ch 14 mendel and the gene idea exam 3

Question 1

mendel

Answer 1

used the scientific approach to identify two laws of inheritance by using basic principles of heredity by breeding garden peas

Question 2

character

Answer 2

a heritable feature that varies among individuals such as flower color

Question 3

trait

Answer 3

each variant for a character, such as purple or white color of flowers

Question 4

mendel’s experiment

Answer 4

chose to track only those characters that occurred in two distinct alternative forms. he started with varieties that were true-breeding (plants that produce offspring of the same variety when they self-pollinate)

Question 5

hybridization

Answer 5

mendel mated two contrasting, true-breeding varieties

Question 6

p generation

Answer 6

true-breeding parents

Question 7

F1 generation

Answer 7

the hybrid offspring of the p generation

Question 8

F2 generation

Answer 8

F1 individuals self-pollinate or cross-pollinate with other F1 hybrids which produces F2 generation

Question 9

what did mendel reason?

Answer 9

mendel said only purple flower factor was affecting flower color in the F1 hybrids. he said purple was a dominant trait and white was a recessive trait but white flowers were not diluted or destroyed bc they reappeared in the F2 generation

Question 10

mendel’s hypothesis to explain the 3:1 inheritance pattern he observed in F2 offspring: first

Answer 10

first: alternative versions of genes (alleles) account for variations in inherited characters. each gene resides at a specific locus on a specific chromosome

Question 11

mendel’s hypothesis to explain the 3:1 inheritance pattern he observed in F2 offspring: second

Answer 11

second: for each character, an organism inherits two alleles (one from each parent). two alleles at a particular locus may be identical, as in the true-breeding plants of mendel’s p generation. or the two alleles

Question 12

mendel’s hypothesis to explain the 3:1 inheritance pattern he observed in F2 offspring: third

Answer 12

third: if two alleles at a locus differ, then one (the dominant allele) determines the organim’s appearance, and the other (recessive) has no noticeable effect on appearance

Question 13

mendel’s hypothesis to explain the 3:1 inheritance pattern he observed in F2 offspring: fourth

Answer 13

law of segregation: two alleles for a heritable character separate during gamete formation and end up in different gametes. thus an egg or sperm gets only one of the two alleles that are present in the organism. this segregation of alleles corresponds to the distribution of homologous chromosomes to different gametes in meiosis

Question 14

punnett square letters

Answer 14

possible combinations of sperm and egg can be shown using a punnett square. capital letter represents dominant allele and lowercase letter represents a recessive allele

Question 15

homozygote

Answer 15

an organism with two identical alleles for a character. homozygous: gene controlling that character

Question 16

heterozygote

Answer 16

an organism with two different alleles for a gene. heterozygous: for a gene controlling that character

Question 17

various forms of a gene at a given locus are called?

Answer 17

alleles

Question 18

testcross

Answer 18

an individual with the dominant phenotype could be either homozygous dominant or heterozygous: to determine the genotype we can carry out a testcross: briefing the mystery individual with a homozygous recessive individual to determine the genotype. if any offspring display the recessive phenotype, the mystery parent must be heterozygous

Question 19

law of independent assortment

Answer 19

the alleles of two or more different genes get sorted into gametes independently of one another

Question 20

dihybrids

Answer 20

crossing two true-breeding parents differing in two characters produces dihybrids in the F1 generation, heterozygous for both characters

Question 21

dihybrid cross

Answer 21

a cross between F1 dihybrids can determine whether two characters are transmitted to offspring as a package or independently

Question 22

using a dihybrid cross, mendel developed the law of independent assortment

Answer 22

each pair of alleles segregates independently of any other pair of alleles during gamete formation. this law only applies to genes on different nonhomologous chromosomes or those far apart on the same chromosome. genes located near each other on the same chromosome tend to be inherited together

Question 23

inheritance patterns

Answer 23

are often more complex than predicted by simple mendelian genetics. inheritance of characters by a single gene may deviate from simple mendelian patterns in the following situations: when alleles are not completely dominant or recessive, when a gene has more than two alleles, when a gene produces multiple phenotypes

Question 24

complete dominance

Answer 24

occurs when phenotypes of the heterozygote and dominant homozygote are identical

Question 25

incomplete dominance

Answer 25

the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties

Question 26

codominance

Answer 26

two dominant alleles affect the phenotype in separate, distinguishable ways

Question 27

multiple alleles

Answer 27

most genes exist in populations in more than two allelic forms

Question 28

multiple alleles example

Answer 28

the four phenotypes of the ABO blood group in humans are determined by three alleles for the enzyme that attaches A or B carbohydrates to RBC: IA, IB, and i. the enzyme encoded by the IA allele adds the A carbohydrate, whereas the enzyme encoded by the IB allele adds the B carbohydrate; the enzyme encoded by the i allele adds neither

Question 29

pleiotropy

Answer 29

multiple phenotypic effects. pheiotropic alleles are responsible for the multiple symptoms of certain hereditary diseases such as cystic fibrosis and sickle cell disease.

Question 30

mendelian genetics

Answer 30

certain patterns of how traits are passed from parent to offspring. some traits may be determined by two to more genes

Question 31

polygenic inheritance

Answer 31

multiple genes independently affect a single trait

Question 32

epistasis

Answer 32

expression of a gene at one locus alters the phenotypic expression of a gene at a second locus. one gene affects the phenotype of another due to interaction of their gene production

Question 33

epistasis example

Answer 33

in lab retrievers and other mammals, coat color depends on two genes. one gene determines the pigment color (with alleles B for black and b for brown) the other gene (with alleles E for color and e for no color) determine whether the pigment will be deposited in the hair

Question 34

polygenic inheritance

Answer 34

an additive effect of two or more genes on a single phenotype. height is a good example: over 180 genes affect height

Question 35

quantitative characters

Answer 35

quantitative characters: those that vary in the population along a continuum

Question 36

why are humans not good subjects for genetic research

Answer 36

generation time is too long, parents produce relatively few offspring, breeding experiments are unacceptable. however, basic mendelian genetics endures as the foundation of human genetics

Question 37

recessively inherited disorders

Answer 37

inherit two mutated genes one from each parent. RID show up only in individuals homozygous for the allele

Question 38

carriers

Answer 38

heterozygous individuals who carry the recessive allele but are phenotypically normal. most individuals with recessive disorders are born to carrier parents

Question 39

recessively inherited disorder example

Answer 39

albinism is a condition characterized by a lack of pigmentation in skin and hair

Question 40

dominantly inherited disorders

Answer 40

only need one copy of the mutated gene from one parent to cause the disorder. can cause lethal diseases are rare and arise by mutation

Question 41

huntington’s disease

Answer 41

a degenerative disease of the nervous system. it has no obvious phenotypic effects until the individual is about 35 to 40 years old. once the deterioration of the nervous system begins the condition is irreversible and fatal

Question 42

complete dominance of one allele

Answer 42

heterozygous phenotype same as that of homozygous dominant ex: PP and Pp

Question 43

incomplete dominance of either allele

Answer 43

heterozygous phenotype intermediate between the two homozygous phenotypes

Question 44

codominancee

Answer 44

both phenotypes expressed in heterozygotes ex: both enzymes in RBC to determine blood type

Question 45

multiple alleless

Answer 45

genes that have two or more alleles

Question 46

pleiotropyy

Answer 46

one gene affects multiple phenotypic characters ex: sickle cell disease

Question 47

epistasiss

Answer 47

the phenotypic expression of one gene affects the expression of another gene

Question 48

polygenic inheritancee

Answer 48

a single phenotypic character is affected by two or more genes