The human karyotype

The human karyotype.

In human genetics we focus on Mendelian inheritance and molecular genetics as those subjects impact the phenotypic traits and medical health of human beings. Human genetics encompasses all of the other topics of genetics and molecular biology. As a topic it is especially relevant to future doctors because of its importance the the understanding of certain diseases and the development of effective treatments.

WikiPremed Resources

Human Genetics Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Human Genetics
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Know how to apply Mendelian concepts to human genetics including interpreting a pedigree chart for patterns of inheritance as well as sex-linked traits.

Be familiar with the procedures involved in human karyotyping.

Be able to describe the basis of techniques based on RFLP analysis including screening and fingerprinting.

Be prepared to describe the karyotype and symptoms associated with the most prominent human chromosomal, allelic (autosomal), and sex-linked genetic abnormalities.

Understand the process of X-chromosome inactivation (Barr bodies).

Suggested Assignments

Review the basic terms for human genetics using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Conceptual Vocabulary for Human Genetics

Genetic fingerprinting
Genetic fingerprinting is a technique used to distinguish between individuals of the same species using only samples of their DNA, exploiting highly variable repeating sequences called minisatellites.
Nondisjunction is the failure of chromosome pairs to separate properly during meiosis or mitosis.
Aneuploidy is a change in the number of chromosomes that can lead to a chromosomal disorder.
Widow's peak
A widow's peak is a descending V-shaped point in the middle of the hairline. This is a dominant genetic trait.
The recessive trait albinism is a form of hypopigmentary congenital disorder, characterized by a lack of melanin pigment in the eyes, skin and hair. It is a recessive genetically inherited trait.
Dimples are visible indentations of the skin, a dominant genetic trait which shows on some people's cheeks when they smile.
Freckles are small colored spots of melanin on the exposed skin. Having them is genetic and is related to the presence of the melanocortin-1 receptor MC1R gene variant, which is a dominant trait.
Down syndrome
Down syndrome or trisomy 21 is a genetic disorder caused by the presence of all or part of an extra 21st chromosome.
Turner syndrome
Turner syndrome encompasses several chromosomal abnormalities, of which monosomy X is the most common.
Klinefelter's syndrome
Klinefelter's syndrome or XXY syndrome is a condition caused by a chromosome aneuploidy in which affected males have an extra X sex chromosome.
A minisatellite is a section of DNA that consists of a short series of 10-100 bases. These types of sequences occur at more than 1000 locations in the human genome.
Chromosome 21
Chromosome 21 is the smallest human chromosome.
Triple X syndrome
Triple X syndrome is a form of chromosomal variation characterized by the presence of an extra X chromosome in each cell of a human female.
Phenylthiocarbamide, also known as PTC, or phenylthiourea, is an organic compound which either tastes very bitter, or virtually tasteless, depending on the genetic makeup of the taster.
Sexadactyly or hexadactyly is dominant genetic condition in which a person has six fingers on one or both hands, or six toes on one or both feet.
Cri du chat
Cri du chat syndrome is due to a partial deletion of the short arm of chromosome number 5.
XYY syndrome
XYY syndrome is an aneuploidy of the sex chromosomes in which a human male receives an extra Y chromosome.
Brachydactyly is an inherited, usually dominant trait, which leads to shortness of the fingers and toes relative to the length of other long bones of the body.
Mitochondrial Eve
Mitochondrial Eve is the name given by researchers to the woman who is defined as the matrilineal most recent common ancestor for all living humans.
Y-chromosomal Adam
Y-chromosomal Adam is the patrilineal human most recent common ancestor from whom all Y chromosomes in living men are descended.
Mosaicism denotes the presence of two populations of cells with different genotypes in one individual
Human mitochondrial DNA haplogroup
A human mitochondrial DNA haplogroup is a large group of haplotypes defined by differences in human mitochondrial DNA.
Advanced terms that may appear in context in MCAT passages
Human Y-chromosome DNA haplogroups
Human Y-chromosome DNA haplogroups are large groups of haplotypes defined by differences in the non-recombining portions of DNA from the Y chromosome.
Edwards syndrome
Trisomy 18 or Edwards Syndrome is the most common trisomy after Down Syndrome.
Patau syndrome
Patau syndrome is a syndrome in which a patient has an additional chromosome 13.
Robertsonian translocation
Robertsonian translocation is a common form of chromosomal rearrangement that occurs in the five acrocentric human chromosome pairs, namely 13, 14, 15, 21, and 22.
The Genographic Project
The Genographic Project is a five-year genetic study that aims to map historical human migration patterns by collecting and analyzing DNA samples from hundreds of thousands of people across five continents.
Uniparental disomy
Uniparental disomy occurs when a person receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other parent.