Creating genetic variation and continuous/discontinuous variation

Question 1

Why does inheritance lead to variation?

Answer 1

• genetic variation is created by the versions of genes you inherit from your parents
• for most genes there are a number of different possible alleles or vairants
• the individual mixture of alleles an organism inherits influences the characteristics they will display

Question 2

HOW does inheritance lead to genetic variation?

Answer 2

• the combination is determined by sexual reproduction involving meiosis (formatipoon of gametes)
• and the random fusion of gametes at fertilisation

Question 3

What genes are inherited?

Answer 3

• two alleles are inherited
• they may be the same or different version of the gene

Question 4

What is an organisms genotype?

Answer 4

• the combination of alleles an organims inherits for a characteristics is known as their genotype
• this is the genetic make-up of an organism in respect of that gene

Question 5

What is an organism’s phenotype?

Answer 5

• the observable characteristics of an organism are known as its phenotype

Question 6

What are modifications?

Answer 6

• the actual characteristics that an organism displays are also often influenced by the environment
• any changes the environment makes to a person’s phenotype are not inherited
  
  • these are referred to as modifications

Question 7

What is a dominant allele?

Answer 7

• the version of the gene that will always be expressed if present in an organism
• an individual showing the dominant characteristic in their phenotype could have one or two copies of the dominant gene
  
  • you can’t tell from their appearence

Question 8

WHat is a recessive allele?

Answer 8

• a recessive allele will only be expressed if two copies of this allele are present in an organism
• this means if an individual has a recessive phenotype, you will also know their genotype
  
  • they must have two alleles coding for the recessive phenotype

Question 9

What is the difference between homozygous and hetrozygous?

Answer 9

• homozygous
  
  • they have two identical alleles for a characteristics
  • the organism could be homozygous dominant or homozygous recessive
• hetrozygous
  
  • two different alleles for a characteristic
  • in this case the dominant allele will be expressed

Question 10

What is discontinuous variation?

Answer 10

• a characteristic that can only appear in discrete values
  
  • individuals fall into distinct groups
    
    • e.g. blood groups
• normallly only one gene is involved and the environment has little effect

Question 11

What is continuous variation?

Answer 11

• a characteristic that can take any value within a range
• there are two extremes
  
  • with every degree of variation possible in between
• e.g. height or weight
• many genes will be involved
  
  • environment has a large effect
  • polygenes