Mendel

Question 0

Inheritance patterns are often more complex than predicted by simple Mendelian genetics.

Answer 0

many heritable characters are not determined by only one gene with two alleles.

-relationship between genotype and phenotype is rarely as simple as in the pea plant characters Mendel studied

Question 1

Law of independent assortment

Answer 1

each pair of alleles segregates independently of each others pair of alleles during gamete formation
(this law applies only to genes on different, non homologous chromosomes)

Question 2

Inheritance of characters by a single gene may deviate from simple mendelian patterns in the following situations:

Answer 2

• when alleles are not completely dominant or recessive
• when a gene has more than two alleles
• when a gene produces multiple phenotypes

Question 3

Degrees of dominance:

Answer 3

1: complete dominance
2: incomplete dominance
3: co dominance

Question 4

1 complete dominance

Answer 4

occurs when phenotypes of the heterozygote and dominant homozygote are identical

Question 5

2 incomplete dominance

Answer 5

the phenotype of F1 hybrids is somewhere b/w the phenotypes of the two parental varieties

Question 6

3 codominance,

Answer 6

two dominant alleles affect the phenotype in separate, distinguishable ways

Question 7

Relation b/w dominance and phenotype

Answer 7

• a dominant allele does not subdue a recessive allele; alleles don’t interact
• alleles are simply variations in a gene’s nucleotide sequence
• for any character, dominance/recessiveness relationships of alleles depend on the level at which we examine the phenotype

Question 8

Most genes exist in populations in more that _____ allelic forms

Answer 8

two

ex. blood group use three alleles. iA iB i ( which are associated with carbohydrates)

Question 9

some traits may be determined by two or more genes

Answer 9

ex. in mice and many other mammals, coat colour depends on two genes

Question 10

epistasis

Answer 10

a gene at one locus alters the phenotypic expression of a gene at a second locus

Question 11

quantitative characters

Answer 11

are those that vary in the populations along a continuum

Question 12

Quantitative variation usually indicates …

Answer 12

polygenic inheritance (an additive effect of two or more genes on a single phenotype EX, skin colour on humans)

Question 13

Another departure from mendelian genetics arises when the phenotype for a character depends on…

Answer 13

environment as well as genotype

Ex. hydrangea flowers of the same genotype range from blue-violet to pink, depending on soil acidity

Question 14

Mendelian inheritance has its physical basis in the behaviour of chromosomes

Answer 14

• miltos and meiosis were first described in the late 1800’s
• chromosome theory

Question 15

chromosome theory of inheritance

Answer 15

mendelian gens have specific loci (positions) of chromosomes

chromosomes undergo segregation and independent assortment

Question 16

The behaviour of chromosomes during meiosis was said to account for…

Answer 16

mendel’s laws of segregation and independent assortment