Genetic Stuff

Question 1

Gene definition

Answer 1

Sequences of DNA that contain the instructions for making a protein

Question 2

Allele definition

Answer 2

Alternate form of a gene due to a change, deletion or insertion of nucleotides.
Two alleles of each autosomal gene are found in each cell. They are either dominant or recessive.

Question 3

Homozygous

Answer 3

Two identical alleles for a gene

Question 4

Heterozygous

Answer 4

Two different alleles for a gene

Question 5

Hemizygous

Answer 5

Only one allele for a gene

Question 6

Phenotype

Answer 6

Characteristic or trait that can be measured or observed and is based on genotype

The physical characteristics

Question 7

Locus

Answer 7

The location of a gene on the chromosome

Question 8

Multifactorial inheritance explained

Answer 8

Most diseases are complex and involve an interplay between genes and environment

Question 9

Epistasis

Answer 9

Interaction between two or more genes (Example- one gene can increase or decrease the expression of a second gene)

Question 10

Genetic homogeneity

Answer 10

Only a single SNP causes the mutation

SNP-Single nucleotide polymorphism

Question 11

Genetic heterogeneity

Answer 11

Different mutations cause identical or similar phenotype

Question 12

What are the two types of genetic heterogeneity?

Answer 12

Allelic heterogeneity- Different mutations at the same location
Locus heterogeneity- Mutations at different loci producing the same phenotype

Question 13

Karyotype

Answer 13

Organization of the pairs of chromosomes from a metaphase cell based on their size

Question 14

Mosaicism

Answer 14

When two or more cells of an individual have distinct karyotype
This results from chromosomal changes due to mitotic errors that occur after conception

Question 15

Lyonization

Answer 15

The process where almost all genes on one X chromosome are inactivated in females

Question 16

What does an Xi dark spot indicate?

Answer 16

Barr body

Question 17

Expressivity

Answer 17

Spectrum of phenotypic expression with the same genetic mutation
Variable organ involvement, severity, and onset of disease

Question 18

Penetrance

Answer 18

Likelihood that individuals with a mutant genotype express the phenotype

Question 19

Genetic imprinting

Answer 19

Gene inactivation occurs on chromosome regions of autosomes leading to expression of only one parental allele

Question 20

Aneuploidy

Answer 20

Loss or gain of one or more chromosomes

Results from failure of a chromosome pair to separate

Question 21

Polyploidy

Answer 21

Many multiples of the entire set of chromosomes

Question 22

What are the four types of chromosomal breakages?

Answer 22

Deletion, duplication, inversion, translocation

Question 23

Trinucleotide repeat disorders

Answer 23

Due to expansion of a repetitive sequence of nucleotides in a gene

Question 24

Genetic anticipation

Answer 24

Worsening of the disorder with subsequent generations due to the number of repeats of nucleotides increasing as the mutation goes from generation to the next