Genetics

Question 1

100% penetrance

Answer 1

Proportion of people with the genotype who develop clinical disease. This certainty is described as 100 percent penetrance

Question 2

Chromosome disorders

Answer 2

A missing, extra, or irregular portion of chromosomal

DNA

Question 3

Single-gene disorders

Answer 3

The result of a single mutated gene. >4000 human

diseases are caused by single gene defects

Question 4

Non-classical disorders

Answer 4

Mitochondrial, imprinting, epigenetic

Question 5

Multi-factorial disorders

Answer 5

Combination of gene(s) and environmental factors

Question 6

Allelic heterogenity

Answer 6

Different mutations at
The same locus causing different phenotypes.
Ex.: Infantile and adult Tay-Sachs disease

Question 7

Locus heterogenity

Answer 7

Mutations in different genes
causing same/similar phenotypes
Ex.: Retinitis pigmentosa- autosomal dominant,
autosomal recessive and x-linked forms

Question 8

Autosomal dominant

Answer 8

Only one mutant allele needed to show phenotype
• Both males and females are equally affected
• Phenotype usually seen in several generations of a
family
In a mating of affected x wild-type, at each birth, there is the same recurrent risk of having An affected child ½ or 50% An unaffected child 1/2 or 50% No matter what the genotype/phenotype of any previous children.

Question 9

Autosomal recessive

Answer 9

• Two mutant allele needed to show phenotype
• Individuals with one mutant allele (heterozygotes) usually do
not show phenotype
• Both males and females are equally affected
• Affected phenotype usually seen in only one generation
At birth: affected child 25%, heterozygous 50%, normal child 25%. SAME RECURRING RISK - No matter what the genotype/phenotype of any previous children.

Question 10

Single nucleotide polymorphism (SNP)

Answer 10

• Single base difference in DNA sequence in paired chromosomes in an indivisual
• Simplest form of DNA differences with most snps having
two alleles
• Occur once in every 300 nucleotides on average =
roughly 5-10 million SNPs in the human genome
• On all chromosomes but not uniformly distributed
• There are several million SNP Differences between any
two individuals

Question 11

Simplest form of DNA differences

Answer 11

TYPE OF VARIATION IN THE GENOME.
-0.5% of DNA sequences that are different in each individual and accounts for their uniqueness – Most of the variability is due to SNPs (~3x106 bases/genome)

Question 12

Chromosomes

Answer 12

Genes are located on chromosomes. There are 22 pairs of autosomal chromosomes and 2 sex chromosomes (total of 46). An example of a chromosomal disorder is autosomal trisomy (aka down syndrome)

Question 13

Copy number variant

Answer 13

Structural variation with abnormal copy number changes involving DNA fragments that results in gains, losses, or complex rearrangements of the genome. On average, a human has over 1,000 CNVs across the genome

Question 14

Frameshift mutation

Answer 14

Genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence

Question 15

Insertion

Answer 15

Addition of one or more nucleotide base pairs into a DNA sequence

Question 16

Melting point

Answer 16

At a certain melting point, DNA will denature (two strands will break apart). This is dependent on the amount of C-G bonds that are found within the DNA (C and G are bound with 3 hydrogen bonds). The greater the amount of C-G, the higher the melting point

Question 17

Mendelian disease

Answer 17

Study of inheritance in humans that is becoming a central component of our understanding of most major diseases

Question 18

Missense point mutation

Answer 18

A single nucleotide change results in a codon that codes for a different amino acid

Question 19

Mutation

Answer 19

Permanent change in the DNA sequence which results in a harmful change

Question 20

Nonsense point mutation

Answer 20

Mutation in DNA sequence that results in a premature stop codon or a nonsense codon that results in a nonfunctional protein product

Question 21

Penetrance

Answer 21

Frequency of expression of an allele when it is present in the genotype of the organism

Question 22

Polymorphism

Answer 22

Alternative phenotypes, variant that is relatively common within a population. It is a change in DNA sequence that is neither good nor bad (ex: ABO blood type). Single nucleotide polymorphisms account for most of the variation in the human genome- SNPs are single base differences in DNA

Question 23

Reannealing

Answer 23

Putting DNA strands back together after they have been separated

Question 24

Reduced penetrance

Answer 24

Refers to when an individual known to carry the dominantly inherited mutated gene shows no clinical evidence of the condition

Question 25

RNA

Answer 25

ribonucleic acid. It is necessary to have RNA primer make a strand of RNA from the DNA strand before synthesis can occur

Question 26

Whole exome sequencing of DNA

Answer 26

3% of our DNA bases- sequence of only the exons (22,000) genes (coding DNA). cheap

Question 27

X-linked

Answer 27

Mutations that are found on the X chromosome- males only have one X so will have severe phenotype if get that X while females are heterozygous and will only show variable clinical symptoms