Chapter 10: Mendelian genetics

Question 1

Why did Gregor Mendel use pea plants for his experiment?

Answer 1

1. Mating could be controlled
2. Generation time is short
3. Easily observable characters
   * flower colour, pea colour, pea shape

Question 2

What are Mendel’s laws?

Answer 2

1. Law of segregation
2. Law of independent assortment

Question 3

What are Mendel’s definitions?

Answer 3

• Character: a detectable, inheritable feature
  o Ex: hair colour, flower colour
• Trait: variant of a character
  o Ex: brown or blonde hair, purple or white flower

Question 4

What are alleles?

Answer 4

Alternative forms of genes
(same locus different allele)

Question 5

What is a locus?

Answer 5

Specific location on a chromosome (genes are at specific loci)
GPS coordinate system on the chromosome

Question 6

Why do diploid organisms have two alleles for every trait?

Answer 6

They inherit one from each parent

Question 7

Do homologous chromosomes have the same gene loci?

Answer 7

yes

Question 8

Do homologous chromosomes have the same alleles?

Answer 8

no

Question 9

Do non-homologous chromosomes have the same gene loci?

Answer 9

no

Question 10

What is the law of segregation?

Answer 10

• 2 alleles for a character segregate during gamete formation
• End up in different gametes
• Egg or sperm gets only ONE of two alleles present in somatic cells

Question 11

What is a true-breeding individual?

Answer 11

• All gametes have identical alleles for particular
  character
• if mated with itself, offspring has identical traits

Question 12

What is a phenotype?

Answer 12

observable traits of an organism

Question 13

What is a genotype?

Answer 13

genes of an organism ex: PP, pp, Pp

Question 14

What determines the phenotype?

Answer 14

the genotype (like the code)

Question 15

What are the possible genotypes?

Answer 15

• Homozygous (both alleles are the same)
• PP, pp
• Heterozygous (2 different alleles)
• Pp

Question 16

If a trait is dominant does that mean it is most common in the population?

Answer 16

No dominance and prevalence of the trait are not linked

Question 17

What is the law of independent assortment?

Answer 17

Characters are independently sorted from each other (inherited separately)
o Genes (on chromosomes) separate independently during gamete formation
o Paternal genes do not have to stay together / maternal genes do not have to stay together
(Genes that were inherited together do not have to be passed on together!)

Question 18

How to calculate probabilities of more complex dihybrid crosses?

Answer 18

Break it down into smaller monohybrid crosses then multiply each probability of the desired traits

Question 19

How is the law of segregation explained by meiosis?

Answer 19

• Homologous chromosomes
  separate during gamete
  formation
• Allele pairs segregate during
  gamete formation
• A plant that was Pp (carries
  one P allele, and one p
  allele) gives rise to gametes
  that carry either P or p but
  not both, because sperm
  and egg are haploid

Question 20

How is the law of independent assortment explained by meiosis?

Answer 20

• During metaphase I of
  meiosis paternal
  chromosomes do not have to
  all be on the same side and
  neither do maternal
  chromosomes.
• Each gamete has a 50/50
  chance of getting the
  maternal or the paternal
  chromosome