5.3 Common Ancestry

Question 1

_____ and ____ carry genetic information.

Answer 1

DNA, RNA

Question 2

The genetic code is shared by ______.

Answer 2

All living systems

Question 3

Gregor Mendel studied _____ and created two ____ that can be applied to the study of _____.

Answer 3

Inheritance, laws, genetics

Question 4

Who was Gregor Mendel, what did he experiment on, and what did he discover?

Answer 4

• Austrian monk
• experimented on pea plants
• discovered the basic principles of heredity

Question 5

Why did Gregor Mendel experiment on pea plants? (3)

Answer 5

• many varieties
• controlled mating
• relation short generation time

Question 6

Mendel only tracked characteristics that came in two distinct forms. Give two examples.

Answer 6

1. Colour (either purple or white)

2. Seed shape (round or wrinkled)

Question 7

To help control his experiments, Mendel used _____

Answer 7

True breeding plants

Question 8

What does the term “true breeding” mean?

Answer 8

• organisms that produce offspring of the same variety over many generations of self-pollination

Question 9

Give an example of true breeding.

Answer 9

• true breeding purple plant will only produce purple offspring with self pollination

Question 10

What is the P generation?

Answer 10

True breeding parental generations

Question 11

What is the F1 generation? (2)

Answer 11

• first filial

- hybrid offspring of P generation

Question 12

What is the F2 generation? (2)

Answer 12

• second filial

- offspring of the F1 generation

Question 13

What are Punnett squares?

Answer 13

• diagrams used to predict the allele combinations of offspring from a cross with know genetic compositions

Question 14

What does homozygous mean? Give an example for homozygous dominant and recessive.

Answer 14

• an organism that has a pair of identical alleles for a character
• dominant: AA
• recessive: aa

Question 15

What does heterozygous mean? (2)

Answer 15

• hybrids
• organism that has two different alleles for a gene
• ex. Aa

Question 16

What is a genotype?

Answer 16

The genetic makeup (alleles) of an organism

Question 17

What is a phenotype?

Answer 17

• an organism’s appearance (physical) which is determined by the genotype

Question 18

What do testcrosses help to determine?

Answer 18

• if the dominant trait is homozygous dominant or heterozygous

Question 19

Mendel’s experiments allowed him to develop two fundamental principles of heredity. What are they?

Answer 19

1. The law of segregation

2. The law of independent assortment

Question 20

Mendel discovered that the cross between purple (P) and white (p) true breeding plants produced only purple F1 offspring. Did the white characteristic disappear? (2)

Answer 20

• no because the white pea flower characteristic comes back in the F2 generation
• he hypothesized that the purple flower must be a dominant trait to the white flower

Question 21

Mendel performed the same crosses for each of the seven characteristics of pea plants and found the same result. What did he find?

Answer 21

The F2 generation was always a 3:1 ratio

Question 22

To explain the 3:1 ratio, he observed the F2 generation and created a model with four concepts. What are these concepts?

Answer 22

1. Alternative versions of genes (alleles) account for variations in inherited characteristics
2. For each character(istic), and organism inherits two copies (two alleles) of a gene, one from each parent
3. If two alleles at a locus (location on xmes) differ, then the dominant allele determines the appearance (phenotype) and the recessive ales has no noticeable effect
4. Law of Segregation: the two alleles for the same trait separate during gamete formation and end up in different gametes

Question 23

Why are somatic cells diploid? (2) what are alleles

Answer 23

• they contain 2 copies of each xmes

- alleles: alternate versions of a gene

Question 24

State the Law of Segregation for the P generation. after, state if for true breeding.

Answer 24

1. Each gamete for the P generation will contain one allele for flower colour
2. True breeding plants (pure or homozygous) will have two identical alleles
   Please see page 18 for a good example

Question 25

The Law of Segregation was determined by doing crosses between ____ ____ plants which produced F1 hybrids, known as _______. What is that?

Answer 25

1. True breeding
2. Monohybrids
   - monohybrids are a cross between the F1 hybrids

Question 26

Mendel’s second principle is The Law of Independent Assortment. State Mendel’s Law of Independent Assortment.

Answer 26

• genes for one trait are not inherited with genes of another trait
• instead of following one trait in his crosses, this time Mendel followed two traits (ex. Peapod colour and shape)

Question 27

What does the Law of Independent Assortment only apply to? (2)?

Answer 27

1 Genes that are located on different chromosomes (not homologous)
OR
2. Genes that are very far apart on the same xmes

Question 28

The Law of Independent Assortment was determined by doing crosses between plants that were true breeding for ___ traits, which produces F1 hybrids called ___.

Answer 28

Two, dihybrids

Question 29

What is a dihybrid cross?

Answer 29

• a cross between F1 dihybrids

Question 30

What phenotypic ratio does a dihybrid cross produce?

Answer 30

• 9:3:3:1 phenotypic ratio

Question 31

The laws of segregation and independent assortment reflect rules of ____.

Answer 31

Probability

Question 32

What is the multiplication rule for the law of probability?

Answer 32

• the probability that two or more independent events will occur together in some specific combination
  Ex. Flip a coin twice, what is the probability it will land heads both times? You multiply

Question 33

What is the addition rule of the Law of Probability?

Answer 33

• the probability that two or more mutually EXCLUSIVE events will occur
  Ex. Chance of rolling a dice and it lands on a 1 OR 6