3A5 Mendelian Genetics

Question 1

What is an allele?

Answer 1

One of two or more versions of a gene.

An individual inherits two alleles for each gene, one from each parent.

Question 2

What is a gene?

Answer 2

The segment of DNA that determines a trait or characteristic.

Question 3

Define:

homozygous

Answer 3

Having two identical alleles for a given gene.

Question 4

Define:

heterozygous

Answer 4

Having two different alleles for a given gene.

Question 5

What is a genotype?

Answer 5

The genetic makeup of an organism in terms of its alleles.

Depicted as 2 letters: BB, Bb, bb

Question 6

What is a phenotype?

Answer 6

The observable characteristics or traits of an organism.

Question 7

How is genotype translated into phenotype?

Answer 7

By considering the relationship between alleles to determine the physical expression of traits.

Question 8

What are dominant and recessive genes?

Answer 8

• Dominant gene: A trait expressed in the heterozygous state.
• Recessive gene: A trait not expressed in the heterozygous state.

Question 9

What is a key characteristic of a dominant trait?

Answer 9

It is expressed in the heterozygous state and tends to be more prominent in populations.

Question 10

How is a dominant trait symbolized in genetics?

Answer 10

By capital letters

Question 11

What is a key characteristic of a recessive trait?

Answer 11

It is not expressed in the heterozygous state and only appears when both alleles are recessive (homozygous recessive).

Question 12

Who is known as the Father of Genetics?

Answer 12

Gregor Mendel

Question 13

How did Mendel begin studying inheritance?

Answer 13

By focusing on singular inherited traits from crosses of his pea plants.

Question 14

What are the three laws credited to Gregor Mendel?

Answer 14

• Law of Segregation
• Law of Dominance
• Law of Independent Assortment

Question 15

What did Mendel’s First Law of Inheritance state?

Answer 15

Genes on chromosomes are segregated or separated during sexual reproduction (meiosis).

Also known as the law of segregation.

Question 16

What is the process that happens during meiosis according to Mendel’s Law of Segregation?

Answer 16

Segregation occurs between the first and second meiotic cell divisions, where alleles eparate and are randomly distributed from each parent to form the offspring.

Question 17

How did Mendel confirm his First Law of Inheritance?

Answer 17

By crossing pea plants that differed in observable and scoreable traits.

Question 18

What is a Punnett square used for?

Answer 18

To predict the likelihood of each possible combination of alleles.

Question 19

What does ‘mono’ mean in a monohybrid cross?

Answer 19

One

Question 20

What does ‘hybrid’ mean in a monohybrid cross?

Answer 20

Having a combination of different alleles for a trait.

Question 21

Define:

monohybrid cross

Answer 21

It involves the creation of a new generation from two organisms that are being compared for a single characteristic or trait.

This may involve parents that are heterozygous for that trait.

Question 22

What is the purpose of monohybrid crosses in genetics?

Answer 22

Help determine if a trait is dominant or recessive.

Question 23

What are the steps in performing a monohybrid cross?

Answer 23

1. Determine the genotypes of the parents.
2. Write down the possible gametes for each parent.
3. Arrange the parents’ gametes around the edges of a Punnett square.
4. Complete the Punnett square to show possible offspring genotypes.
5. Interpret the results.

Question 24

How many rounds of monohybrid crosses are usually sufficient to determine if a trait is dominant or recessive?

Answer 24

Typically, two generations (F1 and F2) are needed.

Question 25

What does '**F1**' stand for in genetics?

Answer 25

Filial ## Footnote Filial generation (from Latin *filialis*, meaning 'offspring').

Question 26

What is the outcome of a monohybrid cross between two true-breeding, homozygous parents?

Answer 26

An F1 generation where all offspring are heterozygous and all show the dominant phenotype.

Question 27

What is the phenotypic ratio in the F2 generation of a monohybrid cross?

Answer 27

3 dominant : 1 recessive

Question 28

How does Mendel's Law of Segregation relate to Punnett squares?

Answer 28

Punnett squares illustrate how alleles segregate during meiosis.

Question 29

What did Mendel's Second **Law of Independent Assortment state**?

Answer 29

Each pair of alleles separates independently of other allele pairs during gamete formation.

Question 30

What is a **Dihybrid Cross**?

Answer 30

A cross between individuals that are **heterozygous at two different loci**.

Question 31

What is the **purpose** of a dihybrid cross?

Answer 31

To analyze the inheritance of two characteristics or genes at the same time.

Question 32

What did Mendel's **dihybrid cross** experiments demonstrate?

Answer 32

The seed shape and seed color traits would segregate independently of each other.

Question 33

What **ratio** did Mendel's Second Law predict in a dihybrid cross?

Answer 33

9:3:3:1 ## Footnote A dihybrid cross examines the inheritance of two independent traits and typically yields a 9:3:3:1 phenotypic ratio in the F2 generation if the genes assort independently.

Question 34

What is the **difference** between a monohybrid cross and a dihybrid cross?

Answer 34

* A monohybrid cross studies the inheritance of a single gene. * A dihybrid cross studies the inheritance of two genes simultaneously.

Question 35

What is a **pure-breeding** strain in Mendel's experiments?

Answer 35

A strain that gives offspring with 100% of its given trait when self-pollinated.

Question 36

# Define: Purity Law of Gametes

Answer 36

It states that only **one allele** from each parent enters the gamete, resulting in a 'pure' gamete. Paired alleles behave **independently** and do not impact or change each other.