Module 6 Flashcards
What are two ways that gene mutations can be classified?
- Hereditary (aka germline)
- Acquired (or somatic)
What is a hereditary mutation?
- inherited from parent
- occurring in germ cells (egg and sperm)
- present throughout a person’s life
- in EVERY cell in the body
What is an acquired (or somatic) mutation?
- occur at some time during a person’s life
- occurs in somatic cells
- NOT in every cell in the body, only effect certain areas
- NOT passed on to offspring
What are 3 endogenous sources to causing gene mutations?
- replication stress
- inflammation
- metabolism
What are 3 exogenous sources to causing gene mutations?
- UV/ionizing radiation
- chemicals
- pathogens (infectious agents)
What is a chromosomal genetic damage?
- arise during cell division
- can involve:
1. number of chromos
2. structure –> atypical configuration
What is aneuploidy?
- abnormal number of chromosomes
- arise from errors in meiosis –> maternal meiosis 1
- most lethal (deadly)
- monosomy = missing one chromo
- cells very sensitive to loss of chromos!
What is a frameshift mutation?
caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read
What are 3 point mutations in DNA?
- silent
- nonsense
- missense
What are the 7 types of genetic alternations in genes?
- insertion
- deletion
- duplication
- inversion
- transpositions (moved around)
- intron/exon inclusions and exclusions
- mutations in regulatory regions (affects how much protein is made, not the DNA itself)
Most rare diseases are not genetic in origin. true or false
false –> they are
Is autism highly heritable? How do we know?
YES
- from twin studies
What factors contribute to autism?
environmental factors –> in utero exposure to a maternal immune response
What condition is associated with autism that stems from a mutation in a single gene?
Fragile X syndrome
How many genes are linked strongly to autism?
100
What do the mutations look like in the brains of autism?
- combo of germline and somatic mutations
- specifically, deleterious somatic mutations (causing damage)
- strong association of de novo (not inherited) copy number mutations
- a lot of mutations were deletions
What are 3 things that can have an affect on fetal outcomes (germline mutations)?
- age
- diet
- endocrine disrupting chemicals (EDCs)
What is number one risk factor for germline mutations?
age!
What is a selfish mutation in sperm?
- cancer-like process in the testicles
- certain mutations make stem cells divide abnormally
- overtime can increase
- explains why we have brain disorders –> autism and schizophrenia
What are polyaromatic hydrocarbons (PAH)?
-come from natural or anthropogenic (human-made) sources
- carcinogenic
- teratogenic
- genotoxic
What are minisatellites?
highly unstable, largely non coding genetic elements that are used to demonstrate that environmental factors can affect the germline mutation
What was 3 PAHs that showed increased mutations in germline?
- paternal smoking before the partner became pregnant
- BaP
- ENU
WHat is BaP? How is sperm affected by BaP?
- male germ cell mutagen
- dividing sperm are more sensitive to its effects
- impacts tandem repeat DNA
- affects testes weight, concentration, motility , and liver weight in utero exposure for male offspring repoductive parameters
chemical exposures induce microsatellite mutations/ true or false
true
How was ovaries affected by BaP?
the more BaP, the less healthy ovarian follicles
What are the BaP effect in reproductive tissues?
- highly susceptible
- affects sperm development and function
- affects amount of healthy ovarian follicles
- have a significant impact on health and disease across generations
What is genomic imprinting?
inheritance process
- epigenetic process that involves DNA methylation and histone methylation without altering the genetic sequence
- one gene is silenced from one parent while the gene from another parent is expressed
What is the epigenetic mark that homolgous chromosomes in order to achieve parental specific expression?
Differently Methylated Region (DMR)
What are the two types of DMR?
- germline –> methylation during gametogeneis
- somatic –> other one becomes methylated after fertilization
What are the 2 major clusters of imprinted genes that are in humans?
- short arm of chromosome 11
- long arm of chromosome 15
What are the 2 major genome wide epigenetic reprogramming events that take place during germ cell development?
- parental specific imprints are “erased”
- new imprints reflecting the sex of embryo are established
children conceived with ART are more likely to have imprinting disorders. true or false
true
parental allele-specific epigenetic marks are heritable to daughter cells, but must be reset in each generation to establish specific imprints. true or false
true
What are 2 human diseases that are prevalent because of genomic imprinting?
- angleman syndrome
- prader-willi syndrome (PWS)
What chromosome is affected in angelman syndrome and PWS?
deletion on chromosome 15 paternal –> PWS
deletion on chromosome 15 maternal –> angelman
What is X-chromosome inactivation?
occurs randomly for one of the two X chromosomes in female cells
What are the steps in X-chromosome inactivation (x4)?
- RNA transcribed from the Xist gene on the X chromosome from which it is expressed spread to coat the whole X chromosome (Xist RNA coating)
- once inactivated, Xist and Tsix are differently regulated on the X that will become the active X chromosome (XA) and one that will become the inactive X chromosome (XI)
- X chromos that become XI –> Xist transcripts spread and coat entire X chromo to establish “transcriptional silencing”
- Tsix is silenced on the XI