ch12: mendels experiments and heredity

Question 1

why did gregor mendel pick pea plants to experiment on (4 bullets)

Answer 1

1. many pea varieties (“mutants”) available
2. short generation times
3. many offspring per plant (each individual pea is one offspring)
4. peas can self-fertilize OR be cross-fertilized

Question 2

true-breeding strains

Answer 2

has been “inbred” for many generations; offspring has identical phenotypes to parent

Question 3

female part of a flower

Answer 3

stigma or carpel

Question 4

male part of the flower

Answer 4

anther

Question 5

how did mendel cross pollinate the pea plants

Answer 5

he took the anther of one plant (so it cant self pollinate) and added pollen from another plant

Question 6

mendels experimental method (5 steps)

Answer 6

1. produce true-breeding parental strains for each trait he was studying (P)
2. cross-fertilize two true-breeding strains that have alternate forms of a trait to produce F1 generation (hybrid)
3. also perform reciprocal crosses to make sure the results werent dependent on which variety came from male vs female parental (F1)
4. allow the hybrid (F1) offspring to self-fertilization to produce the F2 generation and count the number of offspring showing each for of the trait (F2)
5. allow the F2 generation to self-fertilize to produce F3 generation and count number of offspring with each trait (F3)

Question 7

monohybrid cross

Answer 7

cross to study only two variations of a single trait; mendel produced true-breeding pea strains for seven different traits

Question 8

F1 generation

Answer 8

first filial generation; produced by crossing two true-breeding strains; dominant trait

Question 9

F2 generation

Answer 9

second filial generation; results from the self-fertilization of F1 plants; recessive trait

Question 10

what was the ratio of dominant to recessive traits

Answer 10

3:1

Question 11

F3 generation

Answer 11

third filial generation; F2 plants self-fertilize;
recessive F2 plants were always true-breeding;
1/3 of F2 dominant plants were true-breeding;
2/3 of F2 plants were not (acted like the F1 generation)

Question 12

how many categories of plants were in the F2 generation

Answer 12

three (true-breeding dominant, non-true breeding dominant, true-breeding recessive)

Question 13

mendel’s observations (5 bullets)

Answer 13

1. parents transmit genes for particular traits
2. not all copies of a gene are identical (homozygous and heterozygous)
3. presence of allele does not guarantee expression (dominant and recessive)
4. each individual receives one copy of a gene from each parent (child receives one set of chromosomes containing genes from each parent)
5. alleles segregate randomly to form gametes for next generation-no blending

Question 14

phenotype

Answer 14

physical appearance of an individual

Question 15

genotype

Answer 15

total set of alleles an individual contains

Question 16

allele

Answer 16

alternate form of a gene (homozygous vs heterozygous)

Question 17

dominant allele

Answer 17

expressed gene; capitol letter

Question 18

recessive allele

Answer 18

hidden by dominant allele; lowercase letter

Question 19

homozygous

Answer 19

two copies of the same allele; “true-breeding”

Question 20

heterozygous

Answer 20

two different alleles

Question 21

progeny

Answer 21

another word for offspring

Question 22

physical basis for allele segregation is the behavior of

Answer 22

chromosomes during meiosis

Question 23

punnett square

Answer 23

technique developed to easily visualize and anticipate genotypes for the various crosses

Question 24

which shape represents which sex in a pedigree analysis

Answer 24

squares represent men, circles represent women

Question 25

if you see an affected child with a recessive trait and both parents are unaffected

Answer 25

both parents must be carrier/heterozygous

Question 26

how do you know if a disease is dominantly inherited

Answer 26

the disease will not skip a generation, at least one person will always be affected

Question 27

autosomal dominant

Answer 27

affected males and females appear in each generation of the pedigree; affected mothers and fathers transmit the phenotype to both sones and daughters (huntington disease)

Question 28

autosomal recessive

Answer 28

the disease appears in male and female children of unaffected parents (cystic fibrosis)

Question 29

dihybrid crosses

Answer 29

examination of two separate traits in a single cross; traits sort independently on different chromosomes

Question 30

dihybrid cross ratio for an F2 generation

Answer 30

9:3:3:1

Question 31

rule of addition

Answer 31

the probability of any combination of results is the sum of their individual probabilities

Question 32

rule of multiplication

Answer 32

probability of two independent events occurring at the same time is the product of their individual probabilities

Question 33

how to perform a test cross (also known as a back cross)

Answer 33

cross an unknown dominant (P__) with a homozygous recessive (pp)
-if the dominant was homozygous (PP), all offspring will be dominant (Pp)
-if the dominant was heterozygous (Pp), half of the offspring will be recessive (pp)

Question 34

what does chi squared determine

Answer 34

sum of the deviations between observed and predicted frequencies

Question 35

P value of 0.5

Answer 35

critical values (maximum difference between observes and expected) that would occur by chance 95% of the time

Question 36

degree of freedom

Answer 36

number of phenotypes - 1

Question 37

if X^2 is GREATER than the critical value, that means that…

Answer 37

the distribution of phenotypes is greater than expected by chance 95% of the time, meaning you would reject the hypothesis

Question 38

if X^2 is LESS than the critical value, that means that…

Answer 38

the distribution of phenotypes is within the expected by chance 95% of the time, meaning you would accept the hypothesis

Question 39

chi squared equation

Answer 39

x^2 = “the sum of” (observed-expected)^2 / expected

Question 40

mendel’s model of inheritance only works if the following criteria are met:

Answer 40

1) each trait is controlled by a single gene
2) each gene only has two alleles
3) there is a clear dominant/recessive relationship between the two alleles

Question 41

polygenic inheritance

Answer 41

occurs when multiple genes are involved in controlling the phenotype of a trait; these traits show continuous variation and are referred to as quantitive traits (eye color or height)

Question 42

pleiotropy

Answer 42

when an allele has more than one effect on the phenotype; difficult to predict because a gene that affects one trait often performs other unknown functions (cystic fibrosis)

Question 43

multiple alleles

Answer 43

each individual can only have 2 alleles (2n), but may be more than 2 alleles for a gene IN A POPULATION
(Ex. ABO blood types -> 3 alleles)

Question 44

incomplete dominance

Answer 44

-heterozygote is intermediate in phenotype between the two homozygotes
ex. red flower+white flower= pink flower
-written as an exponent (C^R C^R or C^W C^W)

Question 45

codominance

Answer 45

-each allele has its own effect, and heterozygote shows some aspect of the phenotypes of both homozygotes
ex. blood type: A, B, AB, O
-written as “I” + superscript
- I^A I^A = A blood type
-I^B I^B = B blood type
-I^A I^B = AB blood type
-ii= O blood type