3. GENOTYPE VS PHENOTYPE

Question 1

1. Do an organism’s traits always reveal its genetic composition?
   Why?

Answer 1

• no
• this is because of the different effects that the
  dominant and the recessive alleles have

EXAMPLE:
- Pp and PP have the same phenotype
(the purple flowers)
- Pp and PP have different genotypes

Question 2

2. In which two forms can the genotype of a dominant phenotype show itself in an individual?

Answer 2

• the individual must have one dominant allele
• this can occur in a homozygous manner (PP)
• it can also occur in a heterozygous manner (Pp)

Question 3

3. What method can we use to determine the genotype of a dominant phenotype that shows itself in an individual?

Answer 3

• we carry out a Test cross

Question 4

4. What is a Test Cross?

Answer 4

• this is when we breed an unknown genotype individual with a homozygous recessive individual

Question 5

5. We conduct a test cross, and the offspring display recessive phenotypes.
   What does this mean with regards to the genotype?

Answer 5

• the genotype of the unknown parent must be
  heterozygous

Question 6

6. What did Mendel base his First Law
   (the Law of Segregation) on?

Answer 6

• he based it on the inheritance pattern of 1 character

Question 7

7. What can be said about the F1 offspring that were produced in the cross conducted on the Parental Generation?

Answer 7

• they were monohybrids
• they are heterozygous for 1 character

Question 8

8. What is a Monohybrid cross?

Answer 8

• this is a cross between heterozygotes for 1 character
• these heterozygotes are called Monohybrids

Question 9

9. How did Mendel identify his Second Law of
   Inheritance (the Law of Independent Assortment)?

Answer 9

• Mendel observed the inheritance pattern of 2
  characters at the same time
• EG: seed colour (yellow or green)
• EG: seed shape (round or wrinkled)

Question 10

10. Which kind of cross did Mendel use to develop the Law of Independent Assortment?

Answer 10

• Dihybrid Cross

Question 11

11. Provide a definition for the Law of Independent Assortment?

Answer 11

MENDEL’S LAW OF INDEPENDENT ASSORTMENT STATES:
- that the alleles of two (or more) different genes are
sorted into gametes
- they are sorted independently of one another

WHAT THIS MEANS IS THAT:
- the allele a gamete receives for one gene does not
influence the allele the gamete receives for another
gene

Question 12

12. What is a Dihybrid cross?

Answer 12

• this is the cross between F1 hybrids
• it determines whether 2 characters are transmitted to
  offspring together as a package
• OR whether the 2 characters are transmitted to the
  offspring independently

Question 13

13. What happens if 2 genes are located on the same
    chromosome?

Answer 13

• the genes will most likely be inherited together
• this means that the Law of Independent Assortment
  does not apply

Question 14

14. What happens if 2 genes are located on different chromosomes?

Answer 14

• the genes will be inherited independently
• this means that the Law of Independent Assortment
  does apply

Question 15

15. What does the Law of Independent Assortment highlight with regards to Gamete Formation?

Answer 15

• each pair of alleles will segregate independently of
  each other pair of alleles
• this happens during gamete formation

Question 16

16. What does the Law of Independent Assortment apply to?

Answer 16

• the law only applies to genes on non-homologous
  chromosomes
• these chromosomes are different from one another
• this law does not apply to genes on the same
  chromosome

Question 17

17. What happens to genes that are located near each other on the same chromosome?

Answer 17

• these genes tend to be inherited together
• this is the dependent assortment of linked genes

Question 18

18. What laws govern Mendel’s Laws of Segregation and Independent Assortment?

Answer 18

• the laws of probability
• these laws have to do with multiplication and addition

Question 19

19. Provide an example for Independent Events?

Answer 19

WHEN TOSSING A COIN:
- the outcome of one toss has no impact on the
outcome of the next toss

Question 20

20. How do the laws of probability relate to alleles?

Answer 20

• alleles of one gene segregate into gametes
  independently of another gene’s alleles

Question 21

21. List the 3 situations in which a single gene may deviate from simple Mendelian patterns.

Answer 21

1. When alleles are not completely dominant or
   recessive
2. When a gene has more than 2 alleles
3. When a gene produces multiple phenotypes