Non Mendelian genetics disorders Flashcards
Hemophilia and Queen Victoria
A recicive gene that occurred because of a mutation.
She was a carrier, did not have it
Open circle or square with a dot
Shows a carrier
Hemophilia in the royal men
Appeared in alternate generations. They were the only ones who were affected
Products on the x chromosome would be equal for men and women if
- Expression of genes were doublen on male x chromosomes
- Expression of female x chromosome expression is halved
- A chromosome was turned off for women
What actually makes x chromosome expression equal
The turning off a chromosome in women.
Inactivation occurs
During the embryotic development. A complete chance which one will be deactivated.
Barr body
A dense mass of chromatin in female cells made of the inactive chromosome.
The same in all the cells descendants
Can be different from one cell to the next
Heterozygous individuals and deactivation
The dominant allele overpowers the expression of the recessive allele that was not deactivated
Different phenotypes in the body
Also can happen in heterozygous individuals. The deactivated cells differ so the areas they are active are different
Phenotype differences example
Calico cats
What breaks chromosomes
Radiation, chemicals, enzymes, change in chromosome number
Broken genes can…
Get lost, reattach to the same of different genes
Alterations after breakage
Deletion
Duplication
Translocation
Inversion
Deletion
A broken segment is lost
Duplication
A broken segment enters into a homologue. 2 fragments of the same chromosome in a row
Homologue
a different chromosome with the exact same DNA
Translocation
A broken segment attaches to a different, non homologous chromosome
Inversion
A broken segment attaches to the same area but backwards
Criduchat
Deletion of chromosome 5
Duplication can be
Evolutionarily beneficial or harmful, or have no effects
Duplication example
Hemoglobin in mammals
Translocation is often
Reciprocal
Reciprocal
2 non homologous chromosomes exchange segments.
Burkitt lymphoma
Chromosome 8 and 14 ends exchange resulting in over expression
Inversion effects
Similar to translocation. Can be beneficial or harmful
Nondisjunction
The failure of a homologous chromosome to separate during meiosis I or the mis division of chromosomes during meiosis II
Improper division in Meiosis I
Doesn’t have an effect of meiosis II division
Aneuploids
Individuals that don’t have 46 chromosomes
Euploid
An individual who has 23 pairs of chromosomes
Polyploids
1+ extra copies of chromosomes.
Triploids
3 copies of a chromosome
Tetraploid
4 or more copies of a chromosome
Aneuply results
Often debilitating or lethal. Miscarriages are common
Down syndrome
An extra chromosome 21
Results in a short stature, cognitive impairment, and being sterile
Aneuploidy in sex chromosomes
Less drastic effects. In women, x chromosome deactivation mechanisms can make it a barr body
XXX
Taller, high risk for a learning disability, and mensural irregularities
How are polyploids created
When the spindle fails to divide chromosomes
Polyploid in plants
They become hardier and more successful in growth and regulation. Common
Polyploid in animals
Lethal to 99% before birth
Recessive allele diseases function because of
Defective proteins (minimal or no function)
Autosomal recessive inheritance
A form of disease where
Homozygous dominant and heterozygous are least affected
Homozygous recessive are affected
Malaria and sickle cell trait
Individuals who are heterozygous are more immune, therefore more people in these countries survive
Cystic fibrosis
Altered membrane proteins resulting in cl- in extracellular fluid
PKU
The enzyme that coverts phenylalanine to tyrosine is not made. Phenylalinine and phenyl pyruvate build up
PKU prevention
If it is caught in infancy it can be altered by diet
Autosomal dominant inheritance
Homozygous dominant/heterozygous individuals are affected
Homozygous recessive are unaffected
Autosomal dominant inheritance example
Achondroplaisa
X-linked recessive inhertiance
Inheritance of the recessive allele. Duchene muscular dystrophy
Why are low income populations higher in disabilities
- Environmental factors
- Gained immunity to other diseases
- Genetic counseling
- Prenatal diagnosing
Genetic counseling
Using pedigrees or DNA test councilors predict if children will inherit a disease
Prenatal diagnosing
Embryonic cells are tested for mutant alleles or chromosomal alterations
Amniocentesis
Cells taken from the amniotic fluid
Chorionic villus sampling
Cells taken from the placenta that developed from the embryo
Genetic screening
Uses biochemical to test for disorders after birth
Cytoplasmic inheritance
Involves genes in the mitochondria and chloroplast
Genomic imprinting
Gene expression occurs differently if the gene was form mom or dada
Cytoplasmic gene difference
- Mendelian ratios are not found because meiosis does not occur
- Genes show unparented inheritance
Unparented inheritance
All offspring inherit the genotype of 1 parent
Why does maternal inheritance occur
In cytoplasmic inheritance because egg cells have more cytoplasm that sperm
Mitochondrial DNA mutations
Have to do with the ATP producing reactions
Imprinted (silent) alleles
The allele that is not expressed in genomic imprinting. Silenced by chemical modifications of its bases
PWS and AS
Caused by genomic imprinting and deletion of homologous genes
PWS genes
PWS is deleted and silenced on the mom’s chromosome and the person has no PWS gene activity
AS gene
Same as PWS but the paternal gene is silenced via deletion
Methylation
The addition of CH3 to cytosine nucleotides to silence a gene
Occurs in a embryo soon after fertilization
Methylation affects
The gene control region not the actual gene
Insulin growth factor 2
Codes for a molecule for cells to divide and grow. Ideally the paternal gene is on and the maternal gene is off
Loss of imprinting
Both genes are turned on leading to double growth factor which leads to cancer
