Chapter 16-Mendel And Monohybrid Crosses Flashcards Preview

Ag Science > Chapter 16-Mendel And Monohybrid Crosses > Flashcards

Flashcards in Chapter 16-Mendel And Monohybrid Crosses Deck (36)
Loading flashcards...
1
Q

Define Genetics

A

The study of inheritance.

2
Q

What is genetics? (USE THIS AS AN EXPLAINATION)

A

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

3
Q

What characteristics do farmers artificially select for?

A

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.

4
Q

Define variations

A

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

5
Q

Define artificial selection

A

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

6
Q

How is artificial selection mainly carried out?

A

Artificial selection is mainly carried out by selective breeding.

7
Q

What does polled mean?

A

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

8
Q

Give an example of a naturally polled animal

A

Aberdeen Angus cattle are naturally polled.

9
Q

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

A

One that causes the animal to be polled and

The one that is for the presence of horns

10
Q

What is it called when genes exist in two different forms

A

Allele

11
Q

What is a gene

A

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

12
Q

What is an allele

A

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

13
Q

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

A

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

14
Q

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

A

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

15
Q

Define dominant

A

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

16
Q

Define recessive

A

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

17
Q

Define genotype

A

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

18
Q

Define Phenotype

A

The outward appearance of the organism.

19
Q

Define Monohybrid Cross

A

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.

20
Q

Define Mendel’s Law of Segregation

A

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

21
Q

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

A
  • 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.
22
Q

Define Homozygous

A

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

23
Q

Define Heterozygous

A

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.

24
Q

Define Hybrid Vigour

A

The increased productivity displayed by offspring from genetically different parents.

25
Q

Give another name for Hybrid Vigour.

A

Heterosis

26
Q

Define Gamete

A

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

27
Q

Define F1

A

First-generation offspring.

28
Q

Define Incomplete Dominance

A

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

29
Q

Define Multiple Alleles

A

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

30
Q

Define Continuous Variation

A

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.

31
Q

How is separation of alleles caused?

A

Separation of alleles is caused by meiosis during gamete formation.

32
Q

What is a back cross?

A

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.

33
Q

Give two examples of what demonstrates incomplete dominance.

A

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

34
Q

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

A

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

35
Q

What dictates the phenotype of an organism?

A

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

36
Q

Define Co-dominant

A

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