4D Genetics

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adenine pairs with?

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thymine

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cytosine pairs with?

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guanine

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phenotype is?

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-gene that can actually be observed
-ex: A person with a phenotype of type A blood could have either an AA genotype or an AO genotype

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genotype is?

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-gene trait of actual alleles are for that trait, not just what can be observed
-ex: phenotype of type A blood can have AO genotype or AA genotype

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mutations

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-DNA changes passed from one generation to another & thus are inherited
-does not just mean human generations but can be cell generations too

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somatic mutations

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-occur in person's cells after conception, the person cannot pass on to his/her children

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germline mutations

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-mutation occurring in sex cells
-can be passed on and each child will consist of mutated DNA

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Autosomal Dominant (AD) Pattern of inheritance criteria

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- dominant gene alleles located on an autosomal chromosome
-dominant gene allele is expressed even when only one allele is dominant
-risk for affected person to pass trait to child is 50% with each pregnancy
-unaffected people do not have affected children, their risk is 0%
-trait is found equally in males and females

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penetrance

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-how often or how well a gene, within a population, is expressed when it is present
- example: Huntington's disease is highly penetrant because the chance of expressing the gene is very high (99.99%). The breast cancer gene however has reduced penetrance, the chance of it being expressed is 60-80%

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expressitivity

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-degree of expression person has when dominant gene is present
-gene is always expressed, but some people have more severe problems than others

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Autosomal recessive (AR) pattern of inheritance

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-gene located on autosomal chromosome
-trait can only be expressed when both alleles are present
-25% of family will be affected and express trait
-children of 2 affected parents will always be affected
-unaffected people who are carriers & do not express trait can transmit trait to children if their partner is also a carrier/affected

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AR pattern of inheritance example

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-type O blood is recessive, both alleles must be type O for person to express type O blood
-if only one allele is type O and the other is either A or B, dominant allele will be expressed and the O is not

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carrier

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-one mutated allele for a recessive genetic disorder
-usually does not have any manifestations
-can pass mutated allele on to kids

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X-linked recessive pattern in males

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-dominant expression because males do not have a second X chromosome to balance presence of recessive gene on the first X chromosome

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X-linked recessive pattern in females

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-recessive expression due to 2 X chromosomes

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Sex-linked (X-linked) recessive pattern of inheritance

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-require that the gene allele be present on both of the X chromosomes in females and on only one X chromosome in males to be expressed
-incidence of the trait is much higher among males in family than females
-trait cannot be passed down from father to son
-transmission of the trait is from father to all daughters
-female carriers have a 50% risk with each pregnancy of passing gene on

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Sex-linked (X-linked) recessive pattern of inheritance

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-require that the gene allele be present on both of the X chromosomes in females and on only one X chromosome in males to be expressed
-incidence of the trait is much higher among males in family than females
-trait cannot be passed down from father to son
-transmission of the trait is from father to all daughters
-female carriers have a 50% risk with each pregnancy of passing gene on

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The client undergoes genetic testing but chooses not to be told the results of the testing once it is completed. Which action is most important for the nurse to implement?

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Respect the client’s right not to know the results of the testing

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The client has a family history of breast cancer. The physician has recommended that she undergo genetic testing. What action is most important for the nurse to take prior to scheduling the client for the procedure?

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Obtaining a signed and witnessed informed consent from the client and place it on their chart
Informed consent is required before genetic testing is undertaken.

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The nurse has been working with a client who has asked to receive the results of genetic testing. What will the nurse do prior to discussing the results with the client?

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Assess the client’s ability to communicate clearly with the nurse and other personnel.The nurse has to assess the client’s ability to receive and process information prior to giving results. Informed consent forms are obtained prior to obtaining blood for testing.The nurse can suggest counseling, if necessary, but does not have to encourage the client to have counseling before giving her or him the results of testing.

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carrier testing

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determine whether patient without symptoms has an allele for a recessive disorder that could be transmitted.
common disorders for testing include sickle cell disease, hemophilia, cystic fibrosis

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predisposition diagnostic testing

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family history or genetic testing indicates risk if high for a known genetic disorder. patient has no manifestations
common disorders for testing are hereditary breast/ovarian cancer/colorectal cancer