Single Gene Inheritance

Front 1

When studying plants, Mendel knew only about what?

Back 1

TRAITS
(he knew nothing about genes)

Front 2

Principle of Segregation

Back 2

Traits segregate into different gametes.

Front 3

Principle of Independent Assortment

Back 3

Some traits ALWAYS segregate into different gametes INDEPENDENTLY with respect to each other.

Front 4

The primary observed phenotype in Mendel's crosses?

Back 4

DOMINANT

Front 5

How can you produce (see) recessive phenotypes?

Back 5

"back-crosses"

Front 6

Combination of traits that enter gametes only in their original parental combinations are due to what?

Back 6

"linked"

Front 7

Combination of traits that enter gametes in combination that DIFFER from those seen in the parental combinations are due to what?

Back 7

"recombination"
or
"Crossing- over"

Front 8

Who is affected by AUTOSOMAL DOMINANTS?

Back 8

Heterozygotes

Front 9

What type of inheritance is observed in autosomal dominance?

Back 9

vertical pattern of inheritance
(disease traits are seen in one generation after the other)

Front 10

In autosomal dominance:
what are the chances of an affected parent + unaffected parent having an affected offspring

Back 10

50%

(regardless of how many affected/ unaffected offsprings they have)

Front 11

In autosomal dominance, are sexes affected differently?

Back 11

No

Both sexes are affected equally and are equally as likely to pass on the mutant allele.

Front 12

Complications of Autosomal Dominance

Back 12

Variable expressivity
Non- or incomplete penetrance
Anticipation
Imprinting
Mosaicism

Front 13

In autosomal dominance, what is variable expressivity?

Back 13

modifying of genes in an individuals

Front 14

In autosomal dominance what is non- or incomplete penetrance?

Back 14

age-related penetrance

an individual looks normal at birth and as they age the disease phenotype presents itself

Front 15

In autosomal dominance, what is "anticipation"?

Back 15

The tendency of some dominant conditions to be come more severe in successive generations.

Cause is usually the EXPANSION OF TRINULEOTIDE REPEATS.

Front 16

In autosomal dominance, what is "imprinting"?

Back 16

The disease genes can be transmitted by either parent of either sex, the disease phenotype is evident ONLY when transmitted by a parent of one particular sex.

Front 17

In autosomal dominance, what is "mosaicism"?

Back 17

Mutations are present in some tissues but not others.

Unaffected looking parent can have affected offspring.

Front 18

Autosomal recessive

Back 18

needs BOTH alleles to be mutated in order to express the phenotype.

Carriers are asymptomatic, heterozygotes

Front 19

What is the pattern of inheritance for autosomal recessive?

Back 19

Horizontal pattern of inheritance

i.e., normal parents have one or more affected children

risk of an affected child with both carrier parents is 25%

Front 20

What is the affect on sex in autosomal recessive traits?

Back 20

Both sexes are affected equally and can equally pass on the genes.

Front 21

Sex linked

Back 21

Can be X- or Y-linked.

disease affects predominantly males.

No Y-linked diseases have been identified, but if there were, only males would be affected

Front 22

What is the most likely genotype of a sex linked trait?

Back 22

recessive

examples:
hemophilia A
Duchenne's muscular dystrophy

Front 23

what is the pattern of inheritance for Sex linked genotypes?

Back 23

"knight's move" inheritance pattern

affected males may have UNaffected maternal uncles

Front 24

Who is the sex linked disease transfered by and who does it affect?

Back 24

Transfered by a carrier mother or an affected father.

Remember, mom has two X's. Thus when she passes her genes to her children, each child has a 50% chance of either getting an normal X or a mutated X.

If a male gets a mutated X, he presents with the phenotype.

If a female gets the mutated X, her other X (from dad) offsets the phenotype.

Front 25

Is there male-to-male transmission for sex linked diseases?

Back 25

NO

Think about it, in order to have a son, the dad donates the Y (which has no mutation)

Front 26

X-linked dominant

Back 26

VERY RARE

affects BOTH sexes

Inheritance pattern looks like AUTOSOMAL DOMINANT

Front 27

Key characteristic of X-linked dominant patter of affected children.

Back 27

Affected males do NOT have affected sons.

However, ALL daughters, of affected males, are affected.

Front 28

What kind of analysis would you use to find genes that cause simple genetic disorders?

Back 28

Candidate gene analysis

Front 29

What is candidate gene analysis?

Back 29

Proposes possible candidate genes whose mutations could give rise to observed phenotypes.

compares unaffected to affected sequences.

looks at family members' genes that have the mutant phenotype

Front 30

If you are looking to find a mutation and you have no obvious candidate genes, what kind of analysis would you use?

Back 30

Linkage analysis

Front 31

Describe Linkage analysis of genes

Back 31

method of searching for a chromosomal locus that is "linked to the disease using POLYMORPHIC MARKERS that have a defined chromosomal location

Front 32

What are polymorphic markers?

Back 32

simple sequences variations that are inherited in a Mendelian fashion.

each of us has 2 markers, one from mom and one from dad

look through many markers to see patterns in family members who have the mutant phenotype and those who don't

Front 33

what is LOD score?

Back 33

used to measure the confidence in the assignment of a chromosomal locus for a genetic disorder based on LINKAGE ANALYSIS

lod >3 significant
lod 1-3 not significant, odds are your mutant gene is not on that chromosome

Front 34

Recessive consequence of functional gene mutations

Back 34

complete loss of functional gene

Front 35

Dominant consequence of functional gene mutations

Back 35

a bit more complicated

some of the function can be transcribed from the non-mutated allele

Two options:
HAPLOINSUFFICIENCY: some product is transcribed by the normal gene

DOMINANT NEGATIVE: product from the mutant allele combines with product from normal allele resulting in <50% functional product

Front 36

in dominant consequence of functional gene mutation, which is more severe, haploinsufficiency or dominant negative?

Back 36

Dominant negative

the bad allele's gene product interfere with whatever product the normal allele is making