CBCL 1

Question 1

What are the characteristics of an autosomal recessive trait?

Answer 1

Both parents of affected child are unaffected carriers Males and females are equally affected

Question 2

How does whole genome sequencing compare to whole exome sequencing?

Answer 2

Whole genome is the entire shabang and the whole exome is only protein coding regions.

Question 3

What is a null allele?

Answer 3

If no product or function results from an allele

Question 4

What is a De Novo mutation?

Answer 4

When a mutation occurs randomly and has a dominant effect. It makes it difficult because you cannot use inheritance patterns

Question 5

What is penetrance?

Answer 5

the likelihood that a characteristic manifests itself

Question 6

What are the characteristics of X-linked dominant inheritance?

Answer 6

Both males and females can be affected, but less evident in females Females are less affected because of random X inactivation and mosaicism May appear autosomal dominant but no male to male transmission

Question 7

What type of pedigree is this?

Answer 7

X-linked recessive

Question 8

What is a haplotype?

Answer 8

a set of polymorphisms in different genes that reside closely on a given chromosome and are often inherited together.

Question 9

What is non-penetrance?

Answer 9

failure for a characteristic to manifest itself

Question 10

What is a dominant negative?

Answer 10

when the normal function of the product is lost due to interference from the abnormal product

Question 11

What are the characteristics of an autosomal dominance inheritance?

Answer 11

Males and females are equally effected Both can transmit the traits Affected person has at least one affected parent There is a 50% probability of transmitting the trait to any offspring

Question 12

What type of pedigree is this?

Answer 12

Autosomal dominant

Question 13

What is variable expressivity?

Answer 13

Different features of a disorder may be evident in different members of the same family.

Question 14

How does somatic mosaicism compare to germline mosaicism?

Answer 14

Somatic only involves the cells of the individual and germline is what is passed down to the next generation

Question 15

What is a modifier gene?

Answer 15

can either increase or decrease the penetrance of a disorder

Question 16

What is a compound heterozygote?

Answer 16

The presence of two different mutant alleles at a particular gene locus, one on each chromosome of a pair. The human genome contains two copies of each gene, a paternal and a maternal allele.

Question 17

What type of pedigree is this?

Answer 17

Autosomal recessive

Question 18

What is a loss of function mutation?

Answer 18

LOF produces a reduced amount or a reduced activity of the product. This has minimal effect unless it is on both alleles (recessive).

Question 19

What type of pedigree is this?

Answer 19

Autosomal Dominant

Question 20

What is haploinsufficiency?

Answer 20

when a 50% product level results in altered phenotype

Question 21

What is anticipation?

Answer 21

The phenotype worsens with successive generations

Question 22

What are the characteristics of fragile X syndrome?

Answer 22

In normal patients within the FMR1 gene the CGG segment is repeated 5-40 times. In fragile X pts this same CGG segment is repeated more than 200 times, which silences the FMR1 gene. Since boys only have one X chromosome it can effect boys more than girls but not always.

Question 23

What are the characteristics of X-linked recessive inheritance?

Answer 23

Males mostly affected All daughters of affected males are carriers No male to male transmission

Question 24

What is gain of function?

Answer 24

increased amount or increased activity of the product usually dominant

Question 25

What is genetic locus?

Answer 25

specific location or position of a gene’s DNA sequence, on a chromosome.

Question 26

What type of pedigree is this?

Answer 26

X-linked dominant

Question 27

What is a polymorphism?

Answer 27

A specific change that occurs commonly in a population and is not associated with a disease phenotype