Chapter 3

Question 1

What is a gene?

Answer 1

An inherited factor (region of DNA) that helps determine a characteristic.

Question 2

What is an Allele?

Answer 2

One of two or more alternative forms of a gene (like A or a).

Question 3

What is a locus?

Answer 3

A specific place on a chromosome occupied by an allele/gene.

Question 4

What is a genotype?

Answer 4

Set of alleles possessed by an individual organism (like AA, Aa, or aa)

Question 5

What is a heterozygote?

Answer 5

An individual organism possessing two different alleles at a locus (Aa).

Question 6

What is a homozygote?

Answer 6

An individual organism possessing two of the same alleles at a locus (AA or aa).

Question 7

What is a phenotype or trait?

Answer 7

The appearance or manifestation of a characteristic.

Question 8

What is a characteristic/character?

Answer 8

An attribute or feature possessed by an organism.

Question 9

What is Dominance?

Answer 9

One dominant allele (A) can “hide” the phenotype of a recessive allele (a).

Question 10

What is a dominant allele?

Answer 10

Mask the effect of the other alleles (capital letter, like A).

Question 11

What is a recessive allele?

Answer 11

An allele whose effect is masked (small letter, like a).

Question 12

What is True-breeding?

Answer 12

Both alleles are the same (same as homozygous).
-Homozygous dominant (AA)
-Homozygous recessive (aa)

Question 13

What is the difference between cross-fertilizing and self-fertilizing?

Answer 13

In cross-fertilization, there are two different organisms. In self-fertilization, it is the same organism.

Question 14

What is a Filial (F1 and F2)

Answer 14

The generations after the parent generation.
P= parental, first generation
F1= second generation
F2= third generation

Question 15

What is a testcross?

Answer 15

If you have an organism with a
dominant phenotype, but you don’t know the genotype, you cross it with a known genotype (usually homozygous recessive) to determine the unknown genotype

Question 16

What is the Wildtype?

Answer 16

The most prevalent allee in a “wild” population (+).

Question 17

What is the difference between a locus and
an allele?

Answer 17

A locus is a place on a chromosome where genetic information encoding a characteristic is located. An allele is a version of a gene that encodes a specific trait.

Question 18

What is the difference between
genotype and phenotype?

Answer 18

A genotype is the set of alleles possessed by an individual organism, and a phenotype is the manifestation or appearance of a characteristic.

Question 19

When did Gregor Mendel publish?

Answer 19

In 1865

Question 20

What were the keys to Mendel’s success?

Answer 20

• A good model organism
• Small number of traits examined
• Easily differentiated characteristics controlled by a single gene
• His math, counting results, and writing everything down.

Question 21

What are Monohybrid Crosses?

Answer 21

Cross between two parents that
differ in a single characteristic. The hybrid of two individuals with homozygous genotypes which result in the opposite phenotype for a certain genetic trait
*Looking at one trait (gene) at a time

Question 22

What were the 4 conclusions of monohybrid crossing?

Answer 22

1: one character is encoded by two genetic
factors.
2: two genetic factors (alleles) separate when
gametes are formed.
3: The concept of dominant and recessive
traits.
4: Two alleles separate with equal probability
into the gametes.

Question 23

What is the Principle of Segregation (Mendel’s first law)?

Answer 23

Each individual diploid organism possesses two alleles for any particular characteristic. These two alleles segregate when gametes are formed, and one allele goes into each gamete.

Question 24

What is the Concept of Dominance?

Answer 24

When two different alleles are
present in a genotype, only the trait encoded by one of them―the “dominant” allele―is observed in the phenotype.

Question 25

What explains monohybrid crosses?

Answer 25

The Principle of Segregation (The symbols in genetic crosses correspond to alleles on chromosomes).

Question 26

What is a Punnett square?

Answer 26

A convenient way to trace the probabilities of particular genotypes/phenotypes occurring from a particular cross.

Question 27

What is probability?

Answer 27

The likelihood of the occurrence of a particular event. Used in genetics to predict the outcome of a genetic cross

Question 28

What are the two probability rules?

Answer 28

- The multiplication rule - The addition rule

Question 29

What is the Multiplication rule?

Answer 29

Calculates the total probability of two or more events that are dependent on each other. (Probability of two fours AND then a five is 1/6x1/6x1/6 = 1/216)

Question 30

What is the Addition rule?

Answer 30

The addition rule calculates the total probability of two or more events that are not dependent on each other. (The total probability of rolling either a three OR a four is 1/6 + 1/6 =2/6 = 1/3).

Question 31

What is a Dihybrid Cross?

Answer 31

Examine two traits (or genes for Mendel) at a time. Led to The Principle of Independent Assortment. Experimentally, dihybrids are similar to monohybrid crosses: two plants that are either homozygous dominant or homozygous recessive for TWO traits are crossed to give an F1 heterozygote. This plant is self-fertilized to give F2 progeny.

Question 32

What is the Principle of Independent Assortment?

Answer 32

States that alleles of two or more different genes assort independently from one another

Question 33

What did Sutton do?

Answer 33

Chromosomal Theory of Heredity. Sutton explained everything by chromosomes, meiosis, and fertilization.

Question 34

What are the Common Ratios for phenotypes and genotypes?

Answer 34

Also common is the 9:3:3:1 ratio, which is a classic Mendelian ratio for dihybrid crosses.

Question 35

What is a Branch Diagram?

Answer 35

Question 35

What are the gamete combinations?

Answer 35

Total number of combinations that can occur in gametes = 2^n (n= haploid number of chromosomes). Example that humans have 23 chromosomes, so they have 2^23 gametes.

Question 36

How are the principles of segregation and independent assortment related, and how are they different?

Answer 36

Both the principle of segregation and the principle of independent assortment refer to the separation of alleles in anaphase I of meiosis. The principle of segregation says that these alleles separate, and the principle of independent assortment says that they separate independently of alleles at other loci.

Question 37

How is probability of dihybrid crosses found?

Answer 37

Question 38

What is statistics?

Answer 38

Provides a way to accept or reject hypotheses in an unbiased manner. In other words, we can accept a hypothesis if certain statistical criteria are met.

Question 39

What does the Chi-Square Test determine?

Answer 39

It determines the expected numbers based on hypothesis.

Question 40

What is the Chi-Square Goodness of Fit?

Answer 40

Indicates the probability that the difference between observed and expected values is due to chance.

Question 41

When do the Observed and Expected values of a Chi-Square test match?

Answer 41

When the x^2 value is to the left of 0.05.

Question 42

When do the Observed and Expected values of a Chi-Square test not match?

Answer 42

The more the x^2 value is less than 0.05

Question 43

What are the steps of a Chi-Square problem?

Answer 43

First find the x^2 value, then find the degrees of freedom (n-1). Then determine the level of significance with these values and the chart.

Question 44

How is the expected value found in Chi-Square Test?

Answer 44

Multiplying the ratio of the expected proportion to the total number observed.

Question 45

What is a pedigree?

Answer 45

Pictorial representation of a family history, a family tree that outlines the inheritance of one or more characteristics

Question 46

What is a proband?

Answer 46

The person from whom the pedigree is initiated.

Question 47

What is an Autosomal dominant trait?

Answer 47

AA or Aa would be affected and aa would not be affected. Aa is the more common genotype of someone with the condition. Examples are Huntington's disease, Waardenburg syndrome.

Question 48

What is an Autosomal recessive trait?

Answer 48

AA would be unaffected, two normal alleles. Aa would be a carrier, with one affected allele. aa would be an affected individual. Examples include sickle cell anemia, cystic fibrosis, albinism.

Question 49

What is the difference between sex-linked and autosomal traits?

Answer 49

Sex-linked traits are due to genes that occur on the chromosomes that determine sex, while autosomal traits are due to genes that occur on any of the other chromosomes

Question 50

What are the symbols used in a pedigree?

Answer 50

Question 51

How are relationships shown in a pedigree?

Answer 51