selective breeding

Question 1

List some examples of desired characteristics

Answer 1

• maximum yield
• disease resistance and good health
• temperament
• speed
• fertility
• attractive flowers/bright colours
• nice flowers

Question 2

list the steps for selective breeding

Answer 2

• select animals from your existing stock with desired characteristics
• breed them
• pick best of offspring and breed together
• continue over several generations
• to make the chances of desireable characteristic being expressed increases as the allele becomes more and more common

Question 3

when doing selective breeding for increased number of offspring, what do you look for in the male?

Answer 3

a mother whohad lots of offspring

Question 4

what is an additional advantage of selective breeding?

Answer 4

• can combine 2 desirable characteristics

Question 5

when trying to breed for high meat yield, what characteristic do farmers look for?

Answer 5

• size/the largest

Question 6

How do you mate bulls and cows together?

Answer 6

• by artifical insermination
• safer for cow
• quicker and cheaper transportation of semen
• semen can be stored after the bull is dead
• semen can impregnate multiple cows

Question 7

Pros and cons of selective breeding:

Answer 7

PROS:
* will usually give desired traits
* done without labatory/ technical skill- accessible for all
* can be economically important eg by producing better quality or a higher quantity of food
* can help with making animals safer to work with eg cattle without horns

CONS:
* lack of genetic diversity
* rare disease genes being unknowingly selected as part of a positive trait, leading to problems with specific organisms, eg a high percentage of Dalmatian dogs are deaf
* The creation of physical problems in specific organisms, eg large dogs can have faulty hips due to not being formed correctly

Question 8

What was the advantage of breeding tall wheat plants and dwarf wheat plants together?

Answer 8

• tall wheat plants have a good grain yield but are easily damaged by wind and rain.
• dwarf wheat plants can resist wind and rain but have a lower grain yield
• these were cross-bred and so were the best offspring, leading to dwarf wheat plants that could resist bad weather and have a high grain yield