Kinde Genetics

Question 1

What is the probing in a pedigree?

Answer 1

I-1

Question 2

Describe autosomal dominant inheritance

Answer 2

• one allele is needed for expression
• unaffected individuals do not pass on the trait
• both males and females equally and in generations equally
• recurrent risk is 50%

Question 3

Describe autosomal recessive inheritance

Answer 3

2 copies of a mutant allele is needed to influence a phenotype; you need both of the recessive copies

Question 4

Describe X-linked recessive inheritance

Answer 4

always expressed in male characters; the allele is hemizygous

• all daughters of affected males are carriers
• never father to son transmission

Question 5

Describe the concept of a threshold in mitochondria diseases

Answer 5

There is a specific number of diseased mitochondria (typically a percentage) that will lead to the presentation of symptoms, which is called the threshold

Question 6

Describe X-linked dominant inheritance

Answer 6

• rare

- only males with the disease allele transmit the trait (only to females)

Question 7

Describe non-disjunctions in meiosis processes

Answer 7

one of the cell lines does not receive an chromosomal help because the chromatids did not separate, which leaves one of the lines completely empty

Question 8

Describe genomic imprinting

Answer 8

only certain genes are expressed only from the mother or the father

The imprinted alleles are silent and only the allele that is not imprinted in the other parent is expressed

imprinting, or gene silencing is secondary to methylation of the 5’ end which leads to chromosome condensation

Question 9

Describe uniparental disomy

Answer 9

individual receives two copies of a chromosome or part of a chromosome from one parents and no copies

Question 10

What are the various chromosome mutations?

Answer 10

1. Inversion: chromosomal DNA is present in the reverse orientation
2. Deletion: segment is lost
3. Duplication: segment is copied, resulting in amplification of the genes that are in that region
4. translocation: switcheroo

Question 11

Describe the two types of translocations within chromosomes

Answer 11

1. reciprocal: exchange of lateral between non homologous chromosomes
2. Robertsonian: long arm of two afrocentric chromosomes combined; short arm is lost

Question 12

Define penetrance

Answer 12

frequency that a gene manifests itself

Question 13

Describe retinoblastoma in regards to penetrance

Answer 13

• Autosomal dominant inheritance that occurs in 90% of individuals
• phenotype in 90% of individuals with the genotype; 90% penetrance

Question 14

Describe variable expressivity

Answer 14

range of phenotypes that are between several people with a specific genetype

-neurofibromatosis: develop tumor like growths; pigmented areas of skin

Question 15

Describe locus heterogeneity

Answer 15

single disorder, trait or pattern of traits that are caused by mutations in the genes at different loci

-only one mutant locus is needed for the phenotype to manifest

Question 16

Describe the Hardy Weinberg principle

Answer 16

specifies the relationship between the gene frequency and the genotype frequency and is able to determine the disease prevalence type

Question 17

Describe multifactorial inheritance

Answer 17

when environment factors cause variation in the trait

typically follow a bell shaped distribution