Patterns of Inheritance

Question 1

Describe Mendel’s rules

Answer 1

Principle of Segregation: ​
genes that occur in pairs ​
-only one member of this pair is transmitted to offspring ​

Principle of independent assortment:​
Genes at different loci are transmitted independently.

-Effects of one allele may mask those of another​

-Alleles may be dominant or recessive​

-A dominant allele exerts effect in both homozygote and heterozygote​

A recessive allele is detected only when it occurs in homozygous form

Question 2

What is a genotype?

Answer 2

an individual’s genetic constitution at a specific locus on a chromosome

Question 3

What is a phenotype?

Answer 3

what is actually observed physically or clinically

The affects of one allele may mask another; heterozygous/homozygousrecessive/dominant

Question 4

What is a karyotype?

Answer 4

display of chromosomes ordered according to length during metaphase

Question 5

Describe 3 types of hormone disorders

Answer 5

Nondisjunction ​(trisomy 21)

Chromosome structure abnormalities​

Translocations (reciprocal and non reciprocal)

Question 6

Autosomal dominant inheritance

Answer 6

Most often from union of normal parent with an affected heterozygote​

Affected parent can pass either a disease gene or a normal gene to his her children​

Each event has a probability of 50%​

Both sexes of children are at equal risk​

No skipping of generations​
-If gene occurs on autosome and is dominant, it is said to be autosomal dominant

Question 7

Autosomal Recessive inheritance

Answer 7

Heterozygous carriers for recessive disease genes are much more common than affected homozygotes​

¼ of offspring of two heterozygotes will be normal, half will be phenotypically normal heterozygous carriers and ¼ will be homozygotes affected with the disease​

If two affected homozygotes mate, all of their children will be affected by the disease​

-If gene occurs on autosome (non sex chromosome) and is recessive, is said to be autosomal recessive.​

Question 8

Pedigree analysis

Answer 8

Family record in how a trait is carried throughout multiple generations​

At least 3 in usually needed

Question 9

Recessive x-linked traits

Answer 9

Recessive x-linked trait only phenotypically seen in males (XY y doesn’t have enough genetic materials to superseed the X)​​
- Genes for X-linked traits are found only on the X chromosome

Question 10

what is a polygenic trait

Answer 10

Polygenic traits controlled by several genes ex. skin

Question 11

Recessive vs. dominant example in achondroplasia

Answer 11

achondroplasia (type of drawfism)​

Heterozygotes have short stature, but a nearly normal life span. Affected homozygotes are much more severely affected and usually die in infancy from respiratory failure.

Question 12

x linked allele passed from male and from female differences

Answer 12

Male with dominant X-linked allele will pass that allele to all of his daughters but to none of his sons. ​

A female with a dominant X-linked allele has a 50% chance of passing the allele to any offspring.

Question 13

Penetration

Answer 13

An individual who has the genotype for a disease may not exhibit the disease, but can transmit the disease to the next generation.