Lec 7. Extensions to Mendels Rules 2 Flashcards
What is an example of Non-Mendelian Inheritance?
Cancer
What are BRCA genes?
Tumor suppressors that are important for DNA repair.
How are BRCA mutations inherited?
Dominant fashion but not 100% penetrant.
True or False? If you inherit the BRCA gene from your mom and youre a female, youre at greater risk than if your inherit the BRCA gene from your father and are female.
True.
Define a lethal allele
Causes death at an early stage of development. Some genotypes may not appear among the progeny
What affects the Mendelian genotypic and phenotypic ratios in progeny?
lethal allele
Define Multiple alleles
For a given locus, more than 2 alleles are present within a group of individuals
What is an example for multiple alleles?
ABO blood group
What is the genotype for blood type A?
(IA IO)=AO. (IA IA)=AA
What is the genotype for blood type B?
(IB IO)=BO. (IB IB)= BB
What is the genotype for blood type AB?
(IA IB)=AB
What is the genotype for blood type O?
(IO IO)=OO
When does gene interaction take place?
When genes at multiple Loci determine a single phenotype
Define Gene interaction
Effects of genes at one locus depend on the presence of genes at other loci
What are the two outcomes with gene interaction
Can produce novel phenotypes, or epistasis.
What is epistasis?
One gene masks the effect of another gene
What is an example for gene interaction?
color peppers
What does Dystrophen do?
Connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix
What happens when theres a Dystrophen mutation?
Muscle dystrophy. Becker’s or Duchennes.
What is recessive epistasis?
When the recessive allele of one gene masks the effects of either allele of the 2nd gene
What is dominant epistasis?
When the dominant allele of one gene masks the expression of all alleles of another gene
What is duplicate recessive epistasis?
2 alleles are involved in producing a characteristic and if either gene has 2 recessive alleles, the phenotype is blocked
What is a good example for Recessive epistasis?
ABO blood types.
How does the bombay phenotype display epistasis?
Its a mutation that prevents completion of the antigenic pathway. These ppl dont make ABO and cant get transfusions from A,B or O.
What is another example of Epistasis?
Coat color and pattern in dogs
What is an example for codominance?
BloodAB :IA IB
What is an example for multiple alleles?
ABO blood group alleles
What is Pleiotropy?
One gene is able to affect multiple phenotypic characters
What is an example of pleiotropy?
Sickle-cell disease
What is complementation?
Occurs when 2 strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype , produce offspring with the wild-type phenotype when mated or crossed.
How can we determine if mutations are at the same locus or in different complimentary genes?
Cross pure breeding strains.
When crossing pure breeding strains, what results when we determine the mutations are at the same locus?
the mutant phenotype
When crossing pure breeding strains, what results when we determine the mutations are at different loci?
Wild type phenotype
Why is sickle cell a good example of pleiotropy?
A single gene mutation results in liver failure, blindness and heart problems
What are the three types of pleiotropy?
Molecular gene, developmental, and selectional
Define molecular gene pleiotropy
Asses how many traits are affected by a gene at the molecular level
Define developmental pleiotropy
Relates to relationships between mutations and different developmental phenotypes.
Define selectional pleiotropy
Relates to how a mutation affects fitness
What is another example of pleiotropy?
Cystic fibrosis
True or False? Sex influences the inheritance and expression of genes in a variety of ways
True
Why does sex influence inheritance and expression of genes?
Sex influenced traits are controlled by genes present on autosomes, hence why genes are present in both sexes but expression is different in males vs females because it responds differently to androgens and estrogens
What is an example of sex influenced traits in humans?
Facial hair. Soft in women. Rough in males. Also male pattern baldness
Which characteristics are inherited according to Mendel’s principles?
Sex-limited characteristics
What is an example of sex-limited characteristics?
Precocious puberty in humans
What is precocious puberty?
When kids start to get into puberty much earlier than they should.
What causes precocious puberty?
Part environmental (more calories) and some are known mutations in genes. Luteninizing hormone receptor defect and makes it constantly active.
What are some examples of sex-influenced and sex-limited characteristics?
Genetic maternal effect, genomic imprinting and epigenetics
What is genomic imprinting?
Differential expression of genetic material depending on whether it is inherited from the male or female parent
What is epigenetics?
Due to alterations to DNA that dont include changes in the base sequence, often affect the way in which the DNA sequences are expressed.
What are imprinted genes?
Genes whose expression is determined by the parent that contributed them
What is an example of imprinted genes?
IGF2. promotes fast growth during embryo development. Moms gene is methylated and inactive and the fathers is operational. If the fathers gets copied everything is good. If the mothers is copied it results in death
What is an epigenetic trait?
heritable phenotype resulting from changes in a chromosome without alteration in the DNA sequence
Define sex-linked characteristic
Genes located on the sex chromosome
Define sex-influenced characteristic
Autosomal genes that are more readily expressed in one sex
Define sex-limited characteristic
Autosomal genes whos expression is limited to one sex
Define genetic Maternal effect
Nuclear genotype of maternal parent
Define cytoplasmic inheritance
Cytoplasmic genes, which are usually inherited from only one parent
Define genomic imprinting
Genes whos expression is affected by the sex of the transmitting parent
Define anticipation
A genetic trait becomes more strongly expressed or is expressed at an earlier stage as it is passed from generation to generation
Why does anticipation occur?
occurs due to expansion of unstable region of DNA from generation to generation
True or False? Anticipation is the expansion of an unstable region of DNA from generation to generation
True
How does Huntington’s disease happen?
Natural happens and results in an increase of repeats. Reinforcing cascade. The clinical phenotype is early neuro degeneration.
What are two examples of anticipation?
Fragile X and Huntington disease
What is Fragile X syndrome?
Results from a mutation of the FMR1 gene on the X chromosome, commonly an increase in the number of CGG repeats. Learning difficulties.
