Traits, Genes, Variations

Question 1

Alleles

Answer 1

The variants of a locus; for autosomal loci, each diploid individuals has two alleles.

Question 2

Autosomes

Answer 2

The chromosomes that are not different between sexes. In humans there are 22 pairs of autosomes.

Question 3

Chromosomes

Answer 3

Linear molecules of DNA packaged with proteins.

Question 4

Codominant

Answer 4

Alleles that are fully expressed in the heterozygote.

Question 5

Continuous, metric, or quantitative

Answer 5

Phenotypic traits that do not show distinguishable forms but a continuous gradation in the population. These traits are also inherited, but they are multifactorial characters controlled by multiple genes (polygenic characters) and affected to varying degrees by the environment and epigenetic modifications.

Question 6

Discrete or discontinuous

Answer 6

Traits that are often encoded by only one gene (monogenic traits) with two different alleles in the population, resulting in alternative forms of the trait.

Question 7

Dominant

Answer 7

An allele that is fully expressed either in the homozygote or in the heterozygote.

Question 8

Intermdediate dominance

Answer 8

One of the alleles is not completely recessive, or the other is not completely dominant.

Question 9

Epistasis

Answer 9

A type of gene interaction. Some traits are affected by more than one gene so that the effect of one gene (epistatic) masks or modifies the effect of another gene (hypostatic).

Question 10

Expressivity

Answer 10

Reflects the degree in which a trait is expressed among individuals with identical genotype.

Question 11

Gene

Answer 11

A segment of the genome that contains the instructions for a functional product. It is considered the molecular unit of heredity.

Question 12

Genome

Answer 12

The heritable material that is transmitted from parents to offspring confers the biological identity of an individual. It is composed of large molecules of nucleic acids, whose sequence contains the instructions to build other functional molecules such as ribonucleic acid (RNA) or proteins.

Question 13

Genotype

Answer 13

The genetic makeup of an organism, the whole set of genes. For a given gene, the genotype is the combination of alleles in a particular individual.

Question 14

Hemizygous

Answer 14

Are males for the genes located in the X chromosome because they only have one copy.

Question 15

Heterozygote

Answer 15

An individual with two different alleles (in sequence or function) at a locus.

Question 16

Homologous Chromosomes

Answer 16

A pair of chromosomes that carry the same gene but are inherited from a different parent. A diploid individual (2n) harbors a number n (haploid) of pairs of homologous chromosomes.

Question 17

Homozygote

Answer 17

An individual with two identical alleles (in sequence or function).

Question 18

Linkage

Answer 18

Is due to the fact that alleles are located along chromosomes and end to being inherited in the same combination that is present in parental chromosomes. Linkage is broken by recombination during meiosis, which creates novel combinations of alleles in the chromosome.

Question 19

Locus

Answer 19

(plural loci) A position (place) in a chromosome; the physical region occupied by a gene, a marker, or any genetic element.

Question 20

Mendelian

Answer 20

Traits that display Mendelian inheritance typical of diploid organisms.

Question 21

Penetrance

Answer 21

The proportion of individuals that show the typical phenotypes associated with a genotype.

Question 22

Phenotype

Answer 22

The collection of observable characteristics of the organism. It is determined by the genotype but also by environmental factors and epigenetic modifications (both inherited and non-inherited)

Question 23

Quantitative trait locus (QTL)

Answer 23

A locus controlling a quantitative trait.

Question 24

Recessive

Answer 24

An allele that is fully expressed only in the homozygote.

Question 25

Sexual chromosomes

Answer 25

The chromosomes that are different in each sex. In humans, females have two X chromosomes, whereas males have one X and one Y chromosome.

Question 26

SNPS (Single-nucleotide polymorphisms)

Answer 26

Polymorphic sites at single nucleotides

Question 27

Structural variants (SVs)

Answer 27

Polymorphisms that affect relatively large segments of the genome (from Kb to Mb).

Question 28

Copy number variation (CNVs)

Answer 28

Regions that are repeated at different number of times in different individuals in the population.

Question 29

DNA

Answer 29

Deoxyribonucleic acid is made up of four different monomers (adenine, guanine, cytosine, and thymine).

Question 30

Traits

Answer 30

The observable characteristics of the organism. These characteristics range from biochemical and physiological properties to morphology or behavior.

Question 31

Nuclear genome

Answer 31

Most of the genome is in the nucleus. Accounts for 99.9995% of genetic information. 37 protein-coding genes maily involved in oxidative phosphorylation.

Question 32

Extranuclear genome

Answer 32

Located in the organelles like mitochondria and chloroplasts (in plants). Accounts form 0.0005% genetic information.