Chapter 20

Question 1

somatic cells

Answer 1

body cells

Question 2

chromosomes are made of ___ and _______.

Answer 2

DNA; protein

Question 3

gene

Answer 3

segment of DNA located on a specific site on a chromosome that contains information for producing a particular protein.

Question 4

Different versions of a gene

Answer 4

alleles

Question 5

Two copies of the same allele of a gene

Answer 5

homozygous

Question 6

Different alleles of a given gene

Answer 6

heterozygous

Question 7

Dominant allele

Answer 7

when the effects of a certain allele can be detected regardless of whether an alternative allele is also present

Question 8

Recessive allele

Answer 8

an allele whose effects are masked in the heterozygous condition

Question 9

genotype

Answer 9

precise set of alleles a person possesses for a given trait

Question 10

phenotype

Answer 10

the observable physical traits

Question 11

law of segregation

Answer 11

for every gene in our chromosomes one of the alleles comes from our mother and one comes from our father

Question 12

law of independent assortment

Answer 12

the mixture of alleles that came from the mother and alleles that came from the father is different in every gamete

Question 13

Diagram used to predict the genetic makeup of the offspring of individuals of particular genotypes

Answer 13

Punnett square

Question 14

monohybrid cross

Answer 14

a cross in which both parents are heterozygous for one trait of interest

Question 15

dihybrid cross

Answer 15

a cross of individuals who are both heterozygous for two traits of interest

Question 16

a chart showing the genetic connections between individuals in a family

Answer 16

pedigree

Question 17

a Carrier

Answer 17

someone who displays the dominant phenotype but is heterozygous for a trait and can pass the recessive allele to descendants

Question 18

complete dominance

Answer 18

a heterozygous individual exhibits the trait associated with the dominant allele but not the recessive allele

Question 19

codominance

Answer 19

the effects of both alleles are apparent in the heterozygous phenotype ex: AB blood

Question 20

incomplete dominance

Answer 20

the expression of a trait in a heterozygous individual is somewhere between the expression of the trait in a homozygous dominant and the expression of the trait in a homozygous recessive individual. ex: sickle cell trait

Question 21

pleiotropy

Answer 21

one gene leading to many effects ex: sickle cell anemia

Question 22

when 3 or more forms of a given allele exist

Answer 22

multiple alleles (in a population) ex: ABO blood types

Question 23

polygenic inheritance

Answer 23

the involvement of two or more genes, often on different chromosomes, in producing a trait

Question 24

20,000-25,000

Answer 24

human genes distributed among the 23 pairs of chromosomes

Question 25

x-linked genes

Answer 25

genes located on the X chromosome. Most X-linked genes have no corresponding allele on the Y chromosome

Question 26

sex influenced traits

Answer 26

the expression of certain autosomal genes influenced by the presence of sex hormones

Question 27

breakage can be caused by

Answer 27

• chemicals
• radiation
• viruses
• crossing over

Question 28

deletion

Answer 28

loss of a piece of chromosome

Question 29

duplication

Answer 29

the addition of a piece of chromosome