Lesson 5 - Variation

Question 1

Variation

Answer 1

The differences in characteristics between organisms

Question 2

Interspecific variation

Answer 2

Between members of different species
Eg. Birds have 2 legs but cats have 4

Question 3

Differences between organisms within a species?

Answer 3

Intraspecific variation

Question 4

Causes of variation?

Answer 4

• Genetic material (inherits from parents leads to genetic variation)
• Environment (environmental variation)

Question 5

How does genetic material lead to variation?

Answer 5

• Alleles (variants)
• Mutations
• Meiosis
• Sexual reproduction
• Chance

Question 6

Explained example of alleles causing genetic variation?

Answer 6

Different alleles produce different effects.
- Three alleles form human blood types.
Depending on parental combination of these alleles 4 different blood groups can be produced.
Individuals in a species population may inherit different alleles of a gene.

Question 7

Mutations cause genetic variation?

Answer 7

Lead to changes in DNA sequence. This can change the proteins that are coded for. This can affect physical and metabolic characteristics.

Mutation in somatic (body) cells: affect individual
Mutation in gametes: passed on to organism’s offspring.

Question 8

Meiosis cause variation?

Answer 8

Before the nucleus divides and chromatids of a chromosome separate, genetic material inherits from the 2 parents is mixed up by independent assortment and crossing over.
Gametes of individual show variation.

Question 9

Sexual reproduction for variation?

Answer 9

Offspring inherits genes from each of the parents.
Individual produced differs from parents.

Question 10

Chance in variation?

Answer 10

Many different gametes produced from the parental genome.
Chance of which two gametes combine (random fertilisation).
- Individuals produced therefore different from siblings and contain a unique combination of genetic material.

Question 11

Asexual or sexual reproduction produces more variation?

Answer 11

Sexual

Question 12

How is variation achieved in organisms that reproduce asexually?

Answer 12

mutations

Question 13

Example of environmental variation: roses?

Answer 13

• Rose bushes planted in different positions in a garden
• One that has greater access to sun will generally grow larger than one in a shadier position.

Question 14

Example of environmental variation?

Answer 14

Scars. These can not be inherited from a parent.
- Occurred as a result of accident or disease.

Question 15

Genetic and environmental effects on height?

Answer 15

Tall parents = tall offspring
Bad diet = small offspring

Question 16

Genetic and environmental effects on skin colour?

Answer 16

Skin colour at birth is decided by genetics.

Skin colour decided by pigment melanin. More melanin = darker skin.
- Expose skin to sunlight, more melanin produced to protect skin from harmful UV rays.
Skin turns darker.

Question 17

Nature VS nurture argument

Answer 17

Scars:
- Cause is environmental
- Genetics affect how easily skin heals.

Question 18

Identical twins

Answer 18

• Brought up in different environments = variation
• Brought up in same environment = variation

Question 19

Jim twins ***

Answer 19

Similar characteristics:
- 6 feet tall
- body mass of 82 kg
- bite fingernails
- suffered migraine headaches

Surprising similar characteristics:
- Both had a dog with the same name
- Both married twice (both wives had the same name)
- Both smoked same brand of cigarettes
- Both studied carpentry and mechanical drawing.

Question 20

Combined affect / interaction?

Answer 20

When an individuals genetics and environment can both influence a particular trait.

Question 21

Interspecific variation definition:

Answer 21

The differences between any two species.

Question 22

Intraspecific variation definition:

Answer 22

Differences between members of the same species.

Question 23

Types of variation within sexual reproduction?

Answer 23

• Random assortment
• Crossing over
• Random fertilisation

Question 24

Types of genetic variation in gene mutations?

Answer 24

Insertion
Deletion
Substitution

Question 25

Types of genetic variation in mutations?

Answer 25

• Chromosome Mutations
• Gene Mutations

Question 26

Non-sense mutation?

Answer 26

• Occurs when a substitution of a base occurs leading to a premature ‘stop codon’ being coded for
• This would lead to the premature end of the synthesis of a polypeptide.
• Successful synthesis of the final protein would be very unlikely and it would almost certainly not be able to function normally
• Stop codons are: UAA, UAG, UGA

Question 27

Mis-sense mutation?

Answer 27

• Mis-sense mutation occurs when a change in base leads to a different amino acid being coded for
• The polypeptide will have a single amino acid that is different
• Effect determined by the role of the amino acid in the final polypeptide. May be involved in the formation of bonds for the structure of the active site. If this occurs then the enzyme will no longer have a specific and complementary structure and will be unable to catalyse a reaction.

Question 28

Silent mutation?

Answer 28

• By changing the base in the mRNA / DNA sequence, there is no change in the amino acid that the sequence codes for.
• This is because genetic code is degenerative.

Question 29

Deletion of bases?

Answer 29

• DNA nucloetide is lost from DNA sequence
• Deleting a base can lead to the codons no longer being read properly
• This is due to the fact that bases are read in triplets, therefore the subsequent bases would all be shifted forward by one base.
• the amino acid sequence of ‘new’ code would be entirely different

Question 30

A population with greater genetic diversity will show…

Answer 30

greater intraspecific variation.

Question 31

Polygenes:

Answer 31

different genes at different loci that all contribute to a particular aspect of phenotype