basic genetics in blood banking

Mendel’s first law

Alleles of genes have no permanent effect on one another when present in the same plant but segregate unchanged by passing into different gametes

Codominance

Both alleles are expressed, and their gene products are seen at the phenotypical level

Law of independent assortment

Genes for different traits are inherited separately from each other which allows for all possible combinations of genes to occur in the offspring

Autosomal

Pertaining to a chromosome that is not a sex chromosome

Sex-linked

Gen mutation is present on a sex chromosome

Dominant

One variant of a gene on a chromosome masking or overriding the effect of a different variant

Codominant

Relating to two alleles of a gene that are both fully expressed

Recessive

An allele that does not produce a characteristic effect when present with a dominant allele

Genotype

Sequence of DNA that is inherited

Phenotype

Expression of the genotype

Locus

Specific location of a gene on a chromosome

Allele

At each locus there may be only one or several different forms of the gene

Homozygous

Presence of two identical alleles

Heterozygous

Inheritance of different alleles

Dosage

Effect of a significant difference in antibody reaction depending on the quantity of the target antigen present on a target RBC

Punnett square

A square diagram that is used to predict the genotypes of a particular cross or breeding event

Autosomal dominant

• trait appears in ever generation with no skipping

• Transmitted by an affected person to half their children

• Unaffected people do not transmit to their children

• Not influenced by sex

Autosomal recessive

• appears only in siblings

• ¼ of siblings of prospositus are affected

• Parents of affected children may be consanguineous (related)

• Males and females equally likely to be affected

X-linked dominant (sex linked)

• affected males transmit to all their daughters and none of their s ones

• Affected heterozygous females transmit to half their children

• Affected homozygous females transmit to all their children

• Can be distinguished from autosomal dominant by offspring of affected males

X-linked recessive

• higher in males than females

• Affected man to all his daughters and half his sons

• Never directly transmitted from father to son

• May be transmitted through series of female carriers, affected males may be seen to skip generations

Population genetics

Study of distribution patterns of genders and the factors that maintain or change the gene/allele frequencies

Frequency

Prevalence at the genetic level

Prevalence

Occurrence of a permanent inherited characteristic at the phenotypic level in any given population

Incidence

The rate of occurrence in a population of a condition that changes over time

How many chromosomes do humans have

46, 22 pairs autosomal, 1 pair sex

Chromatin

Nucleic acids and structural proteins called histones

Heterochromatin

Stains as dark bands

Achromatin

Stains as light bands, consists of highly condensed regions that are usually not transcriptionally active

Euchromatin

Swollen form of chromatin in cels, which is considered to be more active in the synthesis of RNA for transcription

Locus

The specific location of a gene on a chromosome

Allele

One or several different forms of the gene

Hemizygous

One chromosome has a copy of the gene and the other chromosome has that gene deleted or absent