Unit 4: Evolution and genetic change

Question 1

What was the main genetic principle found by Gregor Mendel ?

Answer 1

• Offsprings traits are a blend of parents traits
• Means that favourable traits would be diluted in a population over several generations
• This disapproves Darwins theory

Question 2

What implication did Mendel’s experiment have on the evolutionary theory ?

Answer 2

• Darwin did not have an explanation about how favourable traits would be preserved over generations
• The concept of dominant and recessive alleles explained why some phenotypes disappear and appear again in the next generations

Question 3

What is the chromosome theory of inheritance ?

Answer 3

• The nuclear substance, controls the form and function of every cell, and divides at mitosis to give equal products
• Eggs must lose half their nuclear substance in the polar body before fertilisation- this is replaced by same of sperm
• Because sexual reproduction depends on adding together sperm and egg, each generation must be halving germ cells
• There are no essential differences between nuclear substance of egg or sperm
• Sexual reproduction is a means of producing variability between individuals

Question 4

How many alleles do germ cells have ?

Answer 4

Each germ cell contains one allele for every gene of the organism

Question 5

What are the 5 types of gene mutations ?

Answer 5

1) Gene point mutation
2) Gene duplication
3) Gene deletion
4) Horizontal gene transfer
5) Structural changes in chromsomes

Question 6

What is a selectively neutral mutation ?

Answer 6

A mutation that has no effect and is passed on to offspring- known as silent mutation

Question 7

What is gene flow ?

Answer 7

Movement of alleles from one population to another

Question 8

What is the effect of gene flow on variation ?

Answer 8

Gene flow usually increases variation

Question 9

What is genetic drift ?

Answer 9

Changes in allele frequencies in a population due to random sampling

Question 10

What is the bottleneck effect ?

Answer 10

A form of genetic drift where a large portion of the population is suddenly reduced due to a catastrophic event. This leads to a loss of genetic diversity

Question 11

What is the founder effect ?

Answer 11

Where a few individuals from a population start a new population with allele frequencies different from the original one

Question 12

When does gene flow occur ?

Answer 12

When individuals from one distinct population move to another and interbreed, therefore bringing a distinct new set of allele to the recipient population

Question 13

What is an example of an adaptive chromosome change ?

Answer 13

Cows have a large duplication of B-defensin, caused by chromosome 27, that helps the organism to survive the negative effects of microbes
- Likely made rumination possible