genetics test 2 ch5 epigenetics
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Exceptions to Mendel's prediction.
- -Genotype of indivdual. --X-- phenotype
- - Genes are not found with the nucleus.
Patterns of inheritance that does not involve the actual DNA (base pairs)
DNA, chromatin (histone): modifications -- Do not stay from parents to child, last a life time.
- Examples = -CH3 (methylation) - Histones
- - Nucleic Acids
- -COCH3 acetylations
- -Ubiquitin (small protein)
- - Takes on diff form depending on the species.
- diploid: xx xy
- y- contains hardly any genes.
- x- contains about 1000 genes.
- Takes on diff form depending on the species.
Dosage compensation in Marsupials
1st evidence of X-Activation
- *Cytogenic - stain DNA
Tightly packed, very condensed DNA
- shown as lighter,less stained
- loosely packaged
- -greater gene expression
- -more genes in general
- tightly wound X-chromasome
Molecular Mechanism of X-inactivation
* Which X is silenced is random
Occurs in 3 stages: X ist expressed
@ Early stages of development (~30 cells)
- 1. Initiation: one X is chosen
- (targeted for silencing)
- * It might be Xce ----> lots of genetic variation here
2. Spreading: As embryo is developing, compacting of chromatin begin at Xic, then moves along chromosome.
3. Maintenance:Through adulthood, each mitotic divisio, same x-chromosome (Barr body) is copied as such
* Barr Body *Some genes escape inactivation (example x-ist)
Phenotypic Result: example - Cats
- * Female Calico Cats
- * Patches of color
- B = orange b = black
- o = barr body
- XBXB = orange ---Xinactivation--> XBo
- XbXb = black ---Xinactivation--> Xbo
- XBXb = orange ---Xinactivation--> XBo}patchs
- ---Xinactivation--> Xbo}patchs
- xxy = male calico
- * Methyl groups ---> on DNA
- -affects expression
- -the marks distinquishes between maternal and paternal inherited chromosomes/alleles
- ->->-> mono-allele expression
- *Only a dew human genes are imprinted
- *No change in DNA sequence
- ******Insert Diagram***********
- More CH3 in general = silent gene
- less CH3 = actively/expressed gene
- * promoting proteins that inhibit trxn (transcription)
- * Prevent binding of proteins that allow/enhance trxn
- * Near imprinted gene = Imprinting control region
EX 1 genetic imprinting
- **check powerpoint for result***
Ex 2 genetic imprinting
- genotypically = Tt
- phenotype = appears as tt
- or a a dominant trait
- 1. Circular chromosome
- 2. Double stranded
- 3. serial copies -by size and # variation depending on species.
- 1. mt n13 genes encode protein for mitochondria function
- 2. tRNA, rRNAs
- -necessary to translate genes
- Chloroplast = similar , but bigger 10x
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