2C- Autosomal Dominant/Recessive

Question 1

What is the principle of segregation?

Answer 1

sexually reproducing organisms possess genes that occur in pairs that only one member of this pair is transmitted to the offspring; it segregates

Question 2

What is the principle of independent assortment?

Answer 2

genes at different loci are transmitted independently; transmission of a specific allele at one locus has no effect on which allele is transmitted at the other locus

Question 3

What is a genotype?

Answer 3

An individuals genetic constitution (AA, Aa, aa, etc)

Question 4

Does genotypes always correspond to a specific phenotype?

Answer 4

No. Genotypes do not uniquely correspond to phenotypes; because individuals with two different genotypes (dominant homozygote and heterozygote) can have the same phenotype

Question 5

What are phenotypes?

Answer 5

The physical or clinical manifestations of genes and the environment.

Question 6

In autosomal dominant diseases, what is the probability of having an affected child if one parent is heterozygous affected (Aa) and the other is unaffected (aa)?

Answer 6

1/2

Question 7

In autosomal dominant diseases, what is the probability of having an affected child if one parent is homozygous affected (AA) and the other is unaffected (aa)?

Answer 7

1. The child will be affected (Aa)

Question 8

Is the prevelence of autosomal dominant diseases equal or unequal between men and women?

Answer 8

Equal

Question 9

Are autosomal dominant traits present in every generation or can a generation skip a few?

Answer 9

Present in every generation

Question 10

Is father-to-son transmission possible with autosomal dominant traits?

Answer 10

Yes

Question 11

What is the most common cause of autosomal recessive inheritance?

Answer 11

parents are both heterozygous carriers

Question 12

Having 2 heterozygous parents gives what % chance of having an autosomal recessive baby?

Answer 12

25%

Question 13

Are autosomal recessive traits present in every generation or can a generation skip a few?

Answer 13

They can skip

Question 14

Is the prevalence of autosomal recessive diseases equal or unequal between men and women?

Answer 14

Equal

Question 15

Is father-to-son transmission possible with autosomal recessive traits?

Answer 15

Yes

Question 16

What is the recurrance risk?

Answer 16

probability that an individual offspring will be affected by the disease; each birth is an independent event (such as a coin toss) and therefore the risk remains constant no matter how many affected or unaffected children are born.

Question 17

What are “new” mutations?

Answer 17

results when a child is born with a genetic disease that has not occurred previously in the family.

Question 18

What causes new mutations?

Answer 18

happens when a gene transmitted by one of the parents undergoes a change in DNA sequence, resulting in a mutation from a normal to a disease-causing allele

Question 19

What are germline mosaicism?

Answer 19

type of mosaic (existence of 2 or more genetically different cell lines in an individual) in which the germ line of an individual contains an allele not present in the somatic cells

Question 20

What is reduced penetrance?

Answer 20

situation in which a person has a disease causing genotype does not develop the disease phenotype.

Question 21

What is penetrance?

Answer 21

Penetrance is the probability of expressing a phenotype, given that an individual has inherited a predisposing genotype; all-or-none phenomenon (either you have the phenotype or you do not)

Question 22

What is delay in the age of onset?

Answer 22

age-dependent penetrance; some genetic disorders are not expressed until well into adulthood.
Ex: Huntington Disease

Question 23

What is variable expression?

Answer 23

refers to the degree of severity of the disease phenotype; severity of expression of many genetic diseases can vary greatly

Question 24

What is Locus heterogeneity?

Answer 24

diseases in which mutations at distinct loci can produce the same disease phenotype; single disease phenotype is caused by mutations at different loci in different families

Question 25

What is a good example of Locus heterogeneity?

Answer 25

Osteogenesis imperfecta- Procollagen triple helix is enconded on two genes one on chromosome 17 and the other on chromosome 7

Question 26

What is Pleiotropy?

Answer 26

describes genes that exert (multiple phenotypic effects) multiple aspects of physiology or anatomy; common feature of human genes

Question 27

What is genomic imprinting?

Answer 27

describes process in which genetic material is expressed differently when inherited from the mother than when inherited from the father

Question 28

What is anticipation?

Answer 28

a feature of pedigrees in which a disease is seen at earlier ages or with increased severity in more recent generations

Question 29

What is repeat expansion?

Answer 29

a type of mutation in which a tandem trinucleotide repeat increases in number (ex: Huntington Disease)

Question 30

What is consanguinity?

Answer 30

mating of related individuals; because relatives more often share disease genes inherited from a common ancestor, consanguineous unions are more likely to produce offspring affected by autosomal recessive disorders.