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Human somatic cells have how many pairs of chromosomes
23 pairs with 46 chromosomes
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X-linked Recessive
You have to inherit two copies of the recessive gene for the disease to be fully expressed.
eg. of sex linked recessive: Hemophilia A & B
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Provide examples for:
Genotype is ___
Phenotype is ___
- Genotype: KK or Cc
- Phenotype: K+k- or C+c+
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What is a silent gene that does not produce a detectable antigen (product)?
Amorph
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Sex-linked dominant
Males who transmit a genetic trait to all their daughters but never to their sons.
Females who are heterozygous transmit to both daughters and sons equally
Females who are homozygous transmits trait to to all their children; follows the same pattern as autosomal dominant.
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How to distinquish X-linked dom from Autosomal dom
Distinguished by the offspring of affected males. Showing that males are transmitting to all their daughters.
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Autosomal Dominant
- - Expressed in both males and females.
- - The trait is expressed when the gene is passed on.
- - Expressed in every generation
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Recessive inheritance
The only way it will be expressed is if two copies were inherited (homozygous)
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Linkage Disequlibrium
Is the tendency of specific combination of alleles at two or more linked loci to be inherited together more frequently than would be by random chance.
So, when you calculate a frequency of a certain combination, and the observed phenotypes exceed the calculated amount, we then suspect that the genes are traveling together, or linked.
eg. Expected frequency of MS haplotype is: 0.17. A given population observed 0.24 instead.
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Autosomal Recessive
- - Expressed in both male and female (so not sex linked)
- - Not expressed in every generation
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Segregation
Two members of a single gene pair are never found in the same gamete.
A parent has the genotype JkaJkb. Meisosis occurs and 4 gametes are produced. Two gamets have the Jka gene, and the other two have the Jkb gene.
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Blood Group Systems that have genes which code for no protein.
Duffy, Kidd, Lutheran, Rh (r)
These BGS phenotypes would result in indirect exclusion in paternity cases.
- Ex:
- Mom: Jk(a+b-)
- Alleged Father: Jk(a-b+)
- Child: Jk(a+b-)
- Why indirect - Father could be JkbJk
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Can an alleged father be excluded with Indirect Exclusion?
No
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Define Random Segregation and provide example:
- Individual has pairs of distinct units (alleles); one inherited from each parent.
- Pairs separate during cell division
- Offspring randomly receives alleles from parent.
- EX: Mother is AO, Father is BO
- Child can be: AO,BO, OO, or AB
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Define Independent assortment and provide example:
- Genes inherited independently if carried on different chromosomes.
- Combination of genes are not dependent of other genes (exception: linkage)
Ex: ABO is inherited independently form the Kell blod group.
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Define Antithetical
A pair of antigens that are coded by different alleles of a single gene.
eg. Jka is antithetical to Jkb
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Define Chimera
Person with a dual population of cells derived from more than one zygote
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Define Cis
Alleles that are on the same chromosome
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Define Codominant
Both traits are expressed in the heterozygous state.
eg. AB, Fy(a+b+)
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Define Crossover
Exchange of genetic material during chromosome duplication and separation.
eg. Occurs in HLA genetics
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Define Genogypte
Actual genes present in individual, inherited from parents.
- Can only be determined by family studies or DNA testing
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Define Phenotype
The visible or measurable expression of the pair of genes; biological activity of the genes.
Determine by serological testing
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Define Linkage
Two loci carried on the same chromosome and are usually inherited together; the closer the loci (location of gene), the closer the linkage.
Seen in Rh, MNSs and HLA systems
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Define Linkage Disequillibrium
Genes at closely linked loci tend to be inherited together and are considered haplotypes.
eg. HLA and Rh
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Define Haplotype
A combination of alleles at two or more closely linked loci on the same chromosome; inherited together.
eg. HLA; Rh system
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Define Suppressor Gene
Affect the expression of another gene
eg. In(Lu), In(Jk), GATA-1, RHAG
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Define Trans
Alleles that are on opposite chromosomes.
eg. D and C in R0r1
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