Chapter 16-Mendel And Monohybrid Crosses

Question 1

Define Genetics

Answer 1

The study of inheritance.

Question 2

What is genetics? (USE THIS AS AN EXPLAINATION)

Answer 2

Genetics is the study of how we inherit traits and characteristics from our parents.

Question 3

What characteristics do farmers artificially select for?

Answer 3

Good milk production, high milk solids and good fertility in dairy cattle.

Resistance to disease and high crop yields in plants

Good conformation and fast growth rate in beef animals.

Question 4

Define variations

Answer 4

Variations are differences that exist among individuals of the same population.

Question 5

Define artificial selection

Answer 5

Artificial selection is a process where humans breed plants and animals for certain desirable traits.

Question 6

How is artificial selection mainly carried out?

Answer 6

Artificial selection is mainly carried out by selective breeding.

Question 7

What does polled mean?

Answer 7

Cattle that have the absence of horns are described as being polled.

Question 8

Give an example of a naturally polled animal

Answer 8

Aberdeen Angus cattle are naturally polled.

Question 9

What are the two forms of the gene that controls the polled trait:

Answer 9

One that causes the animal to be polled and

The one that is for the presence of horns

Question 10

What is it called when genes exist in two different forms

Answer 10

Allele

Question 11

What is a gene

Answer 11

A gene is located in a chromosome and contains information to produce a protein.

Question 12

What is an allele

Answer 12

Alternative forms of the same gene, e.g. height in pea plants: Tall (T) and dwarf (t).

Question 13

When different alleles exist for a gene, one is ___ and the other is ___

Answer 13

When two different forms exist for a gene, one is dominant and the other is recessive

Question 14

Dominant alleles are ones that appear ___ within a population and recessive alleles only occur ___

Answer 14

Dominant alleles appear regularly within a population and recessive alleles only occur occasionally.

Question 15

Define dominant

Answer 15

Expressed in the phenotype when present in the genotype, and is usually represented with a capital letter, e.g. T.

Question 16

Define recessive

Answer 16

Expressed only when an individual has no dominant allele present, and is usually represented with a lower case letter, e.g. t.

Question 17

Define genotype

Answer 17

The genes that are present in an organism, whether they are expressed or not, e.g. Tt

Question 18

Define Phenotype

Answer 18

The outward appearance of the organism.

Question 19

Define Monohybrid Cross

Answer 19

Looks at the inheritance of a characteristic that has two alleles, e.g. the study of the polled characteristic, which has a gene expressed in two different forms, one for the presence of horns and one that causes the animal to be polled.

Question 20

Define Mendel’s Law of Segregation

Answer 20

This law states that when gametes are formed only one allele from a pair of alleles is carried in the gamete.

Question 21

Why did Gregor Mendel use pea plants for his inheritance studies?

Answer 21

• Pea plants produce large amounts of seeds
• Peas are easy to grow
• The traits he chose has easily distinguishable alternatives (alleles)
• he concentrated on the inheritance of one characteristic at a time
• He controlled pollination in pea plants, crossing plants with alternative traits by hand.

Question 22

Define Homozygous

Answer 22

The alleles present in the genotype are the same. e.g. PP (homozygous dominant) or pp (homozygous recessive); true breeding.

Question 23

Define Heterozygous

Answer 23

The alleles present in the genotype are not the same, e.g. Pp. Heterozygous genotypes are often referred to as hybrids as they have one dominant and one recessive allele.

Question 24

Define Hybrid Vigour

Answer 24

The increased productivity displayed by offspring from genetically different parents.

Question 25

Give another name for Hybrid Vigour.

Answer 25

Heterosis

Question 26

Define Gamete

Answer 26

Sex cell (egg and sperm); Gametes are haploid (n)

Question 27

Define F1

Answer 27

First-generation offspring.

Question 28

Define Incomplete Dominance

Answer 28

Neither allele present in the genotype is dominant, which results in a blend of the two alleles in the phenotype, e.g. Shorthorn cattle: red x white = roan

Question 29

Define Multiple Alleles

Answer 29

When a characteristic is controlled by two or more alleles, e.g. blood groups in humans.

Question 30

Define Continuous Variation

Answer 30

When a characteristic is controlled by a number of genes interacting with each other to give a range of phenotypes rather than two distinct groups.

Question 31

How is separation of alleles caused?

Answer 31

Separation of alleles is caused by meiosis during gamete formation.

Question 32

What is a back cross?

Answer 32

A back cross involved the mating of a hybrid with a pure-breeding recessive animal or plant. It is used to establish if the hybrid is homozygous dominant or heterozygous.

Question 33

Give two examples of what demonstrates incomplete dominance.

Answer 33

The inheritance of roan coat colour in Shorthorn cattle and pink flowers in snapdragons demonstrates incomplete dominance.

Question 34

In animals, what characteristics show continuous variation? What are these traits controlled by and what do they produce when interacting with each other?

Answer 34

In animals, characteristics such as milk yield, growth rate and carcase quality show continuous variation.

Question 35

What dictates the phenotype of an organism?

Answer 35

The genotype and environmental factors dictate the phenotype of the organism.

Question 36

Define Co-dominant

Answer 36

Both alleles of a gene are equally dominant and both are expressed equally in the phenotype when they occur together in the genotype.