SCT III

Question 1

Comparative genomics

Answer 1

The field of science that studies the similarities between the genome structure and function of different species.

Question 2

Pseudogene

Answer 2

Shows a high degree of sequence homology to a non-allelic functional gene, but which is itself nonfunctional.

i.e. a section of DNA that is similar to a functional gene, but it does not produce a functional protein.

Question 3

Hominins

Answer 3

Extinct species that are more closely related to humans than other great apes.

Question 4

Ideogram

Answer 4

A schematic representation of chromosomes; a standardized, species-specific set of chromosomes with G-banding used to show the relative size of the chromosomes and their characteristic banding patterns.

Question 5

Karyotype

Answer 5

Is an individual’s collection of chromosomes.

It describes the number, appearance, and physical characteristics of chromosomes in the nucleus of a cell in an individual organism.

A verbal description with symbols and abbreviations.

Question 6

Karoygram

Answer 6

A micro-photograph of all chromosomes of a single cell represented in a standard format.

Chromosomes are sorted and re-arranged in pairs by their size and position of their centromeres.

I.e. it is a photograph of the whole set of all 22 identical chromosome pairs plus the 2 gender specific chromosomes (XX/XY)

Question 7

Chimera

Answer 7

An organism derived from more than one zygote.

Question 8

Trisomy rescue

Answer 8

In a nonviable trisomic embryo, chance of loss of one of the trisomic chromsomes by anaphase lag, producing a disomic cell that can eventually form a viable embryo.

A cause of uniparental disomy (UPD). UPD may case:

1. Rare Mandelian diseases
2. Angelman syndrome
3. Prader-Willi syndrome

Question 9

Allelic heterogeneity

Answer 9

Existence of many different mutations but all within the same gene in unrelated people with the same phenotype

Question 10

Anticipation

Answer 10

Tendency for the severity of a condition to increase in successive generations

Commonly due to bias of ascertainment but seen for real with dynamic mutations

Question 11

Coding RNA

Answer 11

Messenger RNA that codes for a protein

Question 12

Common variant

Answer 12

Conventionally, a variant whose frequency is >0.05.

Question 13

Conserved sequence

Answer 13

A sequence (of DNA or sometimes protein) that is identical or recognizably similar across a range of organisms

Question 14

Dominant negative effect

Answer 14

Situation where a mutant protein interferes with the function of its normal counterpart in a heterozygous person

Question 15

Dynamic mutation

Answer 15

An unstable expanded repeat that changes size between parent and child

Question 16

Exome

Answer 16

Totality of exons in a genome

Question 17

Exon junction complex

Answer 17

A set of proteins that are bound to mRNAs during splicing, at the positions where introns have been removed

Question 18

Founder effect

Answer 18

High frequency of a particular allele in a population because the population is derived from a small number of founders, one or more of whom carried that allele

Question 19

Frame-shift mutation

Answer 19

A mutation that alters the triplet reading frame of a mRNA (by inserting or deleting a number of nucleotides that is not a multiple of 3)

Question 20

Gain-of-function mutations

Answer 20

Mutations that cause the gene product to do something abnormal, rather than simply to lose function.

Usually the gain is a change in the timing or level of expression

Question 21

Genotype-phenotype correlation

Answer 21

Extent to which a phenotype can be predicted from a genotype.

Typically poor in humans, better in experimental animals which are inbred and live under standard lab conditions

Question 22

Haploinsufficiency

Answer 22

A locus shows haploinsufficiency if producing a normal phenotype requires more gene product than the amount produced by a single functional allele

Question 23

Heteroplasmy

Answer 23

Mosaicism, usually within a single cell, for mitochondrial DNA variants

Question 24

Homoplasmy

Answer 24

Of a cell or organism, having all copies of the mitochondria DNA identical

Question 25

Loss-of-function mutations

Answer 25

Mutations that cause the gene product to lose its function, partially or totally

Question 26

MicroRNAs (miRNAs)

Answer 26

Short (21-22 nt) RNA molecules encoded within normal genomes that have a role in regulation of gene expression and maybe also of chromatin structure

Question 27

Missense changes

Answer 27

Changes in a coding sequence that cause one amino acid in the gene product to be replaced by a different one.

Question 28

mtDNA

Answer 28

Mitochondrial DNA — DNA of the 16,569 nt mitochondrial genome

Question 29

Mutation

Answer 29

1. Process of DNA sequence change
2. Resultant changed sequence

Question 30

Noncoding RNA (ncRNA)

Answer 30

RNA that does not contain genetic code for a protein.

ncRNA have many different functions in cells.

Question 31

Nonsense mutation

Answer 31

A mutation that replaces the codon for an amino acid with a termination codon

Question 32

Nonsense-mediated mRNA decay

Answer 32

A cellular mechanism that degrades mRNA molecules that contain a premature termination codon (>50 nt upstream of the last splice junction)

Question 33

Pathogenic

Answer 33

Causing disease

Question 34

Penetrance

Answer 34

Frequency with which a genotype manifests itself in a given phenotype

Question 35

Rare variant

Answer 35

A variant whose frequency is <0.01

Question 36

Homologous recombination

Answer 36

1. Normal recombination that is part of meiosis
2. A mechanism for repairing DNA damage

Question 37

Lord score (z)

Answer 37

In linkage analysis, the log of the odds that the loci are linked rather than unlinked.

For Mandelian characters a lod score greater than +3 is evidence of linkage; one that is less than -2 is evidence against linkage

Question 38

CentiMorgan (cM)

Answer 38

Unit of genetic distance. Loci 1cM apart have a 1% probability of recombination during meiosis

Question 39

Haplotype

Answer 39

A series of alleles found at linked loci on a single chromosome

Question 40

Haplotype blocks

Answer 40

Blocks of variants that are in linkage disequilibrium with each other, but not with variants in-adjacent blocks.

Cataloged by the International HapMap project. The consequence of shared remote ancestry.

Question 41

Relative risk in epidemiology

Answer 41

Relative risk of developing a condition in people with and without a susceptibility factor

Question 42

Sib

Answer 42

A brother or sister

Question 43

First-degree relatives

Answer 43

Parents, children, or sibs

Question 44

Driver mutation

Answer 44

In cancer, mutations that are subject to positive selection during tumorigenesis because they assist development of the tumor

Question 45

Loss of heterozygosity (LOH)

Answer 45

Homozygosity or hemizygosity in a tumor or other somatic cell when the constitutional genotype is heterozygous.

Evidence of a somatic genetic change.

Question 46

Gene therapy

Answer 46

Treating a disease by genetic modification.

May involve adding a functional copy of a gene that has lost its function, inhibiting a gene showing a pathological gain of function, or more generally, replacing a defective gene.