Chapter 5: Non Mendelian Inheritance Flashcards
What are the 4 rules that genes have to conform to if they have Mendelian Inheritance patterns?
- Expression of the genes in the offspring directly influences their traits
- Genes are passed unaltered from generation to generation
- Genes obey Mendel’s law of segregation
- When crosses involve more than one gene, the genes obey Mendel’s law of independent assortment.
What breaks each of those rules?
- Maternal Effect breaks rule 1
- Epigenetic inheritance breaks rule 2
- Extranuclear Inheritance breaks rule 3
- Linkage breaks rule 4
What is maternal effect?
genotype of the mother directly affects the phenotype of her offspring.
the A/A will determine what the offspring look like even if mom does not look like that!
In snails right is what?
left is ? Female symbol is?
Right = Dextral (more common)
Left = Sinistral
Female symbol is a circle with a cross facing down
Find the F1 - F3 generation for
DD (F) x dd (M) x dd(f) x DD (M)
F1 right side = All Dd (dextral)
F1 left side = Dd (sinistral)
F2 = Dd x Dd, all are facing right, so 1:2:1 ratio
F3= 3 right 1 left ratio
What is the role of maternal effect in gene development?
encodes RNA + proteins that play important roles in the early steps of embryogenesis like cell division, cleavage pattern, and body axis orientation
What are nurse cells?
- the accumulation of MEG before fertilization allows these steps to proceed very quickly after fertilization
- express mRNA and/or protein from genes of the D + d allele and then transfer those products to the egg
A Female snail coils to the left (sinistral) has offspring that coil to the right (dextral). What are the genotypes of mom and maternal grandma?
D/d, d/d
A female snail coils right (dextral) has offspring that coil to the left (sinistral). What are the genotypes of mother and maternal grandma?
d/d, D/d
What is epigenetic inheritance?
- Involves genes in the nucleus
- genes are modified by methylation (CH3) during either gametogenesis
or Dosage compensation
What does methylation do?
will shut off genes or silence them
Epigenetic inhertitance happens during
- gametogenesis
- early embryonic development
Epigenetic inheritance is a pattern in which a modification occurs to a nuclear gene or chromosome that alters gene expression but
this expression is not permanently change over the course of many generations
aka reversible
What is dosage compensation in mammals?
- Occurs by chromosome condensation
- Females have 2 xxs (1 is a barr body (inactive)) other X is active
Give an example of dosage compensation
- Mice with variegated coat colors (will have black from XB from dad and Xb from mom = white)
- Calico cats (black and orange are both on X chromosomes just depends what is being expressed on the gene)
what is genomic imprinting?
- A segment of the DNA is marked and the effect is maintained throughout the life of the organism inheriting the marked DNA
What is mono allelic expression?
the offspring expresses either maternally or paternally inherited allele (NOT BOTH)
- under genomic imprinting
For the IgF2 gene, what parent is being expressed?
Dad !
mom is silenced or imprinted on
Genomic imprinting occurs in several species like insects, mammals, + flowering plants it may involve
- a single gene
- a part of a chromosome
- an entire chromosome (like barr bodies)
- all the chromosomes from one parent
- can be used for X inactivation in some species
What is the Imprinting control region (ICR)?
- its located near the imprinted gene, close to it or next to it as well
- methylates either sperm or egg NOT BOTH
- contains binding sites for one or more transcription factors that regulate the imprinted gene
Explain the process of tags being ripped off
The tags or CH3s are stripped off and reattached during gametogenesis, so male sperm gets demethylated and then reattaches to both sperms
- female eggs are methylated in the very very beginning but finally product is not.
What is Extranuclear inheritance? and what else is it called?
Involves genetic material outside the nucleus like the Mitochondria and chloroplast
also called Cytoplasmic inheritance
Where is the majority of the mitochondria coming from?
Mom because the egg is larger and has more cytoplasm than the sperm
Where is the genetic material of mitochondria and chloroplast located?
Nucleoid
- have their own DNA
