Mendel and the Gene Idea

Question 1

what are characters and traits?

Answer 1

characters = heritable features, aka genes
traits = variations of that character, aka alleles

Question 2

what is the law of segregation?

Answer 2

the two alleles for one character separate during meiosis and end up in different gametes
(you cant have one gamete with two hair colour alleles, they HAVE to separate)

Question 3

what are true breeding genes and the types of dominance for them?

Answer 3

true breeding = has two identical alleles for a certain trait, homozygous dominant or homozygous recessive
in complete dominance, this stuff, the dominant will ALWAYS mask the recessive

Question 4

what is the law of independent assortment?

Answer 4

one character [gene] sorts independently of another
keep in mind this only applies to genes / allele pairs either on different chromosomes or very far apart on the same chromosome

Question 5

what are mutually exclusive events?

Answer 5

the idea that each event is random and is independent of previous events

Question 6

what are the two rules of probability?

Answer 6

1. rule of multiplication - probability of two independent events occurring in sequence is the sum of their individual probabilities
   (probability of x AND y)
2. rule of addition - probability of 2+ mutually exclusive events occurring is the sum of separate probabilities
   (probability of x OR y)

Question 7

what are the 8 types of inheritance?

Answer 7

1. complete dominance
2. incomplete dominance
3. codominance
4. multiple alleles
5. pleiotropy
6. epistasis
7. polygenic inheritance
8. environmental influence

Question 8

what is complete dominance?

Answer 8

one allele is fully expressed, another is fully masked. for one character you have 3 genotypes, but 2 phenotypes

Question 9

what is incomplete dominance?

Answer 9

no allele is recessive, the heterozygote is an intermediate between both. 3 genotypes, 3 phenotypes

Question 10

what is codominance?

Answer 10

each allele is fully expressed in a heterozygote, not an intermediate between them. an example is blood types - A is dominant, B is dominant, so a codominant would be AB

Question 11

what are multiple alleles?

Answer 11

traits that have more than 2 alleles - such as blood type (A,B,O). if 3 alleles - then 6 possible genotypes

Question 12

what is pleiotropy?

Answer 12

a single gene having multiple phenotypic effects
ex - siamese cats have a gene that controls fur colour AND controls cross-eyed condition

Question 13

what is epistasis?

Answer 13

epistasis is when the phenotype of one gene is affected by the genotype of another gene
ex - coat colour of labs. black is dominant, brown is recessive. BUT if the lab has a dominant E gene, it will always be yellow, regardless of the black/brown genes

Question 14

what is polygenic inheritance?

Answer 14

when 2 or more genes are “additive” and determine a single phenotype
ex- skin colour in humans is the product of 3 genes

Question 14

what is environmental influence for genetics?

Answer 14

when the environment plays a role in determining what genes are expressed
ex- hydrangea flower colour genes are expressed differently depending on the pH of the soil they are in

Question 15

what are the three autosomal traits?

Answer 15

1. recessive disorders
2. dominant disorders
3. sex INFLUENCED traits

Question 16

what are recessive disorders?

Answer 16

disorders that only show up if a gene is homozygous recessive. people who are heterozygous carry the gene but are phenotypically normal
ex- sickle cell disease is homozygous recessive, but people who are heterozygous are immune to malaria (pleiotropy)

Question 17

what are dominant disorders?

Answer 17

disorders that are expressed if the gene has the allele
ex - polydactyly, or huntingtons disease

Question 18

what are sex influenced traits?

Answer 18

traits that are not on the sex chromosomes, but are affected by whether a person is male or female
ex - male pattern baldness gene becomes dominant in the presence of testosterone