Chapter 2 - Transmission Genetics

Question 1

Mendel’s blending theory of heredity

Answer 1

viewed the traits in offspring as a mixture of the parental traits
(rejected by Mendel’s results)

Question 2

5 features of mender’s experiment critical to success

Answer 2

1. controlled crossed
2. pure-breeding strains
3. dichotomous traits
4. quantification of results
5. replicate, reciprocal and test crosses

Question 3

results of Mendel’s pure breeding crosses

Answer 3

1. dominance of one phenotype over the other in F1
2. re-emergence of recessive phenotype in F2
3. ration of 3:1 dominant to recessive phenotypic ratio in F2

Question 4

particulate inheritance

Answer 4

genetic info is transmitted from one generation to the next as discrete units of heredity (known as alleles)

Question 5

Mendel’s First Law

Answer 5

also known as Law of Segregation

• separation of alleles of a gene during gamete formation
• random union of gametes into progeny in predictable proportions
• came from monohybrid crosses

Question 6

test cross

Answer 6

cross of possible heterozygous dominant with homozygous recessive
-produces 1:1 ratio

Question 7

Mendel’s Second Law

Answer 7

also known as Law of independent assortment

• random distribution of alleles of unlinked genes into gametes
• illustrated by 9:3:3:1 for combined phenotypes (3:1 for individual trait)
• came from dihybrid crosses
• occurs at metaphase I of meiosis I

Question 8

number of gamete genotypes

Answer 8

= 2^n
where n=number of genes
(n=3 for tri-hybrid crosses)

Question 9

chi-square test

Answer 9

used for quantifying how closely an experimental observation matches the expected outcome

Question 10

autosomal inheritance

Answer 10

transmission of traits carried on autosomes (chromosomes found in both males and females)

Question 11

autosomal dominant pedigrees

Answer 11

1. each affected individual has at least one affected parent
2. affects males and females equally
3. either sex can transmit the disease allele
4. no skipping of generations

Question 12

autosomal recessive pedigree

Answer 12

1. affects males and females equally
2. skips generations
3. 2 affected parents will produce only affected offspring

Question 13

sex-linked diseases

Answer 13

affect males more often than females

Question 14

product rule for probability

Answer 14

determines likelihood of simultaneous events by multiplying the probabilities of both events
P(A and B) = P(A) x P(B)

Question 15

sum rule for probability

Answer 15

only for mutually exclusive events

P(A or B) = P(A) + P(B)

Question 16

monohybrid cross

Answer 16

cross between organisms that are heterozygous for one gene

produces 3:1 ratio

Question 17

dihybrid cross

Answer 17

cross between organisms that are heterozygous for two loci

produces 9:3:3:1 ratio

Question 18

number of phenotypes =

Answer 18

2^n

Question 19

number of genotypes =

Answer 19

3^n

Question 20

Probability value (P value)

Answer 20

probability that the results of another experiment of the same size and structure will deviate as much of more from expected results by chance

Question 21

high P value

Answer 21

low chi-squared value which occur when the observed and expected results are very similar (chance alone explains deviation)

Question 22

low P value

Answer 22

high chi-squared value which indicates substantial difference between observed and expected outcomes