Genetic variation

Question 1

Chromosome

Answer 1

A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.

Question 2

Crossing over

Answer 2

the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

Question 3

Gene

Answer 3

sequence of DNA that codes for a protein and thus determines a trait

Question 4

Trait

Answer 4

A characteristic that an organism can pass on to its offspring through its genes.

Question 5

Locus

Answer 5

Location of a gene on a chromosome

Question 6

Mutation

Answer 6

change in a DNA sequence that affects genetic information

Question 7

Mutagen

Answer 7

A chemical or physical agent that interacts with DNA and causes a mutation.

Question 8

Meiosis

Answer 8

a type of cell division that results in four daughter cells each with half the number of chromosomes (haploid) of the parent cell, as in the production of gametes.

Question 9

Crossing over

Answer 9

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Question 10

Chiasma

Answer 10

site of crossing over

Question 11

Independent assortment

Answer 11

the random distribution of the pairs of genes on different chromosomes to the gametes

Question 12

Segregation

Answer 12

Separation of alleles during gamete formation

Question 13

Gamete

Answer 13

Sex cell, e.g. egg (ovum) or sperm in humans

Question 14

Somatic cell

Answer 14

any cell of a living organism other than the reproductive cells.

Question 15

Diploid

Answer 15

An organism or cell having two sets of chromosomes or twice the haploid number

Question 16

Haploid

Answer 16

An organism or cell having only one complete set of chromosomes

Question 17

Gene pool

Answer 17

All the genes, including all the different alleles for each gene, that are present in a population at any one time

Question 18

Dihybrid cross

Answer 18

A cross between two individuals, concentrating on two definable traits

Question 19

Homozygous dominant

Answer 19

Both alleles (factors) for a trait are the same and dominant (AA)

Question 20

Heterozygous

Answer 20

An organism that has two different alleles for a trait

Question 21

Pure breeding

Answer 21

Individuals that are homozygous that will always produce the same offspring when crossed together

Question 22

Pedigree chart

Answer 22

A chart which shows several generations of related families and how traits are passed down through the offspring.

Question 23

Incomplete dominance

Answer 23

Situation in which one allele is not completely dominant over another allele, so heterozygotes will be a blend of the two phenotypes.

Question 24

Co-dominance

Answer 24

situation in which both alleles of a gene contribute to the phenotype of the organism, so heterozygotes will have BOTH shown in their phenotype

Question 25

Multiple alleles

Answer 25

three or more forms of a gene that code for a single trait

Question 26

Lethal alleles

Answer 26

Alleles that cause an organism to die when present in homozygous condition.

Question 27

Allele frequency

Answer 27

Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene

Question 28

Evolution

Answer 28

The gradual change in a species over time

Question 29

Genetic drift

Answer 29

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Question 30

Natural Selection

Answer 30

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits (and how suitable they make the organism to the environment).

Question 31

Founder effect

Answer 31

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.

Question 32

Bottleneck effect

Answer 32

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.

Question 33

Allele

Answer 33

An alternative form of a gene.

Question 34

Test cross

Answer 34

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

Question 35

Linked genes

Answer 35

Genes located on the same chromosome that tend to be inherited together in genetic crosses.