Module 3—Mendelian Genetics

Question 1

pangenesis

Answer 1

idea that all parts of the body contribute to gamete formation

Question 2

germ-plasm theory

Answer 2

germline tissues in reproductive organs form gametes

Question 3

correct replacement for pangenesis

Answer 3

germ replacement theory

Question 4

inheritance of acquired characteristics

Answer 4

idea that traits acquired in life, like dyeing your hair, are passed on to offspring

Question 5

preformationism

Answer 5

idea that a miniature adult (homunculus) resides in gametes (especially sperm)

suggests that a person’s traits are inherited from the father

Question 6

homunculus associated with…

Answer 6

preformationism

Question 7

blending inheritance

Answer 7

idea that offspring have a blend of parental traits

Question 8

particulate hypothesis

Answer 8

idea that parents pass on discrete heritable units (genes)

Question 9

Walter Sutton

Answer 9

chromosomal theory of heredity

Question 10

chromosomal theory of heredity (3)

Answer 10

genes are located on chromosomes

homologs separate in anaphase I

homologs assort independently

Question 11

character

Answer 11

heritable feature that varies among individuals; ie color

Question 12

trait

Answer 12

each variant for a character

Question 13

true breeding

Answer 13

homozygous crosses - offspring are always same genotype as parent

Question 14

hybridization

Answer 14

crossing of two true-breeding varieties

Question 15

testcross

Answer 15

breeding a dominant phenotype organism with unknown genotype to a recessive organism

Question 16

2 possibilities for a testcross

Answer 16

• If the unknown is homozygous dominant, all offspring will be dominant phenotype
• If the unknown is heterozygous dominant, ½ offspring will be dominant phenotype, and ½ will be recessive

Question 17

monohybrid cross ratios (genotype & phenotype)

Answer 17

• Genotype ratio—1:2:1
• Phenotype ratio—3:1

Question 18

law of segregation

Answer 18

the two alleles for a heritable character segregate during gamete formation and end up in different gametes

Question 19

law of independent assortment

exceptions

Answer 19

two or more genes assort independently during gamete formation

only applies to genes located on different chromosomes, or very far apart on the same chromosome

Question 20

dihybrid cross ratio

Answer 20

9:3:3:1

Question 21

Mendel used to discover independent assortment

Answer 21

dihybrid crosses

Question 22

independent events

Answer 22

outcome of any particular trial is unaffected by what has happened on previous trials

Question 23

multiplication rule

Answer 23

to determine the probability of one event and the other occurring, we multiply their probabilities

Question 24

addition rule

Answer 24

to determine the probability of one of two mutually exclusive events occurring, we add their probabilities

Question 25

complete dominance

Answer 25

heterozygous and homozygous dominant phenotypes are indistinguishable from one another

Question 26

incomplete dominance

Answer 26

neither allele is completely dominant, resulting in a phenotype that is a mixture/dilution

Question 27

codominance

Answer 27

two alleles affect phenotype in separate, distinguishable ways - no dilution

Question 28

levels of dominance in Tay Sachs disease

Answer 28

recessive trait at organismal level incompletely dominant trait at biochemical level (heterozygous individuals also have some defective enzymes, but functional enzymes are “enough” to keep symptoms from appearing) codominant at molecular level

Question 29

penetrance

Answer 29

percentage of individuals having a genotype that expresses the expected phenotype

Question 30

penetrance is always…

Answer 30

less than the ratios predicted by Mendelian genetics

Question 31

expressivity

Answer 31

degree to which a character is expressed

Question 32

yield non-Mendelian ratios in offspring

Answer 32

lethal alleles

Question 33

pleiotropy

Answer 33

genes with multiple phenotypic effects

Question 34

a range of phenotypes

Answer 34

continuous traits

Question 35

epistasis

Answer 35

phenotypic expression of a gene at one locus alters that of a gene at a second locus

Question 36

epistasis example

Answer 36

black labs, brown labs, yellow labs

Question 37

epistasis produces ratios which are…

Answer 37

variations on 9:3:3:1

Question 38

polygenic inheritance

Answer 38

additive effect of 2+ genes on a single phenotypic character

Question 39

quantitative characters associated with…

Answer 39

polygenic inheritance

Question 40

most common polygenic traits in population

Answer 40

individuals heterozygous for many or all of the genes involved

Question 41

used in personalized medicine

Answer 41

polygenic risk score

Question 42

multifactorial traits

Answer 42

influenced by genetic and environmental factors

Question 43

phenotypic plasticity

Answer 43

a trait’s reaction to the environment

Question 44

carriers

Answer 44

heterozygotes carrying a recessive allele for a certain phenotype