Flashcards in Genetics 2038 test 1 ch 5-9 Deck (83):
Level of Dominance can alter outcome name 3 types
Complete dominance, incomplete dominance, and codominance
Complete dominance, incomplete dominance, and codominance are ALL the result of the relationship between
two alleles at a particular locus, but with VERY different outcomes
Type of dominance in which the phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes
Type of dominance in which the same phenotype is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote (
in which the phenotype of the heterozygote is not intermediate between the phenotypes of the homozygotes; rather, the heterozygote simultaneously expresses the phenotypes of both homozygotes. An example of codominance is seen in the MN blood types of humans.
Penetrance is the percent of individuals with
a genotype that express the expected phenotype
Expressivity is the DEGREE to which
a trait is expressed in an individual (Polydactyly)
Long fingers as RECESSIVE TRAIT. If penetrance is 80%, and two people HETEROZYGOUS for the finger length trait have offspring, what is the probability that a child will have LONG fingers?
1/4 *8/10=8/40 or 1/5
test cross is between
heterozygote and homozygote
Lethal Allele: causes
death at early development stage
how do Lethal alleles affect both genotypic and phenotypic ratios of offspring
Yellow mice; Yy is genotype; YY offspring die, so ratio is Yy:yy, 2/3 to 1/3 now only 3 offspring not 4.
Multiple alleles means that you have
more than two choices of alleles at a particular locus (ABO blood group
The effect of genes at one locus depend on
the presence of genes at other loci
Gene Interactions can produce
novel phenotypes, or perhaps masking gene effects (epistasis) (Table 5.2)
Type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus.
what is the bombay Phenotype
in a process referred to as epistasis - a gene for compound H is located at another locus on the gene. If that gene locus does not allow compound H to be produced than the AB antigens will not be expressed (added) to the surface of the RBC. hence the gene for A and B are masked even if present.
Production of yellow color in summer squash requires
if neither enzyme is produced in squash the squash is what color?
If only the first enzyme is produced the squash is what color?
Coat color in dogs is VERY complex because
Inherited in Mendelian fashion, but express differently in males and females
Inherited, encoded by autosomal genes, expressed in only ONE sex
Cytoplasmic inheritance typically refers to
mitochondrial DNA, typically maternally inherited; results in extensive phenotypic variation
Genetic maternal effect means that the
genotype of mother determines phenotype of offspring
Genomic imprinting causes
differential expression depending on parental inheritance
Epigenetics effects are due to
DNA changes which are not changes in base sequences, but expression
What are 4 different ways Inheritance of Continuous Characteristics work ?
discontinuous, continous, polygenic, Pleiotropy
how does Pleiotropy effect genes and charateristics?
one gene affects multiple characteristics
Polygenic charicteristics are
encoded by genes at many loci, but don’t interact
inheritence of CONTINUOUS characteristic would mean that a ----range of -----
WIDE RANGE of phenotypes, due to interactions between genes at MANY loci
Inheritance of Continuous Characteristics
Most are DISCONTINUOUS and
affect relatively FEW phenotypes ie round or wrinkled with few other options.
Study of Human Genetics is Difficult because
controlled mating not possible, long generation time, and small overall family size
A Pedigree is a pictorial representation of
family history, outlining inheritance of one of more characteristics
Twins studies help us understand what 3 things
Help determine concordance of a trait (percent that a trait is SHARED by both members of a twin pair)
Useful in studying genetic, AND environmental effects on traits
the Interpretation of Genetic Tests is complicated by what factors?
1. diseases that are caused by numerous mutations, not just single one
2. environmental factors and incomplete penetrance
3. the enforcement of the Genetic Information Non-Discrimination Act (2008)
Linked genes DO NOT
sort independently so they do not follow Mendelian rules
Linked gene alleles may or may not
separate during meiosis; they MAY or MAY NOT sort into new combinations
what causes recombination of linked genes?
“crossing over” during meiosis moves alleles that were once “linked” to possibly become “unlinked”. Anaphase 1
Formula for recombination frequency
(# recombinants / # total offspring) x 100%
wild type alleles on one chromosome, mutants on other chromosome of pair is callled________________and is in what conformation?
Coupling (cis Configuration)
when the wild type allele and the mutant type of allele are on the same chromosome it is callled ___________ and is in ______configuration
what type of test is done to determine the amount of linkage between genes.
test cross of heterozygous with recessive homozygous (AaBb*aabb)
independent assortment of a test cross for AaBb with an aabb would result in
25% in each group
completely linked genes in a test cross would result in how many outcomes
only 2 of the possible 4 outcomes.
why would a test cross produce any results other than 2 or 4?
difference from those ratios would indicate linkage with SOME crossing over
A GENE LINKAGE MAP can be constructed using
recombination frequencies; test crosses help determine order
in a gene linkage map with 3 genes involved you are looking for
double crossovers (least numerous) and the nonrecombinants (most numerous). different phenotype between the two is the gene between them
what are 2 ways of Determining gene locations:
1. Somatic cell hybridization
2. Deletion mapping
Somatic cell hybridization is used to determine
which chromosome a gene is on
Deletion mapping is used to determine the
location on a particular chromosome (can also use in situ hybridization)
Chromosome mutations include
rearrangements, aneuploids, and polyploids
Rearrangement mutations include which 4 categories
duplication, deletion, inversion, translocation
gene product imbalances (gene dosage
gene product imbalances, expression of recessive gene (pseudodominance
Inversions: can be
paracentric or pericentric (centromere location important)
do not include the centromere; more detrimental
include the centromere; some viable gametes
translocations can be classified in which 3 types
Non-reciprocal, reciprocal, or Robertsonian
Robertsonian: translocation trades?
Two long arms of chromosomes recombine, as do the short arms;
which chromosome is viable after a Robertsonian translocation
one chromosome becomes very large, the other too small and non-viable
In a non-reciprocal translocation, one chromosome transfers genes
to another chromosome (uni-directional)
In reciprocal translocation, two non-homologous chromosomes
transfer genes to each other
Aneuploid is Caused by
non-disjunction in meiosis and mitosis
examples of aneuploid include
Robertsonian translocations; deletion of centromere during mitosis and meiosis. This is the loss or gain of certain chromosomes or homologous pairs of chromosomes. (Remember Turner syndrome and Kleinfelter syndrome?) Also – Down Syndrome (trisomy 21)
Polyploidy: can arise from
non-disjunction in mitosis or meiosis, or hybridization between two species followed by chromosome doubling. It is the presence of more than two complete sets of chromosomes
what is autopoyploidy
presence of 2 complete sets of chromosomes from single species
what is allopolyploidy
2 complete sets of chromosomes from two species. Confers some advantages – increased cell size and larger attributes in plants.
why is it advantagous to study Bacterial and Viral Genetic Systems
rapid reproduction and many progeny; haploid genome allows direct mutation expression; growth in lab requires little space; medically important; techniques exist to manipulate genes.
what type of bacteria are wild type and require minimal media to grow
what type of bacteria are mutant and require complete media? What does complete media mean?
auxotrophic, complete media contains all substances/additives the bacteria needs to grow.
how are auxotrophic media selected for?
with media that includes nutrients that favor one species or is missing for a different species
why does genetic analysis of bacteria require special techniques
due to circular DNA and presence of plasmids; some plasmids are freely replicating on their own (F factor – fertility factor is one example)
some plasmids are freely replicating on their own (F factor – fertility factor is one example) These extra circular segments are called
episomes are extra circular segements that can be transfered via
Conjugation for sure (possibly includs- transformation, transduction)
transfer of DNA from one bacterium to another (F factor experiments; Lederberg and Tatum); is called
we now use Hfr (High frequency strains with F factor incorporated into the bacterial chromosome directly) for many experiments; F’ (F prime) is the standard bacterial cell with F factor in a plasmid with some bacterial gene. what type of transfer is this?
bacteria taking up free DNA is called a__________
for dna transfer via _______ the cells must be competant to take up free DNA
Co-transformed cells are those transformed by
2 or more genes
bacterial viruses take DNA from one bacterium to another
provide three facts about transduction
1. Useful because of viral incorporation into host bacterial DNA
2. Usually occurs between bacteria of same or closely related
3. Viruses can also affect many OTHER species (humans, for example – HIV and influenza, Zika virus)
R factor plasmids are those
conferring antibiotic resistance