exam 3 ppt 2

Question 1

how did Mendel discover the principle of independent assortment?

Answer 1

he discovered this by studying dihybrid crosses with 2 true breeding traits (homozygous genotypes)

Question 2

what were the dihybrid crosses that Mendel studied?

Answer 2

yellow vs. green and round vs. wrinkled

Question 3

what gametes does the genotypes AA bb produce?

Answer 3

gametes Ab

Question 4

what gametes does the genotype aa BB produce?

Answer 4

gametes aB

Question 5

what ratio did Mendel always observe in the F2 generation in dihybrid crosses?

Answer 5

9:3:3:1

Question 6

what do dashes in a genotype mean?

Answer 6

it means that either allele can be present

Question 7

definition of Mendel’s principle of segregation

Answer 7

individuals inherit two copies of each gene, one from the mother and one from the father, and when individuals form reproductive cells, the two copies separate equally in the eggs and sperm (equal amounts of each type of gametes)

Question 8

what type of cross is associated with the principle of segregation?

Answer 8

monohybrid crosses

Question 9

what type of cross is associated with the principle of independent assortment?

Answer 9

dihybrid crosses

Question 10

definition of the principle of independent assortment

Answer 10

the two copies of each gene segregate into gametes independently of the two copies of another gene

Question 11

what happens to the pairs of alleles in the principle of segregation?

Answer 11

the pairs of alleles are separated during meiosis I in the formation of gametes (equal gamete types of both alleles)

Question 12

in the principle of independent assortment, is each gamete combo equally likely?

Answer 12

yes

Question 13

why do the genes for seed shape and seed color assort independently?

Answer 13

because 1) they are located on different chromosomes, and 2) these chromosomes have two equally likely ways of lining up before they are segregated (each gamete type is equally likely to occur)

Question 14

is there an exception to the principle of independent assortment?

Answer 14

yes

Question 15

what are the exceptions to the principle of independent assortment?

Answer 15

if two genes are close together on the same chromosome, they will likely not assort independently -> they are linked

Question 16

what does it mean if two genes are linked?

Answer 16

this means that the genes are close enough together on the same chromosome that they will likely not assort independently

Question 17

do yellow, green, wrinkled, and round assort independently regarding the dihybrid crosses?

Answer 17

yes

Question 18

what is an example of complete dominance seen in Mendel’s crosses?

Answer 18

in his yellow vs. green seed trait, yellow is dominant because the protein produced by the green allele is non-functional; we only see the result of the protein produced by the yellow allele

Question 19

are all alleles completely dominant or recessive?

Answer 19

no -> there can be codominance or incomplete dominance

Question 20

definition of complete dominance

Answer 20

a relationship in which one allele is completely dominant over another

Question 21

definition of codominance

Answer 21

situation in which both alleles of a gene contribute to the phenotype of the organism

Question 22

when does codominance occur?

Answer 22

it occurs when an individual displays phenotypes of BOTH alleles

Question 23

definition of incomplete dominance

Answer 23

a pattern of inheritance in which two alleles, inherited from the parents, are neither dominant or recessive; the resulting offspring have a phenotype that is a blending of the parental traits

Question 24

what are heterozygotes like in incomplete dominance?

Answer 24

heterozygotes have a phenotype in between the homozygous phenotypes (intermediate phenotype)

Question 25

exp of incomplete dominance

Answer 25

parental has red and white flowers; produce 1/4 red, 2/4 pink, and 1/4 white

Question 26

what phenotypic ratio always appears in incomplete dominance?

Answer 26

1:2:1

Question 27

why does incomplete dominance occur?

Answer 27

one R allele doesn’t produce enough pigment to produce full red color; as opposed to complete dominance, one allele is sufficient

Question 28

what can patterns of inheritance in humans be drawn as?

Answer 28

it can be drawn as a pedigree

Question 29

in a pedigree, are affected traits empty or filled in?

Answer 29

affected traits are filled in

Question 30

definition of an autosome

Answer 30

chromosome that is not a sex chromosome

Question 31

definition of autosomal dominant trait

Answer 31

inheritance pattern of a dominant allele on an autosome

Question 32

exp of an autosomal dominant trait

Answer 32

Huntington disease

Question 33

definition of an autosomal recessive trait

Answer 33

inheritance pattern of a recessive allele on an autosome

Question 34

exp of an autosomal recessive trait

Answer 34

sickle-cell disease

Question 35

will we have half shaded in individuals in our pedigrees we see?

Answer 35

no

Question 36

in autosomal recessive traits, are males or females more likely to be affected?

Answer 36

males and females are equally likely to be affected

Question 37

in autosomal recessive traits, what parents do affected offspring often have?

Answer 37

affected offspring often have unaffected parents

Question 38

in autosomal recessive traits, what are the characteristics of unaffected parents of affected offspring?

Answer 38

unaffected parents of affected offspring are heterozygous (carriers)

Question 39

in autosomal recessive traits, what is the genotype of affected offspring?

Answer 39

affected offspring are homozygous

Question 40

in autosomal recessive traits, what will be offspring be if both parents are heterozygous?

Answer 40

if both parents are heterozygous, about 1/4 of the offspring will be affected

Question 41

in autosomal recessive traits, do traits appear in every generation?

Answer 41

no, traits often skip generations

Question 42

in autosomal dominant traits, are males or females more likely to be affected?

Answer 42

males and females are equally likely to be affected

Question 43

in autosomal dominant traits, do affected offspring have affected parents?

Answer 43

affected offspring have at least one affected parent

Question 44

in autosomal dominant traits, if only one parent is affected, what are the genotypes of affected offspring?

Answer 44

affected offspring are heterozygous if only one parent is affected

Question 45

in autosomal dominant traits, what is the genotype for unaffected offspring?

Answer 45

unaffected offspring are homozygous recessive

Question 46

in autosomal dominant traits, how many offspring will be affected if one parent is heterozygous?

Answer 46

if one parent is heterozygous, about 1/2 of the offspring will be affected

Question 47

in autosomal dominant traits, do the traits skip generations?

Answer 47

no, the trait does not skip generations