Genetics Flashcards
Autosomal dominant
when someone is homozygous or heterozygous for the gene it is expressed because it is dominant. Pedigree pattern shows equal numbers of men and women and passed through every generation. Depending on parental phenotype (homozygous or heterozygous) could be passed to all children or ~50% of children
autosomal recessive
equal amounts of men and women. Need to be homozygous for the gene in order to express it, people that are heterozygous are considered carriers for the disease, do not present with the trait. This can skip generations- need to have a second parent with the trait in order to have homozygous child. Very rare in society not usually found in members inside of the family (because you need a parent with trait as well) except for other siblings.
X linked recessive
Men are mostly affected by this as they receive their X chromsome from their father. women tend to be carriers as they need to have two X chromosomes in order to be affected. Example: Mcleod phenotype (acanthocytes compensated hemolytic anemia) These are NEVER passed father to son- son only receives Y from father.
X linked dominant
women have a higher incidence of the trait because they have two opportunities of inheriting- though they pass down to all of their sons. These are NEVER passed father to son. Example= Xga
Connection between recombination and gene location
The closer two genes are together the higher the chance that they will stay together during recombination events and therefore be inherited together. The greater the distance the increased chance of recombination of the genes- that they will not be inherited together.
Linkage disequilibrium
two genes are linked therefore they are inherited together. The statistically probability they are both inherited might be smaller than what is actually seen due to their location on the gene and the fact that they get inherited together rather than independently. HLA genes: A1 B8
Fisher-Race theory
the idea that the Rh, C and E antigens come from three separate genes at the RH locus as opposed to two which is correct.
cis-modifier effect
Kpa+ expression of the other Kell system antigens is suppressed. they are on the same haplotype, weakens the expression.
null
person possesses allele however, allele is nonfunctional or creates a nondetectable product (different than a deletion)
what percentage of children from heterozygous parents will have autossomal recessive trait
25%
In blood group genetics what does recessive mean?
homozygous for rare phenotype: i.e. Rh null- no expression of Rh antigens
Two types of Rh null
- Regulator type RHAG - nucleotide changes in RHAG leads to Rh null- implying that RHAG has a large role in Rh antigen insertion into the RBC membrane 2.amorph- multiple mutations in RHCE gene and common deletion of RHD together.
Cepellini effect
When C is in Trans to RHD the RHD antigen is weakened in expression, occurs in r’ individuals with R on other haplotype
O blood type change
261 deletion of G that causes a frameshift and premature truncation that lacks enzymatically active domain of AorB.
genetic difference in A or B
three amino acid subsitutions 235 Gly>Ser 266 Leu>Met 268 Gly>Alan
i adult
i adult without cataracts, there is a dysfunction in the GCNT2 gene- only effects exon that controls protein on RBCs, i adult with cataracts mutations on or gene deletions of GCNT2 gene loss of I antigen synthesis throughout out the body.
RhD gene and RhCE
each has 10 exons, parallel to one another 97% same coding between the two, differ by 32-35 amino acids
Lack of RhCE
found in all but rare D- - individuals
gene
segment of DNA that encodes a protein
gene locus
location of gene
alleles
variations of a particular gene, for example Jka or Jkb
how many choromosomes in gametes
1N haploid- half the number of chromosomes than normal, 23. This is a because when it comes together with another gametes it forms the 46 chromosomes total needed to make another human
how many chromosomes are there
46-22 pairs of autosomes, 1 set of sex choromosomes
Karyotype
Xy or XX, JkaJka or JkaJkb, it’s the combination of two alleles together that create the presence or absence of certain phenotypes, listing of traits from each chromosome inherited
