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Flashcards in Definitions Deck (18):
1

Define Hypomorphic

Phenotype with partial wild-type activity.
Hypomorph = an allele that produces a reduced amount or activity of a product

2

Define Sex-limiting

Sex-limited genes are genes which are present in both sexes but expressed only in one sex. Causes the two sexes to show different traits or phenotypes.
Examples: lactation in females and beard growth in males.

3

Define Haploinsufficiency:

A situation in which half amount of a gene product is not enough to maintain normal function for instance, individual with heterozygous mutation or Hemizygous at a particular locus is clinically affected.

4

Define variable expressivity

Variable extent or intensity of phenotypic signs among people with a given genotype

5

Define penetrance

Refers to the proportion of people with a particular genetic change who exhibit signs and symptoms of a genetic disorder. If some people with the mutation do not develop features of the disorder, the condition is said to have reduced (or incomplete) penetrance.

6

Define compound heterozygous

The presence of two different mutant alleles at a particular gene locus, one on each chromosome of a pair. These 2 mutations are different and not identical to each other (identical mutations on both alleles called Homozygous).

7

Define age related mosaicism

The accumulation of somatic/germline mutations over the course of a person’s life resulting in mosaicism. Normal part of ageing considering number of cells dividing and mutation rate of DNA.

8

Define hemizygous

a state of having a gene with no counterpart allele in a diploid cell. E.g. men are normally hemizygous for genes on the X chromosome.

9

Define UPD

When there's 2 copies of a chromosome/region of chromosome received from one parent
Types of UPD
Uniparental isodisomy (UPID) (likely MII NDJ / mitotic error)
Uniparental heterodisomy (UPHD) (likely MI NDJ)
** can have segmental UPID & UPHD on 1 chrom due to recombination

10

Define Anticipation
Name 2 syndromes that have this

Phenomenon in which the age of onset of a disorder is reduced
and/or the severity of the phenotype is increased in successive generations. typically occurs with disorders that are caused by an unusual type of mutation called a trinucleotide repeat expansion.

Huntingtons disease
Myotonic dystrophy
?fragile x (controversial)

11

Define imprinting

An epigenetic phenomenon that leads to parent- specific expression of a subset of genes between alleles

12

Define mosaicism

The presence of two or more genetically different cell lines with in one individual that have arisen in a single zygote

13

Define homozygous

When both alleles in a diploid organism are the same eg aa, AA, BB, bb

14

Define heterozygous

When two alleles in a diploid organism are different eg aA, bB

15

Define autozygosity

Termed identity by descent. IDB
Where homozygous alleles are both inherited from a common ancestor.
(Similar to UPID but it's not a meiotic error- it's due to consanguinity)

16

Define paralogous

2 distinct non-allelic regions of DNA with highly similar DNA sequences

17

Define clinical utility

The benefit to the patient the test/ results will be

18

Define clinical validity in terms of a test for a patient

The results of the test will be of clinical significance