Chapter 5: 5.4 Laws of Inheritance [Mendel's Laws]

Question 1

What is Mendel’s First Law?

Answer 1

Law of Segregation

Question 2

State:

The Law of Segregation

Answer 2

States that gametes receive only one allele of each gene

Question 3

Mendel’s most important discovery was the – ——- from parental strains with different traits were not…

Answer 3

1. F1 progeny
2. True-breeders

Question 4

What is a true-breeding organism?

Answer 4

Organisms that always pass down their phenotypic traits to its offspring

Question 5

In Mendel’s Law of Segregation:

Where does the F2 Generation come from?

Answer 5

Comes from the F1 generation self-fertilizing

Question 6

In Mendel’s Law of Segregation:

What did Mendel discover in the F2 Generation?

Answer 6

The recessive trait reappeared
* Reappeared consistently at a dominant : recessive ratio close to 3 : 1

Question 7

True or False:

In true breeding parental strains, the two alleles are identical

Answer 7

True

Question 8

Two identical alleles means the plants are…

Answer 8

Homozygous

Question 9

True or False:

Each gamete contains two of alleles of one gene

Answer 9

False, each gamete contains just one allele of each gene

Question 10

What is a reproductive cell known as?

Answer 10

A gamete

Question 11

Each gamete contains — allele of each gene

Answer 11

One

Question 12

State:

The Principle of Segregation

Answer 12

When gametes are formed, the two alleles of a gene segregate
* Half of the gametes get one allele, while the other half get the other allele

Question 13

True or False:

In heterozygous plants, all the gametes will have the same allele

Answer 13

False, in homozygous plants all the gametes will have the same allele

Question 14

Describe:

1. When a zygote is formed
2. How it is formed

Answer 14

1. Formed after fertilization
2. Comprised of the union of two gametes - one from each parent

Question 15

When the two gametes that formed the zygote carried different alleles for a gene, the resulting zygote…

Answer 15

Is heterozygous
* A hybrid containing two different alleles

Question 16

How can the resulting progeny of the F2 generation be determined?

Answer 16

Using a Punnett square

Question 17

True or False:

The dominant phenotype has to be the same genotype

Answer 17

False, since it is dominant the phenotype is the same but the genotype can be different

Question 18

State:

The Law of Segregation

Answer 18

Alleles must segregate equally into gametes such that the progeny (F2) have an equal likelihood of obtaining one of the two alleles

Question 19

What can be used to test segregation?

Answer 19

Testcross

Question 20

How is a testcross done? What will the results show

Answer 20

Cross the F1 progeny with the true-breeding recessive strain instead of allowing them to self-fertilize
* The recessive trait will only be observed if the F1 strain is heterozygous

Question 21

True or False:

All traits follow the Mendelian rules of dominance

Answer 21

False

Question 22

List two ways that traits don’t follow the Mendelian rules of dominance

Answer 22

1. Incomplete dominance: The phenotype of the heterozygote is somewhere in-between the homozygote phenotypes
2. Codominance: When both traits are expressed

Question 23

What is Mendel’s Second Law?

Answer 23

Law of Independent Assortment

Question 24

State:

Mendel’s Second Law (Law of Independent Assortment)

Answer 24

Alleles of different genes assort independently of one another during gamete formation

Question 25

There are --- possibilities at meiosis when an individual is...

Answer 25

1. Two 2. Heterozygous at two loci

Question 26

How did Mendel find support for the Second Law?

Answer 26

By performing **dihybrid crosses**

Question 27

What does the law of independent assortment allow for in trait combinations?

Answer 27

All trait combinations are possible * Four equally likely gametes in the F2 generation

Question 28

What would happen if the Law of Independent Assortment was not true?

Answer 28

The progeny would all be heterozygous for both genes

Question 29

# Punnett Square Rules: How large should the grid be?

Answer 29

Should fit all the alleles from the parents on either side

Question 30

# Punnett Square Rules: Do the parents have to be placed in specific places on a Punnett Square?

Answer 30

No, it is arbitrary

Question 31

# Punnett Square Rules: How should alleles be written in a Punnett Square?

Answer 31

1. Dominant alleles written first 2. In alphabetical order

Question 32

# Define: Locus

Answer 32

The physical location of a gene on a chromosome | (Plural: Loci)

Question 33

# Define: Alleles

Answer 33

The different versions of a single gene or locus

Question 34

In diploid organisms, how many alleles will the individual inherit for each gene?

Answer 34

2 alleles of every gene * One from mother * One from father

Question 35

What are some common short-hands for alleles?

Answer 35

1. B and b 2. B and B' 3. B1 and B2

Question 36

# Define: Trait

Answer 36

Each variant for a character

Question 37

Alleles for a given gene affect the same character but...

Answer 37

Can specify different traits

Question 38

# Define: Genotype

Answer 38

The specific alleles in an individual (the genetic makeup)

Question 39

# Define: Phenotype

Answer 39

The physical appearance of an individual

Question 40

# True or False: Phenotype helps determine genotype

Answer 40

Not exactly, genotype helps determine phenotype

Question 41

What does transmission of alleles depend on?

Answer 41

Depends on events in meiosis and fertilization

Question 42

# Mendel's Law of Segregation: --- alleles for a heritable character segregate during ------- formation and end up in different gametes

Answer 42

1. Two 2. Gamete

Question 43

When do members of an allelic pair segregate during meiosis I come together?

Answer 43

Fertilization

Question 44

# In Mendelian Inheritance: How many characters are controlled by each gene?

Answer 44

One

Question 45

# In Mendelian Inheritance: How many alleles do each genes have?

Answer 45

Two * Each accounts for variations in inherited characters

Question 46

# In Mendelian Inheritance: What do dominant alleles do?

Answer 46

Determines an organisms appearance

Question 47

# In Mendelian Inheritance: What do recessive alleles do?

Answer 47

Have no noticeable effect if the two alleles at a locus differ

Question 48

# In Mendelian Inheritance: When does the segregation of the two alleles for a heritable character occur?

Answer 48

During gamete formation

Question 49

# In Mendelian Inheritance: The alleles or two different genes are...

Answer 49

Inherited independently (independent assortment)

Question 50

# True or False: Alleles remain unchanged

Answer 50

Mostly. They can be rarely be mutated

Question 51

Can a character be affected by the environment?

Answer 51

Yes

Question 52

In the real-world population, pairs of --------- mate with frequencies that depend on their proportions in the ----------

Answer 52

1. Genotypes 2. Populations