene.
What is Androgen-insensitivity syndrome
Genetically male but the dude is missing the SRY gene to make him a true male, no testosterone, only noticeable at puberty
What is polygenic?
One trait coded by hundreds of genes
What is pleiotrophy?
One gene affecting multiple traits
What genotype will be the lethal allele?
Homozygus.
