LG 1.18 - Genetics of Autosomal Inheritance

Question 1

Factors affecting expression of disease genes

Answer 1

i. Some spontaneous, de novo mutations
ii. Germline mosasicism—occurs in utero
iii. Age dependent penetrance can skew pedigree analysis
iv. Heterzygotes are clinically affected in dominant disease, but usually not in recessive diseases

Question 2

Penetrance

Answer 2

Proportion of individuals that carry an allele that also express the phenotype

Question 3

Expressivity

Answer 3

Complete penetrance>Highly penetrant>reduced> low penetrance

Question 4

Dosage

Answer 4

Dosage the effect of on the phenotype of the active number of working alleles

-When that allele is functioning. Other is not working

The phenotype is generated by the interaction of both alleles and the environment

–How the two alleles interact and create a phenotype is based upon the “strength”

Question 5

Duplication of one chromosome

Answer 5

Trisomy

Question 6

How many strand of DNA are in the human cell when the chromosomes look like this (looks like an X)?

c. 23
d. 46
e. 92

Answer 6

e. 92

23 from mom and 23 from dad. DNA duplicates from 46 to 92.

Question 7

When does it go back from 92 to 46 chromosomes?

Answer 7

During Metaphase

Question 8

Genotype

Answer 8

The sequence (alleles) that is found in the individual’s genome

Question 9

Phenotype

Answer 9

The “visible” expression. Physical expression of the traits defined by the genetic material

Question 10

Monogenic Trait

Answer 10

phenotypes created by the action of one gene

Question 11

Dominant traits

Answer 11

Dominant traits are generated by the presence of 1 allele.

Can override “normal” allele.

Question 12

Recessive Traits

Answer 12

Recessive traits only seen when 2 alleles must interact.

One allele is not strong enough to overtake the dominant.

Question 13

Co-dominant

Answer 13

Co dominant traits are generated by the presence of two dominant traits.
Both traits are shown.

Question 14

Incomplete dominance

Answer 14

Incomplete dominance is a MIXING of phenotypes of two dominant alleles

Question 15

What is mendelian inheritance?

Answer 15

• Inheritance of phenotypes form single gene traits (aka monogenic traits).
• Mendelian inheritance patterns are demonstrated by pedigrees

Question 16

Euchromatin, heterochromatin?

Answer 16

• Euchromatin: functional chromatin.
• Heterochromatin: condensed chromatin.
• the euchromatin that is open and functional varies between different cell-types - this can help determine cell differentiation (e.g., euchromatin that corresponds with liver enzyme synthesis will be found in… the liver)

Question 17

how are chromosomes shaped?

Answer 17

linear - one DNA strand - we have 23 pairs of these per non-dividing, autosomal cell

Question 18

what happens in interphase and metaphase of mitosis?

Answer 18

1. interphase - genetic material is replicated - cell makes EXACT copies of its 46 chromosomes (one cell has 92 chromosomes at the end of interphase)
2. metaphase - genetic material lines up in the middle of the cell and the cell divides into 2 cells - each identical with 46 chromosomes

Question 19

allele

Answer 19

• allele = alternative codes at the same loci
• most genes have multiple alleles, making them polymorphic (most human traits are polymorphic)
• identical alleles are homozygous the the gene