41. Interactions between alleles and genes. and 42. Deviations from Mendel’s Laws - main causes.

Question 1

Lethal allele’s - A lethal allele is one that has the potential to cause the death of an organism (typically the result of mutations in essential genes)

Answer 1

Lethal allele’s - A lethal allele is one that has the potential to cause the death of an organism (typically the result of mutations in essential genes)

Question 2

Types of lethal alleles:

• many lethal alleles prevent cell division
• some lethal allele’s exert their affect later in life - e.g. Huntington’s diease
• conditional lethal alleles may kill an organism only when certain environment conditions are present
• a lethal allele may produce traits that seemingly deviate from Mendelian ratios

Answer 2

Types of lethal alleles:

• many lethal alleles prevent cell division
• some lethal allele’s exert their affect later in life - e.g. Huntington’s diease
• conditional lethal alleles may kill an organism only when certain environment conditions are present
• a lethal allele may produce traits that seemingly deviate from Mendelian ratios

Question 3

Incomplete dominance (intermediary inheritance)

• The heterozygote exhibits a phenotype that’s intermediate between the corresponding homozygotes

Answer 3

Incomplete dominance (intermediary inheritance)

• The heterozygote exhibits a phenotype that’s intermediate between the corresponding homozygotes

Question 4

Overdominance

• heterozygous is more vigorous than both of the corresponding homozygotes
• sickle cell anaemia (autosomal recessive disorder in which affected individual produce abnormal form H6

Answer 4

Overdominance

• heterozygous is more vigorous than both of the corresponding homozygotes
• sickle cell anaemia (autosomal recessive disorder in which affected individual produce abnormal form H6

Question 5

Epistasis - when a gene masks the phenotypic effect of another gene

• epistatic interactions often occur because 2 or more different proteins participate in a cellular function e.g. an enzymatic pathway, instead of expected 9:3:3:1 we may get 9:7 ratio - flower colour in sweet pea

Answer 5

Epistasis - when a gene masks the phenotypic effect of another gene

• epistatic interactions often occur because 2 or more different proteins participate in a cellular function e.g. an enzymatic pathway, instead of expected 9:3:3:1 we may get 9:7 ratio - flower colour in sweet pea

Question 6

Gene interactions

• gene interactions occur when 2 or more different genes influence the outcome of a single trait
• morphological traits are affected by many different genes in combination with environmental factors

Answer 6

Gene interactions

• gene interactions occur when 2 or more different genes influence the outcome of a single trait
• morphological traits are affected by many different genes in combination with environmental factors

Question 7

Over dominance: carriers of sickle cell anaemia have resistance to malaria - homozygotes have no resistance - heterozygotes have a partial resistance to both

Answer 7

Over dominance: carriers of sickle cell anaemia have resistance to malaria - homozygotes have no resistance - heterozygotes have a partial resistance to both