genetics definitions

Question 1

DNA

Answer 1

paired double-stranded helical molecule capable of replicating and responsible for directing an organism’s inherited activities by directing the expression and composition/structure of cellular proteins

Question 2

bases

Answer 2

the basic chemical building blocks of DNA that determine its sequence
Purine bases - Adenine (A) Guanine (G)
Pyrimidine bases - Thymine (T) Cytosine (C)

Question 3

base pair

Answer 3

a single pair of complementary bases from opposite strands of the DNA double helix; A and T, G and C

Question 4

gene

Answer 4

the basic hereditary unit, initially defined by phenotype (currently) defined by a DNA sequence that encodes either a protein or a non-coding RNA

Question 5

non-coding regions

Answer 5

regions of the chromosome in-between genes which don’t code for proteins

Question 6

chromosome

Answer 6

thread-like structure in the nucleus consisting mainly of a long DNA molecule comprising 50-300,000 base pairs which code for thousands of genes
Humans = 23 pairs of chromosomes containing a total of 20,000 genes

Question 7

genome

Answer 7

an organism’s complete set of DNA

Question 8

transcription

Answer 8

production of RNA from a DNA template initially in the form of a primary transcript

Question 9

exon

Answer 9

blocks of a gene whose DNA sequence will ultimately determine amino acid sequence

Question 10

introns

Answer 10

blocks of a gene which do not code for protein and which are removed during the processing of primary transcript to generate mRNA

Question 11

translation

Answer 11

process in which protein is made using messenger RNA sequence as a template

Question 12

mutation

Answer 12

change in DNA sequence

Question 13

nonsynonymous mutation

Answer 13

mutation that ultimately results in a change in protein sequence

Question 14

allele

Answer 14

one member of a number of different forms/variations of a gene

Question 15

genotype

Answer 15

combination of alleles for a given gene within an individual

An individual’s genotype is defined by the 2 alleles present [chromosomes are paired]

Question 16

SNP

Answer 16

DNA sequence variation when a single base differs at the same genetic location between different chromosomes
(either within an individual or between individuals of the same species) – most common type of genetic variation

Question 17

haplotype

Answer 17

combination of SNPs present at different genetic locations that are transmitted together on the same chromatid

Question 18

phenotype

Answer 18

observable characteristics (morphological, clinical; biochemical, or molecular) or disease

Question 19

allele

Answer 19

one of the alternate versions of a gene present in a population

Question 20

wild-type allele

Answer 20

normal functional version

Question 21

mutant allele

Answer 21

rare genetic change often non-functional

Question 22

variant allele

Answer 22

common genetic variation, may have minor differing properties for same function

Question 23

locus/loci

Answer 23

where a gene maps

Question 24

dominant trait

Answer 24

a characteristic that is seen in a heterozygote

Question 25

recessive trait

Answer 25

a characteristic is hidden in a heterozygote

Question 26

chromatid

Answer 26

replicating chromosome

Question 27

genetic heterogeneity

Answer 27

different mutation in the same gene can lead to different diseases

Question 28

multifactorial inheritance

Answer 28

the inheritance and expression of a phenotype being determined by cumulative action of multiple genes at multiple loci in the gene

Question 29

penetrance

Answer 29

fraction of cases carrying a given gene that manifests in a specified phenotype

Question 30

dominant alleles

Answer 30

will have a dominant effect which causes the disease

Question 31

epistatic alleles (modifier genes)

Answer 31

only have an effect when in conjunction with another mutation

Question 32

protective alleles

Answer 32

reduce the risk of getting the disease

Question 33

‘risk alleles’/susceptibility alleles

Answer 33

genes which are associated with increasing the risk of a disease

Question 34

heritability

Answer 34

proportion of the disease variation due to genetic variation

Question 35

concordance

Answer 35

• probability that twins (identical and non-identical) will both have a disease
• given that one of the pair has the disease

Question 36

triosmy

Answer 36

extra chromosome present in nuclei

Question 37

monosomy

Answer 37

extra chromosome present in nuclei