Congenital and Genetic Abnormalities

Question 1

What is a Congenital Abnormality?

Answer 1

Any defect present at birth due to development or formation during embryogenesis.

Question 2

What is embryogenesis?

Answer 2

The formation and development of an embryo.

This is a time of rapid and complex growth. There is a lot of potential for development errors. There is also variation in vulnerability as different organs are effected depending on the time of occurance

Question 3

Critial Period?

Answer 3

Each organ has a specific time or critical period where it is developing.

Question 4

What is organogenesis?

Answer 4

The time period when the bodies organs are developing with-in an embryo. This typically last for the first 8 weeks of pregnancy.

Question 5

Critial Period (Organ + Time)?

Answer 5

Central Nervous System: 2 - 5 wks
Heart: 2.5 - 5.5 wks
Extremities: 3.5 - 7 wks
Eyes: 3.5 - 7.5 wks
External Genitalia: 6.5 - 8.5 wks

Question 6

What is a teratogen?

Answer 6

A teratogen is an environmental factor that causes a developmental defect.
Examples: Smoking, Malnutrition, Alcohol, Lack of Folic Acid
Drugs (thalidomide, given in 60’s for morning sickness, caused limb defects).

Question 7

What is a gene?

Answer 7

A gene is a unit of heredity transferred from a parent to offspring, used to determine a characteristic of the offspring.

A sequence of nucleotides forming a part of a chromosome.

Question 8

What is a gene mutation?

Answer 8

A permanent alteration in the DNA sequence that makes up a gene.

Question 9

What is an allele?

Answer 9

An allele is an alternate form of a gene that arise by mutation and are found at the same place on a chromosome.

An allele is a mutated gene that takes the place of gene.

Question 10

How many chromosomes do humans have?

Answer 10

Humans have 46 chromosomes

44 of these are autosomes, and look the same in males and females
2 of the chromosomes are sex chromosomes and determine the sex of the human.

Question 11

Name 4 types of genetic abnormalities?

Answer 11

1. Monogenic
2. Mitochondrial Gene
3. Complex trait (multifactorial)
4. Chromosomal (# and structure)

Question 12

How many different types of Monogenic defects are possible?

Answer 12

3

Question 13

What are the different monogenic defects?

Answer 13

1. Autosomal dominant
2. Autosomal recessive
3. X-linked recessive

Question 14

What is a monogenic defect?

Answer 14

A defect that only affects one specific gene. Monogenic defects can be dominant, recessive, or X-linked.

Question 15

What is autosomal dominant?

Answer 15

A single gene in which an offspring has a 50% chance of inheriting because there only needs to be one defective gene. This can come from the paternal or maternal side.

Question 16

What is an autosomal recessive trait?

Answer 16

A recessive trait requires the gene to be delivered from both the paternal and maternal parent. Thus, there is a 25 % chance of having the disease.

Question 17

What is an x-linked recessive defect?

Answer 17

This defect is carried on the X sex chromosome. It is possible for both male and females to have this defect.

However, in females there are 2 X genes, thus the defective X is made up by the second X chromosone. These defects are more common in Male, because they only have one X chromosome.

Question 18

What is a complex trait (multifactorial) gene disorder?

Answer 18

These disorders involve many (polygenic) genes. They also almost always have an environmental factor involved.

An genetic predisposition + environmental factor that brings about a disease..

Ex. Cleft Palate, Diabetes, Congenital Heart Disease.

Question 19

What is a mitochondrial gene disorder?

Answer 19

A disorder that effects the 37 mitrochondrial genes. Because ATP is produced in the mitrochondria it results in defects due to poor growth. GI Issues, organ failures, neurological problems, and autism spectrum all all the result.

Typically they are of maternal inheritance because most paternal mitochondria is located in the flagellum (tail) of the sperm and falls off when entering the egg.

Question 20

What is a chromosomal genetic abnormality?

Answer 20

A adnormality which results from an issue with the number or structure of the chromosomes.

The issue can pertain to the number or the structure.

Question 21

What is an aneuploidy?

Answer 21

An incorrect number of chromosomes

Examples: Trisomy, Monosomy

Question 22

What is trisomy?

Answer 22

An extra chromosome in a pair (3 in total). The chromosome pair will be specified as we have 23 pairs.

Example: Trisomy21 = Down’s Syndrome, and Klinefelter’s Syndrome.

Klnefelter’s syndrome is when males are born with an extra x chromosome (1 in 500).

Question 23

What is monosomy?

Answer 23

1 Chromosome in a pair (one is missing). We often do not see this because the individual typically dies.
Ex. Turner’s Syndrome - Female born with only one X chromosome (1 in 3000)

Question 24

What is a structural chromosomal defect?
What are the 3 kinds?

Answer 24

A defect that has a structural defect in one of the chromosomes. There is no change in the number of the chromosomes.

Can be: 1. Inversion. 2. Translocation. 3. Deletion

Question 25

What is a centromere?

Answer 25

The middle of a chromosome. (Inversion can occur on the same side of a chromosome (Paracentric) or switch to the opposite side of the centromere (Paricentric).