VARATION

Question 1

Define Varation

Answer 1

Variation is the differences between individuals within a species

Question 2

State the causes of variation

Answer 2

Causes of variation

• Crossing over
• Independent Assortment
• Mutation
• Fertilization

Question 3

What is crossing over and when do it occur

Answer 3

When two chromosomes exchange genetic material

•  Occurs during prophase I of meiosis, homologous chromosomes swap genes.
• As a result, each offspring will have a new combination of traits different from the parent and any other offspring.

Question 4

What is Independent Assortment

Answer 4

The random alignment of homologous chromosomes during metaphase I

Question 5

Define Mutation

Answer 5

Mutations are changes in the genetic make up of an organisms.

Question 6

Define Mutagen and give examples

Answer 6

Any substance or chemical that causes a mutation.
Examples of mutagens include radioactive substances, x-rays, ultraviolet radiation, and certain chemicals

Question 7

Define Gene Mutation

Answer 7

• A gene mutation involves a change in the order of the bases (A, C, G, 1) that make up the gene

Question 8

what are the four bases in DNA

Answer 8

The four bases in DNA are adenine (A), cytosine (C), guanine (G), and thymine (T).

(A with T, and G with C) (URACIL IN RNA SUB T )

Question 9

What are the three types of gene mutation

Answer 9

There are three types of gene mutations:

• Deletion (base missing)
  AGTCTGC -> AGCTGC
• Addition (extra base added)
  AGTCTGC -> AGTCGTGC
• Substitution (one base is substituted for another)
  AGTCTGC -> AGGCTGC

Question 10

What are the disorders caused by gene mutation?

Answer 10

• Cystic fibrosis
• Sickle cell anemia
• Hemophilia
• Huntington’s Disease

Question 11

What is Chromosome Mutation?

( GIVE EXAMPLES)

Answer 11

• A chromosome mutation is a change in the structure or arrangement of a chromosome.
• Examples include: Down’s Syndrome, Cri du chat syndrome, Turner’s syndrome, klienfelter syndrome

Question 12

What is Fertilization?

Answer 12

fertilization is the fusion of the nuclei of both sperm and egg cells to form a zygote

• Since fertilization is a random process, there are many possible different combinations of genes in a zygote.
• E.g. the sperm that fertilizes an egg determines whether the new offspring will be a boy (XY) or girl (XX)

Question 13

What are the types of variation?

Answer 13

• Continuous Variation
• Discontinuous Variation

Question 14

What is Continuous variation

Answer 14

• In continuous variation there is a complete range of measurements from one extreme to the other.
• Height is an example of continuous variation - individuals can have a complete range of heights, for example, 1.6, 1.61, 1.62, 1.625 etc meters high.
• Continuous variation in a group of individuals can be shown using a histogram or line graph.

Question 15

Provide examples of continuous variation

Answer 15

• Weight
• Hand span
• Shoe size
• Milk yield in cows
• Hair, eye, and skin color
• Arm length

Question 16

What is Discontinuous Variation

Answer 16

• is when individuals fall into a number of distinct classes or categories, and is based on features that cannot be measured across a complete range. You either have the characteristic or you don’t.
• • A bar graph is used to represent discontinuous variation.

Question 17

Provide Examples of discontinuous variation include:

Answer 17

• Blood group
• Gender
• Tongue rolling
• Attached ear lobes
• Widows peak

Question 18

Define Natural Selection

Answer 18

• the process whereby organisms better adapted to their environment tend to survive and produce more offspring. This is dominated by environmental factors.

Question 19

What is the Evolution by Natural Selection

Answer 19

• Struggle for existence
• Members of each species compete for food, space, and necessities of life.
• Predators that can run faster to catch more prey
• Prey that are better camouflaged avoid being caught.

Question 20

EXAMPLES OF NATURAL SELECTION (sickle cell anemia)

Answer 20

• Sickle Cell Anemia

Sickle Cell Anemia is a mutation that has provided an advantage in Malaria prone areas.

In these areas it is favored by natural selection and therefore Sickle Cell Anemia persists in many heterozygous individuals since the homozygous recessive condition is lethal.

Question 21

What is Natural Selection- Phenotypic ratio

Answer 21

• Changes in the physical environment and predation reduce the number of organisms with certain features (those not adapted)

Question 22

What is Artificial Selection?

Answer 22

• *Artificial selection (selective breeding) - This is when humans choose parents with particular characteristics to breed together and produce offspring with more desirable characteristics. Selecting breeding may include ranchers breeding cows and buffalo to get a certain kind of meat.
• It may also include mating male and female English Bull dogs that exhibit characteristics and selling their off spring.

Question 23

Explain Artificial Selection- Phenotypic ratio

Answer 23

• Humans select for and against features in pets and plants… changing the phenotypic ratio
• Artificial Selection is also known as Selective breeding.

Question 24

Differentiate between Natural Selection vs. Artificial Selection

Answer 24

• Natural Selection
• Dominated by environmental factors
• Where nature chooses organism with best traits for survival
• Ex: tigers developed stripes to sneak up on prey
• Artificial Selection
• Controlled by humans, “goal-directed”
• Person chooses which traits of the organism they want it to have
• Ex: dogs

Question 25

Exaplain how DDT creates Resistant Insects

Answer 25

DDT was used to kill mosquitoes (stopping malaria spread) Most insects were killed while others mutated making them resistant. These resistant insects reproduced Pesticide spray was less effective Spraying with DDT produces the selective pressure which favours the resistant mosquitoes. Because they can resist the effects of DDT, the resistant mosquitoes are said to have a selective advantage