Exam 3 - mendel

Question 1

What are true-breeding strains?

Answer 1

Homozygous

Question 2

What is the genetic terminology for crosses?

Answer 2

P1=>F1=>F2=>F3=>etc

Question 3

in Mendel’s pea plants, the violet allele is ________ and the white allele is __________.

Answer 3

B) Dominant; recessive

Question 4

What were the F1 products of a Violet x White cross?

Answer 4

All of the offspring were violet

Question 5

What were the F2 products of a F1 x F1 cross?

Answer 5

A phenotypically 3:1 (Violet: White ratio)

Question 6

What are Mendel’s first three postulates?

Answer 6

1) Unit factors occur in pairs
2) Dominance/ Recessiveness
3) Segregation.

Question 7

What are the phenotypic ratios of all of Mendel’s F2 generations?

Answer 7

3:1 (mendelian ratio)

Question 8

a method that is used to predict the genotypes and phenotypes that will be present in the offspring of a genetic cross, and their relative frequencies.

Answer 8

Punnett square

Question 9

In a standard monohybrid cross, what is the probability that an F2 individual will be heterozygous?

Answer 9

50% (1/2)

Question 10

In a standard monohybrid cross, what is the probability that an F2 individual displaying the dominant phenotype is a heterozygote?

Answer 10

66% (2/3)

Question 11

What is a testcross used for?

Answer 11

To distinguish between GG and Gg genotypes

Question 12

A method to determine whether an individual displaying the dominant phenotype has a heterozygous or homozygous dominant genotype.

Answer 12

testcross

Question 13

To carry out a testcross, the individual expressing the dominant phenotype (but having an unknown genotype) is crossed with a known ___ ___ individual.

Answer 13

homozygous recessive

Question 14

in a testcross, if the recessive phenotype appears in the progeny, the tested individual must be a ___

Answer 14

heterozygote (carrier)

Question 15

lines can only produce one gamete type, no matter how many genes or traits are under consideration.

Answer 15

“True-breeding”

Question 16

an individual that is heterozygous for two genes is known as

Answer 16

dihybrid

Question 17

used to predict the frequency with which two independent events will occur simultaneously.
3/4 x 3/4 = 9/16

Answer 17

Product law

Question 18

a mendelian ratio, typical of the F2 generation of dihybrid cross

Answer 18

9:3:3:1

Question 19

the expected ___ phenotypic ratio holds true for each individual trait

Answer 19

3:1

Question 20

What is Mendel’s fourth postulate?

Answer 20

Independent assortment

Question 21

What is the probability that an F2 plant with round yellow seeds has the genotype GgWw?

Answer 21

4/9

Question 22

Summarize Mendel’s work:

• Inheritance is ___, not blending
• Inheritance is controlled by _____ ____
• Mendel’s four postulates

Answer 22

particular; discrete factors (genes)

Question 23

What is the Mendelian ratio for monohybrid selfcross (AaxAa)?

Answer 23

1:2:1 genotypic ratio
3:1 phenotypic ratio

Question 24

What is the Mendelian ratio for monohybrid testcross (Aaxaa)?

Answer 24

1:1 genotypic ratio
1:1 phenotypic ratio

Question 25

What is the Mendelian ratio for dihybrid selfcross (AaBbxAaBb)?

Answer 25

9:3:3:1 phenotypic ratio

Question 26

What is the Mendelian ratio for dihybrid testcross (AaBbxaabb)?

Answer 26

1:1:1:1 genotypic ratio 1:1:1:1 phenotypic ratio

Question 27

- The molecular nature of genes and alleles - The biochemical roles of gene products (RNA and protein) - The cytological behavior of chromosomes during meiosis

Answer 27

What created the Mendelian principles?

Question 28

monohybrids can produce ___ gamete types

Answer 28

two Aa --> A & a

Question 29

dihybrids can produce ___ gamete types

Answer 29

four AaBb --> AB, Ab, aB, ab

Question 30

How many different gamete types can a trihybrid (AaBbCc) individual produce?

Answer 30

8

Question 31

Gametes are morphologically indistinuisghable, but are often divided into mating types (a and alpha in yeast, + and - in Chlamydomonas)

Answer 31

isogamy

Question 32

Gametes are morphologically distinct (usually different size); the individual that produces larger gametes is "female", the smaller gametes come from the "male"

Answer 32

anisogamy (or heterogamy)

Question 33

One of a variety of mechanisms which controls whether an embryo (or individual cell) will display male or female sexual characteristics

Answer 33

sex determination

Question 34

Sex is determined genetically, by the chromosome or gene composition of a cell or organism

Answer 34

genotypic sex determination (GSD)

Question 35

Sex is determined by environmental conditions encountered during an organism's development (temperature, day length, proximity of conspecifics, etc)

Answer 35

environmental sex determination (ESD)

Question 36

A chromosome that exhibits sex-specific differences in individuals of the same species (eg. human X and Y chromosomes)

Answer 36

sex chromosome

Question 37

Any chromosome that is not a sex chromosome (eg. human chromosomes 1-22)

Answer 37

autosome

Question 38

In organisms with GSD, the sex in which both sex chromosomes are the same (females in humans)

Answer 38

homogametic sex

Question 39

In organisms with GSD, the sex which has two different sex chromosomes (males in humans)

Answer 39

heterogametic sex

Question 40

What is the sex determination of birds?

Answer 40

GSD ZW = female ZZ = male

Question 41

What is the sex determination of crocodilians?

Answer 41

ESD low/high temp = female intermediate temp = male

Question 42

sex determination of Drosophila?

Answer 42

GSD XX = female XY = male

Question 43

- Haplodiploidy - No sex chromosomes - Females are diploid - Males are haploid

Answer 43

sex determination of bees

Question 44

What is the name of the group where sex is determined by the number of chromosome sets?

Answer 44

Hymenopterans (bees, ants, wasps)

Question 45

The ratio of X chromosomes to sets of autosomes determines sex. - This is known as the "X to autosome" or "X to A" (X:A) ratio. - X = number of X chromosomes - A = number of haploid sets of autosomes (normally, 2)

Answer 45

sex determination in drosophila

Question 46

sex-determining region Y (___) is a gene on the Y chromosome that initiates "male" development

Answer 46

SRY

Question 47

What does SRY encode for?

Answer 47

Testis determining factor (TDF) which is a key regulator of male-specific gene expression

Question 48

________ mutations in SRY can promote female development in XY individuals

Answer 48

loss of function

Question 49

______ of SRY can promote male development in XX individuals

Answer 49

Translocation of SRY (transfer to a different chromosome)

Question 50

XXY = __ X0 = ___

Answer 50

Klinefelter syndrome (male); Turner syndrome (female)

Question 51

- X:A chromosome ratio determines sex - Y-chromosome is not involved in sex determination - Y-chromosome is required for male fertility

Answer 51

Drosophila

Question 52

SRY gene (sex determining region Y) on the Y chromosome determines maleness

Answer 52

Human

Question 53

in flies and mammals, males and females have different numbers of copies ("doses") of X-linked genes - males have __ copy - females have __ copy

Answer 53

dosage compensation one; two

Question 54

What happens to inactivated X chromosomes?

Answer 54

They condense into Barr bodies

Question 55

What is the equation to find the number of Barr bodies?

Answer 55

Barr bodies = (X chromosomes -1) in either sex

Question 56

- Either the maternal or paternal X chromosomes in inactivated in each cell - Inactivation occurs randomly in early embryos - X-inactivation is heritable through mitosis (the same X chromosome will be inactive in all daughter cells) - X-inactivation is rest (erased) during meiosis

Answer 56

the Lyon hypothesis

Question 57

intact X chromosomes which are highly condensed and transcriptionally repressed

Answer 57

Barr bodies

Question 58

if a male is hemizygous for a recessive allele, he will display the ___ phenotype

Answer 58

recessive