Unit 6: Classical Genetics

Question 1

An organism’s physical appearance, or visible traits

Answer 1

phenotype

Question 2

genetic makeup of an organism

Answer 2

genotype

Question 3

DNA segments that serve as the key functional units in hereditary transmission.

Answer 3

Gene

Question 4

An alternative form of a gene.

Answer 4

allele

Question 5

An organism that has two identical alleles for a trait

Answer 5

homozygous

Question 6

An organism that has two different alleles for a trait

Answer 6

heterozygous

Question 7

first law of heredity stating that pairs of alleles for a trait separate when gametes are formed

Answer 7

law of segregation

Question 8

A cross between individuals that involves one pair of contrasting traits

Answer 8

monohybrid cross

Question 9

An allele that is masked when a dominant allele is present

Answer 9

recessive

Question 10

A chart that shows all the possible combinations of alleles that can result from a genetic cross

Answer 10

punnett square

Question 11

situation in which one allele is not completely dominant over another

Answer 11

incomplete dominance

Question 12

A condition in which neither of two alleles of a gene is dominant or recessive.

Answer 12

codominance

Question 13

combined effect of two or more genes on a single character

Answer 13

polygenic

Question 14

22 chromosome pairs that control traits NOT related to gender–same in females and males.

Answer 14

autosomal chromosome

Question 15

XX or XY. The last chromosome

Answer 15

sex chromosome

Question 16

a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell. This probably occurs most commonly in meiosis, but it may occur in mitosis to produce a mosaic individual

Answer 16

nondisjunction

Question 17

sex-linked

Answer 17

refers to characteristics (or traits) that are influenced by genes carried on the sex chromosomes. In humans, the term often refers to traits or disorders influenced by genes on the X chromosome, as it contains many more genes than the smaller Y chromosome